Article: 218471 of rec.radio.amateur.antenna From: "Roger Conroy" Subject: Re: Aluminum tubing? Date: Thu, 13 Oct 2005 14:58:53 +0200 Message-ID: References: <1128562179_21@isp.n> <4348f9f7.286775451@news.blueyonder.co.uk> "Gene Fuller" wrote in message news:hm83f.133870$qY1.14837@bgtnsc04-news.ops.worldnet.att.net... > Roger Conroy wrote: > > [snip] > >>>>>>>Why do you guys in the US always omit the "i" in aluminium ? >>> >>> >>>You mean the second "i"? Probably because we spell it correctly: >>>Aluminum. >>>;~) >> >> >> But you do it ONLY to Alumin(i)um. What about Lithium, Barium, Chromium, >> Ruthenium, Titanium, Uranium, and so on......? > > Hmmmm, does "so on" also include Lanthanum, Molybdenum, Platinum, and > Tantalum? > > 73, > Gene > W4SZ We're in complete agreement about those too. We have 2 "groups" of metals that differ in having "um" or "ium" endings. It is only Alumin(i)um that "switches groups" in crossing the Atlantic. When, how and why did it happen? The other one that is a consistent transatlantic difference is the group of words that include colo(u)r, odo(u)r, favo(u)r, hono(u)r...... I can't think of any "equivalent" anomalies there. ISTR hearing a radio show on language that mentioned that there is at least one variety of North American English that has kept the "u" - but I just can't remember who/where that is. 73 Roger ZR3RC Article: 218472 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Date: Thu, 13 Oct 2005 14:31:22 GMT Dave wrote: > math please??? where do you get 4.17watts?? to me it looks like a 50 ohm > load on a 50 ohm meter so zero reflected power. Here's the setup. 100W--tuner--75 ohm coax--Bird--1/2WL 75 ohm coax--50 ohm load Assumptions: Losses are negligible. The tuner provides a Z0-match so 100 watts is delivered to the load, i.e. all reflected power is re-reflected. I think this was actually the case for the experiment. Also assume that the impedance bump caused by the insertion of the Bird is negligible, i.e. the same net voltage and net current exists whether the Bird is in or out of the circuit. The voltage reflection coefficient at the load is (50-75)/(50+75) equals -0.2. That makes the power reflection coefficient (-0.2)^2 equals 0.04, i.e. 4% of the power incident upon the load is reflected. If 100 watts is delivered to the load while 4% is being reflected then the power incident upon the load is 100w/(1-0.04)=100w/0.96= 104.1667 watts. Incident power minus delivered power = reflected power so the reflected power on the 75 ohm coax is 4.1667 watts. The SWR on the 75 ohm coax is (1+|rho|)/(1-|rho|)= 1.2/0.8 = 1.5 THE SWR ON THE 75 OHM COAX IS 1.5:1. The Bird is in error when it reports the SWR to be 1:1. The SWR is *NOT* 1:1 anywhere on the load side of the system. The Bird reports a forward power of 100w. The actual forward power is 104.1667w. The Bird reports a reflected power of near zero. The actual reflected power is 4.1667w. The Bird reports an SWR of 1:1. The actual SWR is 1.5:1. The Bird is reporting false values because it is embedded in a 75 ohm environment and is calibrated for 50 ohms. If the ratio of voltage to current equals 50 within a 75 ohm system, there exists an SWR of 1.5:1 and an SWR meter calibrated for 75 ohms will verify that fact. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218473 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Thu, 13 Oct 2005 14:35:00 GMT Cecil Moore wrote: > The SWR is *NOT* 1:1 anywhere on the load side of the system. Sorry, this should have read: The SWR is *NOT* 1:1 anywhere on the load side of the tuner. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218474 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Thu, 13 Oct 2005 15:08:04 GMT Dave wrote: > math please??? where do you get 4.17watts?? to me it looks like a 50 ohm > load on a 50 ohm meter so zero reflected power. Let's compare the following two configurations. 100W--tuner--75 ohm coax--Bird--1/2WL 75 ohm coax--50 ohm load 100W--tuner--75 ohm coax--Bird--1/4WL 75 ohm coax--50 ohm load The actual SWR on the coax is the same in both cases. The actual forward power and reflected power are the same in both cases. The SWR on the coax is 75/50 = 1.5:1. The actual forward power is 104.1667w and the actual reflected power is 4.1667w. In the first case the Bird will report an SWR of 1:1, a forward power of 100w, and a reflected power of zero simply because the ratio of net voltage to net current is 50 ohms at the Bird measurement point. In the second case the Bird will report an SWR of 2.25:1, a forward power of 117.4w and a reflected power of 17.4w simply because the ratio of net voltage to net current is 112.5 ohms at the Bird measurement point. The ratio of net voltage to net current alone is useless for calculating SWR unless the Z0 environment (characteristic impedance) exists and is known. Minus the humor, I believe this is Reg's main point. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218475 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Thu, 13 Oct 2005 15:43:25 GMT Dave wrote: > "Cecil Moore" wrote in message >>Also assume that the impedance bump caused by the insertion of the >>Bird is negligible, i.e. the same net voltage and net current exists >>whether the Bird is in or out of the circuit. > > you can not assume this, especially if you consider the actual results of > the experiment. the bird is a 50 ohm transmission line segment and it is > seeing a 50 ohm load. the 50 ohm load plus 1/2 wave of anything is 50 ohms. > so as far as the bird knows there is no reflected power and the real world > reading is correct. Remove the Bird, reconnect the two pieces of 75 ohm coax, and I'll bet you will measure 70.7 volts and 1.414 amps at that point, 1/2 WL back from the 50 ohm load. If so, the Bird is NOT changing the conditions when it is inserted. And we know there has to be reflected power all up and down the 75 ohm coax. There is no place in the system on the load side of the tuner where reflected power is zero. The reflected power exists and the Bird reports a bogus reading for it. With or without the Bird in the circuit the ratio of net voltage to net current at the measurement point, 1/2WL away from the 50 ohm load, will be 50 ohms according to transmission line theory. That's all the Bird is seeing - a V/I ratio of 50 which is irrelevant to SWR unless Z0 is known and Z0 is known to be 75 ohms, NOT 50 ohms. The ratio of net voltage to net current is All THE BIRD EVER SEES. "As far as the bird knows ..." it is embedded in a 50 ohm environment. But the Bird is not all-knowing. In this case, it is embedded in a 75 ohm environment and is giving bogus readings because all it sees (samples) is a net voltage to net current whose ratio is 50 ohms. It is what the Bird doesn't know that is important. The Bird doesn't know that it is not embedded in a 50 ohm environment, and in its ignorance of that fact, reports bogus results. The actual SWR on a lossless line doesn't change. Yet, in another posting, I showed that moving the Bird 1/4WL closer to the load caused a reported SWR change by the Bird from 1:1 to 2.25:1. How could both results possibly be right? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218476 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2Vu3f.10492$y_1.7568@edtnps89> Message-ID: Date: Thu, 13 Oct 2005 15:58:49 GMT Frank wrote: > Did I miss something? As far as the Bird is concerned, all it sees is 50 > ohms, indistinguishable from a 50 ohm termination, on its connector. Exactly the point, Frank. The Bird doesn't know it is embedded in a 75 ohm environment and reports bogus results because it assumes it is embedded in a 50 ohm environment, which it is not. This is Reg's main point in wanting to call the SWR meter a TLI meter. The Bird is not to blame for reporting bogus results. It is the operator who is to blame for using a 50 ohm meter in a 75 ohm environment and reporting the bogus results as valid. 100w--tuner--75 ohm coax--x--1/2WL 75 ohm coax--50 ohm load Without a Bird installed at point 'x', most everyone would agree that the SWR all up and down the 75 ohm coax is 1.5:1 and the voltage and current at point 'x' are the same as the in-phase voltage and current at the 50 ohm load. The voltage at point 'x' is 70.7 volts, and the current at point 'x' is 1.414 amps. The SWR on the line is 1.5:1. Now, installing the Bird at point 'x' doesn't change anything appreciably. The voltage at point 'x' is still very close to 70.7 volts and the current at point 'x' is still very clost to 1.414 amps. Those two parameters are what the Bird samples and all the Bird sampoles. And since the Bird is calibrated for 50 ohms, it reports a bogus SWR of 1:1. If the Bird is recalibrated for 75 ohms, it will report the correct SWR of 1.5:1. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218477 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <7dqdndDq5IH3GdPeRVn-qQ@crocker.com> Message-ID: <9Kv3f.864$q%.22@newssvr12.news.prodigy.com> Date: Thu, 13 Oct 2005 16:15:01 GMT Dave wrote: > obviously at 1/4 wave from the load the impedance seen by the bird is not 50 > ohms. That's the whole point, Dave. The poor ignorant Bird doesn't know what is going on external to itself. You and I have to be smarter than the Bird and not report its bogus results as "correct". The Bird reports a 9:1 SWR on a matched-line 450 ohm ladder-line. Is the SWR really 9:1? > this is just how it works, you > can't wish it to be anything else, especially when the actual measurements > prove me correct. The actual measurements prove you wrong! The forward power reported by the Bird is NOT the actual forward power. The reflected power reported by the Bird is NOT the actual reflected power. The SWR reported by the Bird does not exist anywhere in the system on the load side of the tuner. The Bird is totally confused because it is being abused by the operator. The operator is totally ignorant when he reports the readings are "correct". > you have to realize that the bird is not measuring what > is going on outside it's case, the only thing it can measure is the voltage > and current in its little 50 ohm internal world. That's exactly the point and that's why some readings reported by the Bird are obviously bogus when compared to the broader knowledge of actual external conditions. The operator needs to be smarter than the Bird. > so look at it from the > meter's point of view... it looks out the load side and sees 50 ohms, it > can't know that it is really a 75 ohm line, in fact it can't know there is > any line there at all, it just sees a 50 ohm load, therefore no reflection > into the meter, and no reflected power reading. qed. But you and I know that 75 ohm reflected energy is flowing through the Bird and the Bird is ignoring it. Of course, we cannot blame the Bird for the bogus readings. We can only blame the ignorant operator who reports that the bogus readings are "correct" when they are obviously false. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218478 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 09:25:43 -0700 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Cecil Moore wrote: > The actual SWR on a lossless line doesn't change. Yet, in another > posting, I showed that moving the Bird 1/4WL closer to the load > caused a reported SWR change by the Bird from 1:1 to 2.25:1. How > could both results possibly be right? You need to keep thinking about that. What if they are both right? Is it really one continuous, uniform transmission line? Is SWR the same everywhere in a tee stub circuit? ac6xg Article: 218479 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 16:45:51 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> "Cecil Moore" wrote - > Minus the humor, I believe this is Reg's main point. ==================================== Dear Cec, I assume you are referring to me, Reg Edwards, G4FGQ. Before responding I have found it necessary to have several glasses of Australian, Banrock Station, 2004, Shiraz Mataro, Red. It can be recommended with confidence. I have only ever had ONE point. It is that arguments and discussions about SWR, invariably involving "ifs" and "buts" and vivid imaginations of the contributors, are of entertainment value only. In any event, CB-ers and novices are unlikely to learn anything from it. There is only one transmission line on which SWR matters. It is that which runs between the so-called SWR meter or tuner and the antenna. It is generally unknown. But whatever it is the so-called SWR meter, even a Bird, is incapable of measuring it. Having got that off my chest. now perhaps I can finish the bottle with a cigarette. ---- Reg, G4FGQ. Article: 218480 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Thu, 13 Oct 2005 17:10:30 GMT Jim Kelley wrote: > > Cecil Moore wrote: >> The actual SWR on a lossless line doesn't change. Yet, in another >> posting, I showed that moving the Bird 1/4WL closer to the load >> caused a reported SWR change by the Bird from 1:1 to 2.25:1. How >> could both results possibly be right? > > You need to keep thinking about that. What if they are both right? Here's the example sans the Bird. Between the tuner output and the load, where exactly is the actual SWR = 1:1 and where exactly is the actual SWR = 2.25:1? Answer: nowhere! XMTR--tuner---1 WL 75 ohm coax---50 ohm load -- 73, Cecil http://www.qsl.net/w5dxp Article: 218481 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <7dqdndDq5IH3GdPeRVn-qQ@crocker.com> <9Kv3f.864$q%.22@newssvr12.news.prodigy.com> <072dnTd0AvMiFtPenZ2dnUVZ_s2dnZ2d@crocker.com> Message-ID: Date: Thu, 13 Oct 2005 17:12:56 GMT Dave wrote: > well DUH! obviously if you want to measure swr on a 450 ohm ladder line you > don't use a 50 ohm bird! Yes, now you are getting it. If you want to measure SWR on a 75 ohm coax line, you don't use a 50 ohm Bird. I couldn't have said it better myself. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218482 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Message-ID: Date: Thu, 13 Oct 2005 17:27:01 GMT Richard Clark wrote: > Cecil Moore wrote: >>The Bird is in error when it reports the SWR to be 1:1. > > This is the poor carpenter blaming his tools. Exactly! You got my point. It is operators who refuse to recognize the errors in the Bird's readings and report a bogus SWR as "correct" who are at fault. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218483 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 17:46:27 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> "Reg Edwards" wrote > CB-ers and novices are unlikely to learn anything from it. > ================================ And it appears some professional IEEE engineers and university professors also remain in difficulty. Just because, from it's sales blurb and scale markings, an instrument is purported to measure SWR with forward and reflected power, should not be taken as being the gospel truth. It can be highly misleading. And from this newsgroup it seems it is! There's still some left in the bottle. Hic! Hic! ---- Reg. Article: 218484 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 10:30:03 -0700 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Cecil Moore wrote: > Jim Kelley wrote: > >> >> Cecil Moore wrote: >> >>> The actual SWR on a lossless line doesn't change. Yet, in another >>> posting, I showed that moving the Bird 1/4WL closer to the load >>> caused a reported SWR change by the Bird from 1:1 to 2.25:1. How >>> could both results possibly be right? >> >> >> You need to keep thinking about that. What if they are both right? > > > Here's the example sans the Bird. Between the tuner output > and the load, where exactly is the actual SWR = 1:1 and where > exactly is the actual SWR = 2.25:1? Answer: nowhere! > > XMTR--tuner---1 WL 75 ohm coax---50 ohm load And the answer would be different still in this circuit. XMTR---1/4 WL 75 ohm coax---50 ohm load Amazin', what happens when you change the circuit! ac6xg Article: 218485 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Thu, 13 Oct 2005 18:41:59 GMT Jim Kelley wrote: > > > Cecil Moore wrote: >> Here's the example sans the Bird. Between the tuner output >> and the load, where exactly is the actual SWR = 1:1 and where >> exactly is the actual SWR = 2.25:1? Answer: nowhere! >> >> XMTR--tuner---1 WL 75 ohm coax---50 ohm load > > And the answer would be different still in this circuit. > > XMTR---1/4 WL 75 ohm coax---50 ohm load No, it wouldn't. The answer is exactly the same. *NOWHERE* is the SWR 1:1 or 2.25:1. In both examples, the SWR on the coax is 1.5:1. The SWR is *always* set by the relationship of Z0 to the load. In both examples above, that relationship is *identical*. > Amazin', what happens when you change the circuit! Z0 didn't change. The load didn't change. Therefore, the SWR didn't change. What exactly do you think changed? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218486 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Message-ID: Date: Thu, 13 Oct 2005 18:48:05 GMT Richard Clark wrote: > Cecil Moore wrote: >>Exactly! You got my point. It is operators who refuse to >>recognize the errors in the Bird's readings > > There was no error in the reading beyond the inherent ±5% specified as > the meter movement's. The Bird is supposed to measure power. The Bird's forward power readings are in error unless used in a 50 ohm environment. I previously talked about using a hammer on a screw. I was hoping even you could understand that metaphor without me having to explain it to you. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218487 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Message-ID: <7py3f.967$dO2.323@newssvr29.news.prodigy.net> Date: Thu, 13 Oct 2005 19:17:23 GMT Richard Clark wrote: > Cecil Moore wrote: >>The Bird is supposed to measure power. The Bird's forward >>power readings are in error > > That has not been demonstrated by Owen's example. Richard, if you don't understand why a 50 ohm power meter yields erroneous readings when installed in a 75 ohm environment, I don't know what else to tell you. What is it about using a hammer on a screw that you don't understand? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218488 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 11:57:29 -0700 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Cecil Moore wrote: > Z0 didn't change. The load didn't change. Therefore, the > SWR didn't change. What exactly do you think changed? I think the circuit changed. Don't you? I also think that if you change the circuit, it's possible to measure the effect of that change. The meter measures what takes place at its insertion point in the circuit. What you seem to be upset about is that it might not in every case accurately display the conditions at some arbitrary position away >from its insertion point. Like within a shorted quarterwave stub for example. Are you still unwilling to accept that the meter itself can present a perturbation? ac6xg Article: 218489 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <7dqdndDq5IH3GdPeRVn-qQ@crocker.com> <9Kv3f.864$q%.22@newssvr12.news.prodigy.com> <072dnTd0AvMiFtPenZ2dnUVZ_s2dnZ2d@crocker.com> Message-ID: Date: Thu, 13 Oct 2005 19:22:58 GMT Dave wrote: > then why are you complaining about it not showing the swr on the 75 ohm > coax?? you should know that no one in their right mind would expect it to > do that. You at first essentially implied that a Bird wattmeter calibrated for 50 ohms yields valid readings in a 75 ohm environment. I was questioning whether you were in your right mind or not. Others have been strangely silent on the subject. Still others seem not to have gotten it yet. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218490 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> Date: Thu, 13 Oct 2005 19:26:52 GMT Jim Kelley wrote: > Cecil Moore wrote: >> Z0 didn't change. The load didn't change. Therefore, the >> SWR didn't change. What exactly do you think changed? > > I think the circuit changed. Don't you? The circuit changed without changing the forward power, reflected power, and SWR so nothing of interest to the present topic (V/I ratio) changed. Do you know what dictates the SWR in a distributed network? Certainly not the length of the feedline or the removal of a tuner (assuming lossless conditions). -- 73, Cecil http://www.qsl.net/w5dxp Article: 218491 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Thu, 13 Oct 2005 19:32:48 GMT Dave wrote: > obviously the problem here is that cecil thinks he is the only one that > knows better than to try to measure reflected power with a 50 ohm meter in a > 75 ohm coax. From your posturing, it wasn't readily apparent to me that you were agreeing with me. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218492 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Aluminum tubing? Message-ID: References: Date: Thu, 13 Oct 2005 20:01:05 GMT "Roger Conroy" bravely wrote to "All" (13 Oct 05 14:58:53) --- on the heady topic of "Re: Aluminum tubing?" RC> From: "Roger Conroy" RC> Xref: core-easynews rec.radio.amateur.antenna:218675 RC> . ISTR hearing a radio RC> show on language that mentioned that there is at least one variety of RC> North American English that has kept the "u" - but I just can't RC> remember who/where that is. RC> 73 RC> Roger ZR3RC Canadian English. A*s*i*m*o*v ... Department of the Interior, in charge of everything outdoors.. Article: 218493 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Need RDF Yagi alternative Date: Thu, 13 Oct 2005 15:02:18 -0500 Message-ID: References: "Sluggo" wrote in message news:m9mrk11o8c4umdsqpj5gca0o4e4ge12tdj@4ax.com... > ... > > > Thanks for the correction; I'm only in my 40's but I've been > hamming a long time, and the years are starting to blur...... > Sluggo Damn young whipper snappers... (;-) 73, Steve, K,9.D;C'I Article: 218494 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Thu, 13 Oct 2005 21:22:01 GMT On Thu, 13 Oct 2005 16:45:51 +0000 (UTC), "Reg Edwards" wrote: >Before responding I have found it necessary to have several glasses of >Australian, Banrock Station, 2004, Shiraz Mataro, Red. It can be >recommended with confidence. Entirely OT: Reg, you are way to impatient. There are very few Australian Shiraz that should be taken in less than three years. I can't recall the "instructions" on the back of the bottle that tell one what to drink it with and when to drink it, but Banrock Station produce "everday drinking" quality reds that should stand a few years cellaring, but most wines in this part of the market will state "enjoy now" for marketing purposes. IIRC, the labels carry a bit of a story on their wildlife refuge, do they get to tell you what to eat with it? Anyway, now that it is open, enjoy it. Owen -- Article: 218495 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Date: Thu, 13 Oct 2005 21:25:21 GMT On Thu, 13 Oct 2005 09:53:08 -0700, Richard Clark wrote: > >Owen, > >To respond to your last question: >>>Has anyone experimental evidence to the contrary? >is consistently NO. Your own time at the bench has already drained >the pool of ability in that regard. Your only expectation ever after >having bellied up to the bench is to watch your work being gummed to >death. > I fully expected someone to object, not only to object, but to do so without any original experimental evidence and to devalue the experiment that I did so that some readers who do not have even a meager understanding of transmission line theory fall to being convinced by whoever is most tenacious is defending their position. >However, for completeness' sake, and as no one here really understands >what accuracy is about anyway, there is one factor to be considered. >The numbers offered verge on the limit of the Bird's ability to >resolve a power anyway. There is a built in probability of ±5W of >error from the get-go, and any snake oil salesman can craft an >argument leveraging that error to prove anything. We have seen that >±5W error in the form of an argument that uses both + and - (not >simply one or the other) to please a theory. > >Owen, the same experiment with a deliberate mismatch of 3:1 would be >just as effective at busting the myth AND providing data that >overwhelmed the inherent meter inaccuracy. Indeed, and I considered a number of other experiments that did so, but this one was based on components at hand, and should have been easily understood by a person with the most basic understanding of transmission line theory. It was important to surround the Bird with line different to 50 ohms. I expect the argument to twist an turn, to focus on everything but the assertions that: - there should be approximately a 50+j0 Z presented to the load side terminals of the Bird Thruline (ie the ratio of V/I is 50+j0 where V is the net or forward and reflected voltages, and I is the net of forward and reflected currents); - the Bird Thruline is a 120mm section of 50 ohm transmission line; - in the region of the Bird Thruline sampler element, the ratio of V/I is approximately 50+j0; and that the observed Bird 43 readings were reasonably consistent with those assertions. The arguments that knowing that the Bird measurements are valid at the point of measurement is of little value are unrelated to the issue and a diversionary tactic, but wrong nevertheless. I won't add to the diversion to identify them. I will extract the essence of the analysis and write a separate web page on it that may in the longer term assist others in their development, go being "gummed to death" doesn't totally devalue the information behind the case, and it might just be the cost of exposing the proposition to review. Thank you for your support. Owen PS: I am planning my next mythbusters (oh no! I hear...) Myth: SWR meters measure SWR. Now this is not to bag SWR meters, I think that they are very useful instruments, but they have limitations, and the greatest problem is not the meters, but probably the knowledge base of those (ab)using them. -- Article: 218496 of rec.radio.amateur.antenna From: "David Howard" References: <73063$433c14ac$97d56a13$3806@ALLTEL.NET> <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Subject: Re: Fractal Antennas Message-ID: Date: Thu, 13 Oct 2005 22:06:01 GMT Kinky antennas?! Gotta love it. check out this patent on non-fractal kinky antennas: US6603440: Arrayed-segment loop antenna http://www.delphion.com/details?pn=US06603440__ I have many EZNEC4 models of just such antennas, and have constructed may of them (which makes sense, since I'm the author). By the way, it was challanging to get this patent through primarily because of the nearly all encompasing Fractal antenna patents. But I did it. David Howard "Richard Clark" wrote in message news:rbtsk11ouecv3l23fflv15vd8lqpf5cm3h@4ax.com... > On Thu, 13 Oct 2005 00:02:33 -0700, N7ZZT - Eric Oyen > wrote: > > >so, my question is this: whats the real deal with fractal antennas and why > >is it that all information that can be found about them so vague in nature? > > Hi Eric, > > In a nutshell, the fractalists have hi-graded the field to offer us > what they say are the characteristics of the "class" of fractals. > > Hi-grading is a mining term to mean that only the best ore deposits > are sought and mined, leaving the rest for waste. A miner might sell > you Gold Mountain, but to be sure, that mine follows only the vein, > already tapped out, and the rest of that dung hill is exactly that. > > Hence, the fractalists have looked at everything that has a fractal > form, and discarded the losers. They keep the best performers, polish > them up for papers and trade shows and present them as the exemplars > of this new mathematics of RF. > > Problem is, that when you ask about that mathematics, and how it fails > to explain the losers of that same class they discarded, the > scientific enquiry turns to legal suit pivoting on the point of your > attempt to poison the commercial market place. > > In other words, there is never an explanation of why some are so good, > according to this new math, nor that other examples of that math are > so bad (according to that same math). To put it bluntly, they have no > method to forecast just what it is in the math that points to > performance. The math, as it always did, points to the shape - > interesting doodles. Unfortunately, this is not something that you > can stand up in front of the VC crowd and offer as a way to achieve > ROI. > > On the other hand, in my work has shown a correlation to the math. It > is a very simple correlation. The more kinks you put in the wire, the > more resonances appear. > > Simply put, examine a standard dipole over a range of frequencies, say > from 0.1F to 5F of the dipole's resonant F. There are n resonances > for a dipole. Taking that same length of wire and changing its shape > to a fractal (or any other for that matter) will produce m resonances. > You will find that m > n. Also, at the high end of the F scale > (towards 3F,4F and 5F or more), and for a characteristic of 300 Ohms, > the antenna becomes quite broadbanded. > > This points out one of those "marketing" opportunities so often > visited upon us here in years past. The claim that fractals offer > multiband operation AND are broadbanded is true, separately, but the > claim is often crafted to sound as this is simultaneously achievable. > Whenever we examined this crafted claim, the arguments were always > turned away or the claim "explained" by parts, but never as a whole. > In other words, only the best examples of a fractal ever exhibited > such dual characteristics, and often barely then and frequently from a > practical Ham perspective (as to which bands) never very different > than say an OCF Dipole (which can make the same claims by the way). > > So, once you got your foot in the door, understood the basis of > design, and the return on your investment (roi in less than caps); > then you could stand back and try to imagine a third iteration > Sierpinski dragon in your back yard for 2M through 160M. Then the > blood would drain away, and you would black out. > > All such fractal qualities have been investigated by me and reported > at: > http://www.qsl.net/kb7qhc/antenna/fractal/index.htm > This offer of a link rarely fails to put the reader to sleep, so > indulge only late at night if you prize the day. To my experience, > absolutely no writer that has offered any interest in fractals has > ever pursued it more than half a dozen postings. Once you strip away > all the claims and simply look at the data, and the most general > characteristics; then there is something to discuss - none seem > interested even though it goes to the heart of antenna design. > > 73's > Richard Clark, KB7QHC Article: 218497 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 15:02:37 -0700 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Owen Duffy wrote: > The arguments that knowing that the Bird measurements are valid at the > point of measurement is of little value are unrelated to the issue and > a diversionary tactic, but wrong nevertheless. Hi Owen, If it's wrong to argue that Bird wattmeter measurements are valid at the point of measurement, I don't wanna be right. ;-) > PS: I am planning my next mythbusters (oh no! I hear...) Undoubtedly it's the collective "oh goody!" that you hear. > Myth: SWR > meters measure SWR. Now this is not to bag SWR meters, I think that > they are very useful instruments, but they have limitations, and the > greatest problem is not the meters, but probably the knowledge base of > those (ab)using them. You must be new around here. :-) 73, ac6xg Article: 218498 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Thu, 13 Oct 2005 16:01:44 -0700 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> Cecil Moore wrote: > Jim Kelley wrote: > >> Cecil Moore wrote: >> >>> Z0 didn't change. The load didn't change. Therefore, the >>> SWR didn't change. What exactly do you think changed? >> >> >> I think the circuit changed. Don't you? > > > The circuit changed without changing the forward power, > reflected power, and SWR so nothing of interest to the > present topic (V/I ratio) changed. > > Do you know what dictates the SWR in a distributed network? > Certainly not the length of the feedline or the removal > of a tuner (assuming lossless conditions). Well, it's certainly true that both circuits are missing the 50 ohm impedance discontinuity in the middle, which is at least one of the "present topics" (and my point). I'll just go ahead and say what you really want me to say: You're good enough, you're smart enough, and doggone it, people like you! :-) ac6xg Article: 218499 of rec.radio.amateur.antenna From: "Jack" References: Subject: Re: Any experience using a Wonderpole? Date: Fri, 14 Oct 2005 01:08:55 +0100 Message-ID: <645dd$434ef719$8b372f7d$11056@ALLTEL.NET> I would love to have a BIG OLE WONDERPOLE FOR MYSELF! Any offers boys? dxAce Michigan USA "greg knapp 5" wrote in message news:h56dneQ3QPo8O9DeRVn-vQ@speakeasy.net... > I was seriously thinking of plunking down the $250 plus for the 40-foot > Wonderpole (www.wonderpole.com) to support parallel dipoles (probably 14 > gauge stranded copper wire dipoles cut for 80, 40, and 20 meters), fed with > 600 ohm open wire, but I am concerned about: > > 1.. Is the pole strong enough to hold up 80, 40, and 20 meter dipoles, > especially the top section? > 2.. Do they, like most pushup fiberglass antenna, collapse or come loose > over time? > 3.. How do they stand up over time.I'd like to use it in a permanent > installation. > 4.. Do they need to be guyed (how badly do they flop around in 15-30 mph > wind)? > 5.. How much overlap do you leave between the sections for extra strength? > 6.. Are they a good company to deal with? > I am thinking about mounting it on top of my 45 foot light-weight steel > crank-up tower (no beam on it) to get my dipoles up 80 feet or so. > > I called the company in Oregon (I believe), and they didn't know how it > would work in such an application and the guy who is the mechanical expert > never returned my call. > > If anyone has any ACTUAL experience using a 40-foot wonderpole you could > share with me, it would be much appreciated. > > BTW, the reason for the multiple wires is to broaden the narrow pattern a > single 80 meter dipole would exhibit on on the higher frequency bands (20-10 > meters). But if it won't support it, I'll probably go with a single 80 meter > dipole for now. > > Thanks, and 73, > > Greg, N6GK > > Article: 218500 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Fri, 14 Oct 2005 00:11:34 GMT Dave wrote: > i'm not agreeing with how you assume the 50 ohm impedance of the meter out > of the circuit. I don't think you understand what I was saying. It takes a certain length of feedline to establish a Z0 environment for the forward and reverse traveling TEM waves, i.e. to force Vfor/Ifor = Vref/Iref = Z0. > and i am not agreeing that there should be reflected power > measured by the meter in the case of the 50 ohm load on the end of a 1/2 > wave 75 ohm line. I never said it "should" measure that reflected power. What I said is if it doesn't measure the reflected power that exists, it is not giving a valid measurement of reflected power. A properly calibrated meter will indeed measure the reflected power that exists. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218501 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> <7py3f.967$dO2.323@newssvr29.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 00:13:23 GMT Richard Clark wrote: > Any error of misunderstanding Owen's post is entirely your own. Thanks, Richard, that really helps a lot. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218502 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 00:20:05 GMT Jim Kelley wrote: > Well, it's certainly true that both circuits are missing the 50 ohm > impedance discontinuity in the middle, which is at least one of the > "present topics" (and my point). Jim, if the ratio of net voltage to net current is already 50 ohms, then your Bird "impedance discontinuity" should cause that to change but there is no evidence whatsoever that it changes anything. Conclusion: The insertion of the Bird does not appreciably change the V/I ratio. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218503 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 00:24:09 GMT Owen Duffy wrote: > I fully expected someone to object, not only to object, but to do so > without any original experimental evidence ... Owen, there was absolutely no reason for anyone else to do any additional experiments. Your own experiment proved that the Bird wattmeter was ignoring the 4.1667 watts of reflected energy flowing through it when installed in the 75 ohm environment. You proved exactly the opposite of what you were trying to prove. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218504 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> Message-ID: Date: Fri, 14 Oct 2005 00:30:36 GMT Tam/WB2TT wrote: > "Cecil Moore" wrote:> >>The actual SWR on a lossless line doesn't change. Yet, in another >>posting, I showed that moving the Bird 1/4WL closer to the load >>caused a reported SWR change by the Bird from 1:1 to 2.25:1. How >>could both results possibly be right? > > The Bird does not know squat about transmission lines, foreward, or > reflected. It only cares about impedance. If you connect a 50 Ohm load to it > through 1/4 wave of 75 Ohm coax, the impedance the Bird sees will be > transformed to 112.5 Ohms; hence the 2.25 SWR. (Actually, a 2.25:1 impedance > ratio) Yes, that's exactly what I said in the other posting. But some people seem to believe that inserting a Bird into a transmission line with a Z0 other than 50 ohms magically changes it to a 50 ohm environment. The 40mm of transmission line inside the Bird is supposed to accomplish that miracle. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218505 of rec.radio.amateur.antenna From: crb Subject: What is SINAD? Date: Thu, 13 Oct 2005 17:27:14 -0700 Message-ID: Is it only valid for AM and FM measurements? I know its receiver sensitivity. Is it Signal divided by Noise with distortion?? 12 dB SINAD means what? The signal is 12 dB greater than noise and distortion or is it more complicated than that? Article: 218506 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> <5tutk1pm8t5959iv6u60djcqdaf99akmdm@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 00:51:02 GMT Richard Clark wrote: > On Fri, 14 Oct 2005 00:24:09 GMT, Cecil Moore wrote: > >>Your own experiment proved that the Bird wattmeter was ignoring >>the 4.1667 watts of reflected energy flowing through it > > This fiction is entirely your own invention ... Sorry, I am just quoting Owen's results. There was 4.1667 watts of reflected energy flowing back through the Bird. The Bird indicated zero watts. That's an infinite percentage error on reflected power for the Bird and proves my point that a 50 ohm wattmeter used in a 75 ohm environment is like using a hammer on a screw. To paraphrase: when the only tool one has is a 50 ohm Bird, every Z0 environment looks like 50 ohms. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218507 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> <5tutk1pm8t5959iv6u60djcqdaf99akmdm@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 00:53:03 GMT Richard Clark wrote: > What reflections exist, exist at the input port of the Bird which is > 50 Ohms by design, and which is attached to a 50 Ohm load by > deliberate selection. But the 50 ohm load is attached through a piece of 75 ohm coax supporting an SWR of 1.5:1. If you don't realize that fact, I feel sorry for you. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218508 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: Date: Fri, 14 Oct 2005 00:58:35 GMT On Thu, 13 Oct 2005 17:27:14 -0700, crb wrote: >Is it only valid for AM and FM measurements? > >I know its receiver sensitivity. > >Is it Signal divided by Noise with distortion?? > >12 dB SINAD means what? The signal is 12 dB greater than noise and >distortion or >is it more complicated than that? Thats about it. It is the ratio of signal to noise and distortion, and it is measured by setting up a test where the receiver produces output from a SSG (typically for a 1KHz audio output) and notching out the 1KHz output to measure the noise and distortion wrt the filtered 1KHz output. I wrote a handy little calculator for converting rx senstivity metrics, it is at http://www.vk1od.net/sc/RxSensitivityCalc.htm . The conversions assume that the signal distortion component of the Noise+Distortion is zero, in other words that the demodulation and amplification process is linear. SINAD is used widely to express the sensitivity of AM, FM and SSB receivers. It is a much better method of measuring FM receivers than the older "quieting" measurement. Owen -- Article: 218509 of rec.radio.amateur.antenna From: David Subject: Re: What is SINAD? References: Message-ID: <8tD3f.17277$U51.15549@news-server.bigpond.net.au> Date: Fri, 14 Oct 2005 01:03:00 GMT Does anyone happen to know where there is a circuit diagram for a home brew SINAD meter ? Owen Duffy wrote: > On Thu, 13 Oct 2005 17:27:14 -0700, crb wrote: > > >>Is it only valid for AM and FM measurements? >> >>I know its receiver sensitivity. >> >>Is it Signal divided by Noise with distortion?? >> >>12 dB SINAD means what? The signal is 12 dB greater than noise and >>distortion or >>is it more complicated than that? > > > Thats about it. > > It is the ratio of signal to noise and distortion, and it is measured > by setting up a test where the receiver produces output from a SSG > (typically for a 1KHz audio output) and notching out the 1KHz output > to measure the noise and distortion wrt the filtered 1KHz output. > > I wrote a handy little calculator for converting rx senstivity > metrics, it is at http://www.vk1od.net/sc/RxSensitivityCalc.htm . The > conversions assume that the signal distortion component of the > Noise+Distortion is zero, in other words that the demodulation and > amplification process is linear. > > SINAD is used widely to express the sensitivity of AM, FM and SSB > receivers. It is a much better method of measuring FM receivers than > the older "quieting" measurement. > > Owen > -- Article: 218510 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: <4b1uk1lg0uoes59g60irk8scvvbk9l4p0s@4ax.com> References: <8tD3f.17277$U51.15549@news-server.bigpond.net.au> Date: Fri, 14 Oct 2005 01:11:02 GMT On Fri, 14 Oct 2005 01:03:00 GMT, David wrote: >Does anyone happen to know where there is a circuit diagram for a home >brew SINAD meter ? You should also consider searching the net for software that will use the PC sound card to make a SINAD measurement. Owen -- Article: 218511 of rec.radio.amateur.antenna From: "John N9JG" Subject: Re: Any experience using a Wonderpole? Date: Thu, 13 Oct 2005 20:45:51 -0500 Message-ID: References: <645dd$434ef719$8b372f7d$11056@ALLTEL.NET> Unless you need the retracting feature, don't fool around with those baby poles and buy one of the mothers featured at http://www.excelsails.com/flagpole.htm If you buy one of their 40 feet models, you get a rustic rod with a butt diameter of 5.25" tapering to 2.5" at the top. Compare this with the puny wonderpole's dimensions of 2" and 0.75" respectively. "Jack" wrote in message news:645dd$434ef719$8b372f7d$11056@ALLTEL.NET... >I would love to have a BIG OLE WONDERPOLE FOR MYSELF! > > Any offers boys? > > dxAce > Michigan > USA > "greg knapp 5" wrote in message > news:h56dneQ3QPo8O9DeRVn-vQ@speakeasy.net... >> I was seriously thinking of plunking down the $250 plus for the 40-foot >> Wonderpole (www.wonderpole.com) to support parallel dipoles (probably 14 >> gauge stranded copper wire dipoles cut for 80, 40, and 20 meters), fed > with >> 600 ohm open wire, but I am concerned about: >> >> 1.. Is the pole strong enough to hold up 80, 40, and 20 meter dipoles, >> especially the top section? >> 2.. Do they, like most pushup fiberglass antenna, collapse or come >> loose >> over time? >> 3.. How do they stand up over time.I'd like to use it in a permanent >> installation. >> 4.. Do they need to be guyed (how badly do they flop around in 15-30 >> mph >> wind)? >> 5.. How much overlap do you leave between the sections for extra > strength? >> 6.. Are they a good company to deal with? >> I am thinking about mounting it on top of my 45 foot light-weight steel >> crank-up tower (no beam on it) to get my dipoles up 80 feet or so. >> >> I called the company in Oregon (I believe), and they didn't know how it >> would work in such an application and the guy who is the mechanical >> expert >> never returned my call. >> >> If anyone has any ACTUAL experience using a 40-foot wonderpole you could >> share with me, it would be much appreciated. >> >> BTW, the reason for the multiple wires is to broaden the narrow pattern a >> single 80 meter dipole would exhibit on on the higher frequency bands > (20-10 >> meters). But if it won't support it, I'll probably go with a single 80 > meter >> dipole for now. >> >> Thanks, and 73, >> >> Greg, N6GK >> >> > > Article: 218512 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 01:44:02 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> "Owen Duffy" wrote > Entirely OT: > > Reg, you are way to impatient. There are very few Australian Shiraz > that should be taken in less than three years. ====================================== I'm 80 next month. ====================================== > > I can't recall the "instructions" on the back of the bottle that tell > one what to drink it with and when to drink it, but Banrock Station > produce "everday drinking" quality reds that should stand a few years > cellaring, ========================================== The bottle was chosen at random by my daughter from the supermarket shelf. Following your message I retrieved it from the trash bin. The label did not mention a 'drink by' date. But it does mention eat with a mature blue cheese which is a firm favorite of mine. I've long given up worrying about cholesterol. ==================================== > > IIRC, the labels carry a bit of a story on their wildlife refuge, do > they get to tell you what to eat with it? > ==================================== Yes. I looked up Banrock Station's website about their contributions, internationally, towards preservation of wetlands, nature reserves, and the many forms of wildlife therein. There's even a photograph of a water snail. Very interesting. I guess you are far more knowledgeable about wines than I am. Thanks for drawing my attention to the bottle. ---- Reg, G4FGQ Article: 218513 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Fri, 14 Oct 2005 01:55:28 GMT On Fri, 14 Oct 2005 01:44:02 +0000 (UTC), "Reg Edwards" wrote: >I guess you are far more knowledgeable about wines than I am. Thanks >for drawing my attention to the bottle. Not at all to both. But, I do enjoy a glass of red... unfortunately my feet are getting less happy about that. Owen -- Article: 218514 of rec.radio.amateur.antenna From: David Subject: Re: What is SINAD? References: <8tD3f.17277$U51.15549@news-server.bigpond.net.au> <6rE3f.13526$vw6.1680@newsread1.news.atl.earthlink.net> Message-ID: Date: Fri, 14 Oct 2005 02:23:51 GMT Thanks, that's what I was after. Ralph Mowery wrote: > "David" wrote in message > news:8tD3f.17277$U51.15549@news-server.bigpond.net.au... > >>Does anyone happen to know where there is a circuit diagram for a home >>brew SINAD meter ? >> >> > > While not homebrew , here is where you can find a manual and schematic for a > sinad meter. > > http://www.repeater-builder.com/other-mfrs/sinadd.pdf > > > Article: 218515 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 03:22:21 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> "Cecil Moore" wrote > The insertion of the Bird does not appreciably change the V/I ratio. > ==================================== Cec, I have tried to avoid entering this argument. But it appears to me that ALL SWR meters work on the principle of a common, identical, take off point for both voltage and current samples. Therefore, anything inside the meter which could constitute a transmission line, no matter how long or short, if it separates the two effective take-off points, it is a small source of error and its actual length otherwise plays no part in the measuring process. ( I mean its actual length is not included in the basic design calculations, except perhaps in rare instances to minimise the error.) ( The error arises from a phase-shift error in tapping off the current sample. There may be no problem with defining the location of the voltage sample. All depends on meter construction and the tapping methods which vary but do not affect the basic design principle of a common tapping point.) I am not trolling. Please read very carefully. Try to limit yourself to HF and VHF. Do you agree? Yes or No? ---- Reg, G4FGQ. Article: 218516 of rec.radio.amateur.antenna From: "David Howard" References: <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Subject: Re: Fractal Antennas Message-ID: Date: Fri, 14 Oct 2005 04:09:06 GMT Sorry for the link to delphion ... it works for me, but then I have an account, and my web browser auto logs me in --- ooops. No worries about the cold here --- I'm in sunny N. California. David Howard "Richard Clark" wrote in message news:euotk1hpa9mbml7snqsh6vn8kkkqgq6ajs@4ax.com... > On Thu, 13 Oct 2005 22:06:01 GMT, "David Howard" > wrote: > > >Kinky antennas?! Gotta love it. > As they say here in Ballard > > Ya, sure. You betcha. > > >check out this patent on non-fractal kinky antennas: > >US6603440: Arrayed-segment loop antenna > >http://www.delphion.com/details?pn=US06603440__ > > Hi David, > > http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=6,603,440.WKU.&OS=PN/6,603,440&RS=PN/6,603,440 > is free access, and faster. > > > >I have many EZNEC4 models of just such antennas, and have constructed may of them > >(which makes sense, since I'm the author). By the way, it was challanging to > >get this patent through primarily because of the nearly all encompasing Fractal antenna > >patents. But I did it. > > Mail a copy to fraudtenna and wait for the lawyer's letters. Winter > is coming and you can pin them to the wall for extra insulation. > > 73's > Richard Clark, KB7QHC Article: 218517 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: <94iuk1lcti9ebelcuhmo6k37ol3fju214g@4ax.com> References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <90huk19kep3j8km04og4901qsjdq7i3g0b@4ax.com> Date: Fri, 14 Oct 2005 05:57:45 GMT On Thu, 13 Oct 2005 22:37:43 -0700, Richard Clark wrote: >Gout? Of course. Owen -- Article: 218518 of rec.radio.amateur.antenna From: kashe@sonic.net Subject: Re: Aluminum tubing? Message-ID: <8akuk19nasdmc1hhcea6o86g965c6g2kp4@4ax.com> References: <1128562179_21@isp.n> <4348f9f7.286775451@news.blueyonder.co.uk> Date: Fri, 14 Oct 2005 06:34:14 GMT On Thu, 13 Oct 2005 14:58:53 +0200, "Roger Conroy" wrote: > >"Gene Fuller" wrote in message >news:hm83f.133870$qY1.14837@bgtnsc04-news.ops.worldnet.att.net... >> Roger Conroy wrote: >> >> [snip] >> >>>>>>>>Why do you guys in the US always omit the "i" in aluminium ? >>>> >>>> >>>>You mean the second "i"? Probably because we spell it correctly: >>>>Aluminum. >>>>;~) >>> >>> >>> But you do it ONLY to Alumin(i)um. What about Lithium, Barium, Chromium, >>> Ruthenium, Titanium, Uranium, and so on......? >> >> Hmmmm, does "so on" also include Lanthanum, Molybdenum, Platinum, and >> Tantalum? >> >> 73, >> Gene >> W4SZ > >We're in complete agreement about those too. >We have 2 "groups" of metals that differ in having "um" or "ium" endings. It >is only Alumin(i)um that "switches groups" in crossing the Atlantic. When, >how and why did it happen? > >The other one that is a consistent transatlantic difference is the group of >words that include colo(u)r, odo(u)r, favo(u)r, hono(u)r...... I can't think >of any "equivalent" anomalies there. ISTR hearing a radio show on language >that mentioned that there is at least one variety of North American English >that has kept the "u" - but I just can't remember who/where that is. > >73 >Roger ZR3RC > > Hollywood -- glamour. Article: 218519 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: Fractal Antennas References: <73063$433c14ac$97d56a13$3806@ALLTEL.NET> <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Message-ID: Date: Fri, 14 Oct 2005 01:19:05 -0700 Dave wrote: > the links no good. try it again. it worked perfectly here. -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218520 of rec.radio.amateur.antenna From: "W3JDR" References: Subject: Re: What is SINAD? Message-ID: Date: Fri, 14 Oct 2005 11:06:57 GMT It is the ratio of (Signal + Noise+Distortion) to (Noise+Distortion) as measured at the receiver audio output. It is measured using an RMS-reading AC voltmeter , typically with a 1Khz modulation tone on the signal applied to the receiver under test. First you measure the audio signal out of the receiver using the AC RMS meter. Then you apply a notch filter at the modulation frequency and measure the residual noise+distortion, again using the RMS AC voltmeter. SINAD is the ratio of the two measurements. Joe W3JDR "crb" wrote in message news:dimtor0skl@enews1.newsguy.com... > Is it only valid for AM and FM measurements? > > I know its receiver sensitivity. > > Is it Signal divided by Noise with distortion?? > > 12 dB SINAD means what? The signal is 12 dB greater than noise and > distortion or > is it more complicated than that? Article: 218521 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: Date: Fri, 14 Oct 2005 11:44:57 GMT On Fri, 14 Oct 2005 00:58:35 GMT, Owen Duffy wrote: >It is the ratio of signal to noise and distortion, and it is measured >by setting up a test where the receiver produces output from a SSG >(typically for a 1KHz audio output) and notching out the 1KHz output >to measure the noise and distortion wrt the filtered 1KHz output. > That should be: It is the ratio of signal and noise and distortion to noise and distortion, and it is measured by setting up a test where the receiver produces output from a SSG (typically for a 1KHz audio output) and notching out the 1KHz output to measure the unfiltered output wrt the noise and distortion. I should also have mentioned the EIA test requires the receiver be set to rated output with 1mV RF input at 60% of rated modulation, then the RF output reduced to find the input level for 12dB SINAD. You could measure it with soething like a HP334A Distortion Analyser, but it is pretty tedious if you are trying to find the RF input for a particular SINAD. Hence you see boxes that have an AGC controlled amplifier deliving a constant voltage to the filter block. I have a Motorola one (R1013A) that works ok, there were also Sinadders. Even more convenient are the ones integrated into a communications monitor. I don't believe these boxes do true RMS measurements. An alternative if you have a standalone SSG and want to do SINAD measurement is to use a PC sound card and software that does an FFT and calculates the SINAD (using true RMS measurement). Spectrum Lab does it, its free, but it is such a flexible / general tool, it may be a bit daunting to get it working. The SpectrumLab menu "Quick Settings / Rx Equipment Tests / SINAD test" is a quick path to setup... but it is still a quite complex package. A whole lot better than the style of a HP334A though! SL is at http://www.qsl.net/dl4yhf/spectra1.html . Owen -- Article: 218522 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 12:17:35 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <90huk19kep3j8km04og4901qsjdq7i3g0b@4ax.com> > > I did not know that red wine caused gout! :-) > It's port wine and pheasant which causes gout. Article: 218523 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: What is SINAD? References: <8tD3f.17277$U51.15549@news-server.bigpond.net.au> <4b1uk1lg0uoes59g60irk8scvvbk9l4p0s@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 08:45:03 -0500 I use Baudline (http://www.baudline.com - Linux) for doing measurements like that. Works well. One should calibrate the soundcard first though. There are a host of others.. Cheers Bob VK2YQA Owen Duffy wrote: > > On Fri, 14 Oct 2005 01:03:00 GMT, David wrote: > > >>Does anyone happen to know where there is a circuit diagram for a home >>brew SINAD meter ? > > > You should also consider searching the net for software that will use > the PC sound card to make a SINAD measurement. > > Owen > -- Article: 218524 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> Message-ID: <1tP3f.2535$tV6.1783@newssvr27.news.prodigy.net> Date: Fri, 14 Oct 2005 14:42:05 GMT Dave wrote: > ah, but if the bird does establish a 50 ohm 'environment' within its 40mm > housing then the reading that was actually obtained is indeed correct. so > now, how else could you read zero reflected power at that point if it didn't > establish that environment? Would you like for me to go through the math of a voltage and current sampled at a point without disturbing anything? Assume the voltage is sampled such that 100v of net voltage is sampled as 10 volts. Assume the current is sampled such that two amps of net current is sampled as 10 volts. If these samples are in phase, adding them will result in 20v. That equals 200 watts of forward power on the meter. Subtracting them will result in zero volts. That equals zero watts of reflected power on the meter. The sampled net voltage and net current determine the 50 ohm calibration. No 50 ohm environment required. If the sample point is in 75 ohm coax with no reflections, the sample voltage will be 12.3 volts and the sample current will 8.165 volts. Subtracting those sample values doesn't yield zero so 41.35 watts of reflected power will be reported where none actually exists. So unless the mere writing of my words on this newsgroup establishes a 50 ohm environment, the Bird doesn't need to establish a 50 ohm environment to obtain the same above results. If the Bird indeed did control the environment into which it was inserted, it would be violating a design goal for measuring instruments and Bird wouldn't be selling many of those highly intrusive devices. Bird wants the meter to be as unobtrusive as possible and it is. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218525 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> Message-ID: Date: Fri, 14 Oct 2005 14:45:34 GMT Dave wrote: > now, someone please put a bird meter on a tdr and > see what the characteristic impedance of it is internally. then put it on a > network analyzer and see if it does indeed transform the 'environment' from > 75 to 50 ohms in its 40mm length. oh and while you are at it calculate the > s factors for all the transitions, those will come up in the discussion here > shortly. Probably all that is needed is to measure the Bird's s11 parameter while sitting in a 75 ohm environment. I'll bet it's very close to zero. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218526 of rec.radio.amateur.antenna From: "Bill Ogden" Subject: MFJ 2006 Catalog Message-ID: <3oQ3f.24271$dl2.426@fe08.lga> Date: Fri, 14 Oct 2005 11:56:22 -0400 The recent MFJ catalog contains several new loop tuners. These seem almost too good to be true, given the wonders of "small loops" discussed many times in this newsgroup. Has anyone tried these new products? Also, MFJ has a new Clamp-On RF Ammeter (calibrated for .3, 1, and 3 amps) for only $50. Any thoughts -- might it be useful for measuring currents in radials (just to verify that each radial is doing something!). Bill W2WO Article: 218527 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> <5tutk1pm8t5959iv6u60djcqdaf99akmdm@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 16:16:39 GMT Richard Clark wrote: > It has no doubt slipped your mind that on one of those turns, the > requirement for x length of line was lost into the byways of this > labyrinth you traverse. Nope, it hasn't slipped my mind. So here's a question for you. Is a zero length of 50 ohm coax sufficient to establish a 50 ohm environment? -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218528 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> Message-ID: <0TQ3f.2550$tV6.37@newssvr27.news.prodigy.net> Date: Fri, 14 Oct 2005 16:18:04 GMT Richard Clark wrote: > Cecil Moore wrote: >>bet it's very close to zero. > > Another one of your rounding errors like where light 10 times brighter > than the sun is black. I see you understand this subject just as well as you understood that one. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218529 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> <1tP3f.2535$tV6.1783@newssvr27.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 16:22:39 GMT Dave wrote: > but there will be a reflection at the 50 ohm to 75 ohm transition on the > load side of the meter. It was previously reported that the path through the Bird is 40mm. The path through the Bird is actually about five inches which is probably long enough to establish a 50 ohm environment. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218530 of rec.radio.amateur.antenna From: chuck Subject: Re: What is SINAD? References: Message-ID: Date: Fri, 14 Oct 2005 16:31:52 GMT Good info, Owen. I think the EIA test procedures really have FM or AM in mind, rather than SSB or, what is exactly the same for SINAD purposes, CW. The 60% figure just doesn't apply to SSB or CW. You would simply use an unmodulated signal generator with the frequency offset to produce a 1 kHz tone in the receiver's audio output, preferrably centered in the receiver's passband. Then a measure of rms af voltage at the receiver's output with and without the 1 kHz filter would be made. We don't hear much about SINAD testing procedures for SSB and CW. Even the ARRL's test procedure manual glosses over the procedure for other than FM. Chuck NT3G Owen Duffy wrote: > On Fri, 14 Oct 2005 00:58:35 GMT, Owen Duffy wrote: > > > >>It is the ratio of signal to noise and distortion, and it is measured >>by setting up a test where the receiver produces output from a SSG >>(typically for a 1KHz audio output) and notching out the 1KHz output >>to measure the noise and distortion wrt the filtered 1KHz output. >> > > > That should be: > It is the ratio of signal and noise and distortion to noise and > distortion, and it is measured by setting up a test where the receiver > produces output from a SSG (typically for a 1KHz audio output) and > notching out the 1KHz output to measure the unfiltered output wrt the > noise and distortion. > > I should also have mentioned the EIA test requires the receiver be set > to rated output with 1mV RF input at 60% of rated modulation, then the > RF output reduced to find the input level for 12dB SINAD. > > You could measure it with soething like a HP334A Distortion Analyser, > but it is pretty tedious if you are trying to find the RF input for a > particular SINAD. Hence you see boxes that have an AGC controlled > amplifier deliving a constant voltage to the filter block. I have a > Motorola one (R1013A) that works ok, there were also Sinadders. Even > more convenient are the ones integrated into a communications monitor. > I don't believe these boxes do true RMS measurements. > > An alternative if you have a standalone SSG and want to do SINAD > measurement is to use a PC sound card and software that does an FFT > and calculates the SINAD (using true RMS measurement). Spectrum Lab > does it, its free, but it is such a flexible / general tool, it may be > a bit daunting to get it working. The SpectrumLab menu "Quick Settings > / Rx Equipment Tests / SINAD test" is a quick path to setup... but it > is still a quite complex package. A whole lot better than the style of > a HP334A though! SL is at http://www.qsl.net/dl4yhf/spectra1.html . > > Owen > -- Article: 218531 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <_cu3f.846$q%.565@newssvr12.news.prodigy.com> <2r2tk1hsl1svdo1ns76eid67dftkhs654f@4ax.com> <5tutk1pm8t5959iv6u60djcqdaf99akmdm@4ax.com> Message-ID: Date: Fri, 14 Oct 2005 16:54:51 GMT Dave wrote: > "Cecil Moore" wrote: >>Nope, it hasn't slipped my mind. So here's a question for you. >>Is a zero length of 50 ohm coax sufficient to establish a >>50 ohm environment? > > you build it and i'll measure it and let you know. It's in the middle of a piece of 75 ohm coax. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 218532 of rec.radio.amateur.antenna From: "avidfan" Subject: Mosley Ta-33 Date: Sat, 15 Oct 2005 13:02:24 +0200 Message-ID: I need a manual for this antenna. Looking for a link to a website that has one as a freebie. Article: 218533 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Fri, 14 Oct 2005 13:08:22 -0500 Message-ID: References: Owen, (& crb) Your words are contrary to the way we measured it (Motorola). You say ..."It is the ratio of signal to noise and distortion,..", but we measured not just the signal, but everything for the "top" of the ratio (which is used more like a reference as it is the more stable as signal level varies). I believe your last line saying wrt to the filtered tone supports this. It implies that the tone is (bandpass) filtered for one of the measurements and we don't do that. Joe's is a bit better of an explanation (the RMS meter and quantities ratioed). A meter, a pure 1kHz tone modulated signal generator and a 1kHz notch is all that is needed. What happens if you don't have a "real" RMS meter? I don't know. 73, Steve, ,K.9;D'C'I "W3JDR" wrote in message news:ljM3f.39197$q81.11651@trnddc06... > It is the ratio of (Signal + Noise+Distortion) to (Noise+Distortion) as > measured at the receiver audio output. It is measured using an RMS-reading > AC voltmeter , typically with a 1Khz modulation tone on the signal applied > to the receiver under test. > > First you measure the audio signal out of the receiver using the AC RMS > meter. Then you apply a notch filter at the modulation frequency and measure > the residual noise+distortion, again using the RMS AC voltmeter. SINAD is > the ratio of the two measurements. > > Joe > W3JDR > > > > "crb" wrote in message news:dimtor0skl@enews1.newsguy.com... > > Is it only valid for AM and FM measurements? > > > > I know its receiver sensitivity. > > > > Is it Signal divided by Noise with distortion?? > > > > 12 dB SINAD means what? The signal is 12 dB greater than noise and > > distortion or > > is it more complicated than that? > > Article: 218534 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 12:21:17 -0700 Message-ID: References: <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> <0TQ3f.2550$tV6.37@newssvr27.news.prodigy.net> Richard Clark wrote: > On Fri, 14 Oct 2005 18:44:06 -0000, "Dave" wrote: > > >>guess the v/i discussion is over now. > > > Hi Dave, > > It may have been tailored in that vernacular, but it was actually > never about that at all. As the last "thin-film" comment reveals, it > has always been about how one mind can encompass two contradictory > positions (total cancellation - non total cancellation) about the same > mechanism (a quarterwave matching section). > > In other words: A Troll. > > The humor here is that supposedly the thin-film offers "total" > cancellation for the same reason that the quarter wave from this bench > test does not. :-) > > In fact, neither exhibit "total" cancellation, but to maintain the > charade one or the other does, then that charade must fail, and these > recent arguments have just revealed that fracture. > > Some time ago I offered results from the bench in just how much light > was in fact returned from a thin-film section, and this was rejected > as impossible - hence the allusion to brighter than the sun light > being rendered as black to satisfy this illusion of "totality" in > cancellation. This reflected light was buried in the digits, but > still and all, far brighter than the sun (such is the vast range of > accommodation that the eye offers as a measuring device). > > On the flip side, any leakage (reflection back) from a quarterwave > section suffers identical issues. Those reflections are buried in the > digits too. This is orders of magnitude different from the speculated > 4.17 watts which is a farrago. Does a Bird have the same scope of > resolution as the eye? Hardly. The inherent error of the meter at > ±5% vastly overwhelms such products (the eye does not suffer such > error for other reasons - imagine what a driver's eye-check test would > be like if it did). > > So, to advance this itinerant concept of Owen's demonstration not > busting the myth of the requirement for line sections, this troll has > diverged from the topic to haul out a spurious argument that is in > direct conflict with other discussions of the same topic, from the > same troll. It necessarily demands a villain to suit the melodrama > offered. That villain is the Bird and its failure is to reveal a > power. Left unsaid is that actual power is, as I said, buried in the > digits and wholly irresolvable. Further, it is NOT the claim of 4.17 > watts which was rummaged up. The Bird would be incapable of resolving > the actual reflection products from a real quarterwave section. Thus > it cannot absorb the sin of this counter-proof (sic). > > Let's just say that statements that arbitrarily assign ideal concepts > like "totality" suffer across the board - and when these forced > assignments are used as the link pin to "theories," then they can lead > to amusing contradictions and failures of logic like those we've been > witness to here. > > 73's > Richard Clark, KB7QHC I think it might also be interesting to discuss the instance in which the Bird is interfaced with a real halfwave section. ac6xg Article: 218535 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 14:51:55 -0500 Message-ID: <5575-43500C5B-448@storefull-3251.bay.webtv.net> References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Owen wrote: "The myth that measurements with a Bird 43 of conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself is busted." Bird says the wattmeter can be placed anywhere in the line. That precludes a requirement to have minimum lengths of 50-ohm cable on both sides of the wattmeter. Particular total lengths of line woould be a function of wavelenth. The Model 43 Thruline Wattmeter accurately measures forward or reverse power in transmission lines under any load condition. Regardless of the load impedance, the forward and reflected powers are forced by construction of the coax to conform to Zo. Line volts divided by line amps in either direction has an absolute value of 50 ohms. Bird plug-in elements are designed for insertion into a precision coaxial rigid air line which is a part of the Model 43. Elements are available in a wide variety of frequency ranges and maximum power levels.. Cancellation of response to one direction of power flow while responding to the to the other is accomplished by careful balance of the current and voltage samples within an element. The samples which are in-phase add. The samples for the other direction are out-of-phase and cancel. To make sure cancellation is complete in the undesired direction, Zo must be as specified in the design. Accuracy can`t be expected in the wrong Zo environment. Best regards, Richard Harrison, KB5WZI Article: 218536 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> <0TQ3f.2550$tV6.37@newssvr27.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 20:09:28 GMT Richard Clark wrote: > This is an amusing irony of where you have found power where you have > always posited there is none, and where you have rejected there is > power when it has been shown to exist. Each example exposes your lack > of experience in the scale of the error and its relation to the > equipment measuring it. In exactly the same way that forward power can exceed generated power in a 1/4WL matching section of transmission line, so can the forward irradiance in 1/4WL of thin film exceed the forward irradiance in the air before incidence. That you are still so terribly confused about such a simple fact of light physics is sad. You obviously don't understand the information on the Melles-Groit web page. http://www.mellesgriot.com/products/optics/oc_2_1.htm Please study it until you understand it. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218537 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> <0TQ3f.2550$tV6.37@newssvr27.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 20:15:04 GMT Richard Clark wrote: > As the last "thin-film" comment reveals, it > has always been about how one mind can encompass two contradictory > positions (total cancellation - non total cancellation) about the same > mechanism (a quarterwave matching section). > > In other words: A Troll. If the incident irradiance is a single frequency coherent signal, the requirement for TOTAL CANCELLATION OF REFLECTIONS is still that the index of refraction of the 1/4WL thin-film be the square root of the medium upon which it is deposited. QED -- 73, Cecil http://www.qsl.net/w5dxp Article: 218538 of rec.radio.amateur.antenna From: "W3JDR" References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> Subject: Re: What is SINAD? Message-ID: Date: Fri, 14 Oct 2005 20:28:17 GMT Richard, What you said is largely accurate, however at low S/N ratios, or where the distortion becomes comparable to the signal level, the reading of the composite signal (signal+noise+distortion) with anything other than an RMS meter could produce erroneous results. Joe W3JDR "Richard Clark" wrote in message news:0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com... > On Fri, 14 Oct 2005 13:08:22 -0500, "Steve Nosko" > wrote: > > >A meter, a pure 1kHz tone modulated signal generator and a 1kHz notch is all > >that is needed. What happens if you don't have a "real" RMS meter? I don't > >know. > > Hi Steve, > > You don't need a "real" RMS meter. The expressed requirement for a > pure 1kHz tone provides the necessary sine wave shape such that it > simply becomes a matter of scale calibration. If you had said a > square wave 1KHz tone (nothing pure about that), then you would have > to dig deep for a "real" RMS meter. That too, could be scaled, but I > wouldn't count on it because it would be a rare amplifier chain that > could faithfully keep it square - and the notch would inject it into > the measurement as distortion and noise. > > 73's > Richard Clark, KB7QHC Article: 218539 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: Date: Fri, 14 Oct 2005 20:32:14 GMT On Fri, 14 Oct 2005 13:08:22 -0500, "Steve Nosko" wrote: > >Owen, (& crb) > Your words are contrary to the way we measured it (Motorola). You say >..."It is the ratio of signal to noise and distortion,..", but we measured >not just the signal, but everything for the "top" of the ratio (which is >used more like a reference as it is the more stable as signal level varies). >I believe your last line saying wrt to the filtered tone supports this. It >implies that the tone is (bandpass) filtered for one of the measurements and >we don't do that. It was a shabby description in my first post Steve, I wrote filtered instead of unfiltered, had the "wrt", terms back to front at the and, as you quoted signal to (N+D) when it is the total to (N+D). Wasn't really worth 2/10, was it! I re-read it when I came back to add some detail re a software approach and redrafted it. My recollection was then when the scheme was introduced, one used a Distortion Analyser, and I can't remember the early HP instrument, the HP334A I mentioned in my follow up was a newer one. They are tedious, whereas the R1013 or Sinadder or much more convenient, and the integrated ones (like in the R2000) are much better. Once you sort the issues of getting audio samples to a PC sound card without hum and clipping, that approach can work well, and Spectrum Lab works well... just it is a multipurpose tool for a simple job. There are probably other software tools that are more targetted and simpler to use. > >Joe's is a bit better of an explanation (the RMS meter and quantities >ratioed). Yes, but I don't believe most of the instruments acutally incorporate a true RMS meter. I set about measuring the difference about six months ago when I was doing calibration / validation measurements for FSM (http://www.vk1od.net/fsm/) using custom software against the R1013, and R2000, and a couple of HP334As. The error in using a rectifier-average responding meter (as is typically done) is small relative to the variance of such readings because of the variance of the noise component. > >A meter, a pure 1kHz tone modulated signal generator and a 1kHz notch is all >that is needed. What happens if you don't have a "real" RMS meter? I don't >know. Yes, I didn't mention that the 1KHz tone needs to be relatively low distortion. For measuring 12dB SINAD, the demand is not onerous, but it is important. The frequency of the tone is important as the notches in semi automatic instruments are typically +/10Hz or so, so one needs to verify that the SSG modulation oscillator is close enough. More importantly when testing an SSB receiver (where you use a CW carrier), that the carrier is kept "on frequency" for a 1KHz beat note. Owen -- Article: 218540 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> <1tP3f.2535$tV6.1783@newssvr27.news.prodigy.net> Date: Fri, 14 Oct 2005 20:42:13 GMT On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote: >It was previously reported that the path through the Bird >is 40mm. The path through the Bird is actually about five Cecil, If you are referring to my statement in another thread, it was that the sampling element is about 40mm inside the 50 ohm Thruline section (ie that there is about 40mm of 50 ohm transmission line between the Bird 43 terminals and the sampling element), not as you have stated above. Owen -- Article: 218541 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <5KSdnTRgwb3IJtLeRVn-qA@crocker.com> <0TQ3f.2550$tV6.37@newssvr27.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 20:49:44 GMT Jim Kelley wrote: > I think it might also be interesting to discuss the instance in which > the Bird is interfaced with a real halfwave section. If the Bird is inserted at a point where the net voltage divided by the net current is equal to 50, apparently a 50 ohm Z0-match is achieved at that point and any length of lossless 50 ohm coax can be inserted without altering the forward/reflected conditions in the adjacent transmission lines. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218542 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> <1tP3f.2535$tV6.1783@newssvr27.news.prodigy.net> Message-ID: Date: Fri, 14 Oct 2005 21:07:24 GMT Owen Duffy wrote: > On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote: >>It was previously reported that the path through the Bird >>is 40mm. The path through the Bird is actually about five > > If you are referring to my statement in another thread, it was that > the sampling element is about 40mm inside the 50 ohm Thruline section > (ie that there is about 40mm of 50 ohm transmission line between the > Bird 43 terminals and the sampling element), not as you have stated > above. I'm sorry, Owen, I took your statement to mean that the total length of path through the Bird is 40mm (1.5") which is not enough length to force a 50 ohm environment. I downloaded the Bird manual this morning and discovered that, unlike an MFJ, the path through the Bird is about 5 inches and coaxial. I apologize to Bird and you Bird experts for that bad assumption. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218543 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <0yy3f.970$dO2.383@newssvr29.news.prodigy.net> <1tP3f.2535$tV6.1783@newssvr27.news.prodigy.net> Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Fri, 14 Oct 2005 17:20:22 -0400 Message-ID: That explains why my new tuner failed to work. I have a rotary switch that selects 40mm of 50, 75,300, 450, and 600 ohm coax. I thought it should match anything! Now I see I have to go to 5" lengths. I should know better than to build anything before all the errata sheets are in. I can use some additional diversion as almost all the soldering iron burns have healed. "Cecil Moore" wrote in message news:g6V3f.2344$BZ5.1010@newssvr13.news.prodigy.com... > Owen Duffy wrote: > > > On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote: > >>It was previously reported that the path through the Bird > >>is 40mm. The path through the Bird is actually about five > > > > If you are referring to my statement in another thread, it was that > > the sampling element is about 40mm inside the 50 ohm Thruline section > > (ie that there is about 40mm of 50 ohm transmission line between the > > Bird 43 terminals and the sampling element), not as you have stated > > above. > > I'm sorry, Owen, I took your statement to mean that the total length > of path through the Bird is 40mm (1.5") which is not enough length > to force a 50 ohm environment. I downloaded the Bird manual this > morning and discovered that, unlike an MFJ, the path through the Bird > is about 5 inches and coaxial. I apologize to Bird and you Bird > experts for that bad assumption. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 218544 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Fri, 14 Oct 2005 21:23:25 GMT On Wed, 12 Oct 2005 22:09:51 GMT, Owen Duffy wrote: >The myth: Measurements with a Bird 43 of the conditions on the >Thruline section are invalid unless it has some minimum length of 50 >ohm line on both sides of itself. > All, Can I offer the suggestion that the key to understanding why this is so, it to understand the sampler. I don't have the detail of the physical and electrical parameters of the Bird sampler, however I suspect that like so many other reflectometers, it comes down to a device that samples independently the net current and the net voltage associated with any travelling waves, and those RF samples are in proportion and phase relationship that when algebraicly added and rectified, they produce a DC voltage that is proportional to the power flow in one direction only (provided that Zo is real). The proportions calibrate the instrument for a specific V/I ratio. Apart from mentioning that Zo must be real, and I will address that in another thread, Zo in the region where the sample is unimportant to the "proportion and phase relationship..." bit. Zo of the through line is important only to the extent that you would generally: - not want a significant transformation of impedance between the load terminals and the calibrated sensor at that calibrated V/I ratio. - not want a significant transformation of impedance between the generator and load terminals at that calibrated V/I ratio to minimise disruption to the system being measured. Everyday we use instruments to measure something, somewhere and apply that knowledge to infer something else, somewhere else using appropriate other knowledge. For example, you might measure the voltage drop across a cathode resistor and make some reasonable inference about anode current using appropriate other knowledge. Making measurements with a Bird 43 in one place and inferring the situation somewhere else using appropriate other knowledge is reasonable. For example, I may have an antenna system (say a loop) that uses a transmission line transformer (TLT) to transform the loop terminal Z to 50 ohms. I can attach the generator end of the TLT to the Bird 43, attach the Bird 43 via 50 ohm cable to a transceiver that is rated for a nominal 50+j0 ohm load, and proceed to adjust the antenna / TLT for zero reflected power indication on the Bird 43 knowing that I can reasonably infer that the load presented to the transceiver will be approximately 50+j0 ohms using the knowledge that Bird readings indicate Z at that point is 50+j0 and there will be insignificant transformation on the 50 ohm cable to the transceiver. This is a proper and sound application of the instrument. Did I get that wrong? Did I need to mention environments? Owen -- Article: 218545 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: Fractal Antennas References: <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Message-ID: Date: Fri, 14 Oct 2005 15:03:49 -0700 Dave wrote: > it gets me to their web site, but says: > > "Details for publication US06603440 were not found. > Please use your browser's "back" button to return to the previous page, or > follow one of the links on this page." > > Thats wierd. I got right to the details page no problem... could be a browser thing. -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218546 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: Date: Fri, 14 Oct 2005 22:28:19 GMT On Fri, 14 Oct 2005 10:50:03 -0700, Tim Wescott wrote: >bandpass filter for CW. This is _not_ the kind of thing you could do >with FM. Indeed Tim. The complications as I see it in predicting the SINAD for FM when you know the receiver NF is that most narrow band communications applications of FM are closer to PM because of the pre-emphasis characteristic. FM + 6dB/octave preemphasis over the entire modulation passband is PM. (PM is where the modulation index (dev/fm) is independent of fm (the modulating frequency)). However, the receivers in my experience are over de-emphasised (at the top end) presumably to get better SINAD. In fact, I think specifications of the de-emphasis curve are commonly stated along the lines of +1 to -3dB of -6dB demphasis relative to 1Khz over 300 to 3000Hz. This accomodates a over de-emphasis at the high end for little loss in intelligibility and a dB or so improvement in sensitivity figures. Filter / demodulators and CTCSS IM also contribute to distortion products significantly. The result of demod distortion, PM with a slope across the passband, and uncertain high pass filtering to accomodate CTCSS makes prediction of S/N out from C/N in a bit of a guess in FM comms receivers, not nearly as accurate as you suggest for linear receivers. Owen -- Article: 218547 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> Date: Fri, 14 Oct 2005 23:59:36 GMT On Fri, 14 Oct 2005 21:23:25 GMT, Owen Duffy wrote: >that when algebraicly added and rectified, they produce a DC voltage >that is proportional to the power flow in one direction only (provided >that Zo is real). The proportions calibrate the instrument for a Sorry, that should be: "that when algebraicly added and rectified, they produce a DC voltage that is proportional to the square root of power flow in one direction only (provided that Zo is real). The proportions calibrate the instrument for a..." Owen -- Article: 218548 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: Fractal Antennas References: <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Message-ID: Date: Fri, 14 Oct 2005 17:08:42 -0700 Dave wrote: > couldn't be a browser problem, i'm using IE! > I am an old user of mozilla (netscape, et al). I don't use !E! because its a windows product and I don't use windows (because its the biggest security hole known to man or beast alike) -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218549 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Sat, 15 Oct 2005 00:12:24 GMT On Thu, 13 Oct 2005 01:43:48 GMT, Cecil Moore wrote: >and not to be a myth at all. There's 104.17 watts of forward power >through the Bird and 4.17 watts of reflected power back through the >Bird. Why does the Bird ignore those actual power values? I did not report or even measure such a thing. It is your report based on something that you know or something that you measured without evidence of either measurements or detail of construction. With respect Cecil, the statement is more an elaboration of the myth than convincing support for it. This unsubstantiated premise seems the basis for nearly a hundred posts by many. Owen -- Article: 218550 of rec.radio.amateur.antenna From: "W3JDR" References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> Subject: Re: What is SINAD? Message-ID: <6eY3f.305$W32.212@trnddc06> Date: Sat, 15 Oct 2005 00:40:34 GMT Richard, I understand the historical difficulties of making accurate RMS measurements, however I didn't know the original post only solicited ways to make the measurement with "current generation of commercial surplus equipment ". My intention was to point out some measurement nuances that might not be obvious at first glance. Recently, it has become quite easy to do true RMS measurement at audio frequencies using DSP techniques. In fact at audio you can even do an accurate RMS measurement in DSP using a PIC microcontroller to sample the signal and perform the calculations. Joe W3JDR "Richard Clark" wrote in message news:m4b0l1prao1vs8dmq20ahu6im9d8552t3l@4ax.com... > On Fri, 14 Oct 2005 20:28:17 GMT, "W3JDR" wrote: > >>Richard, >>What you said is largely accurate, however at low S/N ratios, or where the >>distortion becomes comparable to the signal level, the reading of the >>composite signal (signal+noise+distortion) with anything other than an RMS >>meter could produce erroneous results. > > Hi Joe, > > In the practical world of SINAD (having tuned a number of GE and > Motorolas), one is not very interested in how poor your set is, but > rather meeting a service standard (that 12 dB which is as arbitrary as > any). > > I doubt if many of the current generation of commercial surplus > equipment comes with a stock tester employing what would have been an > expensive converter chip to insure RMS measurements. I come by that > assessment by noting those I used employed standard meter movements. > The first RMS meters I calibrated in the mid 70s came from Fluke (just > up the highway), and the components of that circuit were scrubbed of > all identification numbers or cast in epoxy. Such was the cachet of > being hi-priced, and having others try to break into the market with > knock-offs. > > My Radio Shack multimeter makes that claim (ca 1995) and if memory > serves, that Micronta's "True RMS" was barely capable of poor voice > grade bandwidth. This was 20 years after Fluke, costing about as much > (economic inflation), and not performing as well (technical > deflation). > > 73's > Richard Clark, KB7QHC Article: 218551 of rec.radio.amateur.antenna From: Jim - NN7K Subject: Re: What is SINAD? References: Message-ID: Date: Sat, 15 Oct 2005 01:25:34 GMT Originally, two way shops set FM rigs up for 20 dB quieting, on a volt meter (crank up the signal until the AUDIO VOLTAGE, UNMODULATED, was 1/10th the voltage of a no signal audio output . Tho, for the most part, this works well, there are constraints on sensitivity, because of bandwidth concerns, and , as bandwidth is halved, the signal improvement is 6 dB (quadrupled). Sinad is Signal/Noise /signal/(noise+distortion) and in fact, in recent times , devices that will measure it are built into many pieces of test equipment (IFR meters comes to mind), also look for an outfit called "SINADDER" . The main thing is that it adds a "Bandwidth" component to the sensitivity equasion. It is measured with a 1 KHz tone, at (in FM), 3 KHz deviation- and the smaller the signal that is detectable , with this constraint, the more sensitive the reciever is considered to be! This also works at SSB/AM. Tho, it is true that this measures Sensitivity, it includes a BANDWIDTH component, that a (noise figure/ quieting) would NOT consider (at least fully!) Hopefully, this is helpful-- Jim NN7K > For SSB and CW, on the other hand, the noise is purely additive so all > you need to know is the receiver noise figure. Once you know that > (assuming that it's not a really strange radio) you know everything > about it's performance. Given the noise figure in dB you can easily > calculate the 12dB SINAD should you be so inclined, as well as any other > signal vs. noise figure you should want. You have a good reason to > believe that the noise is white so you can even take an SSB receiver and > calculate the noise figure of the thing after you tack on an audio > bandpass filter for CW. This is _not_ the kind of thing you could do > with FM. > Article: 218552 of rec.radio.amateur.antenna From: "k" References: <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Subject: Re: Fractal Antennas Message-ID: Date: Sat, 15 Oct 2005 01:26:38 GMT Well, why don't you just remove windows from your computer? What the hell, use another OS or write one that suits you and doesn't have any 'holes'...har.. J "N7ZZT - Eric Oyen" wrote in message news:OKX3f.754$v_5.276@dukeread07... : Dave wrote: : : > couldn't be a browser problem, i'm using IE! : > : I am an old user of mozilla (netscape, et al). : : I don't use !E! because its a windows product and I don't use windows : (because its the biggest security hole known to man or beast alike) : : -- : DE N7ZZT : Eric Oyen : Phoenix, Arizona : e-mail: n7zzt(at)hotmail(dot)com : the difference between intelligence and stupidity is that intelligence : has its limits. Article: 218553 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 03:13:51 GMT Owen Duffy wrote: > On Wed, 12 Oct 2005 22:09:51 GMT, Owen Duffy wrote: >>The myth: Measurements with a Bird 43 of the conditions on the >>Thruline section are invalid unless it has some minimum length of 50 >>ohm line on both sides of itself. >> > Can I offer the suggestion that the key to understanding why this is > so, it to understand the sampler. Again Owen, your own experiment using 75 ohm coax on each side of the Bird proved why the above is not a myth. The Bird didn't read the correct forward power on the 75 ohm coax. The Bird didn't read the correct reflected power on the 75 ohm coax. The SWR calculated using the Bird's readings does not represent the SWR on the 75 ohm coax. > The proportions calibrate the instrument for a specific V/I ratio. Yes, that ratio is 50 ohms for the Bird. Only a piece of 50 ohm coax will guarantee that Vfor/Ifor=Vref/Iref=50 ohms. You proved that a piece of 75 ohm coax will not do it. > Did I need to mention environments? No, but you should have. The Bird gives the correct forward and reflected power readings on the attached coax only in a 50 ohm environment. Your experiment proved that to be true. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218554 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <1129331264.484540.307460@o13g2000cwo.googlegroups.com> Message-ID: Date: Sat, 15 Oct 2005 03:25:26 GMT jgboyles@aol.com wrote: > 4.17 watts does not flow back thru the Bird as reflected power, and > the Bird, of course acknowledges. Yes, I later realized that the Bird's internal feedline forms a 50 ohm Z0-match. Interference at the input and output of the Bird causes no reflected energy to flow through the Bird. The reflected energy from the load is re-reflected at the Bird output. The input of the Bird causes reflections on the source side of the Bird. I actually calculated all the interferring signals. > I acknowledge that the Bird does not report the actual forward/reverse > power in this example That was the main point. If the Bird is embedded in something other than a 50 ohm environment, it does not report the actual forward/reverse power on the coax on either side of the Bird. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218555 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <1129331264.484540.307460@o13g2000cwo.googlegroups.com> Message-ID: Date: Sat, 15 Oct 2005 03:27:43 GMT Richard Clark wrote: > Who would approach a Bird and expect it to in the first place? Someone who says that the environment surrounding the Bird doesn't matter? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218556 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 03:37:16 GMT Owen Duffy wrote: > Cecil Moore wrote: >>and not to be a myth at all. There's 104.17 watts of forward power >>through the Bird and 4.17 watts of reflected power back through the >>Bird. Why does the Bird ignore those actual power values? > > I did not report or even measure such a thing. Since I realized the Bird forms a Z0-match at its output that statement should be ammended to say: There 104.17 watts of forward energy flowing in the 75 ohm coax on each side of the Bird and 4.17 watts of reflected energy flowing in the 75 ohm coax on each side of the Bird. Why does the Bird ignore those actual power values existing in the actual system? 100W--tuner---75 ohm coax---Bird--1/2WL 75 ohm coax--50 ohm load Pfor=104.17W--> Pfor=104.17W--> 100W delivered <--Pref=4.17W <--Pref=4.17W The Bird is not reading the proper values of forward and reflected power on the 75 ohm coax because it is embedded in a non-50 ohm environment. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218557 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <1129331264.484540.307460@o13g2000cwo.googlegroups.com> Message-ID: Date: Sat, 15 Oct 2005 03:58:22 GMT Richard Clark wrote: > Who would approach a Bird and expect it to in the first place? Someone who says that the environment surrounding the Bird doesn't matter? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218558 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 04:00:14 GMT Richard Clark wrote: > Who would approach a Bird and expect it to in the first place? Someone who thinks reflections cannot be eliminated by 1/4WL of thin-film? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218559 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Sat, 15 Oct 2005 04:16:37 GMT On Sat, 15 Oct 2005 03:37:16 GMT, Cecil Moore wrote: >Owen Duffy wrote: > >> Cecil Moore wrote: >>>and not to be a myth at all. There's 104.17 watts of forward power >>>through the Bird and 4.17 watts of reflected power back through the >>>Bird. Why does the Bird ignore those actual power values? >> >> I did not report or even measure such a thing. > >Since I realized the Bird forms a Z0-match at its output that >statement should be ammended to say: There 104.17 watts of forward >energy flowing in the 75 ohm coax on each side of the Bird and 4.17 >watts of reflected energy flowing in the 75 ohm coax on each side >of the Bird. Why does the Bird ignore those actual power values >existing in the actual system? > >100W--tuner---75 ohm coax---Bird--1/2WL 75 ohm coax--50 ohm load > Pfor=104.17W--> Pfor=104.17W--> 100W delivered > <--Pref=4.17W <--Pref=4.17W > >The Bird is not reading the proper values of forward and reflected >power on the 75 ohm coax because it is embedded in a non-50 ohm >environment. This has nothing to do with the stated myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Nothing in the myth stated or implied direct application of the measured conditions on the thruline section to any other connected (or disconnected for that matter) transmission line, that is entirely your construction. It is a diversion Cecil. Owen -- Article: 218560 of rec.radio.amateur.antenna From: crb Subject: What is so special about '12 dB' SINAD? Date: Fri, 14 Oct 2005 22:09:38 -0700 Message-ID: Still not sure what it is. I know I do a test at work where I put in a 3 KHz deviated, 1 KHz tone into the FM receiver port while probing an audio point going to the SINAD port on the test equipment. Increasing the input level makes for a larger SINAD value (which makes sense) Looking for at least 12 dB SINAD. What is so special about 12? Can't get my mind around it. Is the test tone 12 dB stronger than noise + distortion? Is the the input value in dBm on the test equipment the sensitivity of the receiver at 12 dB SINAD. The 'at 12 dB SINAD' still gets me. Article: 218561 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is so special about '12 dB' SINAD? Message-ID: References: Date: Sat, 15 Oct 2005 05:40:08 GMT It is probably a good enough ratio to express the lower limit of usable sensitivity for telephony applications. If you mean why isn't it 11 or 13dB, it may hark back to the early instruments that were intended for measuring THD and were scaled in % distortion. 12dB SINAD corresponds to 25% distortion on such an instrument. Owen -- Article: 218562 of rec.radio.amateur.antenna Message-ID: <4350BD36.2000507@killspam.internode.on.net> Date: Sat, 15 Oct 2005 18:26:30 +1000 From: Alan Peake Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> > Sorry, that should be: > > "that when algebraicly Actually, that should be "algebraically" :) Interesting thread though. BYW, is the Bird using the Bruene type bridge or some other topology? Alan Article: 218563 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> <4350BD36.2000507@killspam.internode.on.net> Date: Sat, 15 Oct 2005 08:27:46 GMT On Sat, 15 Oct 2005 18:26:30 +1000, Alan Peake wrote: > >> Sorry, that should be: >> >> "that when algebraicly >Actually, that should be "algebraically" :) Thanks. There were some other typos along the way, but that was clearly a spelling mistake and the spell checker didn't find it. >Interesting thread though. BYW, is the Bird using the Bruene type bridge Is that BTW? I understand that the Breune type bridge is one of the bothways detector designs with a untapped toroidal current transformer. I doubt the Bird sampler element is of that type. It appears to have a flat section of line that is parallel to the coax centre conductor and is presumably capacitively and inductively coupled, and it uses some form of frequency compensation to give it broadband response. You rotate the sampler element for measurement of the opposite direction. Someone here may have dismantled one to see how it works. I suspect that all of these probe designs try to sample net V and I at a point, and the extent by which they depart from a point sample limits their upper frequency of usefulness. Though there are several designs, they seem to broadly fall into two main types, those where the sampler response is inherently proportional to frequency (though they may be compensated as in the Bird elements) or those where they are inherently broadband (as the Bruene circuit). Trust you are well. I heard you on 40m the other day, but only just! Propagation has been pretty shabby. Owen -- Article: 218564 of rec.radio.amateur.antenna From: "harrogate2" References: Subject: Re: What is so special about '12 dB' SINAD? Message-ID: Date: Sat, 15 Oct 2005 08:36:40 GMT After 36+years in the radcoms industry as a technician I have seen the move from S/N to SINAD at first hand. SINAD has been around throughout my career but it is really on in the last 20 years that it has become most prevalent. The only reason that I can think that this has become so is the improvement in technology in the production of semiconductors and the consequent reduction in their noise levels, and the much wider use of FETs in front ends, which has resulted in S/N becoming an unrealistic measurement, the noise floor now being so low. Add to this the now commonplace use of SMD - which itself is 'quieter' - and improved circuit design, and the distortion in the modulation becomes of significantly greater importance. Having said that 10% distortion was the norm when I started, whereas 2% or even less is today's standard, such are the improvements in that side of transmission, hence SINAD is probably now the only viable measurement. Think of it like this: in the mid 70's most receivers would do 12dB S/N for around 0.6uV for 60% system modulation on a 12.5KHz channel spacing; today it is not uncommon to see 12dB SINAD (let alone S/N!) at not much above 0.2uV, and if you look at equipments of far eastern origin which may not have such good parameters (selectivity, adjacent channel rejection, etc) as UK/European designed units it can be 3dB better than that! Perhaps that's why you see a lot of oriental mobiles and portables but most associated base stations, especially those used on communal sites, are designed or made elsewhere (UK, USA, Germany, and New Zealand to mention but a few.) Why 12dB? My two penn'uth is that the human ear is very tolerant of even harmonic distortion, especially 2nd which would predominate in the audio chain due to filtration, so someone somewhere defined 12dB (or about 25% distortion) as the maximum tolerable level for usable speech. -- Woody harrogate2 at ntlworld dot com Article: 218565 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <7401l11r26v5e99h4742d34kfeb0c1b081@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 14:26:43 GMT Richard Clark wrote: > Cecil Moore wrote: >>Someone who thinks reflections cannot be eliminated by 1/4WL >>of thin-film? > > Certainly one who thinks it does. And both having been disproved, ... I guess you will take that delusion to your grave. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218567 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> <4350BD36.2000507@killspam.internode.on.net> Message-ID: Date: Sat, 15 Oct 2005 14:42:25 GMT Alan Peake wrote: > Interesting thread though. BYW, is the Bird using the Bruene type bridge > or some other topology? The Bird 43 manual is available at http://www.bird-electronic.com -- 73, Cecil http://www.qsl.net/w5dxp Article: 218568 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1125736373.469540.275780@g14g2000cwa.googlegroups.com> <1129366324.812161.317540@g43g2000cwa.googlegroups.com> Subject: Re: Trying to get AM broadcast at job Message-ID: Date: Sat, 15 Oct 2005 14:22:46 GMT wrote in message news:1129366324.812161.317540@g43g2000cwa.googlegroups.com... > Fedthecat wrote: > >> Fe> Bought a small boombox. It has no antenna connection screws, just a >> Fe> built-in antenna. It gets no AM stations at all, just static. I work >> Fe> in a big GM plant (all steel building). Nobodies radios get AM. >> >> Fe> I mounted a car antenna on a bracket (isolated from the bracket with >> a >> Fe> rubber gromet) and mounted the bracket to a chain link fence 20ft >> from >> Fe> the plant. I hooked a coax center wire to the antenna base. I >> clamped >> Fe> the braided wire to the bracket. At the other end, inside the plant, >> I >> Fe> connected the center wire to the built-in antenna on the radio via >> an >> Fe> alligator clip. I still get no AM. > > > Just thought I'd update on my progress. > First off, I am 'Fedthecat' but I got a new email adderess so now I'm > 'sofasurfer'. > Still haven't got AM to come in at work. But, I have some observations > and clues. > > 1. I now have a differant boombox that has a moveable external AM loop > and external AM (as well as FM) connections. This radio DOES get AM > quite well outside the building. Also cars parked outside, 10 feet from > where I put my antenna receive AM, therefore there IS a signal > available. > > 2. Many people at work say that they've tried to get AM and all have > found that there is no way to get AM in a steel building such as a GM > plant. > > 3. One guy even tried differant types of antennas on the roof. But no > signal would reach his radio inside the building. > > 4. The best I get is 760 AM, very fuzzy, barely understandable. 950 AM > is worse. Those are the only two stations coming in at all. They do not > fade in or out. > > 5.One day as I was fiddling with the wires on the back of the radio AM > suddenly came in loud and clear with no static for about 1 second. I > was unable to repeat this and that makes no sense to me. > > 6. I am concerned about my ground, although the 1 second clear signal > tells me I have a good ground. The antenna is grounded to the chain > link fense post which is set in concrete. Is concrete conductive to the > ground or does it insulate? One person said the galvanized post is > conductive but then said theres a nonconductive coating over the > galvanization. Hmmmm. > > 7. Today I installed an automotive signal amplifier. At first I thought > I detected a slight difference in the reception but then when I > disconnected the amplifier there was no difference. > > 8.If a signal is getting to my outdoor antenna, is it nessessarily > possible to get the signal to the radio or can there be circumstances > which may make this impossible? > > 9.I'm used to working with electricity. If you touch a wire to a fairly > clean metal ground you usually have a ground. Is the ground needed for > radio signals different and much more critical so that anything less > than a perfect ground will result in little or no signal? > > 10.I tried using a long wire antenna also but the result was identical > to the automotive antenna I am currently using. > > 11. I haven't given up on the idea of building a loop antenna or adding > some kind of circuitry but for now I want to try to keep it simple > until I learn more. > > Thanks again. > Sofasurfer It is difficult for me to believe that you installed (properly) an amplified AM antenna from a modern car, on the outside of the metal building, and didnt get decent reception. Do you have some reason to *not* use the radio from a "broken car"? Car radios are designed to work in the environment you have inside the metal building at work. You must already be aware that the problem you are encountering is the result of the AM radio waves being unable to exist within a metal cage. It is necessary to acquire the radio signal on the *outside* of that metal box/building. An amplifier *at the antenna* is required to then send the signal to the radio. Jerry Article: 218569 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 14:56:45 GMT Owen Duffy wrote: > This has nothing to do with the stated myth: Measurements with a Bird > 43 of the conditions on the Thruline section are invalid unless it has > some minimum length of 50 ohm line on both sides of itself. Would you be willing to make the same statement about an MFJ wattmeter? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218570 of rec.radio.amateur.antenna From: ml Subject: tvi Message-ID: Date: Sat, 15 Oct 2005 15:59:59 GMT I was wondering if perhaps somone can help me figure out the best way to track down why i suddenly seem to be giving myself some tvi i didn't make any changes, i had a tv in my shack i have more than one rig so it's not a bad rig seems the tvi is comming from within the room (not from the roof) my grounds seem same as always but the set really is totally wiped out even if i ut the rig to 1w the tv is totally overloaded sometimes the tv even seems sorta turn off if i key my cables to the rig seem ok same as always i seem to be missing something Article: 218571 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 16:07:14 GMT Dave wrote: > "Cecil Moore" wrote: > >>Owen Duffy wrote: >>>This has nothing to do with the stated myth: Measurements with a Bird >>>43 of the conditions on the Thruline section are invalid unless it has >>>some minimum length of 50 ohm line on both sides of itself. >> >>Would you be willing to make the same statement about an MFJ wattmeter? > > now your are just trying to muddy the waters... i wouldn't trust an mfj to > measure anything! No, I'm just trying to get back to the original discussion which was: Do SWR meters need 50 ohm coax surrounding them to establish the assumed 50 ohm environment? The majority of SWR meters have no Thruline and MFJ seems to make no attempt to establish a 50 ohm environment like Bird does. What is the Z0 of a meandering wire surrounded by an aluminum box? The original discussion (V/I ratio is forced to Z0) had nothing to do with Bird wattmeters. The original discussion was about SWR meters in general (which the Bird is not). The mythbusters thing was an interesting diversion away from the original question which remains unanswered. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218572 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <7401l11r26v5e99h4742d34kfeb0c1b081@4ax.com> <4q92l1lr0dbte2fbt4c5mr6k0uh9otl6bn@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 16:18:22 GMT Richard Clark wrote: > Cecil Moore wrote: >>I guess you will take that delusion to your grave. > > Yet more guessing? It's a guess as to whether you are going to correct your errors about thin-film coatings before you expire. What is it about the following that you don't understand? www.mellesgriot.com/products/optics/oc_2_1.htm "Thin-Film Interference" "Thin-film coatings also rely on the principles of interference. Thin films are dielectric or metallic materials whose thickness is comparable to, or less than, the wavelength of light." Speaking of 1/4WL thin-film coatings: "Clearly, if the wavelength of the incident light and the thickness of the film are such that a phase difference exists between reflections of p, then reflected wavefronts interfere destructively, and overall reflected intensity is a minimum. If the two reflections are of equal amplitude, then this amplitude (and hence intensity) minimum will be zero." "Amplitude minimum equal zero" means all reflections have been eliminated. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218573 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 16:26:52 GMT Richard Clark wrote: > Cecil Moore wrote: >>long before you entered the thread Canceled it immediately after I wrote it when I realized the subject line had changed. > More guessing, and certainly poor research. As many may acknowledge, > a glance at the beginning of this thread dominates all speculation > about who entered when. > > No doubt a response is in order as to what you "meant" - as is so > often the case. No doubt an apology is in order. The posting no longer exists on my news-server. I apologize that my canceled posting made it off my news-server. Sorry, my subject line font is so small I cannot read it without a magnifying glass. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218574 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: tvi References: Message-ID: Date: Sat, 15 Oct 2005 16:27:54 GMT ml wrote: > my cables to the rig seem ok same as always i seem to be missing > something Did you try a different band/frequency? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218575 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: What is a 50-ohm environment. ??? Date: Sat, 15 Oct 2005 17:05:56 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> - or even more vague - an assumed 50-ohm environment? Or an evironment of any other impedance. An engineering definition please! In plain English. Then perhaps I can understand what you are all waffling about. Thank you. ---- Reg, G4FGQ. Article: 218576 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: tvi Date: Sat, 15 Oct 2005 17:22:59 +0000 (UTC) Message-ID: References: Something has changed in the vicinity. Has anybody parked a great metal-clad vehicle near to your home? Or shifted anything else which could behave as a reflector of radio waves. Or has the room furniture, including the TV set, been changed around recently? Try changing the TV set. What happens? ---- Reg. ============================= "ml" wrote in message news:m-634C88.11594715102005@news.verizon.net... > I was wondering if perhaps somone can help me figure out the best way to > track down why i suddenly seem to be giving myself some tvi > > i didn't make any changes, i had a tv in my shack i have more than one > rig so it's not a bad rig > > seems the tvi is comming from within the room (not from the roof) > > my grounds seem same as always but the set really is totally wiped out > even if i ut the rig to 1w the tv is totally overloaded sometimes > the tv even seems sorta turn off if i key > > my cables to the rig seem ok same as always i seem to be missing > something Article: 218577 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 17:52:47 GMT Reg Edwards wrote: > - or even more vague - an assumed 50-ohm environment? > Or an evironment of any other impedance. The transmission line reflection model tells us that the Z0 of a transmission lines forces the following relationship. Vfor/Ifor = Vref/Iref = Z0 A "50 ohm environment" used in the context of the previous discussion would be one in which the above relationship is forced on the system at certain points in the system. 600 ohm transmission line going from a tuner/balun to an antenna establishes a 600 ohm environment for the signals on the transmission line. An SWR meter calibrated for 600 ohms will indicate the actual SWR. About a year ago, based on a discussion that you and I were having, I asked the sci.physics.electromag newsgroup how long a piece of RG-213 coax has to be to establish the above relationship. The answer was that the non-TEM product terms decrease at about 1/e every two inches for RG-213. The RG-400 coax leads going to and from my SWR meter are two feet each. So I asserted to you that my SWR meter was reading the actual SWR in the middle of that run of RG-400. I think you disagreed with my assertion but I cannot remember for sure. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218578 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 17:57:35 GMT Dave wrote: > an interesting diversion until everyone was convinced that you were off the > wall. now its time to re-open a dead thread???. No, an interesting diversion that has been resolved. Time to return to the real issue. > as far as cheap swr meters, the daiwa, swan, and mfj manuals all require 50 > ohm coax 'for accurate readings'... a joke by any standard of measurement > for that type of instrument. but just to put this one to rest quickly... i > set up my tdr and ran some quick measurements. this tdr will resolve a 6" > 75 ohm jumper in the 25' or so of 50 ohm test cable that i used. i measured > an mfj-815b and a daiwa ns-660pa and they are indistiguishable from the 50 > ohm line. so the answer is yes, they do internally look like a 50 ohm line > section. Try it with 75 ohm coax. I suspect they will be equally indistinguishable >from 75 ohm line. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218579 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 18:05:11 GMT Dave wrote: > don't bother, its a figment of cecil's imagination and creative vocabulary. Actually, the question logically follows from the reflection model. Under what boundary conditions does a piece of transmission line force Vfor/Ifor = Vref/Iref = Z0 to a specified accuracy? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218580 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: <2Qb4f.2443$BZ5.533@newssvr13.news.prodigy.com> Date: Sat, 15 Oct 2005 18:25:02 GMT Dave wrote: > however, once you change the > reference Zo to 50 ohms inside the meter there is no reflected power to > measure since the load presented at the end of the 75 ohm line is 50 ohms. The question remains: Does the MFJ's physical design ensure the *physical* reference Z0 is 50 ohms or would it perform just as well in a 75 ohm enviornment simply by recalibrating it for 75 ohms? In other words, it is sampling a voltage and current completely divorced from any *physical* reference Z0. The actual reference depends upon an arbitrary setting of a calibration cap which has no effect at all on the *physical* reference Z0. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218581 of rec.radio.amateur.antenna From: "Denton" Subject: Re: tvi Date: Sat, 15 Oct 2005 11:40:19 -0700 Message-ID: <11l2j8q4cjg910f@corp.supernews.com> References: Check the tv connectors....Sometimes the tv coax's center conductor gets a bit of corrosion or the connectors get flakey. "ml" wrote in message news:m-634C88.11594715102005@news.verizon.net... >I was wondering if perhaps somone can help me figure out the best way to > track down why i suddenly seem to be giving myself some tvi > > i didn't make any changes, i had a tv in my shack i have more than one > rig so it's not a bad rig > > seems the tvi is comming from within the room (not from the roof) > > my grounds seem same as always but the set really is totally wiped out > even if i ut the rig to 1w the tv is totally overloaded sometimes > the tv even seems sorta turn off if i key > > my cables to the rig seem ok same as always i seem to be missing > something Article: 218582 of rec.radio.amateur.antenna From: "RB" Subject: can I / can't I ? Message-ID: Date: Sat, 15 Oct 2005 14:06:28 -0500 Any reason I shouldn't use a choke balun out of my tuner to feed ladderline up to a dipole? Article: 218583 of rec.radio.amateur.antenna From: fmmck@aol.com (Fred McKenzie) Subject: Re: What is so special about '12 dB' SINAD? Date: Sat, 15 Oct 2005 15:07:48 -0400 Message-ID: References: In article , crb wrote: > Is the the input value in dBm on the test equipment the sensitivity of > the receiver at 12 dB SINAD. > The 'at 12 dB SINAD' still gets me. CRB- Years ago sensitivity might have been measured using a "20 dB quieting" method. You would inject an unmodulated carrier and increase its level until the noise output of the receiver decreased to one tenth of the no-signal value. This might work for tuning to improve that one receiver's sensitivity, but it isn't the greatest for comparing different receivers with different bandwidths. Isn't SINAD an acronym for "Signal In the presence of Noise And Distortion"? I don't fully understand how it works, but assume there is a 1 KHz filter feeding one channel that is compared to an un-filtered channel. What I want to know is how to build one. Does anyone know of any SINAD construction articles? 73, Fred, K4DII Article: 218584 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Sat, 15 Oct 2005 20:28:43 GMT On Sat, 15 Oct 2005 17:57:35 GMT, Cecil Moore wrote: >Try it with 75 ohm coax. I suspect they will be equally indistinguishable >from 75 ohm line. Cecil, you have got everyone else running around based on your apparent misconceptions. Is it not time you put in some time on the experimental side to support / validate your conceptual contribution? Enough of the "I suspect", "I seriously doubt". Where does that fit in scientific method... you are not the eminent professor running a bunch of PHD students around. Owen -- Article: 218585 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Subject: Re: Mythbusters: V/I ratio is forced to Z0 Date: Sat, 15 Oct 2005 16:47:45 -0400 Message-ID: <30e01$43516b37$97d558d8$11737@ALLTEL.NET> I always see a few that delight in attacking MFJ. Find me another company that produces products for a reasonable price for the Ham. Do they get any props at all, hell no. Some idiot pisses and moans that the MFJ $19.95 what ever is less accurate than their favorite $350.00 supplier. Why would you not "trust" an MFJ to measure anything? If you can't give a specific reason to avoid an MFJ product, then what is gained by your supercilious remark. "Dave" wrote in message news:UtSdnXLlM5PngMzeRVn-ig@crocker.com... > > "Cecil Moore" wrote in message > news:NM84f.16754$6e1.1309@newssvr14.news.prodigy.com... > > Owen Duffy wrote: > >> This has nothing to do with the stated myth: Measurements with a Bird > >> 43 of the conditions on the Thruline section are invalid unless it has > >> some minimum length of 50 ohm line on both sides of itself. > > > > Would you be willing to make the same statement about an MFJ wattmeter? > > now your are just trying to muddy the waters... i wouldn't trust an mfj to > measure anything! > > Article: 218586 of rec.radio.amateur.antenna From: chuck Subject: Re: What is so special about '12 dB' SINAD? References: Message-ID: Date: Sat, 15 Oct 2005 21:02:21 GMT Hello Fred, If you have a calibrated RF signal generator that provides 1 kHz modulation and an rms voltmeter that covers communication audio frequencies (say to 3 kHz), then the only thing you need to make SINAD measurements is a 1 kHz notch filter. You can find schematics for that in the ARRL handbook and elsewhere. Good luck! Chuck NT3G Fred McKenzie wrote: > In article , crb wrote: > > >>Is the the input value in dBm on the test equipment the sensitivity of >>the receiver at 12 dB SINAD. >>The 'at 12 dB SINAD' still gets me. > > > CRB- > > Years ago sensitivity might have been measured using a "20 dB quieting" > method. You would inject an unmodulated carrier and increase its level > until the noise output of the receiver decreased to one tenth of the > no-signal value. This might work for tuning to improve that one > receiver's sensitivity, but it isn't the greatest for comparing different > receivers with different bandwidths. > > Isn't SINAD an acronym for "Signal In the presence of Noise And > Distortion"? I don't fully understand how it works, but assume there is a > 1 KHz filter feeding one channel that is compared to an un-filtered > channel. > > What I want to know is how to build one. Does anyone know of any SINAD > construction articles? > > 73, Fred, K4DII Article: 218587 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: can I / can't I ? Date: Sat, 15 Oct 2005 21:19:06 +0000 (UTC) Message-ID: References: > Any reason I shouldn't use a choke balun out of my tuner to feed ladderline > up to a dipole? ==================================== There's no reason whatsoever. In fact it is the obvious thing to do. The choke allows you to connect an unbalanced tuner to any balanced feedline via the choke. A balanced tuner is entirely unnecessary in almost all circumstances. The choke is simply a pair of wires wound together around a ferrite toroid. Or it is a coaxial pair wound round a toroid (which for various reasons is slightly less efficient and is physically less convenient.) So the pair of parallel wires is the better form of construction. The choke behaves as a short length of transmission line of the same length as the pair of wires wound on the choke. Which is very short when a ferrite toroid is used. Because the length of line is an impedance transformer it transforms the input impedance of the transmission line to somewhat different values especially at the higher frequencies. At the lower frequencies it may just as well not be there. Which means that the tuner L and C settings are different to those which occur when the choke is not there. But often, when the choke is in use, the tuner finds it easier to match the line and antenna to the transmitter. Which is the sole purpose of the tuner. The number of turns wound on the choke must provide an inductance and a reactance of about 4 or 5 times the load resistance required by the transmitter, usually 50 ohms, at the lowest frequency of operation. This depends on the permeability of the ferrite core material. At the higher frequencies it is best that the length of line wound on the torroid should not exceed 1/8th of a wavelength at the free-space velocity. This is usually not too difficult to manage. To simplify, get a 2" outside diameter ferrite ring, of HF grade marerial, wind on 14 or 18 turns, and get on with it. A choke balun is the most simple of radio components to construct, yet its behaviour is amongst the most complicated of components to analyse. ---- Reg, G4FGQ. Article: 218588 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is a 50-ohm environment. ??? Message-ID: References: Date: Sat, 15 Oct 2005 21:20:16 GMT On Sat, 15 Oct 2005 19:02:58 -0000, "Dave" wrote: > >"Cecil Moore" wrote in message >news:rxb4f.2442$BZ5.2186@newssvr13.news.prodigy.com... >> Dave wrote: >>> don't bother, its a figment of cecil's imagination and creative >>> vocabulary. >> >> Actually, the question logically follows from the reflection model. >> Under what boundary conditions does a piece of transmission line >> force Vfor/Ifor = Vref/Iref = Z0 to a specified accuracy? > >then look up article 3.19 in 'fields and waves in communications >electronics' which is where they derive the fringe effects for a step change >in spacing between two plates. this is where they refer you for calculating >the effects of evanescent modes from a more complex problem stating that the >results are identical with the static case in 3.19... in the derivation of >the complex case of a step change in a cable they show that a single lumped >capacitance added at the step is an adequate representation of the >discontinuity when calculating the evanescent modes below cutoff. in 3.19 >if you disregard the fields along the length of the step it ends up in an >equation: Z=h/pi(exp(pi*W/V0)-1-pi*W/V0_j*pi) the important part is >obvioulsy the decay factor in the exponential which goes as exp(-x/h) where >h is the separation in the planes... or you get one 1/e reduction for each >distance equal to the spacing which in rg-58 or rg-8x that i used is >something like 1mm or less.. so how far down do you want to be? in 4.5mm >you are down to 1% which is well under the accuracy of these cheap meters, >and much less than the length of even the connectors on the meters. Dave, I note the work above estimating the rate of decay of the effect of the discontinuity, and we have seen another analysis of the decay rate (mis)quoted. Doesn't the impact of the discontinuity at a distance x depend on the magnitude of the products of the discontinuity times the attenuation at distance X. These discussions do not seem to have attempted to estimate the magnitude of the products of the discontinuity. Think about all the places where we do not preserve nominal Zo, and whether significant power is diverted to other than the dominant mode and subsequently lost. Look inside a HF transceiver, it is full of discontinuities between the PA collector and the coax socket. Design practice for HF transceivers does not consider potential losses from evanescent modes. If there were significant dissapative losses from such discontinuities, don't all the texts on stub tuner design need to be rewritten. Where is the experimental evidence that significant power is diverted in practical circuits and transmission line discontinuities? My experiment reported at the beginning of the thread could be varied to include another Bird at the dummy load, and to compare the power loss between Birds with the expected cable loss (in the dominant mode) to indicate whether there was another dissapative loss mechanism at work. I won't waste the time on the experiment because I anticipate that instrument errors and cable specification errors would swamp any likely effect of the discontinuities. IMHO, a well designed experiment would require more accurate measurement of the dominant mode loss of the 75 ohm cable, and more precise and accurate power measurement equipment. To demonstrate that point, I have just performed a test at 10.1MHz with the Bird 43 and the 5.27m of 9275 on the load side with o/c load. The measured return loss was -0.36dB. (Always seems un-natural specifying a loss as -dB). I estimate the return loss should have been -0.25dB (using the calculator at http://www.vk1od.net/tl/tllce.php), leaving an unaccounted for -0.11dB. The differences are smaller than the tolerances / accuracy of the equipment. Perhaps it does demonstrate that the loss caused by the discontinuity is not significant in terms of the specified accuracy of the Bird 43. Owen -- Article: 218589 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is a 50-ohm environment. ??? Message-ID: References: Date: Sat, 15 Oct 2005 21:35:19 GMT On Sat, 15 Oct 2005 20:49:42 GMT, Cecil Moore wrote: >Kevin Rhodes said, "... the lowest order undesired mode should reduce >intensity by a factor of 1/e in about 2.03"..." for Rg-213. 2.03" is >a lot greater than the spacing in RG-213. Cecil, Go back and read your own post: GaR1f.9892$oO2.4025@newssvr27.news.prodigy.net You quoted Kevin Rhodes: >(1/45m)**2 = (1/.203")**2 + kz**2 >Clearly, kz must be imaginary to make this work. thus an >evanescant, non-propagating wave: >kz**2 = (1/45m)**2 - (1/.203")**2 >To the accuracy used to date, the first term on the right >is negligible, so the decay rate, alpha, can be estimated: >alpha**2 = - (kz)**2 = (1/2.03")**2 How does rearranging the terms here increase 0.203" to 2.03"? In any event 0.203" is an overestimate of the spacing, 0.203" is actually half the overall diameter of RG213. I don't really understand this mathematics, do you understand the thing you are citing? Owen -- Article: 218590 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <2Qb4f.2443$BZ5.533@newssvr13.news.prodigy.com> <7qr2l15ibg31m1d3t15r2rbq1cgh6fdtvb@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 22:36:11 GMT Richard Clark wrote: > On Sat, 15 Oct 2005 20:37:11 GMT, Cecil Moore wrote: >>http://www.mfjenterprises.com/man/pdf/MFJ-816.pdf >>What do you think is the purpose of the 10pf variable cap >>if not to vary the voltage in the voltage divider? > > You don't know, do you? :-) > It adjusts the frequency correction at the high end of the meter's > frequency range. From page 27-8 ARRL Antenna Book 15th edition. "Capacitive voltage dividers, C1-C3 and C2-C4, are connected across the line to obtain equal-amplitude voltages in phase with the line voltage, the division ratio being adjusted so that these voltages match the voltage drops across R1 and R2 in amplitude." In other words, it is the main Z0 calibration setting that sets the sampled voltage equal to the sampled current while driving a dummy load equal to Z0. Frequency response is a completely secondary consideration. If the range of C1 and C2 are great enough, the wattmeter could be calibrated for 75 ohms rather than 50 ohms. >>The question is: Between the "transmitter" terminal and >>the "antenna" terminal, what determines the physical >>characteristic impedance of the sampling circuit? > > It is very lightly loading as a series load by > design and as evidenced by Dave's measurements. Exactly how much effect does that light loading have on the primary voltage/current amplitude and phase? Enough to be detectable if the V/I ratio is not 50 ohms? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218591 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <5es2l1975liei6k1olqc1icc3rigdtcuo8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 22:37:18 GMT Richard Clark wrote: > so much for relying on an obscure poster quoted indirectly by > paraphrase to a new context. Such is third hand information. Which is better? Third hand or under hand? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218592 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: Message-ID: <3Af4f.2089$D13.1036@newssvr11.news.prodigy.com> Date: Sat, 15 Oct 2005 22:41:03 GMT Owen Duffy wrote: > If there were significant dissapative losses from such > discontinuities, don't all the texts on stub tuner design need to be > rewritten. We're not talking about losses, Owen. We are talking about the changing relationships between V and I at an impedance discontinuity. Why do you think they call them discontinuities? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218593 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 22:55:14 GMT Dave wrote: > who is kevin rhodes? The guy from sci.physics.electromag whom I quoted previously in the "V/I forced to Z0" thread. It appears that he accidentally replaced the conductor spacing of 0.203" with 2.03" in his calculations. If that is corrected, his values tend to agree with yours given the different conductor spacing between RG8X and RG213. So can we say, the lowest order undesired mode should reduce intensity by a factor of 1/e in about one conductor spacing, 1/e^2 in two conductor spacings, etc.? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218594 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is a 50-ohm environment. ??? Message-ID: References: <4rt2l117kna6pevem31tq1kuhk0ibbttai@4ax.com> Date: Sat, 15 Oct 2005 22:24:26 GMT On Sat, 15 Oct 2005 15:01:45 -0700, Richard Clark wrote: >On Sat, 15 Oct 2005 21:20:16 GMT, Owen Duffy wrote: > >>Where is the experimental evidence that significant power is diverted >>in practical circuits and transmission line discontinuities? > >A practical example can be found in any RADAR system. You have ATR >tubes that perform power steering in waveguides. The list goes on >with lots of goodies (can anyone explain the Magic-T?) as RADAR is >particularly theatrical in this arena. > >Every connection to a waveguide uses the physics of discontinuity to >suppress leakage. Examine the choke fittings, they are series shorted >tuned cavities used to bridge joints that necessarily have some >prospect of not maintaining entirely mating interfaces. > Yes, I should have qualified the statement to scope it at HF. I am aware of the risk of excitation of undesirable modes in waveguide and the need for mode traps to deal with them where their propagation is undesirable. I am not questioning whether physical discontinuities give rise to electrical changes that can be explained or modelled with by lumped constants or excitation of other propagation modes, I am questioning whether the effects are significant in practical applications below microwave frequencies, and especially at HF. Owen -- Article: 218595 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <6YadnQU_26AF0czeRVn-hQ@crocker.com> Message-ID: Date: Sat, 15 Oct 2005 22:57:40 GMT Dave wrote: > obviously between the tx and ant terminals it looks like a 50 ohm > transmission line. So I repeat, what causes that characteristic? Is there some coax inside the MFJ box? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218596 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: Message-ID: Date: Sat, 15 Oct 2005 23:01:02 GMT Owen Duffy wrote: > How does rearranging the terms here increase 0.203" to 2.03"? Already caught that boo-boo. Correcting it brings Kevin's math in line with Dave's. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218597 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is a 50-ohm environment. ??? Message-ID: References: Date: Sat, 15 Oct 2005 22:38:10 GMT On Sat, 15 Oct 2005 23:01:02 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> How does rearranging the terms here increase 0.203" to 2.03"? > >Already caught that boo-boo. Correcting it brings Kevin's math >in line with Dave's. So you were aware of the apparent defect in the work you were citing as recently as less than two hours ago, and it took someone else to notify the defect here? Owen -- Article: 218598 of rec.radio.amateur.antenna From: ml Subject: Re: tvi References: <0ISdneFaB9TYtMzenZ2dnUVZ_sudnZ2d@crocker.com> Message-ID: Date: Sat, 15 Oct 2005 23:13:41 GMT thanks for all the help guys while i made no changes in the shack i never thought of testing the tv coax ground thou i hand't meesed w/it could be it broke or the set it self is screwy i don't disturb other tv's which are very close to the one in my room and all fed off same main coax so for sure i've narrowed it down to my radio room off i go testing that tv coax ground appreciate the helps all!! > > > > Article: 218599 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: Message-ID: <4jj4f.1617$dO2.191@newssvr29.news.prodigy.net> Date: Sun, 16 Oct 2005 02:56:00 GMT Owen Duffy wrote: > So you were aware of the apparent defect in the work you were citing > as recently as less than two hours ago, and it took someone else to > notify the defect here? You should have been able to figure it out from the posting times. I reported the problem at 5:55pm, after you had reported it but before I had read your posting which reported it. You've heard of two ships passing in the night? Ain't usenet great? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218600 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: Message-ID: Date: Sun, 16 Oct 2005 04:16:56 GMT Dave wrote: > ugh! all of this was over a slipped decimal point??? so we are down to .2" > transition, which pretty much agrees with the one i came up with, and which > basically means that by the time you are out of the connector shell you are > back at Z0. and since the meter takes its own 50 ohm 'environment' with it > for sampling it is reading every thing exactly as it should... and exactly > as has been measured... and there is no requirement for some particular > length of 50 ohm coax on either side of a meter... what a waste of a > perfectly good argument, you better apologize big time for this one cecil! I do apologize for the slip of the decimal point and for not finding it before today but I think you guys completely missed the context of the original argument and instead went off on several interesting tangents. Now back to the original context: As Reg pointed out, you can't have an SWR on a feedline that doesn't exist so how much 50 ohm feedline must exist *external to the SWR meter* to be able to report a valid 50 ohm SWR reading *on that coax*? Turns out to be around an inch, more or less, and that is a good thing to know. Thanks for answering the question even if in a time consuming way. If you had simply said that 0.2" of 50 ohm coax is required to establish a 50 ohm environment *external to the SWR meter*, we could have started arguing from that point and it would have saved a lot of time and effort. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218601 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0 References: <2Qb4f.2443$BZ5.533@newssvr13.news.prodigy.com> <7qr2l15ibg31m1d3t15r2rbq1cgh6fdtvb@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 04:20:01 GMT Richard Clark wrote: > Cecil Moore wrote: >>these voltages match the voltage drops across R1 and R2 >>in amplitude. > > There is NO R1 and/or R2 I gave the reference, Richard, and am looking at it right now. Page 27-9 of the 15th edition of the ARRL Antenna Book. R1 and R2 are 10 ohms each. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218602 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <1n53l1lube4q2f9nfnjqbvh3cm9skj9i1i@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 04:20:58 GMT Richard Clark wrote: > Nice thing about third hand quotes, you can blame them for your > transcription errors and they can't defend themselves. The evidence is always on Google. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218603 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: Fractal Antennas References: <5NX_e.1591$Fi3.75@newssvr29.news.prodigy.net> <1128045830.794934.214900@g14g2000cwa.googlegroups.com> <1129120141.286151.251960@g47g2000cwa.googlegroups.com> <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> Message-ID: Date: Sat, 15 Oct 2005 21:14:17 -0700 k wrote: > Well, why don't you just remove windows from your computer? What the > hell, use another OS or write one that suits you and doesn't have any > 'holes'...har.. > you haven't taken a look at the headers, have you? that is not a windows newsreader I am using. -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218604 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: Fractal Antennas References: <5b34$434d5c2e$97d558d8$9687@ALLTEL.NET> <68q0l1dkupiv31ii0tar0i2lnvqngcgbj5@4ax.com> Message-ID: Date: Sat, 15 Oct 2005 21:34:34 -0700 Richard Clark wrote: > On Sat, 15 Oct 2005 01:26:38 GMT, "k" wrote: > >>Well, why don't you just remove windows from your computer? > > A visit to: > http://grc.com/default.htm > will resolve ALL issues of security that have originated from the > clown act of Windows sicurity development. not sufficient. windows has so many exploits that it is not possible to adequately secure it. :( -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218605 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Date: Sun, 16 Oct 2005 05:53:28 GMT On Sat, 15 Oct 2005 03:37:16 GMT, Cecil Moore wrote: >Owen Duffy wrote: > >> Cecil Moore wrote: >>>and not to be a myth at all. There's 104.17 watts of forward power >>>through the Bird and 4.17 watts of reflected power back through the >>>Bird. Why does the Bird ignore those actual power values? >> >> I did not report or even measure such a thing. > >Since I realized the Bird forms a Z0-match at its output that >statement should be ammended to say: There 104.17 watts of forward Why the belated revelation of the Bird 43 coupler Zo? In a post on 9 Oct on the earlier thread I stated: "My suggestion is that the sampler inside a Bird 43 coupler section is sufficiently far inside the 50 ohm coupler line to provide measurements within the instrument's stated accuracy of what is happening within the 50 ohm coupler, irrespective of whether, for instance, a 75 ohm line is attached to the coupler on the load side." You must have read it, you responded to it with your message e2W1f.5490$Zs3.3003@newssvr25.news.prodigy.net . Perhaps the honest way to deal with the situation is to acknowledge that your statement quoted at the top of this post was just not true, rather than to edit the words to shift the context to somewhere else where it might be true. It would be gracious of you to return to the myth, read it carefully and think about it, and to respond restricting yourself to the myth as stated, without qualification or obfuscation, is it a myth YES or NO. To save you the hassle of finding it, here is: The myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Myth or not, YES or NO? Owen -- Article: 218606 of rec.radio.amateur.antenna Message-ID: <4352068B.3050201@killspam.internode.on.net> Date: Sun, 16 Oct 2005 17:51:39 +1000 From: Alan Peake Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <9e60l15ftmikao31ujkcbliu6t053qgtus@4ax.com> <4350BD36.2000507@killspam.internode.on.net> > Is that BTW? Yes - dear oh dear - pot calling kettle black :) > It appears to have a flat section of line that is parallel to the coax > centre conductor and is presumably capacitively and inductively > coupled, and it uses some form of frequency compensation to give it > broadband response. You rotate the sampler element for measurement of > the opposite direction. Have played with that type of Bird. Worked well as I recall. Have also made a Bruene type - fairly constant readings over wide frequency range. Yes 40m is a bit ordinary at the mo for short distance. Cheers, Alan Article: 218607 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: What is a 50-ohm environment. ??? Date: Sun, 16 Oct 2005 13:32:11 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> OK, Cec, I have a better idea of what you mean by '50-ohm environment'. You refer to: - Vfor/Ifor = Vref/Iref = Z0 with which I agree. But Zo is a pure resistance and the relationship can be true only when there is no phase shift between Vfor/Ifor and Vref/Iref. Which means, in the ideal meter, the voltage tap-off and current tap-off points must be identically located within the instrument. I would now like to go off in a slightly different tack to these extensive threads. There is a length of conductor between the input and output terminals of the meter. It cannot be avoided. For obvious reasons related to the high-frequency response and accuracy, the Zo environment along this conductor has to be maintained as good as is reasonably possible. ( With the common or garden SWR meter nobody bothers very much. It hardly matters anyway.) The location of the voltage and current tapping points along the conductor doesn't matter two hoots. What matters is the distance beween them because of the phase difference. Small errors due to misplacement are unavoidable and have to be lived with. Getting to the point of this message: - The length of transmission line inside the meter and the unknowns regarding 'Zo environment' play no part either in operation or analysis of the meter. The story that the length of line inside the meter is used to detect and measure standing wave ratios is just another old-wives' tale which confuses CB-ers, novices and professional engineers alike. ( By the way, if there is a short transmission line of any sort inside the instrument, its length can be used to set the measuring sensitivity. The longer the line the greater the sensitivity. But the longer the line the greater the measuring errors and the worse the frequency response.) ---- Reg, G4FGQ. =========================================== "Cecil Moore" wrote > > The transmission line reflection model tells us that the Z0 > of a transmission lines forces the following relationship. > > Vfor/Ifor = Vref/Iref = Z0 > > A "50 ohm environment" used in the context of the previous > discussion would be one in which the above relationship > is forced on the system at certain points in the system. > > 600 ohm transmission line going from a tuner/balun to an > antenna establishes a 600 ohm environment for the signals > on the transmission line. An SWR meter calibrated for 600 > ohms will indicate the actual SWR. > > About a year ago, based on a discussion that you and I were > having, I asked the sci.physics.electromag newsgroup how > long a piece of RG-213 coax has to be to establish the > above relationship. The answer was that the non-TEM product > terms decrease at about 1/e every two inches for RG-213. > > The RG-400 coax leads going to and from my SWR meter are > two feet each. So I asserted to you that my SWR meter > was reading the actual SWR in the middle of that run of > RG-400. I think you disagreed with my assertion but I > cannot remember for sure. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 218608 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: What is SINAD? Message-ID: Date: Sun, 16 Oct 2005 14:04:07 GMT "chuck" wrote in message news:Y3R3f.14801$q1.8324@newsread3.news.atl.earthlink.net... > Good info, Owen. I think the EIA test procedures really have FM or AM in > mind, rather than SSB or, what is exactly the same for SINAD purposes, CW. > The 60% figure just doesn't apply to SSB or CW. You would simply use an > unmodulated signal generator with the frequency offset to produce a 1 kHz > tone in the receiver's audio output, preferrably centered in the > receiver's passband. Then a measure of rms af voltage at the receiver's > output with and without the 1 kHz filter would be made. > > We don't hear much about SINAD testing procedures for SSB and CW. Even the > ARRL's test procedure manual glosses over the procedure for other than FM. The old Canadian Department of Communications Document RSS 125 Issue 1, Released August 1st, 1976, precisely describes the method of SINAD measurements for SSB equipment. In the past 25 years or so, HP's distortion analyzers (such as the HP8903B) were used for this measurement. In the late 60s and early 70s I have seen Heathkit distortion analyzers used for SINAD measurements. The latest versions of RSS125 seem to be more in line with FCC standards, where receiver specifications are not required for certification purposes (See http://www.agiletestgroup.com/ICCertifications.html). 73, Frank Article: 218609 of rec.radio.amateur.antenna From: Walter Maxwell Subject: Re: V/I ratio is forced to Z0:was Mythbusters Message-ID: References: <6YadnQU_26AF0czeRVn-hQ@crocker.com> Date: Sun, 16 Oct 2005 10:43:18 -0400 On Sat, 15 Oct 2005 22:57:40 GMT, Cecil Moore wrote: >Dave wrote: >> obviously between the tx and ant terminals it looks like a 50 ohm >> transmission line. > >So I repeat, what causes that characteristic? Is there >some coax inside the MFJ box? I've been reading this thread while biting my tongue concerning the Zo of the SWR measuring device. IMO the basis for the Zo of the device is being overlooked, although Cecil is coming the closest to describing it. We are discussing the Bruene version of the device in which the inductance derives a sample of the current and C1 derives a sample of the voltage. When C1 is adjusted to obtain the correct voltage for the voltage-current ratio to equal Zo at that point, such as 50 ohms, the device provides the correct readings when the line impedance on the load side is Zo. The line impedance Zo on the input side is irrelevant. If C1 is adjusted to obtain the correct voltage for the voltage-current ratio to equal Zo of 75 ohms it will provide the correct reading when the line impedance Zo on the load side is 75 ohms. The line impedance of either the input or load transmission line is irrelevant to the basis for the Zo of the device, therefore a length of line is unnecessary to establish a Zo environment, the current sample and voltage sample establish it.. One can terminate the device with a lumped impedance and get the same answer as with a transmssion line whose input impedance is the same as the lumped impedance. Walt, W2DU Article: 218610 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 14:44:09 GMT Owen Duffy wrote: > Cecil Moore wrote: >>Since I realized the Bird forms a Z0-match at its output ... > > Perhaps the honest way to deal with the situation is to acknowledge > that your statement quoted at the top of this post was just not true, > rather than to edit the words to shift the context to somewhere else > where it might be true. I already admitted that, Owen, when I said the Bird developes a Z0-match at its terminals (above). If you will tell me how many times I have to admit I was wrong, I will prepare the appropriate posting. > The myth: Measurements with a Bird 43 of the conditions on the > Thruline section are invalid unless it has some minimum length of 50 > ohm line on both sides of itself. > > Myth or not, YES or NO? Myth YES. I don't know in how many ways I have to say that. Would me writing an admission in my own blood help calm you down? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218611 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <6YadnQU_26AF0czeRVn-hQ@crocker.com> Message-ID: Date: Sun, 16 Oct 2005 14:58:52 GMT Walter Maxwell wrote: > The line impedance of either the input or load transmission line is irrelevant > to the basis for the Zo of the device, therefore a length of line is unnecessary > to establish a Zo environment, the current sample and voltage sample establish > it.. Walt, there's one thing I don't understand about what Dave reported. As I understand it, these were the test setups. TDR---50 ohm coax---MFJ---50 ohm coax---50 ohm load The TDR doesn't see the MFJ wattmeter. TDR---75 ohm coax---MFJ---75 ohm coax---75 ohm load The TDR sees the MFJ wattmeter. If the MFJ in the second setup were recalibrated for 75 ohms, would the TDR not see it? **************************************************************** The threads for the past few days have all diverged from the original question which was: How long must the 50 ohm coax connected to the SWR meter be for the SWR meter to report a valid SWR on that coax? The answer obviously cannot be zero length. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218612 of rec.radio.amateur.antenna From: Walter Maxwell Subject: Re: Trying to get AM broadcast at job Message-ID: <0mq4l19d87kf40fiv2ci5ifhj2v423fqq5@4ax.com> References: <1125736373.469540.275780@g14g2000cwa.googlegroups.com> <1129366324.812161.317540@g43g2000cwa.googlegroups.com> Date: Sun, 16 Oct 2005 11:01:40 -0400 On 15 Oct 2005 01:52:04 -0700, sofasurfer@blclinks.net wrote: >Fedthecat wrote: >snip >4. The best I get is 760 AM, very fuzzy, barely understandable. 950 AM >is worse. Those are the only two stations coming in at all. They do not >fade in or out. Sounds like you're in the Detroit area with 760 as WJR and 950 as WWJ. Am I close, or what? Walt, W2DU Article: 218613 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 15:10:44 GMT Reg Edwards wrote: > Which means, in the ideal meter, the voltage tap-off and current > tap-off points must be identically located within the instrument. In my MFJ, the toroid and calibration cap are about 1/2" apart. > The story that the length of line inside the meter is used to detect > and measure standing wave ratios is just another old-wives' tale which > confuses CB-ers, novices and professional engineers alike. And if you will remember, the original question didn't involve the SWR meter at all. The question was: Are my 2-foot sections of RG-400 connected to my SWR meter long enough to ensure that the SWR meter reading is valid for the coax? Remember that argument? The threads for the past few days have all diverged from that original question which was: How long must the 50 ohm coax connected to the SWR meter be for the SWR meter to report a valid SWR *on that coax*? The answer obviously cannot be zero length. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218614 of rec.radio.amateur.antenna From: "Dr.Ace" References: <1lihotn31d6fk.a79lqxn15md6$.dlg@40tude.net> Subject: Re: Emergency Messaging, AM/FM *On Locomotive* Date: Sun, 16 Oct 2005 10:33:33 -0500 Message-ID: <4ca1d$435272b9$4e0b7ac$12582@DIALUPUSA.NET> I've got an idea. How about installing flashing lights at rail road crossing, and maybe some bells. Ace - WH2T "Mike Coslo" wrote in message news:CIidnWD3VOKnUszeRVn-oQ@adelphia.com... > Ari Silversteinn wrote: >> On Tue, 04 Oct 2005 19:40:18 -0400, Mike Coslo wrote: >> >> >>> The Republicans are going to take care of all those problems! Darned >>> Democrats anyhow! >>> >>> - Mike KB3EIA - >> > > I won't deny it! > > Now, if you want my honest assessment, I find the whole thing fraught with > ethical questions. > > What if someone isn't listening to the radio when the message is > broadcast? What about the people who don't live near railroad tracks? > > If this thing is to *actually* work, it would have to be space based. Work > with a database of the frequencies in use in the affected areas. broadcast > on them as the need arises. FM will be easy. AM will be some more work. Of > course you'll still have to deal with the people who aren't listening at > the moment! > > Of course if it just a research project to burn up some money, then *that* > is a different subject altogether! > > - Mike KB3EIA - Article: 218615 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 16:00:52 GMT Dave wrote: > "Cecil Moore" wrote: >>And if you will remember, the original question didn't involve the >>SWR meter at all. The question was: Are my 2-foot sections of RG-400 >>connected to my SWR meter long enough to ensure that the SWR meter >>reading is valid for the coax? Remember that argument? > > and the answer is <.2" Not for 6" diameter hard line. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218616 of rec.radio.amateur.antenna From: "johan aeq" Subject: rf-systems WFL antenna? Date: Sun, 16 Oct 2005 18:57:43 +0200 Message-ID: <90f46$43528818$52ad139c$15540@news.versatel.nl> Hello, can you explain this antenna mentioned on this site? http://www.universal-radio.com/catalog/hamwire/2039.html A almost flat swr response with such a small antenna must be a folded T2FD antenna. Is there someone who has tested this antenna? Greetings Johan PE1AEQ Article: 218617 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 17:43:40 GMT Richard Clark wrote: > Cecil Moore wrote: >>Myth YES. > > Third-hand knowledge, Junk or Treasure? Actually, it doesn't rise to the definition of a myth. It wasn't a popular belief. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218618 of rec.radio.amateur.antenna From: Walter Maxwell Subject: Re: V/I ratio is forced to Z0:was Mythbusters Message-ID: References: <6YadnQU_26AF0czeRVn-hQ@crocker.com> Date: Sun, 16 Oct 2005 13:45:16 -0400 On Sun, 16 Oct 2005 14:58:52 GMT, Cecil Moore wrote: >Walter Maxwell wrote: >> The line impedance of either the input or load transmission line is irrelevant >> to the basis for the Zo of the device, therefore a length of line is unnecessary >> to establish a Zo environment, the current sample and voltage sample establish >> it.. > >Walt, there's one thing I don't understand about what Dave reported. >As I understand it, these were the test setups. > >TDR---50 ohm coax---MFJ---50 ohm coax---50 ohm load > >The TDR doesn't see the MFJ wattmeter. The TDR doesn't see the wattmeter because there is no discontinuity. >TDR---75 ohm coax---MFJ---75 ohm coax---75 ohm load > >The TDR sees the MFJ wattmeter. It seems to me the amount of the discontinuity the wattmeter calibrated to 50 ohms the TDR sees would be determined by the tightness of coupling of the sampling inductance and capacitance to the main line. >If the MFJ in the second setup were recalibrated for 75 ohms, >would the TDR not see it? I believe the TDR would not see it. >**************************************************************** > >The threads for the past few days have all diverged from the >original question which was: > >How long must the 50 ohm coax connected to the SWR meter be >for the SWR meter to report a valid SWR on that coax? The >answer obviously cannot be zero length. Cecil, as I explained earlier, if we're considering the Bruene type SWR indicator, the setting of the sampling cap in relation to the inductive sampling determines the measurement reference, not the length or Zo of the coax. So I repeat, with this SWR indicator zero coax length is sufficient. It will produce the same answer with a lumped impedance as the load as it will with the same impedance appearing as the input impedance of a coax. Walt, W2DU Article: 218619 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 17:49:44 GMT Owen Duffy wrote: > The myth: Measurements with a Bird 43 of the conditions on the > Thruline section are invalid unless it has some minimum length of 50 > ohm line on both sides of itself. > > Myth or not, YES or NO? Actually, upon closer examination, the definition of "myth" proves the above is NOT a myth. It is not a traditional story. It is not a parable allegory. It is not a popular belief. So, no Owen, it is not a myth. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218620 of rec.radio.amateur.antenna From: Walter Maxwell Subject: Re: Trying to get AM broadcast at job Message-ID: References: <1125736373.469540.275780@g14g2000cwa.googlegroups.com> <1129366324.812161.317540@g43g2000cwa.googlegroups.com> <0mq4l19d87kf40fiv2ci5ifhj2v423fqq5@4ax.com> Date: Sun, 16 Oct 2005 14:00:12 -0400 On Sun, 16 Oct 2005 09:33:00 -0700, Richard Clark wrote: >On Sun, 16 Oct 2005 11:01:40 -0400, Walter Maxwell >wrote: > >>Sounds like you're in the Detroit area with 760 as WJR and 950 as WWJ. Am I >>close, or what? > >Good job, Walt. Flint. > >73's >Richard Clark, KB7QHC Richard, I grew up listenting to those stations. WJR was originally on 750, but went up one slot after the NARBA agreement in the early 1940's. Incidentally, WJR was originally WCX, transmitter at Pontiac, which I listened to beginning in 1925, but changed to WJR in 1929 when it was purhased by the Jewett Radio Corp. I grew up in Mt. Pleasant, 115 mi NW airline from Detroit. Even with 500 W WBCM on 1440 40 miles away in Bay City, we had no primary BC service, which is what prompted me to build a local station after returning home after WW2. I engineered and built WCEN, 500 W 1150 in 1948, and on the air in 1949. Mt. Pleasant is in almost the exact center of lower MI, it is the home of CMU, Central Michigan University. I considered both WMTP and WCEN for the call sign, but decided on WCEN. However, when I applied for it, FCC said it was already assigned to a Coast Guard vessel. After some research I discovered that vessel had been decommissio;n 10 years earlier, so I contacted Treasury and asked them the release the call back to the FCC for reassignment to me. They did and the FCC did. Sadly, the station was sold in 2004 to a Saginaw based outfit, retaining the FM outlet, but deleting the AM. Walt Article: 218621 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: V/I ratio is forced to Z0:was Mythbusters References: <6YadnQU_26AF0czeRVn-hQ@crocker.com> Message-ID: Date: Sun, 16 Oct 2005 18:03:50 GMT Walter Maxwell wrote: > Cecil Moore wrote: >>How long must the 50 ohm coax connected to the SWR meter be >>for the SWR meter to report a valid SWR on that coax? The >>answer obviously cannot be zero length. > > Cecil, as I explained earlier, if we're considering the Bruene type SWR > indicator, the setting of the sampling cap in relation to the inductive sampling > determines the measurement reference, not the length or Zo of the coax. So I > repeat, with this SWR indicator zero coax length is sufficient. It will produce > the same answer with a lumped impedance as the load as it will with the same > impedance appearing as the input impedance of a coax. But Walt, there no SWR possible on a zero length line. I think it was Reg who said that first. I can now see how the initial confusion arose and why the thread drifted. Source---75 ohm line---SWR meter---load The SWR meter will not report the actual SWR on the external 75 ohm line. Source--75 ohm line--50 ohm line--SWR meter--load The SWR meter will report the actual SWR on the external 50 ohm coax if the external 50 ohm coax is _______ long. Turns out the answer is a lot smaller than I previously thought. The answer is less than one inch for the most popular 50 ohm coax's. I didn't mean for the original question to be a trick question but it apparently turned out that way. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218622 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Trying to get AM broadcast at job Date: Sun, 16 Oct 2005 14:14:53 -0400 Message-ID: <11l564rca8fq2ec@corp.supernews.com> References: <1125736373.469540.275780@g14g2000cwa.googlegroups.com> <1129366324.812161.317540@g43g2000cwa.googlegroups.com> <0mq4l19d87kf40fiv2ci5ifhj2v423fqq5@4ax.com> Let us be clear: Richard Clark is not in the neighborhood of Flint. A few factories still exist in the Flint neighborhood that are likely significantly to attenuate AM broadcast signals (due to the plant's construction). Square miles of such factories have been leveled to bare ground in the I75 corridor. One must conclude that the programming of local AM broadcasting stations is not desired by the person having difficulty. Almost all of the local (to Flint) stations are strong enough where the plants are located to be heard inside of a plant. A scheme that could be used to listen to WJR or WWJ is to have the audio of an AM receiver in a vehicle located in an adjacent parking lot modulate a small FM transmitter. A conventional FM receiver inside of the plant is likely to receive a suitable signal. The power required by the system in the vehicle could be small. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net "Richard Clark" wrote in message news:i405l1p350v2dute5i64464lrh7nipun3i@4ax.com... > On Sun, 16 Oct 2005 11:01:40 -0400, Walter Maxwell > wrote: > > >Sounds like you're in the Detroit area with 760 as WJR and 950 as WWJ. Am I > >close, or what? > > Good job, Walt. Flint. > > 73's > Richard Clark, KB7QHC Article: 218623 of rec.radio.amateur.antenna Subject: Doublet Antenna question From: Ed Message-ID: Date: Sun, 16 Oct 2005 18:28:36 GMT Currently I have a coax fed trapped 75/40M dipole up between two trees. The spacing of the trees (a bit over 110 feet) allows this antenna with no extra length allowed, except for minimal support line and insulator length. I plan on replacing this dipole with 450 ohm ladder line feed doublet so I can operate on more than just 75/40M, however a full 1/4 wave length for 75 would be too long to fit between these trees. My QUESTION(s): How effective would a balanced fed dipole of about 100 feet length be on 75M ? Should it tune OK with a tuner such as the new MFJ balanced tuner? Or, if I were to put either the old 40M traps, or wind coils for the new dipole to shorten 75M resonance, would it then tune OK on all bands from 75M down with balanced feed? Ed K7AAT Article: 218624 of rec.radio.amateur.antenna From: Walter Maxwell Subject: Re: Trying to get AM broadcast at job Message-ID: References: <1125736373.469540.275780@g14g2000cwa.googlegroups.com> <1129366324.812161.317540@g43g2000cwa.googlegroups.com> <0mq4l19d87kf40fiv2ci5ifhj2v423fqq5@4ax.com> <11l564rca8fq2ec@corp.supernews.com> Date: Sun, 16 Oct 2005 14:31:27 -0400 On Sun, 16 Oct 2005 14:14:53 -0400, "J. Mc Laughlin" wrote: >Let us be clear: Richard Clark is not in the neighborhood of Flint. > > A few factories still exist in the Flint neighborhood that are likely >significantly to attenuate AM broadcast signals (due to the plant's >construction). Square miles of such factories have been leveled to bare >ground in the I75 corridor. > > One must conclude that the programming of local AM broadcasting stations >is not desired by the person having difficulty. Almost all of the local (to >Flint) stations are strong enough where the plants are located to be heard >inside of a plant. > > A scheme that could be used to listen to WJR or WWJ is to have the audio >of an AM receiver in a vehicle located in an adjacent parking lot modulate a >small FM transmitter. A conventional FM receiver inside of the plant is >likely to receive a suitable signal. The power required by the system in >the vehicle could be small. > > 73 Mac N8TT Hi Mac, Richard's mention of Flint is that apparently is where sofasurfer lives. Walt Article: 218625 of rec.radio.amateur.antenna From: chuck Subject: Re: What is SINAD? References: Message-ID: <22x4f.15263$vw6.6978@newsread1.news.atl.earthlink.net> Date: Sun, 16 Oct 2005 18:33:34 GMT Thanks for the info, Frank. Actually, the RSS125 on the site doesn't contain the procedure, but RSS181, also available at that site, does. FWIW, the procedure is basically what has been discussed, except that the signal generator output to be recorded as the receiver's sensitivity is that level which produces a 12 dB SINAD at 50% of rated audio output! Probably a more realistic test than allowing the AF stage to operate at a low-distortion level of something like 1% of rated output. 73, Chuck NT3G Frank wrote: > > The old Canadian Department of Communications Document RSS 125 Issue 1, > Released August 1st, 1976, precisely describes the method of SINAD > measurements for SSB equipment. In the past 25 years or so, HP's distortion > analyzers (such as the HP8903B) were used for this measurement. In the late > 60s and early 70s I have seen Heathkit distortion analyzers used for SINAD > measurements. The latest versions of RSS125 seem to be more in line with > FCC standards, where receiver specifications are not required for > certification purposes (See > http://www.agiletestgroup.com/ICCertifications.html). > > 73, > > Frank > > Article: 218626 of rec.radio.amateur.antenna From: "Fred W4JLE" References: Subject: Re: Doublet Antenna question Date: Sun, 16 Oct 2005 15:00:12 -0400 Message-ID: A G5RV would fit and meet your needs for all band operation with a tuner. "Ed" wrote in message news:Xns96F174C016B0Cspectrumhogstarbandn@207.106.93.175... > > Currently I have a coax fed trapped 75/40M dipole up between two > trees. The spacing of the trees (a bit over 110 feet) allows this > antenna with no extra length allowed, except for minimal support line and > insulator length. > > I plan on replacing this dipole with 450 ohm ladder line feed doublet > so I can operate on more than just 75/40M, however a full 1/4 wave length > for 75 would be too long to fit between these trees. > > > My QUESTION(s): How effective would a balanced fed dipole of about > 100 feet length be on 75M ? Should it tune OK with a tuner such as the > new MFJ balanced tuner? Or, if I were to put either the old 40M traps, > or wind coils for the new dipole to shorten 75M resonance, would it then > tune OK on all bands from 75M down with balanced feed? > > Ed K7AAT Article: 218627 of rec.radio.amateur.antenna From: "Denton" Subject: Re: Doublet Antenna question Date: Sun, 16 Oct 2005 12:05:45 -0700 Message-ID: <11l594jaadilp98@corp.supernews.com> References: I am running a 100 ft bowtie antenna ok with link coupled transmatch, fed with 450 ohm twin lead and it tunes 75 thru 10 meters Each side of center feedpoint has a pair of 50 ft wires, that are connected at the ends with a piece of 6 ft wire. "Ed" wrote in message news:Xns96F174C016B0Cspectrumhogstarbandn@207.106.93.175... > > Currently I have a coax fed trapped 75/40M dipole up between two > trees. The spacing of the trees (a bit over 110 feet) allows this > antenna with no extra length allowed, except for minimal support line and > insulator length. > > I plan on replacing this dipole with 450 ohm ladder line feed doublet > so I can operate on more than just 75/40M, however a full 1/4 wave length > for 75 would be too long to fit between these trees. > > > My QUESTION(s): How effective would a balanced fed dipole of about > 100 feet length be on 75M ? Should it tune OK with a tuner such as the > new MFJ balanced tuner? Or, if I were to put either the old 40M traps, > or wind coils for the new dipole to shorten 75M resonance, would it then > tune OK on all bands from 75M down with balanced feed? > > Ed K7AAT Article: 218628 of rec.radio.amateur.antenna From: "Ken Taylor" References: <1lihotn31d6fk.a79lqxn15md6$.dlg@40tude.net> Subject: Re: Emergency Messaging, AM/FM *On Locomotive* Message-ID: Date: Mon, 17 Oct 2005 08:38:14 +1300 "Mike Coslo" wrote in message news:CIidnWD3VOKnUszeRVn-oQ@adelphia.com... > Ari Silversteinn wrote: >> On Tue, 04 Oct 2005 19:40:18 -0400, Mike Coslo wrote: >> >> >>> The Republicans are going to take care of all those problems! Darned >>> Democrats anyhow! >>> >>> - Mike KB3EIA - >> > > I won't deny it! > > Now, if you want my honest assessment, I find the whole thing fraught with > ethical questions. > > What if someone isn't listening to the radio when the message is > broadcast? What about the people who don't live near railroad tracks? > > If this thing is to *actually* work, it would have to be space based. Work > with a database of the frequencies in use in the affected areas. broadcast > on them as the need arises. FM will be easy. AM will be some more work. Of > course you'll still have to deal with the people who aren't listening at > the moment! > > Of course if it just a research project to burn up some money, then *that* > is a different subject altogether! > > - Mike KB3EIA - Space-based wouldn't work. You can't get a spot footprint small enough on the earth's surface to make this do-able. Iridium comes about the closest, but would you put up a constellation to provide the footprints and not use it 99.999999999% of the time? :-) Cheers. Ken Article: 218629 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <90f46$43528818$52ad139c$15540@news.versatel.nl> Subject: Re: rf-systems WFL antenna? Message-ID: Date: Sun, 16 Oct 2005 19:49:43 GMT "johan aeq" wrote in message news:90f46$43528818$52ad139c$15540@news.versatel.nl... > Hello, > can you explain this antenna mentioned on this site? > http://www.universal-radio.com/catalog/hamwire/2039.html > A almost flat swr response with such a small antenna must be a folded T2FD > antenna. > Is there someone who has tested this antenna? > Greetings Johan PE1AEQ > It sounds like someone is trying to sell junk at a high price. Unless the price is also for the supporting poles. Oxygen-free copper wire sounds like the HI-FI boys and their Monster Wire are at it again. Article: 218630 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Mythbusters: V/I ratio is forced to Z0 Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Date: Sun, 16 Oct 2005 19:48:31 GMT On Sun, 16 Oct 2005 17:49:44 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> The myth: Measurements with a Bird 43 of the conditions on the >> Thruline section are invalid unless it has some minimum length of 50 >> ohm line on both sides of itself. >> >> Myth or not, YES or NO? > >Actually, upon closer examination, the definition of "myth" >proves the above is NOT a myth. It is not a traditional story. >It is not a parable allegory. It is not a popular belief. > >So, no Owen, it is not a myth. Cecil, this is the opposite to your stated YES opinion just three hours ago. I am beginning to form the view that your opinion is just the opposite of that expressed in the last posting you read, that you will argue for arguments sake. When I look for consistency in you postings, it is that they are consistently arguments against other propositions, even if it means you have to change your own position to remain opposed. To be kind, the devil's advocate. Owen -- Article: 218631 of rec.radio.amateur.antenna From: "Ralph Mowery" References: Subject: Re: Doublet Antenna question Message-ID: Date: Sun, 16 Oct 2005 19:58:40 GMT "Ed" wrote in message news:Xns96F174C016B0Cspectrumhogstarbandn@207.106.93.175... > > Currently I have a coax fed trapped 75/40M dipole up between two > trees. The spacing of the trees (a bit over 110 feet) allows this > antenna with no extra length allowed, except for minimal support line and > insulator length. > > I plan on replacing this dipole with 450 ohm ladder line feed doublet > so I can operate on more than just 75/40M, however a full 1/4 wave length > for 75 would be too long to fit between these trees. > > > My QUESTION(s): How effective would a balanced fed dipole of about > 100 feet length be on 75M ? Should it tune OK with a tuner such as the > new MFJ balanced tuner? Or, if I were to put either the old 40M traps, > or wind coils for the new dipole to shorten 75M resonance, would it then > tune OK on all bands from 75M down with balanced feed? > > Ed K7AAT If you are not satisified with the antenna you have then I would put up about 130 feet of wire and feed it in the middle with the balanced feed. If you can not get up the full 130 feet or so of wire, put it all up and let the ends hang down. That is the support ropes could be attached 10 to 15 feet from each end and then you let whatever is left over hang down. Just don't let the ends reach close enough to the ground where someone could reach them. Shock and RF burns. If you go to the 100 feet and feed it with open wire , you are trying to make the antenna into a g5rv if you use whatever length of feedline the g5rv calls for. Not really that good of an antenna for working all bands. Article: 218632 of rec.radio.amateur.antenna From: =?ISO-8859-2?Q?Rafa=B3_Likus?= Subject: F9FT website Date: Sun, 16 Oct 2005 22:35:26 +0200 Message-ID: Hello! Because F9FT website is offline for some time and I'm looking for some informations from this www. Have anybody mirrored this website and could share it for me? -- Regards, Rafal Likus SQ9CWN SP5PIP/SN5P Team http://www.sp5pip.waw.pl/eng/ remowe azot. from my email address... Article: 218633 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Trying to get AM broadcast at job Date: Sun, 16 Oct 2005 15:36:26 -0500 Message-ID: <23479-4352B9CA-778@storefull-3257.bay.webtv.net> References: Jerry Martes wrote: "It is difficult for me to believe that you installed (properly) an amplified AM antenna from a modern car, on te outside of the metal building, and didn`t get decent reception." The usual AM car antenna has an impedance of about 5000 ohms. Car coax is special. It has a fine-wire center conductor inside an air-dielectric covered by metal braid. It marches the 5000-ohm antenna. 50-ohm coax makes a capacitive voltage divider (uigh-value attenuator) when used with a car antenna. The longer the 50-ohm coax, the more severe the attenuation. The active (amplified) antenna could easily be designed for a high input impedance and a low output impedance. It coulf use a an emitter follower as an output stage. What Sofasurfer has is unknown. A low-impedance shielded line is less susceptible to noise pickup than unshielded wire. Coax is OK. Balanced twisted pair is not too susceptible to noise. But as Sofasurfer`s experience shows, severe mismatch is a killer. He needs either a low-impedance antenna or a matching device to step the high-impedance antenna output down to the line`s impedance. A hollower can do that almost without losing voltage. A broadcast loop for the AM band is a low-impedance because the wavelengrh is so long or it can be tapped or loop-coupled to a low impedance. Best regards, Richard Harrison, KB5WZI Article: 218634 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Doublet Antenna question Message-ID: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> References: Date: Sun, 16 Oct 2005 21:20:22 GMT On Sun, 16 Oct 2005 18:28:36 GMT, Ed wrote: > > My QUESTION(s): How effective would a balanced fed dipole of about >100 feet length be on 75M ? Should it tune OK with a tuner such as the >new MFJ balanced tuner? Or, if I were to put either the old 40M traps, >or wind coils for the new dipole to shorten 75M resonance, would it then >tune OK on all bands from 75M down with balanced feed? Ed, When you analyse the performance of a centre fed dipole antenna system, you will find that for most practical dipoles, the challenge is getting most of the power to the feed point, rather than the ohmic losses in the radiator itself. By the time the dipole is long enough to obtain acceptable performance >from a practical feed system, the loss in the radiator itself is typically less than 0.5dB (unless you contrive do something pretty silly). It turns out that it becomes quite challenging to implement an efficient feed system (especially over a wide frequency range) where the dipole is less than about 35% of a wavelength at the lowest frequency. Now, the 100' you nominate is so close to the length of a G5RV that you could draw some information from analyes of the G5RV. I wrote one that focusses on the performance of common distortions of G5RV's design and examines particularly the feed system performance, which I suggest to you is the most significant influence on antenna system efficiency in this case. Unlike many other analyses of the G5RV, this does not just consider ham band performance, it models performance every 100KHz from 1MHz to 30MHz, so you can see a continuous view of the behaviour. The article is at http://www.vk1od.net/G5RV/ . But you weren't asking about a G5RV were you. Look at Figure 10 and the "Classic tune feeder" topic which is a 30m dipole fed with 23m of ideal 600 ohm open wire feeder. (Ladder line won't perform quite that well, especially when wet). That topic is directly relevant to your proposal. Nothing in the feed system affects the pattern (in three dimensions), that is determined by the length of the dipole, and its environment. Owen -- Article: 218635 of rec.radio.amateur.antenna From: "Jerry Martes" References: <23479-4352B9CA-778@storefull-3257.bay.webtv.net> Subject: Re: Trying to get AM broadcast at job Message-ID: Date: Sun, 16 Oct 2005 21:36:32 GMT "Richard Harrison" wrote in message news:23479-4352B9CA-778@storefull-3257.bay.webtv.net... > Jerry Martes wrote: > "It is difficult for me to believe that you installed (properly) an > amplified AM antenna from a modern car, on te outside of the metal > building, and didn`t get decent reception." > > The usual AM car antenna has an impedance of about 5000 ohms. Car coax > is special. It has a fine-wire center conductor inside an air-dielectric > covered by metal braid. It marches the 5000-ohm antenna. > > 50-ohm coax makes a capacitive voltage divider (uigh-value attenuator) > when used with a car antenna. The longer the 50-ohm coax, the more > severe the attenuation. > > The active (amplified) antenna could easily be designed for a high input > impedance and a low output impedance. It coulf use a an emitter follower > as an output stage. What Sofasurfer has is unknown. > > A low-impedance shielded line is less susceptible to noise pickup than > unshielded wire. Coax is OK. Balanced twisted pair is not too > susceptible to noise. But as Sofasurfer`s experience shows, severe > mismatch is a killer. He needs either a low-impedance antenna or a > matching device to step the high-impedance antenna output down to the > line`s impedance. A hollower can do that almost without losing voltage. > A broadcast loop for the AM band is a low-impedance because the > wavelengrh is so long or it can be tapped or loop-coupled to a low > impedance. > > Best regards, Richard Harrison, KB5WZI Hi Richard I had assumed that the OP was just interested in just getting an AM radio to work inside the metal building. And, actually I'm no expert on the design of AM receivers. I have considered the "car AM antenna" to be more of a probe of the currents conducted on the outside of the car. I thought the reason that the "high impedance coax" to be used for car AM radios was because that high impedance is more importantly the lowest shunt capacity. I've been considering the car's feed line to be a capacitor shunting the AM signal across the receiver's input, and across the antenna connection. There are many cars today that have amplifiers mounted in the base of their AM antennas. Those "amplified antennas", like in even VWs will work OK even with a lower impedance coax to the receiver. The antenna doesnt need to be on the top of the building. It only needs to be outside, as you know. The cost of the entire radio and antenna amplifier from a wrecked VW is probably affordable in Detroit. I have aQST article that deal with this "amplified AM antennas" subject. I thought it was best to wait for sofasurfer's response before my writing alot about the theory and/or details. Jerry Article: 218636 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <90f46$43528818$52ad139c$15540@news.versatel.nl> Subject: Re: rf-systems WFL antenna? Date: Sun, 16 Oct 2005 17:56:50 -0400 Message-ID: <17958$4352ccea$97d558d8$28903@ALLTEL.NET> Especially since oxygen free is another term for pure copper. "Ralph Mowery" wrote in message news:r9y4f.17193$q1.9848@newsread3.news.atl.earthlink.net... > > "johan aeq" wrote in message > news:90f46$43528818$52ad139c$15540@news.versatel.nl... > > Hello, > > can you explain this antenna mentioned on this site? > > http://www.universal-radio.com/catalog/hamwire/2039.html > > A almost flat swr response with such a small antenna must be a folded T2FD > > antenna. > > Is there someone who has tested this antenna? > > Greetings Johan PE1AEQ > > > > It sounds like someone is trying to sell junk at a high price. Unless the > price is also for the supporting poles. Oxygen-free copper wire sounds like > the HI-FI boys and their Monster Wire are at it again. > > Article: 218637 of rec.radio.amateur.antenna From: "Asimov" Subject: Non Radiative Energy Message-ID: Date: Sun, 16 Oct 2005 22:06:33 GMT Hi, Please, somebody explain the following to me: / What will be the next great invention on the order of the laser? We don't know, but clever new ideas keep coming along. The second-place award in the technological innovation competition went to Marin Soljacic (MIT) for his concept of wireless, non-radiative energy transmission. Just as in the quantum case in which the Schrodinger equation allows for a wave trapped in a box to tunnel out, so Maxwell's equations allow for the leakage of electromagnetic energy from an electromagnetic resonance object. If another such object were placed not far from the first one, and the resonant frequencies of both were the same, then the energy could be transferred between them with very little energy lost to other objects in the nearby environmental that do not share the same resonant frequency. The transmitted energy, although electromagnetic in nature, would not be referred to as "radiation" since it is bound to the resonant objects. It is rather an example of "near-field" physics. Soljacic avoids words like "antenna," since the process does not involve broadcasts of energy in the usual sense. In contrast, the vast majority of energy radiated by antennas is typically wasted and lost into free space, while only a small portion is picked up by the eventual receivers. Instead, Soljacic uses terms like "source" and "drain" in analogy with transistors to describe the movement of energy. An exemplary setup might consist of a transmitter in a ceiling and devices in that room (e.g robots, or computers) being powered wirelessly by this energy. / A*s*i*m*o*v ... Light at the end of the tunnel may be an oncoming train! Article: 218638 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Doublet Antenna question Message-ID: References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> <3pn5l1ddt24q9lln2osdqlu9bdca5862j5@4ax.com> Date: Sun, 16 Oct 2005 23:45:42 GMT On Sun, 16 Oct 2005 16:21:31 -0700, Wes Stewart wrote: > >Hmmm. > >Duffy (http://www.vk1od.net/G5RV/) says, see Cebik >(http://www.cebik.com/wire/g5rv.html) > >Cebik (http://www.cebik.com/wire/g5rv2.html) says, see Duffy >(http://www.vk1od.net/G5RV/) > > >I'm going around in circles. :-) Wes, A bit of mutual citation, bit obvious isn't it when there isn't some indirection like a few intermediate authors / articles! Nevertheless, LB Cebik deals more with patterns, and I deal more with the feed system, and of course the big picture means considering them both. I happily link to LB for people to read some useful info on the other aspect. Is that too cosy for you? More importantly, if you found any faults with my analysis, let me know? Owen -- Article: 218639 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> Message-ID: <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> Date: Mon, 17 Oct 2005 00:04:18 GMT Cecil Moore wrote: > And if you will remember, the original question didn't involve the > SWR meter at all. The question was: Are my 2-foot sections of RG-400 > connected to my SWR meter long enough to ensure that the SWR meter > reading is valid for the coax? Remember that argument? > > The threads for the past few days have all diverged from that > original question which was: > > How long must the 50 ohm coax connected to the SWR meter be > for the SWR meter to report a valid SWR *on that coax*? The > answer obviously cannot be zero length. Cecil, What has become quite clear from this lengthy thread and the experiments reported is that what you seek is impossible. The design and physical configuration of the Bird 43, and probably most or all simple SWR meters, is such that the measurement is completely unaware of the external "environment". The Bird 43 correctly reports system mismatch, such as that from a load that differs from 50 ohms, but it ignores any artificial mismatch from the adjacent coax. A report of the valid SWR *on that coax* will happen only by coincidence. The meter does not care about the length. Zero is just as good an answer as any other length. And who would really care to know such a thing? The unknown of interest is generally a load or matching device, not the improper coax. If you really need to know the "valid SWR" on the mismatched coax you are going to need a different technique and instrument. 73, Gene W4SZ Article: 218640 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> Date: Mon, 17 Oct 2005 00:05:18 GMT On Sat, 15 Oct 2005 00:40:34 GMT, "W3JDR" wrote: >Recently, it has become quite easy to do true RMS measurement at audio >frequencies using DSP techniques. In fact at audio you can even do an >accurate RMS measurement in DSP using a PIC microcontroller to sample the >signal and perform the calculations. I mentioned in an earlier post that I had done some comparisons of true RMS response based SINAD measurements and average responding meters. I have just rerun the test. I have a receiver with 2400Hz wide IF , fed with SSG and connected to a HP334A Distorion Analyser. I have adjusted the SSG for 12dB indicated SINAD on the HP334A. The HP334A's meter is boldly labelled RMS, but it is an average responding meter scaled for RMS with a sine wave. I measured the output from the HP334A using a no-name true RMS voltmeter that covers the audio frequencies involved (trap there... some dont make it past power frequencies), and measured SINAD of 11.3dB. I connected the HP334A output to a PC running FSM and measured the following figures for Vtotal and Vfiltered total filtered V Average 2708 679 V RMS 2753 763 V Peak 4287 2302 (The three detectors in FSM are all calibrated to read the same on a sine wave.) The FSM measurements indicate a SINAD of 11.1dB RMS responding and 12dB average responding. Overall, the two / three methods are reasonably consistent indicating around 12dB SINAD using an average response meter, and around 11.2 dB using RMS responding meters. That suggests to me that using an average responding instrument may overestimate the SINAD by a little less than a dB. However, given the statistical variance of the noise, I would not be fretting about it, especially on an FM rx where it might only need a smaller change in C/N for that SINAD change. I connected the rx to a Motorola R1013A which indicated 12dB SINAD (it is most unlikely to have an RMS responding ALC and meter). Owen -- Article: 218641 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: Message-ID: Date: Sun, 16 Oct 2005 20:18:37 GMT Ed wrote: > My QUESTION(s): How effective would a balanced fed dipole of about > 100 feet length be on 75M ? Make it 102 ft. and you will have the G5RV length about which virtually everything in the world is known. It works so well on 75m that you should not be able to notice the difference. How easy/hard it is to match will depend upon the feedline length. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218642 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: "Fan" Full Wave Loops? References: <96r5l15hkrp526ose6g5prisrnkpdjmij7@4ax.com> Message-ID: Date: Sun, 16 Oct 2005 20:16:44 -0500 Hi Bill Well I quite happily ran a 6M loop inside a 15M one. Seperate feedpoints etc. In my case I was trying to use the same mounting points (trees). I didnt check how effective they were but the TX was happy and I spoke to people on them!. Used 75r Q sections on each. The 40 vs 80 might have some detuning effect on 40M and major pattern change due to the harmonic relationship. You can always try modelling it.. Cheers Bob VK2YQA Bill Cherepy wrote: > > During a discussion of loops someone asked me if you can have a full > wave 40 meter loop inside a full wave 80 meter loop and I don't know > the answer. Anyone? Article: 218643 of rec.radio.amateur.antenna From: Bob Miller Subject: More BPL... Message-ID: Date: Mon, 17 Oct 2005 02:20:23 GMT Dang, dang, dang... http://www.nytimes.com/2005/10/17/technology/17powerlines.html bob k5qwg Article: 218644 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: "Fan" Full Wave Loops? Date: Sun, 16 Oct 2005 21:27:20 -0500 Message-ID: <23479-43530C08-798@storefull-3257.bay.webtv.net> References: <96r5l15hkrp526ose6g5prisrnkpdjmij7@4ax.com> Bill Cherepy wrote: "---can have a full wave 49 meter loop inside a full wave 80 meter loop---?" Bill Orr, W6SAI wrote a book, "All About Cubical Quad Antennas". One topic is "Concentric Quad Antennas" starting on page 49. Bill Orr says: "Interaction between the antennas of a two-band Quad is quite low." Orr suggests separate feedlines for each antenna and making feedline lengths odd multiples of a 1/4-wave so that the open-circuit of the unused feedline will appear as a short-circuit at its antennas resonant frequency at its feedpoint. Thus the unused assembly won`t likely respond much at other frequencies. Of course, antennas have a second resonance at about double their first resonant frequency. Having the open end of the unused feedline available, one could deliberately detune the second antenna to reduce interaction. Best regards, Richard Harrison, KB5WZI Article: 218645 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: Message-ID: Date: Mon, 17 Oct 2005 02:44:54 GMT >> Ed wrote: >> My QUESTION(s): How effective would a balanced fed dipole of about >> 100 feet length be on 75M ? > Make it 102 ft. and you will have the G5RV length about which > virtually everything in the world is known. It works so well > on 75m that you should not be able to notice the difference. > How easy/hard it is to match will depend upon the feedline > length. Thank you, Cecil. Very few here responded to my questions the way I had hoped, although there was some very good info in those responces. I had wondered what the effect of inductance in the dipole legs would have on a balanced fed antenna. It now appears that to get decent results on 75M I don't need to do that, anyway. I had not thought much about adding dropping wires to the ends of my dipole legs, as one fellow suggested, because the trees are so conical shaped that their lower branches would likely be in the way of the vertical wires coming down off the ends. I guess I need to research the G5RV antenna. Someone else here posted a nice URL to a site on it and I will be perusing it more. Cecil, I definitely can make my dipole 102 feet accross the top. I am guesstimating that I will need approximately 35 or 40 feet of feedline >from the shack to the feedpoint. Do you see any issues with that? Ed K7AAT Article: 218646 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: Message-ID: Date: Mon, 17 Oct 2005 02:48:13 GMT > If those bands on the old antenna were already resonant, and they > matched, then you didn't need 450 Ohm ladder line. > > If you are going to use 450 Ohm ladder line on a generic doublet, it > stands to reason you won't be resonant much anywhere (or you don't > count on it) and you anticipate tuning and use this line for low loss. Thanks, Richard. My main concern was that trying to tune a 100 foot dipole on 75M might cause problems due to the dipole being shorter than halfwave on 75M. From what I am now concluding from your comments, and others', this probably won't be an issue? Ed Article: 218647 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 02:52:44 GMT ). > > It turns out that it becomes quite challenging to implement an > efficient feed system (especially over a wide frequency range) where > the dipole is less than about 35% of a wavelength at the lowest > frequency. Yes, my 100 foot length would be about 42% ofthe wavelength of my lowest operating band, 75M.... perhaps it wouldn't be any problem for my cheap MFJ balanced line tuner to feed it? I appreciate your comments. I'm off shortly to study the website you pointed me to. Thanks. Ed K7AAT Article: 218648 of rec.radio.amateur.antenna Subject: Re: Dumb Antenna Questions From: Ed References: <1129516505.077205.187460@g49g2000cwa.googlegroups.com> Message-ID: Date: Mon, 17 Oct 2005 03:00:55 GMT > Hey. I'm newly licensed tech (studying for General). I looked up > my questions in Handbook but could not find info. I am construct- > ing a dipole antenna for 15 Meters from insulated 18 guage battery > wire from the auto parts store. Since I will be going QRP for the > first weeks or month, I am not worried about power handling > capacity. But, will I have to upgrade my wire when I go to 50 > or 100 watts output? Also, I have a question about the insulated > wire: is the insulation an impediment to the functioning of the > antenna on HF? Thanks for being patient with a newbie. > Short answers: 18 guage will handle 100 watt transmitter. Insulated wire will provide no discernable effect to your antenna performance. Ed K7AAT Article: 218649 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> Date: Mon, 17 Oct 2005 03:09:11 GMT On Mon, 17 Oct 2005 00:05:18 GMT, Owen Duffy wrote: This is seriously bad, replying to one's own post... but. It occurs to me a quick test to reveal whether a SINAD meter is RMS responding or average responding is to test it with a 1KHz square wave. I am not suggesting this as a cal procedure, just a test that is more sensitive to the meter response than noise testing. IIRC, the Taylor series coefficients for a square wave are: all even harmonics are 0, the others are 4/pi/n. So, theoretically: - an ideal average responding meter should read (1-2/pi)% which is 36.3% or 8.8dB on an perfect square wave; - an ideal RMS responding meter should read (1-(2^-0.5*4/PI())^2)^0.5*100% which is 43.5% or 7.23dB. Does the maths make sense? I observe that my R1013A indicates 9dB on a good square wave, and the HP334A around 35% (9.1dB)... so another indication that they are average responding. I expect the readings a little low because neither instrument has infinite bandwidth. Owen -- Article: 218650 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: What is a 50-ohm environment. ??? Date: Sun, 16 Oct 2005 22:40:05 -0500 Message-ID: <4152-43531D15-65@storefull-3254.bay.webtv.net> References: <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> Gene, W4SZ wrote: "The unknown of interest is generally a load or matching device, not the improper coax." Bird says: "The Model 43 THRULINE Directional Wattmeter is a portable insertion-type instrument which accurately measures forward or reflected power in coaxial transmission lines under any load condition." I accept the above description as I`ve seen confirmation under many conditions. Bird also says: "Line section: The line section is a high precision 50 ohm coaxial air line designed for transmission line insertion between the transmitter and the antenna or load. A socket is provided in each line section for the plug-in element with the desired power rating and frequency range." The width of the instrument including connectors is given as 4.25 inches. This makes the preciaion coax section longer than its width or spacing. I conclude from this that it is capable of enforcing its 50 ohms. Bird mentions cable lengths in regard to VHF measurements. They suggest that insertion and removal of the 43 with random length cables attached may affect the load match unless it is made exactly a total of 1/2-wavelength. In the 1/2-wave case, insertion and removal have no effect on the load match. I`ve done this countless times and attest to its effectiveness. If there were other possible problems with Bird cable lengths, they would have appeared during the past 50 years and been reported. Best regards, Richard Harrison, KB5WZI Article: 218651 of rec.radio.amateur.antenna From: "Hal Rosser" References: <96r5l15hkrp526ose6g5prisrnkpdjmij7@4ax.com> Subject: Re: "Fan" Full Wave Loops? Message-ID: Date: Mon, 17 Oct 2005 00:09:14 -0400 "Bill Cherepy" wrote in message news:96r5l15hkrp526ose6g5prisrnkpdjmij7@4ax.com... > During a discussion of loops someone asked me if you can have a full > wave 40 meter loop inside a full wave 80 meter loop and I don't know > the answer. Anyone? > > Bill Cherepy > Grayson, GA Many folks use that loop and a tuner for multiple band operation, and therefore the smaller loop would not be needed. Article: 218652 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: Message-ID: Date: Mon, 17 Oct 2005 04:25:45 GMT Ed wrote: > Cecil, I definitely can make my dipole 102 feet accross the top. I > am guesstimating that I will need approximately 35 or 40 feet of feedline > from the shack to the feedpoint. Do you see any issues with that? That's a very good length for 40m, 17m, & 10m. You can analyze the antenna yourself by downloading the free demo version of EZNEC >from www.eznec.com. If you want, I'll send you a model of your antenna so all you have to do is click the mouse. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218653 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: Message-ID: Date: Mon, 17 Oct 2005 04:29:23 GMT Ed wrote: > My main concern was that trying to tune a 100 foot dipole on 75M > might cause problems due to the dipole being shorter than halfwave on > 75M. From what I am now concluding from your comments, and others', > this probably won't be an issue? Walter Maxwell of "Reflections" fame recommends a minimum length for a dipole of 3/8 wavelength. 102 ft is 3/8 wavelength on about 3.6 MHz so it should and does work well. That's the length of my dipole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218654 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Non Radiative Energy Date: Sun, 16 Oct 2005 23:57:18 -0500 Message-ID: <26930-43532F2E-878@storefull-3253.bay.webtv.net> References: Asimov wrote: "The transmitted energy, although electromagnetic in nature, would not be referred to as "radiation" since it is bound to the resonant objects." A mistaken idea is expressed above. Radiation happens from conductors carrying radio frequencies. Radiation escapes. That`s a definition of radio. It`s the energy that gets away. It may be hard to contain. When a conductor is swept by r-f, the current which flows upon or within a conductor depends on its impedance. Unless the conductor is without significant reactance, little current flows. A resonant, and low-resistance conductor may have a large current flow, depeending also on the strength of the electromagnetic (r-f) field. Induced current on a conductor will all be re-radiated if there is no loss to a load or heat conversion. There is coupling between source and receiving conductors. A synonym is mutual impedance. Maximum available power out to a load on an antenna is 50% of that captured. The other 50% is lost in the antenna`s source impedance (its radiation resistance). In other words, it is re-radiated. Mutual impedance does not trap energy on or in a conductor or limit excitation of multiple conductors. Necessity is said to be the mother of invention. Identify the greatest needs and you may forecast some invention. Best regards, Richard Harrison, KB5WZI Article: 218655 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> Date: Mon, 17 Oct 2005 05:09:06 GMT On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: >So, theoretically: >- an ideal average responding meter should read (1-2/pi)% which is >36.3% or 8.8dB on an perfect square wave; I think this is close to the right answer, but for the wrong reason. I think it needs to be evaluated iteratively, and I get an answer closer to 34.3% or 9.3dB. Owen -- Article: 218656 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL... Date: Mon, 17 Oct 2005 10:46:02 +0000 (UTC) Message-ID: References: In article , Bob Miller wrote: > Dang, dang, dang... > > http://www.nytimes.com/2005/10/17/technology/17powerlines.html They laughed at me when I asked them to boycott Google. Now it's come home to roost. Current Communications is funded partily by Google. I hate being right. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (077)-424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Support the growing boycott of Google by radio users and hobbyists. It's starting to work, Yahoo has surpassed Google. Article: 218657 of rec.radio.amateur.antenna From: Richard g4tut Subject: Free Competition - Win an Icom IC-V82 Date: Mon, 17 Oct 2005 11:59:42 +0100 Message-ID: There is a free competition running on the Southgate Amateur Radio Club's website. The prize is a brand-new Icom IC-V82 high-power handheld transceiver, kindly donated by Icom-UK Ltd To enter the competition, you just need to answer a simple question. The competition page can be found at: http://www.southgatearc.org/competitions/ic-v82.htm The competition closes on the 4th January, so there's plenty of time to get your entries in. You can make one entry per day. Good Luck! Daily Amateur Radio News Service http://www.southgatearc.org RSS News Feed http://www.southgatearc.org/sarc.rss Article: 218658 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: More BPL... Message-ID: <1ba7l1t78opgujf92ft4bbh3ieapqt7mcs@4ax.com> References: Date: Mon, 17 Oct 2005 13:40:22 GMT On Mon, 17 Oct 2005 07:36:01 -0400, Amos Keag wrote: >ARRL has recently reported quite acceptable compatibility results in >some BPL programs they have been testing. > >I forget the details, 68 years old and suffering from occasional 'old >timers disease', but the info should be available from ARRL. > >It is possible that acceptable BPL technology has arrived! > >AK Motorola has a system that uses the low voltage side of the pole transformer; supposedly, it has less interferance problems. bob k5qwg > >Bob Miller wrote: >> Dang, dang, dang... >> >> http://www.nytimes.com/2005/10/17/technology/17powerlines.html >> >> bob >> k5qwg Article: 218659 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL... Date: Mon, 17 Oct 2005 14:06:01 +0000 (UTC) Message-ID: References: In article , Amos Keag wrote: > ARRL has recently reported quite acceptable compatibility results in > some BPL programs they have been testing. > > I forget the details, 68 years old and suffering from occasional 'old > timers disease', but the info should be available from ARRL. > > It is possible that acceptable BPL technology has arrived! No. It's acceptable to the ARRL because they "notch out" the ham bands. This means that it interfers with everyone except ham radio operators so they wash their hands of it. What will happen is as people complain about interference from BPL, operators will move the frequencies it uses to avoid the complaints. If they bother at all, an engineer will take a portable radio to the site, pull up the antenna and listen. If he does not hear English, he'll log that there is nothing to prevent them moving the notch there and that frequency will be used. Since HF propigation changes from hour to hour and day to day, a frequency can still be in use but he wouldn't notice it. Eventually due to demand and no one complaining too loudly all frequencies in the HF band will be in use. By that time no one will listen to the few hams that complain. My experience with a starting a Google boycott shows me that hams really don't care. The operator of one very popular site dedicate to ham radio and I discussed it and he said that they could not afford to eliminate the "Ads by Google" and gave me a polite rationalization of why they should do nothing. This is called the boiled lobster effect. A lobster placed in a pot of cold water will be happy for the change. As the pot gets warmer the lobster gets drowsy. By the time the water gets hot enough to cook it, the lobster has been lulled into oblivion. That's what will happen with BPL. It's already started. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (077)-424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 You should have boycotted Google while you could, now Google supported BPL is in action. Time is running out on worldwide radio communication. Article: 218660 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: Message-ID: Date: Mon, 17 Oct 2005 14:58:36 GMT Fred W4JLE wrote: > A G5RV would fit and meet your needs for all band operation with a tuner. Hi Fred, The standard G5RV is a pretty good antenna for 80m, 40m, 20m, & 12m. Not bad on 15m, but the SWR on the coax for 30m, 17m, & 10m is greater than 40:1 according to EZNEC. I have optimized my G5RV for 40m, 17m, & 10m operation by making the series balanced section 36 feet of 450 ohm ladder-line. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218661 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 15:28:36 GMT Owen Duffy wrote: > Cecil Moore wrote: >>Actually, upon closer examination, the definition of "myth" >>proves the above is NOT a myth. It is not a traditional story. >>It is not a parable allegory. It is not a popular belief. >> >>So, no Owen, it is not a myth. > > Cecil, this is the opposite to your stated YES opinion just three > hours ago. Yes, when I'm wrong about something, I change my mind. What do you do when you are wrong about something? Your "myth" is false but it doesn't rise to the definition of a myth so *YOU WERE ABSOLUTELY WRONG TO CALL IT A MYTH*. I was wrong but so were you, so we're even. Get it? If not, close your eyes and concentrate on your legs. :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218662 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 15:53:45 GMT Owen Duffy wrote: > The article is at http://www.vk1od.net/G5RV/ . Owen, that's the best G5RV article I've ever seen. When anyone has questions on the G5RV, I'm going to point them to that article. However, it does contain an error. You say: " ... it ... does not have acceptable feed performance on any WARC bands" Yet your own SWR data shows a low SWR point at 25 MHz. The G5RV actually has a lower SWR on the coax on 24.95 MHz than it does on 21.3 MHz according to EZNEC. Also, someone is preparing an article showing how length selection of the "matching section" using relays can transform the G5RV into a truly all-HF-band antenna requiring no tuner. After that article is published, it would be nice if you included that information in your article. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218663 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> <3pn5l1ddt24q9lln2osdqlu9bdca5862j5@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 16:05:54 GMT Owen Duffy wrote: > More importantly, if you found any faults with my analysis, let me > know? Just found one and replied to your posting. You and Cebik seem to disagree about 12m where you say it won't work on any WARC band and he says the impedance at the twinlead/coax junction is "Resistive (90-100 Ohms)", i.e. SWR=2:1 -- 73, Cecil http://www.qsl.net/w5dxp Article: 218664 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Mon, 17 Oct 2005 16:27:33 GMT Gene Fuller wrote: > What has become quite clear from this lengthy thread and the experiments > reported is that what you seek is impossible. Not true. The question has been answered and it surprised me. Only a half inch or so of ordinary 50 ohm coax is required to ensure the SWR on that half inch of coax is the same as the SWR reported by the SWR meter. I didn't ask the original question in a very understandable manner because I don't know of anyone who understood my original question. > And who would really care to know such a thing? History: Reg and I were arguing about a year ago whether two feet of RG-400 was long enough to ensure that the SWR reported by the SWR meter was the same as the SWR on the RG-400. I said it was but had no references that covered the subject so had no proof. There was no answer to my question forthcoming from this newsgroup at the time, so I asked the question over on sci.physics.electromag. I received an answer on that newsgroup but, unfortunately, didn't question the math. The answer was one foot of RG-213 but the answer was off by a magnitude due to an accidental shift in a decimal point. The correct answer was about an inch to reduce the undesired mode by a factor of 1/e^5, i.e. 1/0.2=5 where 0.2 is the conductor spacing, e.g. estimated for RG-213. The error was caused by using 2" instead of 0.2" as the conductor spacing. I mistakenly ran with the one foot answer but, wrong as it was, proved that my two feet of RG-400 was long enough. Now Dave has set the record straight and caused the decimal point error to be exposed by Owen and me at about the same time. The correct answer is surprising to me. 1/2 inch of ordinary 50 ohm coax is enough to ensure a 50 ohm environment in that 1/2 inch piece of coax, i.e. to ensure Vfor/Ifor=Vref/Iref=50. Nobody else may care, but I learned a lot and thank everyone who contributed. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218665 of rec.radio.amateur.antenna From: chuck Subject: Re: What is SINAD? References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> Message-ID: <1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net> Date: Mon, 17 Oct 2005 16:39:25 GMT Hello Owen, Seems both average-responding and trms meters use rectifiers, so a square wave input with perfect symmetry should result in BOTH meters reading the same: an amount equal to the peak square wave voltage. Am I confused on this? Chuck Owen Duffy wrote: > On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: > > > >>So, theoretically: >>- an ideal average responding meter should read (1-2/pi)% which is >>36.3% or 8.8dB on an perfect square wave; > > > I think this is close to the right answer, but for the wrong reason. I > think it needs to be evaluated iteratively, and I get an answer closer > to 34.3% or 9.3dB. > > Owen > -- Article: 218666 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mythbusters: V/I ratio is forced to Z0 References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2gp3l11c0si7aepeh2v3cblp6t2cvfhalr@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 17:07:44 GMT Dave wrote: > hey cecil, what happened??? worldradio pull your 'series' after only one > installment? Katrina was a monster hurricane whose effects extended all the way to California. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218667 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: What is a 50-ohm environment. ??? Date: Mon, 17 Oct 2005 17:41:12 +0000 (UTC) Message-ID: References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> "Cecil Moore" wrote > I mistakenly ran with the one foot answer but, wrong as it was, > proved that my two feet of RG-400 was long enough. ======================================= Cecil, bearing in mind Lord Kelvin, can you say what the error in the measured value of the SWR, or the reflection coefficient, would be if the (sufficient) two feet of RG-400 was reduced to 1" inch. ---- Reg. Article: 218668 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <440rk1pg559akgta2q4d38s4le3noihnp8@4ax.com> <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Mon, 17 Oct 2005 18:49:49 GMT Reg Edwards wrote: > "Cecil Moore" wrote >>I mistakenly ran with the one foot answer but, wrong as it was, >>proved that my two feet of RG-400 was long enough. > > Cecil, bearing in mind Lord Kelvin, can you say what the error in the > measured value of the SWR, or the reflection coefficient, would be if > the (sufficient) two feet of RG-400 was reduced to 1" inch. According to Dave's calculations, 1" of 50 ohm coax will result in a negligible error in the SWR on that 1" of coax. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218669 of rec.radio.amateur.antenna From: Cecil Moore Subject: Mythbusters: The G5RV on 12m Message-ID: Date: Mon, 17 Oct 2005 18:55:47 GMT The myth: "Contrary to oft stated views, the Classic G5RV is not an all band antenna, it: does not have acceptable feed performance on any WARC bands;" Quoted from: http://www.vk1od.net/G5RV/ 12m is a WARC band. The standard G5RV performs very well on 12m band. Therefore, the above statement is a myth. (Hey, this silly myth game is actually fun.) :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218670 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> <0ms7l19namqav259vsnpgmrm1oc37e8vul@4ax.com> Message-ID: Date: Mon, 17 Oct 2005 19:13:38 GMT Richard Clark wrote: > Cecil Moore wrote: >>According to Dave's calculations, 1" of 50 ohm coax will >>result in a negligible error in the SWR on that 1" of coax. > > Negligible for you, is brighter than the sun for everyone else. When reflections are completely canceled, appear to have disappeared from everyone else's sight, and you say they are brighter than the sun (for you), who am I to argue? You have created your own unreality and everyone who understands the physics of 1/4WL thin-films in this universe laughs at you every time you post that "brighter than the sun" nonsense. In your calculations, you superposed powers which is not a valid thing to do and you apparently haven't even comprehended the error of superposing powers. > No numbers, hmm? Dave provided the numbers. Check his posting. Simply stated: The unwanted mode is attenuated by 1/e with each increment of length equal to the spacing between the two conductors. If the conductor spacing is 0.1", the unwanted mode is down to 0.00000001% in one inch. That's a big surprise to me but I don't see any reason not to believe it. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218671 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Mon, 17 Oct 2005 13:33:51 -0500 Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> "Richard Clark" wrote in message news:0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com... > On Fri, 14 Oct 2005 13:08:22 -0500, "Steve Nosko" > wrote: > > >A meter, a pure 1kHz tone modulated signal generator and a 1kHz notch is all > >that is needed. What happens if you don't have a "real" RMS meter? I don't > >know. > > Hi Steve, > > You don't need a "real" RMS meter. The expressed requirement for a > pure 1kHz tone provides the necessary sine wave shape such that it > simply becomes a matter of scale calibration. If you had said a > square wave 1KHz tone (nothing pure about that), then you would have > to dig deep for a "real" RMS meter. That too, could be scaled, but I > wouldn't count on it because it would be a rare amplifier chain that > could faithfully keep it square - and the notch would inject it into > the measurement as distortion and noise. > > 73's Hi Richard, I don'r know about that. For the un-notched signal, yes, where the dominant component is the sine wave. However, not knowing how a non-RMS meter may respond to the notched-out (predomanantly noise) signal, I'd thing there is a possible cause for error compared to an RMS meter. 73, Steve, K,9.D;C'I Article: 218672 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Mon, 17 Oct 2005 13:42:00 -0500 Message-ID: References: "Owen Duffy" wrote in message news:sg40l11o0pfd08f8jlmtefpmeclb141km7@4ax.com... > On Fri, 14 Oct 2005 13:08:22 -0500, "Steve Nosko" > wrote: > > >Owen, (& crb) > > Your words are contrary to the way we measured it (Motorola). ... > > It was a shabby description in my first post Steve, ...with considerable clarification... > Yes, I didn't mention that the 1KHz tone needs to be relatively low > distortion. ... > frequency of the tone is important as the notches > in semi automatic instruments are typically +/10Hz or so, ... > Owen Not only that, but 1kHz is important because it is the standard and usiang another freq, say 2kHz puts is on another part of the de-emphasis curve and numbers'll change. 73, Steve, K,9.D;C'I Article: 218673 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? RE:Qiock test Date: Mon, 17 Oct 2005 14:01:41 -0500 Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> "Owen Duffy" wrote in message news:fn46l1hajq1vpmcfulj87k38a1nt5vgdaf@4ax.com... > On Mon, 17 Oct 2005 00:05:18 GMT, Owen Duffy wrote: > > This is seriously bad, replying to one's own post... but. > > It occurs to me a quick test to reveal whether a SINAD meter is RMS > responding or average responding is to test it with a 1KHz square > wave. I am not suggesting this as a cal procedure, just a test that is > more sensitive to the meter response than noise testing. > > IIRC, the Taylor series coefficients for a square wave are: all even > harmonics are 0, the others are 4/pi/n. > > So, theoretically: > - an ideal average responding meter should read (1-2/pi)% which is > 36.3% or 8.8dB on an perfect square wave; > - an ideal RMS responding meter should read > (1-(2^-0.5*4/PI())^2)^0.5*100% which is 43.5% or 7.23dB. > > Does the maths make sense? Wait a minute here. You're percents and dB is confusing. I don't know about the 1-2/pi. It's been about a year or so since I went through all this for that QST article using a serise resistor in the power line to figure out power supply (and rig) power consumption - unfortunately ignoring the pulsed nature of capacitor input power supply current, BUT... I don't remember the analytical expressions for these quantities. I'll use the common numbers... For the meter that responds to average (63% peak - I think this is 2/pi) , but shows RMS which is .707 of peak (1/root2), the ratio for average input to reading = 0.707/.63 . For this I get 2/(2* root2) Average of a square wave is equal to the peak. So a 1 volt (pk) square wave should measure 1.11 Volts on one of these (sine average responding, RMS displaying) meters and 1V on an rms meter. I think I did that right? 73, Steve, K,9.D;C'I Article: 218674 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Mon, 17 Oct 2005 14:05:44 -0500 Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> <1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net> Nope. See my previous post. A square wave has an average equal to the RMS equal to the peak. It's just like DC. The "older types" RESPOND to average of a SINE (63% of peak) but display the value for the RMS (71% of peak), so they have a 1.11 correction factor to get from average to RMS. 73, Steve, K,9.D;C'I "chuck" wrote in message news:1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net... > Hello Owen, > > Seems both average-responding and trms meters use rectifiers, so a > square wave input with perfect symmetry should result in BOTH meters > reading the same: an amount equal to the peak square wave voltage. Am I > confused on this? > > Chuck > > Owen Duffy wrote: > > On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: > > > > > > > >>So, theoretically: > >>- an ideal average responding meter should read (1-2/pi)% which is > >>36.3% or 8.8dB on an perfect square wave; > > > > > > I think this is close to the right answer, but for the wrong reason. I > > think it needs to be evaluated iteratively, and I get an answer closer > > to 34.3% or 9.3dB. > > > > Owen > > -- Article: 218675 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is so special about '12 dB' SINAD? Date: Mon, 17 Oct 2005 14:14:49 -0500 Message-ID: References: Let me try my hand at this... "crb" wrote in message news:diq2l9062i@enews4.newsguy.com... > Still not sure what it is. > > I know I do a test at work where I put in a 3 KHz deviated, 1 KHz tone > into the FM receiver port while probing an audio point going to the > SINAD port on the test equipment. > Increasing the input level makes for a larger SINAD value (which makes > sense) Looking for at least 12 dB SINAD. > What is so special about 12? > > Can't get my mind around it. Is the test tone 12 dB stronger than noise > + distortion? That's the simplest way to look at it. The desired signal (tone) is (approximately) 12 dB above the junk. > Is the the input value in dBm on the test equipment the sensitivity of > the receiver at 12 dB SINAD. Yep. That's it! The INPUT level, which gives this special output condition, IS the sensitivity. When measuring sensitivity, you need some kind of a reference point and the signal to noise ratio at the receiver output (after a fashion) is what is used here. . If I recall correctly, way back, AM receiver sensitivity was the input signal (with some standard modulation) which produced the rater power output (audio) with the volume cranked all the way up. Article: 218676 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> <1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net> Date: Mon, 17 Oct 2005 19:50:10 GMT On Mon, 17 Oct 2005 16:39:25 GMT, chuck wrote: >Hello Owen, > >Seems both average-responding and trms meters use rectifiers, so a >square wave input with perfect symmetry should result in BOTH meters >reading the same: an amount equal to the peak square wave voltage. Am I >confused on this? Leaving aside the rectifier point which is arguable: If we accept that the RMS responding instrument reads correctly on all types of waveforms, the issue is with the average responding instrument. The average responding instrument is (usually) calibrated for the form factor of a sine wave, and its scaling in RMS is only valid for waveforms with the same form factor. There are two cases to consider, the square wave, and the square wave with the fundamental removed. The form factor of both are different to the form factor of a sine wave, and more importantly to each other, so the average responding meter does not provide an accurate ratio of the (true) power of each wave. Does that make sense? Owen -- Article: 218677 of rec.radio.amateur.antenna From: "Frank's" References: <22x4f.15263$vw6.6978@newsread1.news.atl.earthlink.net> Subject: Re: What is SINAD? Message-ID: Date: Mon, 17 Oct 2005 20:06:16 GMT "chuck" wrote in message news:22x4f.15263$vw6.6978@newsread1.news.atl.earthlink.net... > Thanks for the info, Frank. > > Actually, the RSS125 on the site doesn't contain the procedure, but > RSS181, also available at that site, does. > > FWIW, the procedure is basically what has been discussed, except that > the signal generator output to be recorded as the receiver's sensitivity > is that level which produces a 12 dB SINAD at 50% of rated audio output! > Probably a more realistic test than allowing the AF stage to operate at > a low-distortion level of something like 1% of rated output. > > 73, > > Chuck > NT3G Thanks Chuck, forgot all about RSS 181, even though I have type approval tested countless SSB transceivers to that specification. Interesting that it has not been updated since 1971. Note that he sensitivity is defined as that input that will produce 12 dB SINAD or that input which will produce at least 50% of the rated audio output. The fact is that most of the testing that I did was measured at full audio output, just below the threshold of audio clipping. I do not recall any unit where the receiver gain was a factor in sensitivity. Also note they still refer to "A3j", and not J3E, etc. All these old specifications are based on tube designs. With TDA2002 type audio chips, you could typically get 5W out at < 1% distortion. It was so easy to drop in an extra IF stage if you could not meet the 50% min audio output at threshold sensitivity. 73, Frank Article: 218678 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is so special about '12 dB' SINAD? Date: Mon, 17 Oct 2005 14:21:16 -0500 Message-ID: References: "Fred McKenzie" wrote in message news:fmmck-1510051507490001@ac8a5544.ipt.aol.com... > In article , crb wrote: > > > > Years ago sensitivity might have been measured using a "20 dB quieting" > method. You would inject an unmodulated carrier and increase its level > until the noise output of the receiver decreased to one tenth of the > no-signal value. [...snip...] > > Isn't SINAD an acronym for "Signal In the presence of Noise And > Distortion"? I don't fully understand how it works, but assume there is a > 1 KHz filter feeding one channel that is compared to an un-filtered > channel. > What I want to know is how to build one. Does anyone know of any SINAD > construction articles? > 73, Fred, K4DII I for got about the 20 dBQ method. That's another reference for sensitivity on FM receivers. That's right Fred. It's explained up thread, but basically it is the ratio of the un-notched audio to the notched audio. The "audio" is the result a 1kHz FM modulation at 60% of rated system deviation. Originally, for 5kc ssytems dev., the 3kc deviation was 3.3kc. WHY is this at around 2/3 maximum? Well, in a well designed Tx, the deviation will get up to this level before the deviation limiting clipper starts to clip and cause distortion. 73, Steve 73, Steve, K,9.D;C'I Article: 218679 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: can I / can't I ? Date: Mon, 17 Oct 2005 14:22:08 -0500 Message-ID: References: "Reg Edwards" wrote in message news:dirroa$bcv$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com... > > > Any reason I shouldn't use a choke balun out of my tuner to feed > ladderline > > up to a dipole? > > ==================================== > > There's no reason whatsoever. In fact it is the obvious thing to do. > > The choke allows you to connect an unbalanced tuner to any balanced > feedline via the choke. > > A balanced tuner is entirely unnecessary in almost all circumstances. > > The choke is simply a pair of wires wound together around a ferrite > toroid. Or it is a coaxial pair wound round a toroid (which for > various reasons is slightly less efficient and is physically less > convenient.) So the pair of parallel wires is the better form of > construction. > > The choke behaves as a short length of transmission line of the same > length as the pair of wires wound on the choke. Which is very short > when a ferrite toroid is used. > > Because the length of line is an impedance transformer it transforms > the input impedance of the transmission line to somewhat different > values especially at the higher frequencies. At the lower frequencies > it may just as well not be there. > > Which means that the tuner L and C settings are different to those > which occur when the choke is not there. But often, when the choke is > in use, the tuner finds it easier to match the line and antenna to the > transmitter. Which is the sole purpose of the tuner. > > The number of turns wound on the choke must provide an inductance and > a reactance of about 4 or 5 times the load resistance required by the > transmitter, usually 50 ohms, at the lowest frequency of operation. > This depends on the permeability of the ferrite core material. > > At the higher frequencies it is best that the length of line wound on > the torroid should not exceed 1/8th of a wavelength at the free-space > velocity. This is usually not too difficult to manage. > > To simplify, get a 2" outside diameter ferrite ring, of HF grade > marerial, wind on 14 or 18 turns, and get on with it. > > A choke balun is the most simple of radio components to construct, yet > its behaviour is amongst the most complicated of components to > analyse. > ---- > Reg, G4FGQ. > > Article: 218680 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Doublet Antenna question Date: Mon, 17 Oct 2005 14:32:12 -0500 Message-ID: References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> No time to read all the other posts, but in short... You are proposing a slightly shorter than 1/2 wave dipole for 75. This should be no problem as it will have a little capacitive reactance and a tuner should handle it. The G5RV is pretty much the same thing, except it has some feed line gymnastics to get a "fairly good" (50 ohm) match on many bands. This is nothing more than an "antenna tuner in feed line" which doesn't require a knob rather than one in a box which does. (:-) My 40M dipole works on 30M as a slightly LONG dipole. [[ It also works on 75 as a really short one, but not too good]] 73, Steve, K,9.D;C'I "Ed" wrote in message news:Xns96F1CA3A2E987spectrumhogstarbandn@207.106.93.175... > ). > > > > It turns out that it becomes quite challenging to implement an > > efficient feed system (especially over a wide frequency range) where > > the dipole is less than about 35% of a wavelength at the lowest > > frequency. > > Yes, my 100 foot length would be about 42% ofthe wavelength of my > lowest operating band, 75M.... perhaps it wouldn't be any problem for my > cheap MFJ balanced line tuner to feed it? > > I appreciate your comments. I'm off shortly to study the website you > pointed me to. Thanks. > > > Ed K7AAT > Article: 218681 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Doublet Antenna question Message-ID: References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> <3pn5l1ddt24q9lln2osdqlu9bdca5862j5@4ax.com> Date: Mon, 17 Oct 2005 20:19:40 GMT On Mon, 17 Oct 2005 16:05:54 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> More importantly, if you found any faults with my analysis, let me >> know? > >Just found one and replied to your posting. You and Cebik >seem to disagree about 12m where you say it won't work on >any WARC band and he says the impedance at the twinlead/coax >junction is "Resistive (90-100 Ohms)", i.e. SWR=2:1 No, I said: "Contrary to oft stated views, the Classic G5RV is not an all band antenna, it: * does not have acceptable feed performance on 1.8MHz; * does not have acceptable feed performance on any WARC bands; * does not have acceptable feed performance on 28MHz." Two main factors were in my mind in determining whether performance was "acceptable", they were: - the magnitude of the losses on this particular model in-band for the band in question; and - whether the losses changed rapidly on adjacent frequencies, such that installations with small differences (eg height, earth parameters etc) were not assured of acceptable losses. For example, it is possible to tweak a G5RV a little to minimise the feed losses on 10.1MHz, and they can be low enough, but it is a very sharp notch and likely to be not realisable with seasonal changes in soil moisture etc. I have reviewed the specific case you mention about 25MHz. Two of the feed arrangments are marginally under the criteria that I set, but they are under it and for consistency they should have been included in the "acceptable" category. Omitting them was an error on my part. I have ammended the article accordingly Cecil, thanks for the feedback. It is important to keep in mind that the article is analysis of a set of common feed configurations of a dipole at a specific height over specific ground, and that the results may vary in other configurations. Owen -- Article: 218682 of rec.radio.amateur.antenna From: chuck Subject: Re: What is SINAD? References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> <1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net> Message-ID: Date: Mon, 17 Oct 2005 20:20:53 GMT You're correct, of course, Steve. I was thinking the average-responding meter was calibrated to display average levels, but it is not: it is calibrated to give the rms value of a true sine wave with that average value. So the only way to measure the average value of a non-sinusoidal ac signal is to use an average-responding meter and correct the displayed reading as you have noted. Not relevant to the SINAD discussion but interesting. Thanks for the clarification. Chuck Steve Nosko wrote: > Nope. See my previous post. > > > A square wave has an average equal to the RMS equal to the peak. It's just > like DC. > > The "older types" RESPOND to average of a SINE (63% of peak) but display the > value for the RMS (71% of peak), so they have a 1.11 correction factor to > get from average to RMS. > > 73, Steve, K,9.D;C'I > > > "chuck" wrote in message > news:1tQ4f.17557$q1.4729@newsread3.news.atl.earthlink.net... > >>Hello Owen, >> >>Seems both average-responding and trms meters use rectifiers, so a >>square wave input with perfect symmetry should result in BOTH meters >>reading the same: an amount equal to the peak square wave voltage. Am I >>confused on this? >> >>Chuck >> >>Owen Duffy wrote: >> >>>On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: >>> >>> >>> >>> >>>>So, theoretically: >>>>- an ideal average responding meter should read (1-2/pi)% which is >>>>36.3% or 8.8dB on an perfect square wave; >>> >>> >>>I think this is close to the right answer, but for the wrong reason. I >>>think it needs to be evaluated iteratively, and I get an answer closer >>>to 34.3% or 9.3dB. >>> >>>Owen >>>-- > > > Article: 218683 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Doublet Antenna question Message-ID: References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> <3pn5l1ddt24q9lln2osdqlu9bdca5862j5@4ax.com> <0857l15mdfh6ms7cnb1bvvk0j4s8cde2h1@4ax.com> Date: Mon, 17 Oct 2005 20:25:45 GMT On Mon, 17 Oct 2005 05:27:08 -0700, Wes Stewart wrote: >>A bit of mutual citation, bit obvious isn't it when there isn't some >>indirection like a few intermediate authors / articles! >> ... > >Clearly you have missed the humo(u)r that I intended. > Wes, I did take it as light hearted, and hence my response above. I am not an academic, nor do I have the experience of that university environment, but I think there is probably more than a little humour to be had from examples of self-citation, mutual-citation, self-citation indirectly by n levels (more subtle than mutual citation)... etc. Thing that had my head spinning was trying to follow the logic (I use the term loosely of course) of some recent threads. Owen -- Article: 218684 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Focused waves WAS: Non Radiative Energy Date: Mon, 17 Oct 2005 14:47:01 -0500 Message-ID: References: All just symmantics. HOWEVER... OT, but... For something that sounds too good to be true search on "Woody" Elwood G. Norris. I researched this and he has something here. Not previously unknown, just previously unused. HyperSonicTM Sound by Elwood G. Norris 6/07/97 73, Steve, K.9.D;C'I "Asimov" wrote in message news:MSGID_1=3a167=2f133.0_4352c300@fidonet.org... > Hi, > > Please, somebody explain the following to me: > > / What will be the next great invention on the order of the laser? We > don't know, but clever new ideas keep coming along. The > second-place award in the technological innovation competition went > to Marin Soljacic (MIT) for his concept of wireless, non-radiative > energy transmission. Just as in the quantum case in which the > Schrodinger equation allows for a wave trapped in a box to tunnel > out, so Maxwell's equations allow for the leakage of electromagnetic > energy from an electromagnetic resonance object. If another such > object were placed not far from the first one, and the resonant > frequencies of both were the same, then the energy could be > transferred between them with very little energy lost to other > objects in the nearby environmental that do not share the same > resonant frequency. The transmitted energy, although > electromagnetic in nature, would not be referred to as "radiation" > since it is bound to the resonant objects. It is rather an example > of "near-field" physics. Soljacic avoids words like "antenna," > since the process does not involve broadcasts of energy in the usual > sense. In contrast, the vast majority of energy radiated by > antennas is typically wasted and lost into free space, while only a > small portion is picked up by the eventual receivers. Instead, > Soljacic uses terms like "source" and "drain" in analogy with > transistors to describe the movement of energy. An exemplary setup > might consist of a transmitter in a ceiling and devices in that room > (e.g robots, or computers) being powered wirelessly by this energy. > / > > A*s*i*m*o*v > > > ... Light at the end of the tunnel may be an oncoming train! > Article: 218685 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? RE:Qiock test Message-ID: <3i28l1hk0af20tfkim7k3hmkss5kl5rtn8@4ax.com> References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> Date: Mon, 17 Oct 2005 20:36:58 GMT On Mon, 17 Oct 2005 14:01:41 -0500, "Steve Nosko" wrote: > >"Owen Duffy" wrote in message >news:fn46l1hajq1vpmcfulj87k38a1nt5vgdaf@4ax.com... >> On Mon, 17 Oct 2005 00:05:18 GMT, Owen Duffy wrote: >> >> - an ideal average responding meter should read (1-2/pi)% which is >> 36.3% or 8.8dB on an perfect square wave; In another post (1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com) I have identified that that expression is wrong. The correct ratios are closer to 34.3% or 9.3dB. > >Wait a minute here. You're percents and dB is confusing. Many Distortion analysers are calibrated in % where the % figure is a voltage ratio. > >I don't know about the 1-2/pi. It's been about a year or so since I went It is wrong, see above. >through all this for that QST article using a serise resistor in the power >line to figure out power supply (and rig) power consumption - unfortunately >ignoring the pulsed nature of capacitor input power supply current, > BUT... > >I don't remember the analytical expressions for these quantities. I'll use >the common numbers... > >For the meter that responds to average (63% peak - I think this is 2/pi) , >but shows RMS which is .707 of peak (1/root2), the ratio for average input >to reading = 0.707/.63 . For this I get 2/(2* root2) > >Average of a square wave is equal to the peak. > >So a 1 volt (pk) square wave should measure 1.11 Volts on one of these (sine >average responding, RMS displaying) meters and 1V on an rms meter. > >I think I did that right? The problem is that while the RMS meter provides a true power indication on the square wave, and the filtered square wave (ie without fundamental), the average responding meter does not give an accurate power ratio because the form factors (RMS/AVG) of the two waveforms is different. Owen -- Article: 218686 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> <3pn5l1ddt24q9lln2osdqlu9bdca5862j5@4ax.com> Message-ID: <2%T4f.17142$6e1.8319@newssvr14.news.prodigy.com> Date: Mon, 17 Oct 2005 20:40:30 GMT Owen Duffy wrote: > I have ammended the article accordingly Cecil, thanks for the > feedback. So one more myth is busted. You had me thinking that I was the only one capable of making a mistake. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218687 of rec.radio.amateur.antenna From: edard Subject: Help identifying tiny coax Date: Mon, 17 Oct 2005 15:46:59 -0500 Message-ID: <11l83bm3ihoavea@corp.supernews.com> I came across a spool of some very small coax in the hopes that it could be used in 802.11 but now not a clue of what it is. It is on a Raychem reel. The Description tag says 5028A1318-0 440086. As best I can measure it is 0.075 inch OD, 0.055 braid diameter, 0.040 insulation OD and the center conductor measures 0.015. The outer jacket is black and the inner insulation is tan in color. The braid is very dense fine wire as is the center conductor. It looks and feels like high quality stuff. Any help or even a good guess appreciated. Article: 218688 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: More BPL... Date: Mon, 17 Oct 2005 15:17:25 -0500 Message-ID: References: "Geoffrey S. Mendelson" wrote in message news:slrndl7bpl.9j0.gsm@cable.mendelson.com... > In article , Amos Keag wrote: > > ARRL has recently reported quite acceptable compatibility results in > > some BPL programs they have been testing. > > > > I forget the details, 68 years old and suffering from occasional 'old > > timers disease', but the info should be available from ARRL. > > It is possible that acceptable BPL technology has arrived! > > No. > It's acceptable to the ARRL ... Geoff., Your words not theirs. "They" (I'm in contact with "them") have reservations and are aware of the outside-notch problem. The advantage of this system (I'm not saying it's the solution or even a great idea, but an attempt to provide an alternative in light of the relentless push to do it regardless of interference potential) is that is takes less energy to get from the pole to the house than down the whole medium voltage power grid. The HomePlug(tm) protocol will be / is in homes already, so even without this style of BPL, the garbage'll be in the air -- and not necessarily with the limited protection mechanisims (for HF users)in this system.. It's an attempt to find an approach to satisfy both sides, which no one else is attempting to do, including the his Ignorance at the top. > ...because they "notch out" the ham bands. This > means that it interfers with everyone except ham radio operators so they > wash their hands of it. ... > ... If they bother at all, an engineer will take a portable radio to > the site, pull up the antenna and listen. There are much better solutions in the works... Again, I'm not a proponent, just saying there are those who are trying to minimize the problems with an, unfortunately, inevitable thing. The thing here is that Motorola at least kept in contact with one of the groups opposing BPL rather than just ramming it into a power grid and totally iognoring all reason/physics, even appropriate complaints. > ...If he does not hear English, > he'll log that there is nothing to prevent them moving the notch > there and that frequency will be used. You mean if he DOES here Engilsh he will move the notch there and the frequency will NOT be used? The notches go where the turned-off carriers are so the residual energy gets attenuated even more. No argument with the rest of this. BPL is an unfortunately ignorant approach to a non existent problem. Interesting that the article ignores the foreign systems which were shut down, but then they were only given the party line... 'nuf said... 73, Steve, K,9.D'C;I Yes, you guessed who I work for and what I have knowledge of... > This is called the boiled lobster effect. I thought it was a Frog ? ! and I call it de-regulation. Article: 218689 of rec.radio.amateur.antenna From: "johan aeq" References: <90f46$43528818$52ad139c$15540@news.versatel.nl> <1129499219.974415.312130@f14g2000cwb.googlegroups.com> Subject: Re: rf-systems WFL antenna? Date: Mon, 17 Oct 2005 22:48:52 +0200 Message-ID: <3640f$43540fc8$52ad139c$8573@news.versatel.nl> Let's hope someone dismantles one to see what is inside.... schreef in bericht news:1129499219.974415.312130@f14g2000cwb.googlegroups.com... > > johan aeq wrote: > > Hello, > > can you explain this antenna mentioned on this site? > > http://www.universal-radio.com/catalog/hamwire/2039.html > > A almost flat swr response with such a small antenna must be a folded T2FD > > antenna. > > Is there someone who has tested this antenna? > > Greetings Johan PE1AEQ > Hi Johan, I think you have the right idea. A broadband power > limited small antenna suggests resistive loading at the feedpoint. It > will work, just not very well until you get above the frequency at > which the wire portion starts having some efficiency. As a guess, this > one might do OK above 14 MHZ. > A magnetic loop generally refers to a small loop with a very narrow > bandwith, tuned by a variable capacitor. The claim that this is a > magnetic loop on low bands does not hold up because of the broad band > claim. > Gary N4AST > Article: 218690 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Dumb Antenna Questions Date: Mon, 17 Oct 2005 15:23:17 -0500 Message-ID: References: <1129516505.077205.187460@g49g2000cwa.googlegroups.com> Ditto. No and no. "Ed" wrote in message news:Xns96F1CB9D1F2ACspectrumhogstarbandn@207.106.93.175... > > ...a dipole antenna for 15 Meters from insulated 18 guage battery > > wire ... > > But, will I have to upgrade my wire when I go to 50/100 watts output? NO > > ...is the insulation an impediment to the functioning NO Put it up. For a 40M dipole, I have insulated 20 guage (with the ends threaded through the end insulators then doubled back and wrapped around the antenns for about three feet, for easy length adjusting if needed). 73, & Enjoy Steve, K.9,D'C;I Article: 218691 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Dumb Antenna Questions Date: Mon, 17 Oct 2005 15:36:21 -0500 Message-ID: References: <1129516505.077205.187460@g49g2000cwa.googlegroups.com> <1129563943.003115.235410@g47g2000cwa.googlegroups.com> "bob/wa2eaw" wrote in message news:1129563943.003115.235410@g47g2000cwa.googlegroups.com... > > Rockinghorse Winner wrote: > > ...is the insulation an impediment to the functioning of the > > antenna on HF? Thanks for being patient with a newbie. > >Rockinghorse Winner KI6AZS > > The only thng that can alter the power output and freq. of the > insulated wire is; if water gets between the insulation and the wire. > As in rain water. Other wise "goforitQRP is great fun!!! > 73 de Bob,WA2EAW...HW8 enthusiast with solar panals. > Bob, Hmmm. I don't think this is a worry either. I have had no protection (nor perceive a need) for this where the insulation ends at the feed point nor at the ends that are just cut (which wrap back on the antenna for about 3 feet for adjusting length. It is stranded wire with lots of opportunity for water egress. The insulation is very brittle after 6 years in the UV & other outdoor environment. I don't see what the problem mechanism could be; a bare wire gets really wet. What are you thinking? As a side note, and unrelated situation, aircraft wiring can burst into flames with help from water (Believe it or not) and insulation cracks, but in bundles of wire and where there is significant 400 cycle power distribution energy _between_ wires in a tight cabling bundle, not a single hanging wire. 73, Steve, K,9'D;C.I Article: 218692 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Dumb Antenna Questions Message-ID: References: <1129516505.077205.187460@g49g2000cwa.googlegroups.com> Date: Mon, 17 Oct 2005 21:34:47 GMT On 16 Oct 2005 19:35:05 -0700, "Rockinghorse Winner" wrote: >or 100 watts output? Also, I have a question about the insulated >wire: is the insulation an impediment to the functioning of the >antenna on HF? Thanks for being patient with a newbie. Don't overlook the fact that in most cases, insulation increases the wind resistance and increases the mass (weight) of wire antennas, so reducing the survival in strong winds, while not improving the radiation performance. Further, the insulation will degrade more quickly than bare copper in all but the most corrosive environments. Don't change your plans now... but something to keep in mind for the future, especially for long spans. You might ask, if insulated stranded annealed copper is a poor choice compared to say single core hard draw copper or Copperweld, why do so many people use insulated stranded annealed copper? I guess it comes down to availability, and that amateurs seem to not design wire antennas to survive high winds. Owen -- Article: 218693 of rec.radio.amateur.antenna From: edard Subject: Re: Help identifying tiny coax Date: Mon, 17 Oct 2005 16:45:06 -0500 Message-ID: <11l86odas2co727@corp.supernews.com> References: <11l83bm3ihoavea@corp.supernews.com> Dave wrote: > a quick visit to raychem.com finds this: > http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&M=BYPN&PID=139441&PN=5028A1318-0&LG=1&I=13 > > Wow Dave thanks. Who would have thought of trying Raychem? Duhhh Article: 218694 of rec.radio.amateur.antenna From: Jim - NN7K Subject: Re: Dumb Antenna Questions References: <1129516505.077205.187460@g49g2000cwa.googlegroups.com> Message-ID: Date: Tue, 18 Oct 2005 00:32:14 GMT The 18 gauge shouldn't present a problem, for Power, nor Loss. It , however may present a problem, in the winter, if you get ice loading (can streatch, and also break, if has enough stress (extra weight) applied to it) , but, as far as qrp, on the low bands, you may ve amazed at the dx you can pull in , even with power in the milliwatt range, and, with a couple of the older (10 watt) rigs, like the ft301-s, or the ft-7 (and kenwood, Icom, and Ten-tec made them, too!), can work reliably several hundred miles on 75-40 meters, and THOUSANDS on 20-15, and 10! Have fun-- Jim NN7K Steve Nosko wrote: > Ditto. No and no. > > > "Ed" wrote in message > news:Xns96F1CB9D1F2ACspectrumhogstarbandn@207.106.93.175... > >>>...a dipole antenna for 15 Meters from insulated 18 guage battery >>>wire ... >>>But, will I have to upgrade my wire when I go to 50/100 watts output? > > > NO > > >>>...is the insulation an impediment to the functioning > > > NO > > Put it up. For a 40M dipole, I have insulated 20 guage (with the ends > threaded through the end insulators then doubled back and wrapped around the > antenns for about three feet, for easy length adjusting if needed). > > 73, & Enjoy Steve, K.9,D'C;I > > Article: 218695 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL... Date: Tue, 18 Oct 2005 00:36:03 +0000 (UTC) Message-ID: References: In article , Steve Nosko wrote: > There are much better solutions in the works... Again, I'm not a > proponent, just saying there are those who are trying to minimize the > problems with an, unfortunately, inevitable thing. I disagree with that. It's inevitable because Google was one of three companies that invested $100,000,000 in Current Communications. If EVERY HAM boycotted Google and made sure they and their advertisers knew it, they would drop it like a hot potato. Google exists because of their Adsense product. If advertising with adsense lost customers instead of gaining them, then advertisers would look for alternate ways to spend their money. If they did that, Google would not continue their support of BPL. > The thing here is that Motorola at least kept in contact with one of the > groups opposing BPL rather than just ramming it into a power grid and > totally iognoring all reason/physics, even appropriate complaints. I have not seen the technical specs of the Motorola system so I can't comment on it, but the rumor is that it does work and does not interfere. > You mean if he DOES here Engilsh he will move the notch there and > the frequency will NOT be used? The notches go where the turned-off > carriers are so the residual energy gets attenuated even more. Yes. If here he hears English, he will assume there is someone who can point to his power lines and show there is a problem. If he hears another language, he will assume that the people whom he will interfere with are too far away to walk up to his wires and show they are a problem. > No argument with the rest of this. BPL is an unfortunately ignorant > approach to a non existent problem. IHMO exactly. > > Interesting that the article ignores the foreign systems which were shut > down, but then they were only given the party line... Yes, it has been a dismal failure just about everywhere it has been tested. It causes too much interference and works so poorly that no one could afford it without a big sum of money up front. If they make $10 a month profit from each customer it will take a long time and a lot of users to get back $100,000,000. >> This is called the boiled lobster effect. > > I thought it was a Frog ? ! and I call it de-regulation. Same thing, but more people know a boiled lobster than boiled frog. To me it does not matter, they are both nonkosher. :-) Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (077)-424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 You should have boycotted Google while you could, now Google supported BPL is in action. Time is running out on worldwide radio communication. Article: 218696 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: wire antenna masts Date: 18 Oct 2005 02:51:18 GMT Message-ID: References: <1129599247.318700.164920@g44g2000cwa.googlegroups.com> On 17 Oct 2005 18:34:07 -0700, esj@harvee.org wrote: > looking to the best option for putting up low band wire antennas. See this November's QST. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 218697 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: <1sf5l1dv5hbee2lour8mijr6vrlsphfh11@4ax.com> Message-ID: Date: Tue, 18 Oct 2005 02:57:28 GMT > > You are proposing a slightly shorter than 1/2 wave dipole for 75. > This should be no problem as it will have a little capacitive > reactance and a tuner should handle it. Thank you, Steve. This was my main concern. > The G5RV is pretty much the same thing, except it has some feed line > gymnastics to get a "fairly good" (50 ohm) match on many bands. This > is nothing more than an "antenna tuner in feed line" which doesn't > require a knob rather than one in a box which does. (:-) I have pretty much decided to just feed ladder line with a balanced tuner rather than make a G5RV. This should give me more flexibility. Ed Article: 218698 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: Message-ID: Date: Tue, 18 Oct 2005 02:59:32 GMT > > That's a very good length for 40m, 17m, & 10m. You can analyze the > antenna yourself by downloading the free demo version of EZNEC > from www.eznec.com. If you want, I'll send you a model of your > antenna so all you have to do is click the mouse. Thanks for the offer, Cecil, but at this time I will decline. I plan on just putting up as much wire as I can effectively mount between the two trees, about 100 feet, and just feed it at the center with ladder line. A new balanced tuner will tune the whole thing. I expect this to give me a bit more flexibility than the G5RV would. Ed K7AAT Article: 218699 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: Message-ID: Date: Tue, 18 Oct 2005 03:18:39 GMT Ed wrote: > Thanks for the offer, Cecil, but at this time I will decline. I plan > on just putting up as much wire as I can effectively mount between the > two trees, about 100 feet, and just feed it at the center with ladder > line. That's the antenna I was offering to model for you. You will, no doubt, run into some pitfalls, for instance an impedance of 8 ohms or 4000 ohms that your tuner may not be able to handle. EZNEC can predict such problems before they bite you. As a data point, the MFJ-974 gives you a matching range of 12-2000 Ohms. EZNEC can also predict your radiation patterns which are important on the high bands if you want to hit certain areas of the world. Rotating my dipole in AZ by 15 degrees made a lot of difference. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218700 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> Date: Tue, 18 Oct 2005 03:46:42 GMT On Mon, 17 Oct 2005 05:09:06 GMT, Owen Duffy wrote: >On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: > > >>So, theoretically: >>- an ideal average responding meter should read (1-2/pi)% which is >>36.3% or 8.8dB on an perfect square wave; > >I think this is close to the right answer, but for the wrong reason. I >think it needs to be evaluated iteratively, and I get an answer closer >to 34.3% or 9.3dB. An analytical approach to solution of the problem. A unit height square wave has a fundamental component of amplitude 4/pi. To find the area under the filtered curve, I think we are looking for the integral from 0 to pi/2 of absolute(1-4/pi*sin(theta))). I will divide the integral at theta=asin(pi/4) to deal with the absolute function since the problem function is positive from 0 to asin(pi/4) and negative from asin(pi/4) to pi/2. Here is some Perl to evaluate the ratio: #find the zero crossing point $theta=asin($pi/4); #find the area under the curve $area=$theta-4/$pi*(-cos($theta)+cos(0)); #first part $area+=4/$pi*(-cos($pi/2)+cos($theta))-($pi/2-$theta); #second part #divide by area under unit square wave $ratio=$area/($pi/2); print "Average response ratio is $ratio \n"; And the answer is 0.3430678471... or 9.3dB. It is about 9.4dB if you only consider the harmonics up to 50KHz. One of you mathematical whizzes might know a better way to put this! Owen -- Article: 218701 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: What is a 50-ohm environment. ??? References: <2UB4f.445105$5N3.395971@bgtnsc05-news.ops.worldnet.att.net> <0ms7l19namqav259vsnpgmrm1oc37e8vul@4ax.com> <8ke8l15ttrohg6ce734mh4odb1559fbpbv@4ax.com> Message-ID: <4g_4f.1944$dO2.953@newssvr29.news.prodigy.net> Date: Tue, 18 Oct 2005 03:48:16 GMT Richard Clark wrote: > Just how big IS your universe? A little less than 2,000,000,000,000,000,000,000,000,000,000,000 cubic light years. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218702 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: EZNEC model of sleeve antenna Date: Mon, 17 Oct 2005 22:54:00 -0700 Message-ID: <11l93fpt7q8tsd9@corp.supernews.com> References: Sorry I missed this -- I've been out of the country and generally unable to access the newsgroups. But it looks like it got resolved satisfactorily. Anyone with a specific question about EZNEC modeling is welcome and encouraged to contact me directly (after making an honest effort at finding the answer in the manual, of course). Roy Lewallen, W7EL Article: 218703 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Help identifying tiny coax Date: Mon, 17 Oct 2005 23:03:09 -0700 Message-ID: <11l940uof4kb6c2@corp.supernews.com> References: <11l83bm3ihoavea@corp.supernews.com> <11l86odas2co727@corp.supernews.com> This sounds similar to some cable I got surplus a number of years ago. The loss was surprisingly high at 7 MHz. I'm quite sure the reason is that the center conductor is made from several strands of very fine copper-clad steel wire. Although the copper is probably a sizeable fraction of the overall wire thickness, it's still thin in terms of skin depth at the lower part of the HF region because of the very small strand diameter. Consequently, significant current flows in the steel, which is very much more resistive than copper at HF. Loss at VHF is about what you'd expect from a copper center wire. So I recommend checking the loss before using the cable at HF if loss might be important to the application. I used it as low-weight feedline for Field Day (I generally backpack my FD gear), and was prepared to accept the loss I thought it would have as a trade for the low weight. But I found the loss to be considerably greater than expected. Roy Lewallen, W7EL Article: 218704 of rec.radio.amateur.antenna From: David Subject: Diameter of cable in coaxial Collinear antenna Message-ID: Date: Tue, 18 Oct 2005 08:00:12 GMT Hi, I am in the process of making a couple of 9dB Collinear antennas for 920 MHz. I was wondering if the diameter of the coax is significant. The design is simply 1/2 wavelength sections soldered centre to braid with a 1/4 wave radiator at the top and a 1/4 wave sleeve choke and a few ferrite toroid baluns at the bottom. The original design uses RG58 coax but I find this difficult to solder in short lengths and the dielectric melts if the iron is left on too long. Instead I am using RG174 PFTE dielectric. The Vp for both is still 0.66. Thanks for any info Regards David Article: 218705 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: Trying to get AM broadcast at job Date: 18 Oct 2005 14:33:39 GMT Message-ID: References: <23479-4352B9CA-778@storefull-3257.bay.webtv.net> <1129622465.240479.33150@o13g2000cwo.googlegroups.com> On 18 Oct 2005 01:01:05 -0700, sofasurfer@blclinks.net wrote: >>He needs either a low-impedance antenna or a >>matching device to step the high-impedance >antenna output down to the >>line`s impedance. A hollower can do that >almost without losing voltage. > > What is a hollower?? Why, in Texas, it's a wire that's hollow in the center. :-) Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 218706 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Doublet Antenna question Message-ID: <9r6al1l55u2ahna0u95h7k5dgvt7ufd61b@4ax.com> References: Date: Tue, 18 Oct 2005 15:58:39 GMT On Tue, 18 Oct 2005 03:18:39 GMT, Cecil Moore wrote: >Ed wrote: >> Thanks for the offer, Cecil, but at this time I will decline. I plan >> on just putting up as much wire as I can effectively mount between the >> two trees, about 100 feet, and just feed it at the center with ladder >> line. > >That's the antenna I was offering to model for you. You will, >no doubt, run into some pitfalls, for instance an impedance >of 8 ohms or 4000 ohms that your tuner may not be able to handle. >EZNEC can predict such problems before they bite you. > >As a data point, the MFJ-974 gives you a matching range of 12-2000 >Ohms. > >EZNEC can also predict your radiation patterns which are important >on the high bands if you want to hit certain areas of the world. >Rotating my dipole in AZ by 15 degrees made a lot of difference. For any given frequency, would that 8 ohms or 4000 ohms be decided by the length of the dipole or the length of the ladderline, or both? bob k5qwg Article: 218707 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Tue, 18 Oct 2005 10:37:15 -0500 Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> Owen, [[[ while I suspect the difference is so small that it makes little difference in the receiver sensitivity number arrived at, I proceed anyway. ]] From your last two posts, it appears you/we have vastly different interpretations of what the question was. You talk about removing the fundamental from the square wave and this puzzles me. I do not believe the intent was to measure SINAD using a square wave modulation. Therefore removing its fundamental and measuring its RMS does not fit the situation. My understanding of the issue was measuring SINAD with the older "Average-measuring-, RMS-reading" type (call it the "AVG-Type") of meter vs, a "true RMS" reading meter. While I did talk about measuring a square wave with the "AVG_Type" meter, that was a digression only ment to show (what I think is) the difference for the previously proposed reference measurement. Namely try simply measuring a square wave for comparing the two meter readings, not SINAD measurements. I did this to show a calculation of how the two meters would read knowing the average and RMS values of _some_ waveform. I was thinking that I could do this for the two SINAD waveforms, but as you see here, I gave up... Back to SINAD. Therefore, the issue I was addressing was the following: (for the normal SINAD technique, 1 kHz sine wave tone): A- Assume the RMS meter gives the "correct" reading. B- What does the "AVG_Type" show on the display/scale? So, B has two parts. 1- What does the "AVG-Type" read for the un-notched signal, and 2- What does the "AVG-Type" show for the notched signal. 1- As a first approximation, lets say the un notched reading is dominated by the sine wave. With this assumption, they both read the same. To refine this estimate, I am unable to assess, easily, the effect of the noise on either measurement except that the True RMS mwter will give an indication of the total tone and noise power (actually Erms^2). As a first approximation, we could say that the "AVG-Type" reads the average of the sine plus the average of the noise voltages...and my estimation powers peter-out right there. 2- What does the "AVG_Type" read on the noise (notched signal)... yep, peter once again. Therefore: GOTO [[ my statement in brackets above ]] Then there's the pronunciation. Some say "sin' add" and some say "sign' add". We said SIN add. Nice exercise, time for me to move on to other things. 73, Steve, K,9.D;C'I "Owen Duffy" wrote in message news:sqp8l1hq26kicok47f5rgevv70apnkv3go@4ax.com... > On Mon, 17 Oct 2005 05:09:06 GMT, Owen Duffy wrote: > > >On Mon, 17 Oct 2005 03:09:11 GMT, Owen Duffy wrote: > > > > > >>So, theoretically: > >>- an ideal average responding meter should read (1-2/pi)% which is > >>36.3% or 8.8dB on an perfect square wave; > > > >I think this is close to the right answer, but for the wrong reason. I > >think it needs to be evaluated iteratively, and I get an answer closer > >to 34.3% or 9.3dB. > > An analytical approach to solution of the problem. > > A unit height square wave has a fundamental component of amplitude > 4/pi. > > To find the area under the filtered curve, I think we are looking for > the integral from 0 to pi/2 of absolute(1-4/pi*sin(theta))). I will > divide the integral at theta=asin(pi/4) to deal with the absolute > function since the problem function is positive from 0 to asin(pi/4) > and negative from asin(pi/4) to pi/2. > > Here is some Perl to evaluate the ratio: > > #find the zero crossing point > $theta=asin($pi/4); > #find the area under the curve > $area=$theta-4/$pi*(-cos($theta)+cos(0)); #first part > $area+=4/$pi*(-cos($pi/2)+cos($theta))-($pi/2-$theta); #second part > #divide by area under unit square wave > $ratio=$area/($pi/2); > print "Average response ratio is $ratio \n"; > > And the answer is 0.3430678471... or 9.3dB. It is about 9.4dB if you > only consider the harmonics up to 50KHz. > > One of you mathematical whizzes might know a better way to put this! > > Owen > -- Article: 218708 of rec.radio.amateur.antenna From: "Jim Leder" Subject: Feedpoint of a Half Square Date: Tue, 18 Oct 2005 12:28:32 -0400 Message-ID: For years I've always fed my 30 meter Half Square at a top corner, and it's done a reasonable job in my opinion. Recently I've discovered 2 Eznec files, one for a Half Square and another for it's big brother, a Bobtail Curtain. Both show the feedpoint down just a little bit on the driven element vertical, and NOT dead on the corner. I've studied both Eznec model outputs (corner feed and not corner feed) and indeed the different feedpoint does show a little more gain, about 1.5 DB without altering the antenna impedance much. The one I modeled for 30 has the feedpoint down about 2 inches from the corner. Is what I am seeing accurate? Or, is this just another Eznec anomaly? I realize that 1.5 DB isn't too much to worry about, but if I should make another one, maybe I should alter the feedpoint. Opinions? Thanks. Article: 218709 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Doublet Antenna question References: <9r6al1l55u2ahna0u95h7k5dgvt7ufd61b@4ax.com> Message-ID: Date: Tue, 18 Oct 2005 17:28:58 GMT Bob Miller wrote: > For any given frequency, would that 8 ohms or 4000 ohms be decided by > the length of the dipole or the length of the ladderline, or both? Both. For instance the resonant impedance of a G5RV on the lower part of 80m is usually about 8 ohms. If the feedline for a one wavelength dipole is 1/2WL, the impedance will be about 4000 ohms. The feedline impedance seen by your tuner is somewhat unpredictable and EZNEC can tell you what ballpark impedance to expect. EZNEC has saved me an enormous amount of time - 10 minutes of simulation Vs 10 hours of antenna erection time. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218710 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Feedpoint of a Half Square References: Message-ID: Date: Tue, 18 Oct 2005 17:35:04 GMT Jim Leder wrote: > For years I've always fed my 30 meter Half Square at a top corner, and it's > done a reasonable job in my opinion. Recently I've discovered 2 Eznec files, > one for a Half Square and another for it's big brother, a Bobtail Curtain. > Both show the feedpoint down just a little bit on the driven element > vertical, and NOT dead on the corner. I've studied both Eznec model outputs > (corner feed and not corner feed) and indeed the different feedpoint does > show a little more gain, about 1.5 DB without altering the antenna impedance > much. The one I modeled for 30 has the feedpoint down about 2 inches from > the corner. Is what I am seeing accurate? Or, is this just another Eznec > anomaly? I realize that 1.5 DB isn't too much to worry about, but if I > should make another one, maybe I should alter the feedpoint. Opinions? For an antenna like the half-square, I would trust the EZNEC results as long as you didn't violate any of the EZNEC guide lines. I once violated the EZNEC guidelines and got an omindirectional antenna with 20 dBi gain in all horizontal directions. :-( Another possibility is to feed the half-square at the lowest point with a matching network to match the high impedance. Another thought just occured to me - that a 600 ohm feed point must exist somewhere down the vertical section. Of course, balancing the currents at that point would be a challenge. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218711 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: Message-ID: Date: Tue, 18 Oct 2005 18:16:02 GMT > That's the antenna I was offering to model for you. You will, > no doubt, run into some pitfalls, for instance an impedance > of 8 ohms or 4000 ohms that your tuner may not be able to handle. > EZNEC can predict such problems before they bite you. OK. I'll take you up on the offer, afterall. Figure 100' of #14 copperweld, centerfed with 450ohm ladderline or with 600 ohm open wire line (2"). Height should be about 45' at ends and 35 feet center. Length of feedline is projected at about 45 feet. I'll go with the 600 ohm wireline feed if I can find it, otherwise, the cheap 450 ohm plastic stuff for now and build wireline next summer. > > EZNEC can also predict your radiation patterns which are important > on the high bands if you want to hit certain areas of the world. > Rotating my dipole in AZ by 15 degrees made a lot of difference. Not real concerned with the patterns of anything above 40M. I'm mainly interested in 80/75/60/40M use. I'll take what I get and see how it goes..... might be nice to see 20M and 10M patterns, though. Thanks. Ed Article: 218712 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Doublet Antenna question Date: Tue, 18 Oct 2005 18:14:27 +0000 (UTC) Message-ID: References: <9r6al1l55u2ahna0u95h7k5dgvt7ufd61b@4ax.com> The loss in a switched transmission line tuner is somewhat greater than in a conventional tuner which can be adjusted for an exact, low-loss, impedance match. --- Reg. From - Wed Oct 19 11:30:33 EDT 2005 Article: 218713 of rec.radio.amateur.antenna From: "Thierry" <-> Newsgroups: rec.radio.amateur.antenna Subject: ESA calls radioamateurs Date: Tue, 18 Oct 2005 21:08:34 +0200 Lines: 15 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-RFC2646: Format=Flowed; Original NNTP-Posting-Host: tvsurf-habscht1-045.pt.lu Message-ID: <43554833$1@news.vo.lu> X-Trace: news.vo.lu 1129662515 213.166.42.45 (18 Oct 2005 21:08:35 +0200) Path: news1.isis.unc.edu!canoe.uoregon.edu!newsfeed.news.ucla.edu!newsfeed.media.kyoto-u.ac.jp!newsfeed.icl.net!newsfeed.fjserv.net!news.tele.dk!news.tele.dk!small.news.tele.dk!npeer.de.kpn-eurorings.net!news.vo.lu!not-for-mail Xref: news1.isis.unc.edu rec.radio.amateur.antenna:218713 Hi, For info http://www.esa.int/SPECIALS/sseti_express/SEMARJ7X9DE_0.html 73 Thierry, ON4SKY -- Auteur de "Un siècle de Physique, 1- La Physique Quantique" aux éditions AEGEUS Détail sur : http://www.astrosurf.org/lombry Article: 218714 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Trying to get AM broadcast at job Date: Tue, 18 Oct 2005 14:11:04 -0500 Message-ID: <23481-435548C8-71@storefull-3257.bay.webtv.net> References: Sofasurfer wrote: "What is a follower?" A follower is an amplifier in which the output signal voltage is nearly the same as it "hollows" the input voltage. Its purpose is to reproduce the input voltage, but make it available at a lower output impedance. Thus it has power gain although it has a slight voltage loss. Its input impedance is high because it has a very large inverse feedback. This gives it a wide frequency response as well. Suppose you have an ordinary r-f transistor, almost any will do, that works well at 1 milliampere of collector current, and it has a current gain of 100. We have a d-c power supply of 12 volts. We want to drop about 6 volts across the emitter resistor so our signal can have equal up and down swings. Ohm`s law tells us that a 6000-ohm emmiter resistor will drop 6 volts with 1 milliampere through it. We can set our forward bias with a pair of 60,000-ohm resistors connected in series to give about 6 volts at their midpoint for the transistor base connection. These are low enough values for stability. That`s all there is to the d-c design. The follower will present about 30,000 ohms load on the 5,000-ohm AM broadcast antenna whip. The transistor loading on the whip is negligible being about current gain times the emitter resistance. The follower will present a very low output resistance to its load, the line to the radio it feeds. It is much less than the 6,000 ohm emitter resistance due to the inverse feedback around the transistor. Capacitors large enough to have negligible reactance at the r-f loads should be used to couple the input and output of the follower to avoid d-c upset. Match transistor and power supply polarities. Transistor manuals have sample circuits. Best regards, Richard Harrison, KB5WZI Article: 218715 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: What is SINAD? Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> Date: Tue, 18 Oct 2005 20:18:34 GMT On Tue, 18 Oct 2005 10:37:15 -0500, "Steve Nosko" wrote: >Owen, > > From your last two posts, it appears you/we have vastly different >interpretations of what the question was. You talk about removing the >fundamental from the square wave and this puzzles me. I do not believe the >intent was to measure SINAD using a square wave modulation. Therefore >removing its fundamental and measuring its RMS does not fit the situation. > Some discussion arose about the extent of errors when using an aveage responding meter to measure SINAD (compared to a true RMS meter). My experimental evidence is that when measuring SINAD on a 2.4KHz wide receiver at SINAD=12dB, the error is less than 1dB. Of course, it will be less for higher SINAD ratios, and worse for lower ones. I offered that a simple test of whether a SINAD meter was average responding or true RMS responding, was to measure the SINAD of a good square wave. The average responding meter will indicate about 9.3dB whereas an RMS responding meter will indicate around 7.3dB. I think we both understood that. > >Back to SINAD. >Therefore, the issue I was addressing was the following: >(for the normal SINAD technique, 1 kHz sine wave tone): >A- Assume the RMS meter gives the "correct" reading. >B- What does the "AVG_Type" show on the display/scale? > >So, B has two parts. > >1- What does the "AVG-Type" read for the un-notched signal, and >2- What does the "AVG-Type" show for the notched signal. > >1- As a first approximation, lets say the un notched reading is dominated by >the sine wave. With this assumption, they both read the same. To refine >this estimate, I am unable to assess, easily, the effect of the noise on >either measurement except that the True RMS mwter will give an indication of >the total tone and noise power (actually Erms^2). As a first approximation, >we could say that the "AVG-Type" reads the average of the sine plus the >average of the noise voltages...and my estimation powers peter-out right >there. >2- What does the "AVG_Type" read on the noise (notched signal)... yep, peter >once again. As I stated above, and you stated, the comparison will depend on the extent to which the sine wave dominates the total signal, and so will depend on the SINAD being measured. I suggest that it will also depend on the noise bandwidth. Repeating, my experimental evidence is that when measuring SINAD on a 2.4KHz wide receiver at SINAD=12dB, the error is less than 1dB. At the end of the day, it doesn't matter that much for normal applications if the SINAD meter is average responding, they appear to overestimate the SINAD, but by a very small amount. > >Therefore: > >GOTO [[ my statement in brackets above ]] > You are trying to send Wes in a loop. >Then there's the pronunciation. Some say "sin' add" and some say "sign' >add". We said SIN add. Dangerous territory, this could become an international incident when you bring pronunciation into scope. There, and you all (mostly) thought I didn't know how to spell... all those esses where they should be zeds, no thats zees isn't it. Owen -- Article: 218716 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: What is SINAD? Date: Tue, 18 Oct 2005 16:29:14 -0500 Message-ID: References: <0510l1d9fbauafptjd41ul5l036qug97g6@4ax.com> <6eY3f.305$W32.212@trnddc06> <1ac6l1lkejh84je8qllbhsj1i1r85d7h4e@4ax.com> "Owen Duffy" wrote in message news:fblal1tavo45g9093j6q35g9hjajalqkgv@4ax.com... > On Tue, 18 Oct 2005 10:37:15 -0500, "Steve Nosko" > wrote: > > [...] > > I offered that a simple test of whether a SINAD meter was average > responding or true RMS responding, was to measure the SINAD of a good > square wave. The average responding meter will indicate about 9.3dB > whereas an RMS responding meter will indicate around 7.3dB. > > I think we both understood that. Nope, I missed that concept. Thanks for the clarify. Article: 218717 of rec.radio.amateur.antenna From: Bob Nielsen Subject: Re: Diameter of cable in coaxial Collinear antenna Date: Tue, 18 Oct 2005 16:05:41 -0700 Message-ID: References: On Tue, 18 Oct 2005 09:00:12 +0000, David wrote: > Hi, > > I am in the process of making a couple of 9dB Collinear antennas for 920 > MHz. > > I was wondering if the diameter of the coax is significant. > > The design is simply 1/2 wavelength sections soldered centre to braid > with a 1/4 wave radiator at the top and a 1/4 wave sleeve choke and a > few ferrite toroid baluns at the bottom. The original design uses RG58 > coax but I find this difficult to solder in short lengths and the > dielectric melts if the iron is left on too long. Instead I am using > RG174 PFTE dielectric. The Vp for both is still 0.66. The Vp for PFTE is more like 0.695. I would suggest semi-rigid for this application. Bob, N7XY Article: 218718 of rec.radio.amateur.antenna From: David Subject: Re: Diameter of cable in coaxial Collinear antenna References: Message-ID: <_ff5f.21729$U51.5235@news-server.bigpond.net.au> Date: Tue, 18 Oct 2005 23:08:42 GMT Bob, Thanks for your response. Why would you recommend semi-rigid ? Bob Nielsen wrote: > On Tue, 18 Oct 2005 09:00:12 +0000, David wrote: > > >>Hi, >> >>I am in the process of making a couple of 9dB Collinear antennas for 920 >>MHz. >> >>I was wondering if the diameter of the coax is significant. >> >>The design is simply 1/2 wavelength sections soldered centre to braid >>with a 1/4 wave radiator at the top and a 1/4 wave sleeve choke and a >>few ferrite toroid baluns at the bottom. The original design uses RG58 >>coax but I find this difficult to solder in short lengths and the >>dielectric melts if the iron is left on too long. Instead I am using >>RG174 PFTE dielectric. The Vp for both is still 0.66. > > > The Vp for PFTE is more like 0.695. I would suggest semi-rigid for this > application. > > Bob, N7XY > Article: 218719 of rec.radio.amateur.antenna From: "Dan/W4NTI" References: Subject: Re: Mosley Ta-33 Message-ID: Date: Wed, 19 Oct 2005 00:13:25 GMT On the way via e-mail. Dan/W4NTI "avidfan" wrote in message news:be3d53526404499026e126f6dd7d2fdf@localhost.talkaboutradio.com... >I need a manual for this antenna. Looking for a link to a website that has > one as a freebie. > Article: 218720 of rec.radio.amateur.antenna From: David Findlay Subject: Ruggedized antenna for NOAA sats? Message-ID: Date: Wed, 19 Oct 2005 00:16:52 GMT I'm currently building a VHF APT image receiver for my vehicle, and need a suitable antenna design that is rugged enough to survive the rigors of being hit by hail and strong winds. It also needs to be relatively compact because I need to fit other antennae on the roof too. I was thinking some sort of helical. Anyone got suggestions of what would be best? Thanks, David Article: 218721 of rec.radio.amateur.antenna From: "Jerry Martes" References: Subject: Re: Ruggedized antenna for NOAA sats? Message-ID: Date: Wed, 19 Oct 2005 00:27:07 GMT "David Findlay" wrote in message news:Ufg5f.21830$U51.18187@news-server.bigpond.net.au... > I'm currently building a VHF APT image receiver for my vehicle, and need a > suitable antenna design that is rugged enough to survive the rigors of > being hit by hail and strong winds. It also needs to be relatively compact > because I need to fit other antennae on the roof too. I was thinking some > sort of helical. Anyone got suggestions of what would be best? Thanks, > > David David I have some experience with APT imaging and antennas for NOAA satellites. You can contact me at my E-mail address for more info and pictures. I wouldnt be optimistic about being able to get good images with an antenna that is permanently mounted above the top of a car. Are you aware that Walter Maxwell frequents this news group? He has to be the best source of guidance on APT antennas *anywhere*. Jerry Article: 218722 of rec.radio.amateur.antenna Subject: Re: Doublet Antenna question From: Ed References: Message-ID: Date: Wed, 19 Oct 2005 00:53:45 GMT > 600 ohm open wire line is available from W7FG [800-807-6146]. > > 50 feet $23 > 100 feet $40. > Thanks. I've noted the number (what an interesting set up numbers!), and will call in a few weeks when I'm ready to order. Ed Article: 218723 of rec.radio.amateur.antenna From: Bob Nielsen Subject: Re: Diameter of cable in coaxial Collinear antenna Date: Tue, 18 Oct 2005 18:27:51 -0700 Message-ID: References: <_ff5f.21729$U51.5235@news-server.bigpond.net.au> On Wed, 19 Oct 2005 00:08:42 +0000, David wrote: > Bob, > > Thanks for your response. Why would you recommend semi-rigid ? In my experience, you can more precisely control the length of the tubing than with a braid shield. There is some mechanical rigidity advantage, as well, although that isn't a big factor if you use some sort of dielectric tube to contain the antenna. > > Bob Nielsen wrote: >> On Tue, 18 Oct 2005 09:00:12 +0000, David wrote: >> >> >>>Hi, >>> >>>I am in the process of making a couple of 9dB Collinear antennas for 920 >>>MHz. >>> >>>I was wondering if the diameter of the coax is significant. >>> >>>The design is simply 1/2 wavelength sections soldered centre to braid >>>with a 1/4 wave radiator at the top and a 1/4 wave sleeve choke and a >>>few ferrite toroid baluns at the bottom. The original design uses RG58 >>>coax but I find this difficult to solder in short lengths and the >>>dielectric melts if the iron is left on too long. Instead I am using >>>RG174 PFTE dielectric. The Vp for both is still 0.66. >> >> >> The Vp for PFTE is more like 0.695. I would suggest semi-rigid for this >> application. >> >> Bob, N7XY >> Article: 218724 of rec.radio.amateur.antenna From: "Bill" Subject: HyGain 18HT HyTower -17Meters Message-ID: Date: Wed, 19 Oct 2005 07:06:57 -0400 Any tricks to adding a 1/4 wave 17 meter stub to the 18HT....??? Do I have to remove the 15 meter stub and replace it with a 17 stub? I looked at the stub Hygain sell for the conversion and it looks about a foot + too long for 17 is there a reason for this? Thanks, before I get more grey hair!! -Bill kc4pe@bellsouth.net