Article: 220215 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 11:43:06 -0600 Message-ID: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> References: Reg, G4FGQ wrote: "There`s no need to do a conjugate match just to measure voltage." True. But, it`s best to measure current and calculate voltage because voltmeter leads are susceptible to induced voltages. One benefit of the conjugate match is elimination of a reactive obstacle to current, but because source and load resistances are equal, exactly one half of the voltage induced in the antenna appears across the receiver. An infinite ipedance does not load a source at all. Reg`s question of how much voltage is induced in 1 m of wire in a field of 1 V/m is answered clearly by Terman in publications which date back at least to 1932, the earliest copyright date I saw on "Radio Engineering". So, many competent and critical reviewers have pored over Terman`s works that it`s almost certain that any errors have been found and corrected long ago. Everybody makes mistakes, but now Terman is as close to infallible on the subject of radio as any author I know. Read page 2 of Terman`s "Electronnic and Radio Engineering" (1955 edition) for complete details. The same information appears in some other Terman authored and edited writings (almost word for word). Best regards, Richard Harrison, KB5WZI Article: 220216 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 10:43:10 -0800 Message-ID: <11qdvpv9kf3rs80@corp.supernews.com> References: <43a6b708_3@newsfeed.slurp.net> Reg Edwards wrote: > . . . > See the works of Sir Ronald Arthur Fisher, the greatest statistician > of all time. Beautifully explained in plain English. He dabbled mainly > in Genetics, Agriculture, the Weather, and the mathematics thereof. > But I'm not aware of anything specifically he had to say about the > statistics of lightning strikes. You will have to work things out for > yourself. In all probability nothing seriously will happen to YOU. So > don't worry about it. > . . . > As for me, I'm 80 years of age, and I'm still alive. I've never won > the national lottery. But perhaps that can be explained by the fact > that I've never entered it. > > I hope the foregoing has helped to set your mind at rest. I'd be willing to wager that there are places in Florida which have more lightning strikes in a single summer than have occurred at your QTH (or mine) in the past 80 years. Roy Lewallen, W7EL Article: 220217 of rec.radio.amateur.antenna From: "dhawo" Subject: Dipole antenna lobes question (wifi base in this example) Message-ID: <6mDpf.7042$3Z.1923@newsread1.news.atl.earthlink.net> Date: Mon, 19 Dec 2005 18:54:58 GMT This question is not just related to wifi of course. My understanding is if the dipoles are opposite of each other (example 1: -----O----- ) then the lobe is an equal donut shape from the center. I would get equal focus upstairs downstairs ends of the house if wifi base is placed in the center. (a big vertical donut sitting in center of the house with edges of donut touching roof, 1st floor, end to end in the house [ O ] <-- house ) (nulled in the front and back of the house. What does the lobe look like if the dipoles are vertically opposite from each other? (Example 2: |_o_| ) Is the majority of the lobe pointing to the sky and less to the ground? Wouldnt that take away strength from the ends of the house? Or am I totally off base? This question comes >from a recommendation that the antennas should be vertical as in example 2. Maybe that is the idea is to lower interference to neighbors. Thanks for all your input... Dean Article: 220218 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna Input Impedance References: <1135011743.774673.140070@g49g2000cwa.googlegroups.com> <1135015762.848150.60880@g49g2000cwa.googlegroups.com> Message-ID: Date: Mon, 19 Dec 2005 19:27:17 GMT K7ITM wrote: > Though what you say about measuring through a feedline is true, is > there some reason you limited it to 1/2 wavelength? I was thinking about my 80m dipole at the time. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220219 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Identify Old HF Vertical Message-ID: <173eq1li33s526o0f2j5s77t82f7sp2vhs@4ax.com> References: Date: Mon, 19 Dec 2005 19:42:46 GMT >>Yes, this was a CB ground plane design. There should have been a bracket >>that attached at bottom (metal coax connector area) and at top of loading >>coil. >> >>The application of heat with a heat gun (NOT a torch or open flame) - should >>allow the plastic composite to slip off the coil. >> >>Greg >> >I am glad I asked! The heat gun sounds like a better way than the >lathe. I will try that first. > >John Ferrell, W8CCW > >John Ferrell W8CCW It came apart pretty easy. If you would like to see what was inside click on http://dixienc.us/AntennaProject.htm I am impressed with the mechanical structure and will try to imitate it going back together. John Ferrell W8CCW Article: 220220 of rec.radio.amateur.antenna From: "RB" Subject: antenna tuner range calculators Message-ID: <65Epf.1835$RZ6.1473@bignews7.bellsouth.net> Date: Mon, 19 Dec 2005 13:46:59 -0600 Anyone know of any calculators which enable a user to get an approximation of the Z range of an antenna tuner by feeding in the variable values ? Article: 220221 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: antenna tuner range calculators References: <65Epf.1835$RZ6.1473@bignews7.bellsouth.net> Message-ID: Date: Mon, 19 Dec 2005 20:05:41 GMT RB wrote: > Anyone know of any calculators which enable a user to get an approximation > of the Z range of an antenna tuner by feeding in the variable values ? If you have MicroSmith, make the load equal to 50 ohms. Set up a series C, a parallel L, and a series C that agrees with the values in your antenna tuner and watch the Smith Chart as the values of C and L are changed. It's pretty interesting to see. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220222 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Dipole antenna lobes question (wifi base in this example) References: <6mDpf.7042$3Z.1923@newsread1.news.atl.earthlink.net> Message-ID: Date: Mon, 19 Dec 2005 20:56:13 GMT Dean, Since anything around an antenna affects/distorts the radiation pattern to some extent, and since a dipole's radiation pattern is sort of directional (depending on a lot of things), the usual vertical antenna, being 'omnidirectional' would mean that the distortion probably won't mean a 'null' somewhere in the house. (Wonder if I could make that sentence a little bit longer??) That 'donut' radiation pattern is the 'ideal', not what actually happens in most cases. (There's not really a hole in the middle either.) Which would be 'beter' in your situation? Beats me. You might try it ans see, but have the vertical antenna just in case... 'Doc Article: 220223 of rec.radio.amateur.antenna From: K7JEB Subject: Re: antenna tuner range calculators Message-ID: <347eq1pf4321finmujo0cmkjuad4loof5o@4ax.com> References: <65Epf.1835$RZ6.1473@bignews7.bellsouth.net> Date: Mon, 19 Dec 2005 13:58:46 -0700 On Mon, 19 Dec 2005 13:46:59 -0600, "RB" wrote: >Anyone know of any calculators which enable a user to get an approximation >of the Z range of an antenna tuner by feeding in the variable values ? > You might have a look at RevLoad written by Jim Tonne, WB6BLD: http://www.tonnesoftware.com/ (Main Site) http://www.tonnesoftware.com/revload.html (RevLoad download) RevLoad takes the settings of the tuner components the system (tuner) impedance (usually 50 ohms) and the operating frequency to calculate the load impedance being matched. It covers all tuner configurations, T-net, pi-net, L-net. And, best of all, it's FREE. Jim, K7JEB Article: 220224 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Passive reradiating antenna Date: Mon, 19 Dec 2005 16:04:02 -0500 Message-ID: References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <1134921266.178997.255510@f14g2000cwb.googlegroups.com> <1134930784.403818.189120@g14g2000cwa.googlegroups.com> Toni wrote in part: > Hi Tom, > > K7ITM wrote: > >>The difference is that the helix is quite directional. > > > The ones used in GPS receivers are exactly the opposite. They should > ideally have a "half orange" radiation pattern, as they should be able > to follow a satellite from horizon to horizon all over your head. Isn't that quite directional? And are you talking about helical as in a helical antenna, or are you talking about rubber ducks? > Before you say this is impossible please think it twice: > > Think of the small coupling loop used in a tuned loop. By itself it is > a very bad antenna, but when an appropiate parasitic structure is added > (the whole tuned loop) the "whole system" becomes a decent antenna. > This is exactly what I'm asking about, about using my GPS antenna as a > coupling to a more efficient structure of some kind. It sounds as if you are proposing something that will be quite beneficial to the radio world if you succeed. - 73 de Mike KB3EIA - Article: 220226 of rec.radio.amateur.antenna From: w4sef@bellsouth.net (Steven Fritts) Subject: MFJ ANTENNA QUESTION Message-ID: <43a72aae.7737125@newsgroups.bellsouth.net> Date: Mon, 19 Dec 2005 21:57:10 GMT Hello all, I wonder if anyone has tried the MFJ collinear dipole that they have in their new catalog. It is two half waves with a quarter wave length of 450 ohm ladder line shorted at the bottom hanging down with an SO 239 connector for the 50 ohn feedline connection. I dont see why one could not build this antenna themselves. The question is, WHERE does the 50 ohm point go on the ladder line? At the bottom? Mid point? Or does it matter where it goes? I have plenty of room to put on up and wondered how well they work. 73s and thanks, Steve W4SEF Article: 220227 of rec.radio.amateur.antenna From: "Richard Fry" References: <43a6b708_3@newsfeed.slurp.net> Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 16:22:45 -0600 Message-ID: <43a731f9_2@newsfeed.slurp.net> "Reg Edwards" wrote > In anticipation of a thunder storm just leave it floating. Not that it > will prevent a direct lightning strike but it MIGHT prevent damage to > equipment and, more important, to yourself. ... etc etc removed by major clippage >I hope the foregoing has helped to set your mind at rest. __________ Possibly you thought this relevant to the original post. But then why not thread it so, rather than to mine? RF Article: 220228 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 22:42:21 +0000 (UTC) Message-ID: References: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> Terman may or may not be perfectly correct when he states the voltage INDUCED in a 1 metre high vertical antenna with a field strength of 1 volt per metre. But Terman is ambiguous. He tells only half of the story. He FAILS to state between WHICH which pair of points the voltage is induced. For the UMPTEEN'th time - what I need to know is the voltage which can actually be MEASURED between the bottom end of the antenna and ground ? I can then draw a circuit and continue with practical calculations. PLEASE, can no-one put me out of my misery ? ---- Reg, G4FGQ. Article: 220229 of rec.radio.amateur.antenna From: "Chuck S." Subject: Z matching of antennas Message-ID: Date: Mon, 19 Dec 2005 22:43:54 GMT This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C604C3.C83D9250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better = to use, an autotransformer or a transformer with an isolated primary and = secondary? I'm looking for the pro's and con's of each. --=20 Yours truly, Chuck=20 WA3IAC FN20la http://www.qsl.net/wa3iac/ ------=_NextPart_000_0006_01C604C3.C83D9250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

With respects to antenna matching, i.e.: 50 to 450 Ohms, which is = better to=20 use, an autotransformer or a transformer with an isolated primary and = secondary?=20 I=92m looking for the pro=92s and con=92s of each.


--
Yours truly,
Chuck
 
WA3IAC
FN20la
 
 
 
------=_NextPart_000_0006_01C604C3.C83D9250-- Article: 220230 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: antenna tuner range calculators Date: Mon, 19 Dec 2005 22:53:50 +0000 (UTC) Message-ID: References: <65Epf.1835$RZ6.1473@bignews7.bellsouth.net> Download and run in a few seconds programs T_TUNER and L_TUNER, from website below. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220231 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 23:17:14 +0000 (UTC) Message-ID: References: <43a6b708_3@newsfeed.slurp.net> <11qdvpv9kf3rs80@corp.supernews.com> "Roy Lewallen" wrote > I'd be willing to wager that there are places in Florida which have more > lightning strikes in a single summer than have occurred at your QTH (or > mine) in the past 80 years. ======================================= Roy, your's is a safe bet. Nevertheless, statistically speaking, the good people of Florida should be more scared of dying from gunshot wounds. But it doesn't seem to worry them very much. ---- Reg. Article: 220232 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Mon, 19 Dec 2005 15:17:51 -0800 Message-ID: <11qeft0bpn1590@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> Toni wrote: > > When talking about loop antennas people talk about "capture area". > Whatever that is, this seems to be what makes a ferrite bar antenna > more sensitive than the equivalent simple coil tuned to the same freq. > I know that by using a ferrite bar you are narrowing the pattern, but > I'd think that the main gain does not come from the pattern narrowing > but from "capture area increase" (again, please bear with my ignorance, > these are only my thoughts on what I've read on the Web) Capture area is exactly the same thing as gain, but expressed in different units. There are two ways of increasing the gain or capture area of an antenna: increase its efficiency, or narrow its pattern. The former increases the gain or capture area in all directions; the latter increases it in some directions at the expense of others. A ferrite loop antenna simply has better efficiency than a standard loop of the same physical size. Hence it has better gain or capture area. >>>I know one can not have more than 0 dB with full omni, I just guess the >>>minimalistic antenna in pocketable gps is way below 0 dB and could >>>maybe be improved a little. >> [RL] >>0 dB relative to what? > > > An isotropic antenna; AFAIK a perfect isotropic antenna would have 0 dB > gain dB is a ratio, in this case of gains, or field strengths with a given power input, or capture areas. (All three ratios are the same for a given pair of antennas.) So the reference always must be specified, otherwise a statement of dB gain is meaningless. When using the gain of a free space isotropic antenna as a reference, gain is expressed in dBi, that is, dB relative to isotropic. The gain of a perfectly omnidirectional antenna over an infinite ground plane is 3 dBi, since the same power is concentrated in half the volume as it is for an isotropic free-space radiator. > > [RL] >>Once you get the desired coverage angle, the only way to improve the >>reception of the GPS is to improve the receiver signal/noise ratio. The >>only way you can do that from outside the GPS is to use an external >>antenna with a preamp having a lower noise figure than the GPS's receiver. > > > Please let me doubt that. For a given coverage angle you can't make > better than a perfect antenna, but you can certainly make worst (think > of a T2FD). If by "perfect" you mean "perfectly efficient", I agree. > >>I'm not sure what the "high loss antenna" is. If you mean the GPS >>antenna, it's not high loss at all, but is likely very efficient. If >>it's a patch antenna, you can't model it at all with EZNEC. But even if >>it's a quadrifilar helix, you can't model it with one segment. > > > I dont know how efficient they are, but I do know that normal > commercial patch antennas are noticeably less efficient than helical > ones, and then, for the helicals, I doubt that something aprox 1/10 wl > is anything close to efficient. If this was to be true I'd love to > build an equivalent 6.5 ft. helix to work on 20m! I wasn't aware of that. So if typical GPS patch antennas are indeed significantly inefficient, the reception could be improved without narrowing the pattern. But I don't know if there would be any practical way to do this externally. The civilian GPS frequencies are about 1228 and 1575 MHz. The wavelength in air of the lower frequency is about 9.6 inches. Patch antennas can be made with a side equal to about 0.25 wavelength divided by the square root of the dielectric constant of the material within the patch. So for Teflon dielectric (er ~ 2.3), a patch would have sides of 1.6 inches. If something like alumina is used (very low loss, dielectric constant ~ 10), the side would be 0.76 inches. Some patches have sides twice this long, but alumina would permit even one of those to be used in a typical GPS receiver. The two versions of patches have different patterns, and I don't know right off which would be preferable for GPS use. At any rate, I believe that patches of those dimensions are quite efficient, assuming the dielectic has low loss. Both Teflon and alumina, as well as others, meet this criterion. Maybe someone with a greater knowledge of patch antennas, and GPS antennas in particular, could provide some additional information. Roy Lewallen, W7EL Article: 220233 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Mon, 19 Dec 2005 15:28:13 -0800 Message-ID: <11qeggdrdllf93d@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <1134921266.178997.255510@f14g2000cwb.googlegroups.com> <1134930784.403818.189120@g14g2000cwa.googlegroups.com> Toni wrote: > . . . > There are many classes of helix antennas, and all the "normal" helix > antennas you will find have dimensions comparable to a full wl if not > greater. Quadrifilar helices typically have four twisted half wave elements. The length for 1228 MHz would be somewhat less than 4.8 inches. Twisting would make the assembly less high that that, and fattening the elements or plating them on a dielectric substrate would further shorten them. This is consistent with the antenna of an older GPS unit I had. > My doubting on pocketable GPSs antenna's efficiency is based merely on > their size. They are about 1/10 wl long. The only other antennas of > comparable size I know are loops, isotrons, fractals, CFA, EH and CB > sticks and, except for tuned loops, we know how they are treated > whenever they appear in this forum. It's possible to make an electrically small antenna that's quite efficient. Typical examples are the small transmitting loops made by AEA and MFJ, or the shortened, top loaded verticals described by Jerry Sevick, W2FMI, in a series of articles in the '70s. What you can't make is a short, efficient, broadband antenna. But GPS antennas don't need to be broadband. And for that matter, they don't have to be that electrically small. > > >>The difference is that the helix is quite directional. > > > The ones used in GPS receivers are exactly the opposite. They should > ideally have a "half orange" radiation pattern, as they should be able > to follow a satellite from horizon to horizon all over your head. This describes the approximate pattern of both quadrifilar helix and patch antennas, which is why those are the types which are commonly used. > . . . Roy Lewallen, W7EL Article: 220234 of rec.radio.amateur.antenna From: "Chuck S." References: <1135035213.671636.52820@g14g2000cwa.googlegroups.com> Subject: Re: Z matching of antennas Message-ID: Date: Mon, 19 Dec 2005 23:57:31 GMT Ok Gary, I would like to match a 50 Ohm radio to a 450 Ohm antenna input. I know an "L" network would work, but what I was looking for is if an auto transformer would be as good or use a transformer with a isolated primary winding. wrote in message news:1135035213.671636.52820@g14g2000cwa.googlegroups.com... > Chuck S. wrote: >> With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better >> to use, an autotransformer or a transformer with an isolated primary and >> secondary? I'm looking for the pro's and con's of each. >> >> >> -- >> Yours truly, >> Chuck >> >> WA3IAC >> FN20la >> >> http://www.qsl.net/wa3iac/ > > Hi Chuck, If I read your question correctly, you want to match a 450 > ohm antenna, with no reactive component, to a 50 ohm transmission line. > In this case a 9:1 transformer would do the trick. > If however you are trying to match an antenna fed with a length of > 450 ohm line down to the transmitter, where it will need to be > transformed to 50 ohms, an "L" network or some other impedance matching > network will be required. The impedance seen at the end of the 450 ohm > line, in this instance, will rarely be 450 ohms resistive. > Gary N4AST > Article: 220235 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 16:02:04 -0800 Message-ID: <11qeiftgbhj3439@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <11q9kt36n4utv5e@corp.supernews.com> <1134924107.312230.237810@z14g2000cwz.googlegroups.com> <11qbi7i9pegj1db@corp.supernews.com> <11qciqd7vlfm4ec@corp.supernews.com> This has been an interesting discussion, and prompted me to do a tiny bit more research. It seems to me that if there's any nonlinear phenomenon which allows some pressure waves to travel through air faster than the speed of sound, surely a nuclear blast would produce enough pressure to excite it. But it doesn't seem to. From http://www.globalsecurity.org/wmd/intro/nuke-blast.htm: "During the time the blast wave is passing through the superheated atmosphere in the fireball, it travels at supersonic velocities. After it leaves the vicinity of the fireball, it slows down to the normal speed of sound in the atmosphere. As long as the blast wave is expanding radially, its intensity decreases approximately as the square of the distance. When the expanding blast wave from a nuclear air burst strikes the surface of the earth, however, it is reflected, and the reflected wave reinforces and intensifies the primary wave." Roy Lewallen, W7EL Article: 220236 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: MFJ ANTENNA QUESTION References: <43a72aae.7737125@newsgroups.bellsouth.net> Message-ID: Date: Tue, 20 Dec 2005 01:21:44 GMT Steven Fritts wrote: > I wonder if anyone has tried the MFJ collinear dipole that they have > in their new catalog. It is two half waves with a quarter wave length > of 450 ohm ladder line shorted at the bottom hanging down with an > SO 239 connector for the 50 ohn feedline connection. Sounds like a Double Zepp with a J-Pole-like matching stub. The antenna feedpoint impedance is very high. The 1/4WL ladder- line stub is shorted at the bottom. At some point up from the bottom, a 50 ohm point can be achieved, just like on a J-Pole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220237 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Z matching of antennas References: Message-ID: Date: Tue, 20 Dec 2005 01:23:32 GMT Chuck S. wrote: > With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better > to use, an autotransformer or a transformer with an isolated primary and > secondary? I’m looking for the pro’s and con’s of each. Where are you going to find a 450 ohm antenna? -- 73, Cecil http://www.qsl.net/w5dxp Article: 220238 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: One experience with noise References: <1134637337.c857a55f3cab0d38109173525afb1f55@roc.usenetexchange.com> Message-ID: <8kJpf.316866$zb5.87687@bgtnsc04-news.ops.worldnet.att.net> Date: Tue, 20 Dec 2005 01:42:28 GMT Wes, You got that right. Perhaps you are even too kind to cable service. After Hurricane Charley hit us head on last year we saw the following outages. Ordinary phone: 4 days (mostly underground) Electric power: 7 days (extensive pole replacement and rewiring) Cell phones: about 2 weeks (temporary towers brought in) Cable service: one month (cable runs on same poles as electric service) There was no flooding from Charley, but the winds were quite a bit stronger than Katrina and Rita. As soon as we got a temporary generator running we were able to watch regular over-the-air analog TV. 73, Gene W4SZ Wes Stewart wrote: [big snip] > And after a natural disaster cable TV systems will be working about as > well as cell phones have. While the old analog TV and radio will keep > chugging along. Article: 220239 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Passive reradiating antenna Date: Tue, 20 Dec 2005 01:49:41 +0000 (UTC) Message-ID: References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <11qeft0bpn1590@corp.supernews.com> "Roy Lewallen" wrote > A ferrite loop > antenna simply has better efficiency than a standard loop of the same > physical size. Hence it has better gain or capture area. ========================================= It's only a minor point, but when a ferrite core is placed inside a loop the efficiency remains the same. It's the same wire, the same coil dimensions, and hence the same loss in the resistance. If anything happens to efficiency it is reduced due to a loss in the ferrite core material. What happens is that the effective cross-sectional area of the loop increases approximately in proportion to the permeability of the core. For small permeabilities the capture area is much increased. But for larger permeabilities, say above 100, the effect diminishes and the effective core permeability settles down to the order of 20 or 30. It depends on the ratio of length to diameter of the core rather than of the coil. To visualise, it should be remembered most of the magnetic circuit lies in the air between and near the ends of a ferrite rod. There is no point in increasing permeability of rod material beyond a certain amount in an attempt to increase capture area. Capture area depends on the volume of the region of the e.m. field surrounding the core which is distorted by the core. See iron filings sprinkled round a bar magnet. When the reluctance of the rod itself is zero compared with that of the air path the limit of permeability has already been reached. And high values of rod permeability are always associated with high core loss. The moral is obvious. The sensitivity of the coil itself to e.m. waves is calculable. I'll stick out my neck and say the best a ferrite core can do is to increase the effective diameter of the coil by crudely 5 or 6 times. Which means that the gain of your tiny pocket MF transistor radio is much better than your super-dooper transceiver which needs a 260-feet long dipole on the 160 meter band. Just for the sake of argument! ---- Reg. Article: 220240 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? References: <43a6b708_3@newsfeed.slurp.net> <11qdvpv9kf3rs80@corp.supernews.com> Message-ID: Date: Tue, 20 Dec 2005 01:52:10 GMT Reg Edwards wrote: > Nevertheless, statistically speaking, the good people of Florida > should be more scared of dying from gunshot wounds. But it doesn't > seem to worry them very much. Now that so many Floridians are packing, it's the criminals who should be worried. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220241 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> Message-ID: Date: Tue, 20 Dec 2005 01:56:47 GMT Richard, There is no problem with Terman's words, but I believe you are missing his intention. His point in bringing up the magnetic flux is merely to say that one can find "exactly the same voltage" in the one meter long conductor by considered either the electric field directly or by considering the sweep of the magnetic field. It is just a statement of equivalence of the two components of the incident plane wave. This same sort of statement is found in many other textbooks. Terman's conductor is in free space. He discusses the voltage difference between one end of the conductor and the other end of the same conductor. He does not address the question at hand, which is the voltage between a perfect ground plane and the bottom of a short conductor near that ground plane. At least two people have explained why that voltage is not one volt for an incident field strength of one volt per meter. 73, Gene W4SZ Richard Harrison wrote: [snip] > Reg`s question of how much voltage is induced in 1 m of wire in a field > of 1 V/m is answered clearly by Terman in publications which date back > at least to 1932, the earliest copyright date I saw on "Radio > Engineering". So, many competent and critical reviewers have pored over > Terman`s works that it`s almost certain that any errors have been found > and corrected long ago. Everybody makes mistakes, but now Terman is as > close to infallible on the subject of radio as any author I know. Read > page 2 of Terman`s "Electronnic and Radio Engineering" (1955 edition) > for complete details. The same information appears in some other Terman > authored and edited writings (almost word for word). > > Best regards, Richard Harrison, KB5WZI > Article: 220242 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Z matching of antennas Date: Tue, 20 Dec 2005 02:00:10 +0000 (UTC) Message-ID: References: "Chuck S." wrote in message news:KIGpf.10022$aU4.4108@trnddc06... With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better to use, an autotransformer or a transformer with an isolated primary and secondary? I'm looking for the pro's and con's of each. ========================================== It all depends on what you want the transformer to do besides perform an impedance matching function. Otherwise there's little to choose between them. The autotransformer will have slightly less loss. More details please. ---- Reg. Article: 220243 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 02:52:28 +0000 (UTC) Message-ID: References: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> <11qeglddhokhvbf@corp.supernews.com> "Roy Lewallen" wrote > Hm. Have my postings gone unread? Or just unbelieved? > ================================== Or, am I trying to find somebody else who believes you ? Terman, Kraus and Balanis and some computer programs are of no help! ;o) ---- Reg. Article: 220244 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 23:16:41 -0600 Message-ID: <26465-43A793B9-961@storefull-3254.bay.webtv.net> References: Gene Fuller wrote: "There is no problem with Terman`s words, but I believe you are missing his intention." I parsed Terman`s words carefully trying to avoid misinterpretation. There is a RCA FM Coverage Calculator (special slide rule) pictured and described on the internet. Text accompanies the rule. This text says the range of the rule is for a radius of urban coverage of 1000 microvolts per meter and a radius of rural coverage of 50 microvolts per meter. They obviously anticipate a much higher urban noise level than found in rural areas. The rule has distance scales of 4 to 100 miles, and 16 to 143 miles.. The text says: "If you hold up 1 meter of wire at exactly the right angle, this is exactly how many millionths of a volt are generated between its ends. If you assume that 50 microvolts per meter in the country gives an acceptable quality signal at the receiver, you`ll be able to calculate how far away you can reach." There is much more text dealing with transmitter powers, broadcast antenna types, and antenna heights. Accuracy is said to be within 10%.. I`ve never seen one of these special slide rules myself, but maybe Walter Maxwell, Richard Fry, or someone else has and can elaborate. I quoted the text because it contained in effect the simple statement that 1 microvolt is generated betweens the ends of a well placed 1 meter long wire when immersed in a 1 microvolt electromagnetic field. I certainly never expected to see that fact debated. Best regards, Richard Harrison, KB5WZI Article: 220245 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 23:33:58 -0600 Message-ID: <26465-43A797C6-962@storefull-3254.bay.webtv.net> References: Gene, W4SZ wrote: "At least two people have explained why that voltage is not one volt per meter." Here are Terman`s exact words again: "The strength of the wave measured in terms of microvolts per meter of stress in space is also exactly the same voltage that the magnetic flux of the wave induces in a conductor 1 m long when sweeping across this conductor with the velocity of light." I see Gene`s statemennt as a contradiction within itself. Definition of field strength is the volts it will generate in a wire 1 meter long. There is no contradiction in Terman`s statement. Best regards, Richard Harrison, KB5WZI Article: 220246 of rec.radio.amateur.antenna Message-ID: <43A80523.E3A51346@shaw.ca> From: Irv Finkleman Subject: Re: Thanks for antenna help. References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 13:20:17 GMT The Eternal Squire wrote: > > All, > > I'm finally back on the air! Thanks for the antenna help, everyone. I > found on the net a 30m collapsible fiberglass pole. I applied copper > tape to one side as the radiator. I used layers of duct tape to > reinforce every joint. I have the ground side tied to the ground rod > of the trailer electrical system. No counterpoise yet. I worked a few > stations tonight on 40m CW. > > I am grateful for all the help, even to those who thought I wasn't > listening at first. > > The Eternal Squire My experience with duct tape is that it doesn't hold up well due to weathering. I'm not sure if it was the cold, the sun, or what, but it gradually let go and fell apart. I have no recommendations for a substitute but someone on the group might. Irv VE6BP -- -------------------------------------- Diagnosed Type II Diabetes March 5 2001 Beating it with diet and exercise! 297/215/210 (to be revised lower) 58"/43"(!)/44" (already lower too!) -------------------------------------- Visit my HomePage at http://members.shaw.ca/finkirv/index.html Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm -------------------- Irv Finkleman, Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP Calgary, Alberta, Canada Article: 220247 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Identify Old HF Vertical Message-ID: References: <173eq1li33s526o0f2j5s77t82f7sp2vhs@4ax.com> Date: Tue, 20 Dec 2005 13:22:02 GMT On Mon, 19 Dec 2005 20:39:38 -0600, "gb" wrote: > >John - > >This antenna model is almost identical to one that my brother was given in >the 1970s. I see you used a torch (scorch marks)..... the corrosion can be >removed with naval jelly or an electrolysis process (described in >boatanchors newsgroup). > >You should be able to wind a proper coil and have a 1/4 or 1/2 wave vertical >for 15 or 17 meters. You could use schedule 40 electrical conduit (gray >PVC) for new cover of coil. > >w9gb > I used a paint stripper gun to loosen the PVC. After I discovered that It would not be difficult to replace the sleeve I lost interest in trying to save it. On the next trip to town I will get some naval jelly for clean up. The bracket hardware needs it as well. My current plan for this project is to experiment with short 80 and 160 meter verticals. This is pretty early in the project, I have not constructed the radial system yet. The focus will be on matching methods, I feel the EZNEC software answers most of my other questions. This is an academic pursuit! John Ferrell W8CCW Article: 220248 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Identify Old HF Vertical Message-ID: References: Date: Tue, 20 Dec 2005 13:27:43 GMT On Mon, 19 Dec 2005 16:59:58 -0500, LarryLurker wrote: >What you have there is a Super Magnum CB antenna, vintage mid-60's. >The Magnum model had 4 foot radials and no top hat. The Super Magnum >has 9 foot radials with the top hat. By rewinding, or retapping the >coil, you can make a great 10 meter vertical. .... or it may be >simpler to change the length of the vertical section. I did the coil >thing in the mid-80's and used it to work all states and 130 >countries. > >LL > That is a pretty impressive testimony! John Ferrell W8CCW Article: 220249 of rec.radio.amateur.antenna From: "Richard Fry" Subject: Antenna Factor Date: Tue, 20 Dec 2005 07:48:03 -0600 Message-ID: <43a80ad7$1_4@newsfeed.slurp.net> With all the earlier/ongoing posts here about the voltage across a receive antenna immersed in a known field, it may be appropriate to recall the affect that "antenna factor" has on these measured values. Here is a website with background on this: http://www.djmelectronics.com/articles/emc-antenna-parameters-p3.html The measured field strength using commercial VHF/UHF field intensity meters needs to be adjusted based on antenna factor to determine the real value of the incident field, using charts included with the test system documentation. RF Article: 220250 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Thanks for antenna help. Message-ID: References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 13:51:07 GMT On 19 Dec 2005 22:55:39 -0800, "The Eternal Squire" wrote: >All, > >I'm finally back on the air! Thanks for the antenna help, everyone. I >found on the net a 30m collapsible fiberglass pole. I applied copper >tape to one side as the radiator. I used layers of duct tape to >reinforce every joint. I have the ground side tied to the ground rod >of the trailer electrical system. No counterpoise yet. I worked a few >stations tonight on 40m CW. > >I am grateful for all the help, even to those who thought I wasn't >listening at first. > >The Eternal Squire I have to ask: Do you really mean 30 feet rather than 30 meters? John Ferrell W8CCW Article: 220251 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Thanks for antenna help. References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <43A80523.E3A51346@shaw.ca> Message-ID: <36Upf.44214$Zv5.21586@newssvr25.news.prodigy.net> Date: Tue, 20 Dec 2005 13:58:23 GMT Irv Finkleman wrote: > My experience with duct tape is that it doesn't hold up well due > to weathering. I'm not sure if it was the cold, the sun, or what, but > it gradually let go and fell apart. I have no recommendations for > a substitute but someone on the group might. Automotive rated duct tape is of a higher quality than air-conditioning duct tape - also more expensive. A coating of clear Krylon also helps. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220252 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <26465-43A797C6-962@storefull-3254.bay.webtv.net> Message-ID: Date: Tue, 20 Dec 2005 14:16:17 GMT Richard, Not only are you misunderstanding Terman, you have twisted my words as well. I said, "At least two people have explained why that voltage is not one volt for an incident field strength of one volt per meter." You removed some of my words and completely changed the meaning. Once more, Terman is undoubtedly correct with his statement. I agree completely. However, the configuration described by Terman is NOT the subject at hand. 73, Gene W4SZ Richard Harrison wrote: > Gene, W4SZ wrote: > "At least two people have explained why that voltage is not one volt per > meter." > > Here are Terman`s exact words again: > "The strength of the wave measured in terms of microvolts per meter of > stress in space is also exactly the same voltage that the magnetic flux > of the wave induces in a conductor 1 m long when sweeping across this > conductor with the velocity of light." > > I see Gene`s statemennt as a contradiction within itself. Definition of > field strength is the volts it will generate in a wire 1 meter long. > There is no contradiction in Terman`s statement. > > Best regards, Richard Harrison, KB5WZI > Article: 220253 of rec.radio.amateur.antenna From: Andy Cowley Subject: Re: Antenna reception theory Message-ID: References: <26465-43A793B9-961@storefull-3254.bay.webtv.net> Date: Tue, 20 Dec 2005 14:40:14 GMT Richard Harrison wrote: > Gene Fuller wrote: > "There is no problem with Terman`s words, but I believe you are missing > his intention." > > I parsed Terman`s words carefully trying to avoid misinterpretation. > > There is a RCA FM Coverage Calculator (special slide rule) pictured and > described on the internet. Text accompanies the rule. This text says the > range of the rule is for a radius of urban coverage of 1000 microvolts > per meter and a radius of rural coverage of 50 microvolts per meter. > They obviously anticipate a much higher urban noise level than found in > rural areas. > > The rule has distance scales of 4 to 100 miles, and 16 to 143 miles.. > > The text says: "If you hold up 1 meter of wire at exactly the right > angle, this is exactly how many millionths of a volt are generated > between its ends. > And just how are you going to measure that voltage without getting an opposite voltage in your voltmeter leads. Or alternatively how can you present that voltage at the input to a receiver? You can't. So the above tells us zip about the question Reg asked. Roy answered the question correctly and you haven't even attempted it. Why is that? Andy Article: 220254 of rec.radio.amateur.antenna Date: Tue, 20 Dec 2005 08:17:49 -0700 From: sjt Subject: grounding Message-ID: I am installing a short tower. The soil is very dry, mostly volcanic ash and low conductivity. I had the backhoe operator dirll several holes 4 feet deep for grounding. It is impossible to drive a ground rod deeper than 4 feet due to bedrock. What should I use to fill the holes after the ground rods are installed? Article: 220255 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 09:38:02 -0600 Message-ID: <25358-43A8255A-47@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "Terman, Kraus, and Balanis and some computer programs are of no help!" My dictionary defines "field strength" as: "3. The strength of radio waves at a distance from the transmitting antenna, usually expressed in microvolts-per-meter. This is not the same as the strength of a radio signal at the antenna terminals of the receiver." The definition looks OK to me. The reason the signal is not the same as the microvolts-per-meter even when the antenna is a 1-meter length of wire with just the right slant is because the induced voltage gets divided between the antenna and its load (the receiver). Maybe Cecil`s IEEE dictionary has something to say about field strength. Best regards, Richard Harrison, KB5WZI Article: 220256 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Message-ID: <%ZVpf.37084$q%.36663@newssvr12.news.prodigy.com> Date: Tue, 20 Dec 2005 16:06:19 GMT Richard Harrison wrote: > Maybe Cecil`s IEEE dictionary has something to say about field strength. magnitude of the electric field vector in volts per meter, or magnitude of the magnetic field vector in amps (or ampere-turns) per meter, or power flux density P in watts per square meter. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220258 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Device insertion loss References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> Message-ID: Date: Tue, 20 Dec 2005 18:28:31 GMT Ron J wrote: > I was curious. If a matching network was designed to make the SWR at a > band of frequency less than 1.4 to 1, then what would happen if I > inserted a power sensor on the line with a rated SWR of 1.05 to 1 at > this frequency band? > > Would that make my overall system SWR 1.4 + .05 = 1.45 to 1? SWRs, like power, cannot be superposed. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220259 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> Subject: Re: Device insertion loss Message-ID: Date: Tue, 20 Dec 2005 18:32:38 GMT "Ron J" wrote in message news:1135102701.893263.244550@o13g2000cwo.googlegroups.com... > Hello, > > I was curious. If a matching network was designed to make the SWR at a > band of frequency less than 1.4 to 1, then what would happen if I > inserted a power sensor on the line with a rated SWR of 1.05 to 1 at > this frequency band? > > Would that make my overall system SWR 1.4 + .05 = 1.45 to 1? > No, SWR does not do a simple addition. If it is a power sensor that uses a short piece of transmission line then you have to know the frequency , the length in wavelengths, the inpedance of the line, and then do some calculations. It could be slightly beter or worse than it was to start with. Probably not enough to show on a simple swr meter. Article: 220260 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Device insertion loss References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> <1135104134.083886.169140@g14g2000cwa.googlegroups.com> Message-ID: <7lYpf.44262$Zv5.18745@newssvr25.news.prodigy.net> Date: Tue, 20 Dec 2005 18:47:31 GMT Ron J wrote: > My main concern is that at the band of design > frequency the transmitter is only designed to handle 1.5 SWR max. I'm > afraid that I might break it since our matching network already changes > the SWR to a peak 1.40 to 1 at certain frequencies on the band. > > I may have other idea. If I add the return loss of the devices, would > that allow me to somehow find the SWR? Measure the impedance of the system (using low power). That's the only way to know for sure. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220261 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Device insertion loss Date: Tue, 20 Dec 2005 20:38:33 +0000 (UTC) Message-ID: References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> I note the subject matter of this thread is "Insertion Loss" Insertion loss is the ratio of power delivered to a load, to the power delivered to the same load when a network is inserted between the load and the same generator. With insertion of a passive network, such as a tuner, the insertion loss can even be a gain. Calculation or measurement of insertion loss ALWAYS involves or implies knowledge of the generator impedance. In the present context the generator is the transmitter. As nobody knows the internal impedance of the transmitter this thread will rapidly degenerate into nonsensical argument if it hasn't already done so. You have been warned! ---- Reg, G4FGQ Article: 220262 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Device insertion loss Message-ID: References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> <1135104134.083886.169140@g14g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 21:00:03 GMT On 20 Dec 2005 10:42:14 -0800, "Ron J" wrote: >Hi Cecil, > >Thanks! I try to explain the affect of the power sensor even if it is >ideally very minimal. My main concern is that at the band of design >frequency the transmitter is only designed to handle 1.5 SWR max. I'm >afraid that I might break it since our matching network already changes >the SWR to a peak 1.40 to 1 at certain frequencies on the band. > >I may have other idea. If I add the return loss of the devices, would >that allow me to somehow find the SWR? As others have told you, no, the system isn't analysed as simply as you suggest. Some thoughts: - your concern that your transmitter will suddenly degrade at VSWR=1.5 is probably unfounded; - if your power sensor is intended for inline monitoring, it should be designed to "monitor" with insignificant impact on the load presented to the transmitter. You didn't tell us enough to give you a definitive answer, but it is likely that you are unnecessarily worried about the sensitivity of the transmitter to VSWR, and the cumulative effect of the monitoring sensor which should be insignificantly small in the real world with suitable / practical components. Owen -- Article: 220263 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 21:22:56 +0000 (UTC) Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> What is the proportion of Black amateur radio licencees to Whites? How does it correspond to the same proportion in the population as a whole? =========================================== Article: 220264 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 15:33:50 -0600 Message-ID: <27842-43A878BE-1151@storefull-3251.bay.webtv.net> References: Andy wrote: "So the above told us zip about the question Reg asked. Roy answered the question correctly and you haven`t even attempted it." I assumed the definition of "field strength" correctly answered Reg`s question and his descrepancy lay elswhere. Field strength of an electromagnetic wave is expressed in microvolts per meter. It is defined as the number of microvolts which would be induced in a properly placed piece of wire one meter long. If a field strength of one microvolt per meter does not induce one microvolt into a piece of wire one meter long, why not? I`ve been looking for an explanation and found a possible answer in Figure 2-9-1 on page 31 of Kraus` 3rd edition of "Antennas". The possible explanation is called the "effective height" in meters of an antenna. It is a "factor", which when multiplied by the microvolts per meter of the field strength, gives the volts induced in the antenna at its terminals. According to Kraus` figure, h is a function of current distribution in the antenna. The text says that for a dipole 0.1 lambda long, h = 0.5X the length of the antenna. Reg did not specify a frequency or wavelength for his antenna, as I recall, and he did specify a ground mounted vertical whip 1 m long for his receiving antenna. For a dipole 0.5 lambda long, Kraus gives (h) as 0.64X the length of the antenna. For all I know, there is a vertical antenna length in terms of wavelength for which h=1. If so, the volts between the antenna base and the ground directly under it would numerically exactly equal the microvolts per meter of the field strength. All we need to do is pick the right frequency. The applicable Formula is (1) on page 30. I suspect that in most cases, h is determined experimentally. I regret I`ve not had a copy of Kraus nearly as long as I`ve had a copy of Terman. I`m still using an edition I`ve had for 58 years. It shows lots of wear and tear. Best regards, Richard Harrison, KB5WZI Article: 220265 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 22:06:20 -0000 Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> "Amos Keag" wrote in message news:DNGdncHNgZZj5zXeRVn-hg@comcast.com... > Reg Edwards wrote: > > What is the proportion of Black amateur radio licencees to Whites? > > > > How does it correspond to the same proportion in the population as a > > whole? > > =========================================== > > > > > > I don't believe that information is required on an application. > Therefore it should be un-obtainable. That percentage must be rising now thanks to the M3/CB'ers licence as so many Hams class it. Before I would say it was very low as it doesn't involve shooting people, stealing mugging or raping. Now it takes no effort there will be plenty of them using the radios to co-ordinate robberies and gangland shootings... yeeee haaaaah good buddy....... So what's wrong with being racist? Why let your neighbourhood turn into a shithole.......... Article: 220266 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 22:06:56 +0000 (UTC) Message-ID: References: <26465-43A793B9-961@storefull-3254.bay.webtv.net> <52hgq1trg07spm2fpm3g515f6nllimpjg1@4ax.com> "Richard Clark" wrote > You make a loop. ====================================== I normally reply, if I reply at all to your idiotic statements, with "Phooey". But on this occasion, to protect innocent, bystanding, novices from your deliberate, inexcusible, misleading statement, it should be said that the voltage induced in a circular loop is altogether different and very much smaller from that induced in a straight wire of the same length. You disgust me! A disgrace to amateur radio! Have a miserable Christmas! ---- Reg, G4FGQ. Article: 220267 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 23:19:48 +0000 (UTC) Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> "Amos Keag" wrote - > Reg Edwards wrote: > > What is the proportion of Black amateur radio licencees to Whites? > > > > How does it correspond to the same proportion in the population as a > > whole? > > =========================================== > I don't believe that information is required on an application. > Therefore it should be un-obtainable. > =========================================== Indeed it is. But you can always have a guess and think about what it means. --- Reg. Article: 220268 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 17:11:21 -0600 Message-ID: <25358-43A88F99-94@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "Have a miserable Christmas!" In the cinema, "The Grinch Who Stole Christmas", the Grinch turned into a kind, green, Santa Claus. Let`s hope Reg has a change of heart too! Merry Christmas, Richard Harrison, KB5WZI Article: 220269 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 17:27:28 -0600 Message-ID: <25358-43A89360-96@storefull-3257.bay.webtv.net> References: Richard Clark wrote: "You make a loop." There is a difference. The small whip has a high capacitive reactance. The small loop has a high inductive reacvtance. Both have low radiation resistance. But, the loop is more often used to determine EM field strength. You just need the right "fudge factor" to convert antenna voltage tto field strength or vice versa. Best regards, Richard Harrison, KB5WZI Article: 220271 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 00:30:31 +0000 (UTC) Message-ID: References: <25358-43A89360-96@storefull-3257.bay.webtv.net> "Richard Harrison" wrote in message news:25358-43A89360-96@storefull-3257.bay.webtv.net... > Richard Clark wrote: > "You make a loop." > > There is a difference. The small whip has a high capacitive reactance. > The small loop has a high inductive reacvtance. Both have low radiation > resistance. But, the loop is more often used to determine EM field > strength. You just need the right "fudge factor" to convert antenna > voltage tto field strength or vice versa. > > Best regards, Richard Harrison, KB5WZI ===================================== For the very last time I will repeat my question :- "What is the voltage measured between the bottom end of a 1 metre vertical antenna and ground when the field strength is 1 volt per metre. The height (length) of the antenna is much less than 1/4-wavelength. The bottom end of the antenna is immediately above the ground. The ground is assumed perfect. The field is vertically polarised. Frequency, loops, reactance, radiation resistance do not enter into the argument. No other information is needed. Terman, Kraus and Balanis' bibles provide answers to a different question in which I am not interested. Mere mention of these learned gentlemen only confuses the issue. The answer is entirely fundamental to e.m. radiation and reception. All I need is a number of volts. What is it please? ---- Reg, G4FGQ. Article: 220272 of rec.radio.amateur.antenna From: "Richard Fry" References: <25358-43A89360-96@storefull-3257.bay.webtv.net> Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 19:10:49 -0600 Message-ID: <43a8aade_2@newsfeed.slurp.net> "Reg Edwards" wrote > For the very last time I will repeat my question :- Pray it so... > "What is the voltage measured between the bottom end of a 1 metre > vertical antenna and ground when the field strength is 1 volt per > metre." Of what relevance is this to anyone but (apparently) you? Please elaborate. RF Article: 220273 of rec.radio.amateur.antenna From: "Dave Pitzer" Subject: Geo coordinates -- didtance Date: Tue, 20 Dec 2005 20:31:56 -0500 Message-ID: <43a8b08c$0$58074$742ec2ed@news.sonic.net> I'm looking for a way to enter two pairs of geographic coordinates (point X and point Y) and have the over-ground distance between them returned. Any help? Dave P Article: 220274 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Geo coordinates -- didtance References: <43a8b08c$0$58074$742ec2ed@news.sonic.net> Message-ID: Date: Wed, 21 Dec 2005 01:46:11 GMT Dave Pitzer wrote: > I'm looking for a way to enter two pairs of geographic coordinates (point X > and point Y) and have the over-ground distance between them returned. > > Any help? > > Dave P The standard formula for the great circle distance is: d=arccos[sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(long1-long2)] There is no magic here; this is simply spherical geometry and trigonometry at work. Of course if you don't care about the great circle distance, the answer can be anything you wish. 73, Gene W4SZ Article: 220275 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 18:12:02 -0800 Message-ID: <11qhefipinecp86@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Richard Harrison wrote: > Reg, G4FGQ wrote: > "Terman, Kraus, and Balanis and some computer programs are of no help!" > > My dictionary defines "field strength" as: > "3. The strength of radio waves at a distance from the transmitting > antenna, usually expressed in microvolts-per-meter. This is not the same > as the strength of a radio signal at the antenna terminals of the > receiver." > > The definition looks OK to me. The reason the signal is not the same as > the microvolts-per-meter even when the antenna is a 1-meter length of > wire with just the right slant is because the induced voltage gets > divided between the antenna and its load (the receiver). > No, that's not why. The terminal voltage of an open circuited 1 meter (electrically short) dipole is 1/2 the field strength in volts/meter. The terminal voltage when terminated with a conjugately matched load can be well over a thousand volts (in the theoretical lossless case). But it's pointless to keep repeating this. Reg keeps asking the same question, and you keep responding with the same incorrect answers. I believe I've gotten through to everyone who really wants to know the answers, so I'll let this be my last repetition. Roy Lewallen, W7EL Article: 220276 of rec.radio.amateur.antenna From: "Joel Kolstad" Subject: Re: One experience with noise Date: Tue, 20 Dec 2005 18:12:55 -0800 Message-ID: <11qhejvjtj1ak38@corp.supernews.com> References: <1134637337.c857a55f3cab0d38109173525afb1f55@roc.usenetexchange.com> "Wes Stewart" wrote in message news:m4keq1tmlrevv8fm3gih3266obcdh725ba@4ax.com... > On Thu, 15 Dec 2005 09:02:17 +0000, Paul Johnson > wrote: > And after a natural disaster cable TV systems will be working about as > well as cell phones have. Only as long as the emergency broadcast system is kept alive. There's no particular reason the funding for it couldn't be shut off/expanded to include cable/switch only to cable/whatever. In fact, one could argue that during a natural disaster cable TV could actually be more reliable in that its infrastructure is somewhat more protected than a huge antenna ever could be. (I seem to recall from Hurricane Katrina that some of the first phone calls getting out -- barring folks with satellite phones -- were VOIP calls over wired Internet connections.) >>4:3 aspect was a technical limitation that really should have died long >>before my birth, much less now. Good riddance. > > What "technical limitation"? Aspect ratios are arbitrary. Not true. In the 'early days' of TV, the glass for CRTs couldn't be blown into such arbitrary aspect ratios; hence 4:3 was chosen as a reasonably compromise between producibility and "well, at least it's not square...!" :-) Presumably 16:9 is a closer match to human vision than 4:3, and for viewing a movie it would seem to make sense to try to match that since you're trying to encompass the viewer. ---Joel Article: 220277 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: One experience with noise Message-ID: References: Date: Wed, 21 Dec 2005 02:34:12 GMT On Sat, 10 Dec 2005 08:06:58 -0700, Wes Stewart wrote: >On Tue, 06 Dec 2005 23:28:15 GMT, Owen Duffy wrote: > >> >>Don't you have digital television? Best thing since sliced bread. >> >>I don't know if you can receive analog television beyond the digital >>coverage ranges, but you probably wouldn't want to watch it. >> >>Digital TV makes weak signals most watchable, DVD quality at weak >>signals. >> >>I use it and I am only 4km from the transmitter, but that is another >>situation where it works a treat, ghost free pictures close to the >>tranmitter in the presence of local reflections (hills, water towers >>etc). > >I suppose you have the Coded Orthogonal Frequency Division >Multiplexing (COFDM) standard there. Yes. I saw STBs in the supermarket this morning for A$69 or about US$55. Owen -- Article: 220278 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 02:41:28 +0000 (UTC) Message-ID: References: <25358-43A89360-96@storefull-3257.bay.webtv.net> <43a8aade_2@newsfeed.slurp.net> "Richard Fry" wrote in message news:43a8aade_2@newsfeed.slurp.net... > "Reg Edwards" wrote > > For the very last time I will repeat my question :- > > Pray it so... > > > "What is the voltage measured between the bottom end of a 1 metre > > vertical antenna and ground when the field strength is 1 volt per > > metre." > > Of what relevance is this to anyone but (apparently) you? Please elaborate. > > RF ========================================= For starters, Have you never heard of field strength measurements? Have you ever designed the input stage of a radio receiver? The topic is fundamental to an understanding of e.m. radiation and reception. Can YOU answer the simple question? Or are you entirely dependent on your gospel faith in 'Bibles'. On this occasion at least, the Bibles are letting dependent people down. The immediate relevance to me is that I have a program which has been reported to have a calculating error. It was reported by a person who is not dependent on bibles. He stated that the conventional/traditional calculating method used in my program was incorrect. I was not entirely convinced so I posed a related question on this newsgroup to which only one person has replied with a number. And he was wrong first time. Other persons who replied, after consulting their bibles, were unable even to answer the question, either rightly or wrongly. They just generated more confusion. The program concerned is GRNDWAV4 which I think, but not absolutely certain, has now been corrected. Why not download it, input a very few standard values, and tell me whether or not it provides the correct answer to receiver power input? You may, of course, prefer not to commit yourself. Is that enough elaboration for you? ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220279 of rec.radio.amateur.antenna From: "west" References: <1135099145.094973.160920@f14g2000cwb.googlegroups.com> Subject: Re: grounding Message-ID: Date: Wed, 21 Dec 2005 02:59:28 GMT wrote in message news:1135099145.094973.160920@f14g2000cwb.googlegroups.com... > You are lucky to have 4 feet. I have 8 inches or less around my house. > Zero behind the garage. > > Is this going to be an antenna or just a tower for an antenna? Is the > area irrigated/watered for grass? If an antenna, you will need to > install a bunch of radials on or just under the ground surface. If you > are trying to ground the tower for lightening protection, I guess I > would mix a bunch of granular commercial fertilizer in with the soil as > I packed it around the ground rods. Then lots of water on the area. > > Did you also have holes placed for guy wire anchors? > > Paul, KD7HB I believe the aim is to get more conductivity from the soil. That being the case, I would pour rock salt in the holes. west > Article: 220280 of rec.radio.amateur.antenna From: "DrDeath" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 21:10:21 -0600 Message-ID: <11qhhsrql5700ef@corp.supernews.com> References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> wrote in message news:do9v67$el4$1@news7.svr.pol.co.uk... > "Amos Keag" wrote in message > news:DNGdncHNgZZj5zXeRVn-hg@comcast.com... >> Reg Edwards wrote: >> > What is the proportion of Black amateur radio licencees to Whites? >> > >> > How does it correspond to the same proportion in the population as a >> > whole? >> > =========================================== >> > >> > >> >> I don't believe that information is required on an application. >> Therefore it should be un-obtainable. > > That percentage must be rising now thanks to the M3/CB'ers licence as so > many Hams class it. Before I would say it was very low as it doesn't > involve > shooting people, stealing mugging or raping. Now it takes no effort there > will be plenty of them using the radios to co-ordinate robberies and > gangland shootings... yeeee haaaaah good buddy....... > > So what's wrong with being racist? Why let your neighbourhood turn into a > shithole.......... > > > > Drug dealers already use FRS and scanners for surveillance. Article: 220281 of rec.radio.amateur.antenna From: "west" Subject: 2 or more Ants. needed Message-ID: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> Date: Wed, 21 Dec 2005 03:08:45 GMT I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from Ham Radio for more than 20 years & would like opinions on what would be the absolute best omni-directional antenna(s) to buy, for this rig? All opinions welcomed. Thank you. west AF4GC Article: 220282 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 22:08:44 -0600 Message-ID: <3647-43A8D54C-984@storefull-3258.bay.webtv.net> References: Reg, G4FGQ wrote: "All I need is a number of volts." I`ll guess, because Reg asked, not because I know aanything. I`ve now discovered Kraus` effective antenna height which may be related to an Icelandic connection. Reg hasn`t told us everything he knows. One reason we don`t know is because the effective antenna height is related to the antenna`s length in terms of wavelength according to Kraus. One of the examples given by Kraus is a dipole of 1/10 of a wavelength. Kraus tells us the effective height of this length gives a factor of 0.5. According to Equation (1) on page 30 of the 3rd edition of "Antennas", Voltage at the terminals of the antenna = effective height X field strength. If we guess that a short whip might have the same effective height as a short dipole, then with a 1 volt per meter field strength X 0.5 as an effective height factor, their product would be 0.5 volts. I`ll assume rms because that`s the convention for expression. I don`t have much confidence in the number because I think you must determine the effective height experimentally. Terman says on page 991 of his 1943 "Radio Enginneers` Handbook: "If an antenna other than a loop is used, the effective height must be determined experimentally. Maybe someone has worked this out since 1943. Best regards, Richard Harrison, KB5WZI Article: 220283 of rec.radio.amateur.antenna Message-ID: <43A8E22D.6070208@bogus.net> Date: Tue, 20 Dec 2005 22:03:41 -0700 From: hayseed Subject: Re: grounding References: I saw a group of reps from MITRE solve a radar grounding issue by tying the ground line to a 4'X8' copper plate and burying the plate in a 6' deep pit filled with copper sulfate crystals. Threw in water, waited and, viola, decent ground in granite rock mountain top. -Bob Article: 220284 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 21 Dec 2005 06:31:44 GMT K7ITM wrote: > There are several possible reasons for being interested in standing > waves (on transmission lines). Some are valid, some are not, and > you'll even get plenty of, um, discussion about what's valid and what > isn't. > > If your goal is to get maximum power delivered to a load, then it's > good to minimize standing waves on the line delivering power to that > load, because a line delivering a particular amount of power to a load > will have greater power lost in the line with greater standing waves. > If the line is being used near its maximum power or voltage rating, > standing waves are a concern because for a given power delivered to the > load, the rms current at current nodes and the peak voltage at voltage > nodes both increase with increased standing waves. And a high standing > wave ratio on a line which is long compared with a wavelength suggests > that the input impedance to the line will vary rapidly with frequency, > whereas a line with low standing wave ratio will present a relatively > constant impedance to the driving source, assuming the load is > reasonably "flat" with frequency. > > As an example of this last point, a 30 meter (~100 foot) 50 ohm line > with 0.8 velocity factor and very low loss, delivering power to a 50 > ohm load at 450MHz, will present a 50 ohm load to the driving source. > But delivering power to a 200 ohm load, the source will "see" almost > 200 ohms at frequencies where the line is an integer number of > electrical half-waves long, and it will "see" just over 12.5 ohms > midway between those frequencies. You get 200 ohms at 440MHz, 12.5 > ohms at 442MHz--and reactive in between. > > It's possible to use stubs and series line sections to effect an > impedance match between a load and a line. For example, the right > length and impedance series section will give you a match at one > particular frequency, at least, and multiple sections can give you a > "perfect" match at multiple frequencies, with (perhaps) quite > acceptable match over a range of frequencies. > > There are lists of analogs among electrical, mechanical, acoustic, and > other media. "electrical hydraulic impedance analog" in a Google > search will give you many hits. > > Cheers, > Tom > Thanks for your reply. I have a few questions. When you say "standing waves", I take it that one can have more than one on the line? I follow your example, but I may come back to it once I've done the calcs. How does one know they want to improve their impedance match? Why doesn't there seem to be a need for this (probably through a balun) on a standard AM radio with a 1/2 wave line antenna or even some ferrite coil? Is there some auto-balun that works this all out? Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet "He who laughs, lasts." -- Mary Pettibone Poole -- Web Page: Article: 220285 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: VHF/UHF Antenna Date: Wed, 21 Dec 2005 06:42:59 -0000 Message-ID: <11qhubj9sg5tm24@corp.supernews.com> References: <1135142322.762859.121600@g44g2000cwa.googlegroups.com> >I'm not sure if this is the correct newsgroup for this type of question >- sorry if I've posted in the wrong newsgroup. I want to ditch my cable >and go with an antenna. I'm trying to figure out what would be the best >type for my location. > >All the channels thatI want to pick up are less than or equal to 25 >miles from my home, except for one. The one that is the greatest >distance away, FOX, is 30 miles away from my home. > >All of the channels that are less than or equal to 25 miles are between >12 o'clock and 1 o'clock. They consist of a mixture of VHF and UHF >channels. FOX (30 miles away) is at my 2 o'clock and is a UHF channel. > >Antennaweb.org says I need a large directional with pre-amp antenna in >order to pick up FOX, but I can't get something that big to put on the >side of my house. My wife will scream bloody murder if I did that. I >have no obstructions of the sky in the directions that the antenna will >have to point. > >What type of antenna would be best for my circumstance? I would prefer >something that is small and not very noticeable (maybe something that >could pass for a DirecTV dish). Also, I would prefer to have it point >in a fixed direction so that I do not have to turn it in order to view >different channels. I'm planning on getting a HDTV in the near future. >Do I need a special type of antenna in order to view a TV program in HD >or will any antenna work? I'd say that AntennaWeb is giving you pretty decent advice. It's perhaps a bit conservative but not excessively so. I'm operating under similar circumstances - I'm near the south of the San Francisco peninsula about 35-40 miles away from the transmitters in San Francisco. We get a good, clean picture using a "medium fringe" UHF/VHF antenna (log-periodic plus corner reflector), mounted on a 18' mast on the roof (antenna height above ground is somewhere around 30'). We do have an amplifier for our indoor signal distribution, but could probably get away without one if we were only driving one or two TVs/tuners. We don't need to use the rotator, since all but one of the stations are north of us. The one exception is a San Jose station, which is right "off the back" of the main antenna. We *would* need to use the rotator, but I built a separate single-channel Yagi antenna and pointed it at San Jose and used a combiner. Most people around here who have roof antennas, have ones which are in roughly the same ballpark as ours... some higher, some not quite so high. The height helps a lot - an antenna down at roof level is going to "see" its horizon only about half as far away as an antenna with an extra 15' of height, and that's enough to make the difference between a clean ghost-free signal and one that's pretty noisy or ghosty. Most TV antennas have a relatively broad forward beamwidth. Your "noon to 2 o'clock" antenna pattern is about 60 degrees, which is probably going to be workable for a standard medium-fringe log-periodic antenna design if you've got the antenna up high enough. If you don't have enough height, then you're going to have a substantially weaker signal hitting the antenna, which would mean you'd need more antenna gain, which means a longer and more obvious antenna and a narrower beam-width, which might require a rotator. A small, roof-mounted, non-obvious antenna which might pass itself off as a satellite dish is likely to be nearly omnidirectional, having little or no gain, and in your situation it won't "get a good look" at the transmitters (they may be over the horizon), and you won't get a good signal. The requirements for digital TV (hi-def or standard-def) are not all that different from the requirements for NTSC analog. If you have a non-snowy, non-ghosty analog TV picture, you'll likely get a good digital-TV signal from any digital TV transmitter operating at full power. However, since most DTV transmitters today seem to be running at reduced power to avoid interference with nearby analog-TV frequencies, you can't necessarily count on getting a good digital signal lock. If your analog TV signal is noisy or ghosty, receiving digital TV properly is likely to be a problem. Unfortunately, there's no real substitute for a good antenna, up on a mast, clear of trees and buildings and other obstructions, pointed in the correct direction. Any compromise you make from that, will probably compromise the signal to some extent. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 220286 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Date: Wed, 21 Dec 2005 07:01:17 GMT "Richard Harrison" bravely wrote to "All" (20 Dec 05 09:38:02) --- on the heady topic of "Re: Antenna reception theory" RH> From: richardharrison@webtv.net (Richard Harrison) RH> Xref: core-easynews rec.radio.amateur.antenna:221565 RH> Reg, G4FGQ wrote: RH> "Terman, Kraus, and Balanis and some computer programs are of no RH> help!" RH> My dictionary defines "field strength" as: RH> "3. The strength of radio waves at a distance from the transmitting RH> antenna, usually expressed in microvolts-per-meter. This is not the RH> same as the strength of a radio signal at the antenna terminals of the RH> receiver." RH> The definition looks OK to me. The reason the signal is not the same RH> as the microvolts-per-meter even when the antenna is a 1-meter length RH> of wire with just the right slant is because the induced voltage gets RH> divided between the antenna and its load (the receiver). Not only that, but also this: the antenna rebroadcasts half of the intercepted energy. A*s*i*m*o*v Article: 220287 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 23:18:36 -0800 Message-ID: <11qi0ecphael065@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Asimov wrote: > . . . > RH> The definition looks OK to me. The reason the signal is not the same > RH> as the microvolts-per-meter even when the antenna is a 1-meter length > RH> of wire with just the right slant is because the induced voltage gets > RH> divided between the antenna and its load (the receiver). > > > Not only that, but also this: the antenna rebroadcasts half of the > intercepted energy. But voltage isn't energy. Or power. Roy Lewallen, W7EL Article: 220288 of rec.radio.amateur.antenna From: "Dave Pitzer" References: <43a8b08c$0$58074$742ec2ed@news.sonic.net> Subject: Re: Geo coordinates -- didtance Date: Wed, 21 Dec 2005 08:23:16 -0500 Message-ID: <43a95747$0$58051$742ec2ed@news.sonic.net> Gene: Thanks. And for those who wish to enter the coordinates of two points and have the distance returned (my original request), this is a Web site that does the caluculation for you: http://www.indo.com/distance/ Dave P. "Gene Fuller" wrote in message news:Dt2qf.175939$qk4.31863@bgtnsc05-news.ops.worldnet.att.net... > Dave Pitzer wrote: > > I'm looking for a way to enter two pairs of geographic coordinates (point X > > and point Y) and have the over-ground distance between them returned. > > > > Any help? > > > > Dave P > > The standard formula for the great circle distance is: > > d=arccos[sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(long1-long2)] > > There is no magic here; this is simply spherical geometry and > trigonometry at work. > > Of course if you don't care about the great circle distance, the answer > can be anything you wish. > > 73, > Gene > W4SZ Article: 220289 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 07:22:58 -0600 Message-ID: <27216-43A95732-40@storefull-3253.bay.webtv.net> References: <4l1iq1h3c85qklsplq3i8d3mndk6r3f7m6@4ax.com> Richard Clark, KB7QHC wrote: "In land stations the actual effective height is from 50 to 90% of the measured height." If the effective height is 50%, volts at the antenna terminals are no more than 50% numericcally of the volts per meter in the field strength when all else is optimum. This could account for Reg`s 2 to 1 discrepancy. I wonder what the speculations of Reg and his Icelandic correspondent are? Do they have a formula to predict effective height? Does Roy have such a formula? It`s a factor which won`t go away, even when ignored.. Best regards, Richard Harrison, KB5WZI Article: 220290 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 21 Dec 2005 15:17:50 GMT W. Watson wrote: > Thanks for your reply. I have a few questions. When you say "standing > waves", I take it that one can have more than one on the line? Standing waves are created by two coherent traveling waves moving in opposite directions in a transmission line. In a conventional system of source, transmission line, and load, one of the traveling waves moves from the source toward the load and is called the forward wave. The other traveling wave moves from the load toward the source as a reverse or reflected wave. The reflected wave is usually the result of a load being mismatched to a transmission line. If no mismatch exists, no standing waves are created and the system is considered to be "flat", i.e. one forward traveling wave. > How does one know they want to improve their impedance match? For a transmitted signal, we establish a Z0-match to our transmitter often at the input of an antenna tuner. When reflected energy is eliminated on the coax between the tuner and transmitter, we know we have a Z0-match by the SWR meter reading of 1:1. We also use our antenna tuners to tune for maximum received signal on our S-meters. At the Z0-match point, maximum available energy is transferred. If you know the input impedance to a receiver, you can match your antenna system to it to achieve maximum available energy transfer >from the antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220291 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> Message-ID: Date: Wed, 21 Dec 2005 15:19:51 GMT Roy Lewallen wrote: > But voltage isn't energy. Or power. True, but voltage cannot exist without energy. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220292 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> Message-ID: Date: Wed, 21 Dec 2005 15:47:38 GMT dansawyeror wrote: > Be carefully, that is not exactly true. Voltage cannot be created > without energy, it is a force. Dan, Stop now, before you further embarrass yourself. 73, Gene W4SZ Article: 220293 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: 2 or more Ants. needed Date: Wed, 21 Dec 2005 11:03:13 -0500 Message-ID: References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> west wrote: > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from Ham > Radio for more than 20 years & would like opinions on what would be the > absolute best omni-directional antenna(s) to buy, for this rig? All opinions > welcomed. Thank you. Ain't no such beast! Anyhow, if you are looking for omni-directional, I guess you are looking at a vertical antenna. Of course it is hard to call most verticals "absolute best". If I had to have only one antenna, it would be a dipole What are you planning on doing, how much land do you have, and are you under any restrictions? And are you going to buy or make? - 73 de Mike KB3EIA - Article: 220294 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> Message-ID: Date: Wed, 21 Dec 2005 16:26:46 GMT dansawyeror wrote: > Be careful, that is not exactly true. Voltage cannot be created > without energy, it is a force. However once it is 'in place' it requires > no energy to sustain. A voltage cannot be sustained without energy. The joule of energy used to create a voltage on a capacitor is stored in the capacitor until something changes. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220295 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: More BPL rollout. sigh... Date: 21 Dec 2005 18:22:46 GMT Message-ID: http://biz.yahoo.com/bizj/051221/1205323.html?.v=4 Under the deal, Current will design, build and operate the "smart grid," which will cover the majority of the TXU Electric Delivery service area -- about 2 million homes and businesses in Dallas-Fort Worth and other communities in Texas. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 220296 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Sloper Questions Date: Wed, 21 Dec 2005 18:47:19 +0000 (UTC) Message-ID: References: For practical receiving purposes, a sloping wire, in the midst of buildings, can be considered to be omi-directional, even isotropic. Any variations in directivity, in either the vertical or horizontal planes, although they exist, are not measurable or noticeable. The random effect of the presence of a nearby building or buildings is greater than the direction in which the wire may or may not slope. Sensitivity is frequency dependent. It falls of rapidly when the length of the antenna is less than 1/6th wavelength at the lowest frequency of interest. Of at least as great importance is the grounding system. With ordinary garden soil you will need at least 5 or 6 shallow buried wires under the antenna, radiating from a common point in random directions. Ground wire length need be no longer than 1/12th wavelengths at the lowest frequency of interest. Lengths and numbers are very non-critical. A sloping wire or inverted-L is the best general-purpose antenna you can get. Just erect something, not forgetting the ground. ---- Reg, G4FGQ. Article: 220297 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL rollout. sigh... Date: Wed, 21 Dec 2005 18:41:04 +0000 (UTC) Message-ID: References: Allodoxaphobia wrote: > Under the deal, Current will design, build and operate the "smart grid," > which will cover the majority of the TXU Electric Delivery service area > -- about 2 million homes and businesses in Dallas-Fort Worth and other > communities in Texas. All because you refused to boycott Google............ Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 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: 220298 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: References: Date: Wed, 21 Dec 2005 20:18:05 GMT On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" wrote: I'm trying to make >some sense out of why the emphasis of standing waves. Here is the short version: A matched transmission line behaves like the theory books say it does. The rated power from the transmitter goes through the transmission line with the lowest possible loss to the antenna where it is radiated just like the book says. A mismatched transmission just MIGHT work OK. If there is any possibility of generating interference, especially TVI, it will. The currents and voltages on a mismatched line are extreme... There MIGHT even be some sparks. Power loss will be at its worst for a given line. RF finds its way every where. Getting zapped once in a while eventually grows old to everyone. I remember the good old days when desk mikes were the only way to go. If you got too close, you got an RF zap on your lip. Solid state rigs don't tolerate a high SWR. They either protect themselves by reducing power or they require a lot of maintenance. You can learn to tolerate high SWR's, but I find it worthwhile to try to keep things matched. The energy has to go somewhere, I prefer it leave here through the antenna... John Ferrell W8CCW Article: 220299 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> References: Date: Wed, 21 Dec 2005 21:29:37 GMT On Wed, 21 Dec 2005 20:18:05 GMT, John Ferrell wrote: >On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" > wrote: > > I'm trying to make >>some sense out of why the emphasis of standing waves. > >Here is the short version: >A matched transmission line behaves like the theory books say it does. >The rated power from the transmitter goes through the transmission >line with the lowest possible loss to the antenna where it is radiated >just like the book says. It is true that reducing SWR for a given line does reduce the loss if the line is long enough. (There are some scenarios where a short line with high VSWR has less loss than matched line of the same length.) But is matched line the real goal? If low loss is the goal, there are often cost effective lower loss solutions possible with lower loss line operated at high VSWR. >A mismatched transmission just MIGHT work OK. If there is any >possibility of generating interference, especially TVI, it will. The Why? How is TVI "generated" by line mismatch? Owen -- Article: 220300 of rec.radio.amateur.antenna From: "Michael" Subject: Re: 2 or more Ants. needed Date: Thu, 22 Dec 2005 11:33:12 -0800 Message-ID: <11qjiil4if6ul5c@corp.supernews.com> References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> If you have the room, a loop antenna is a very good bet. I have used dipoles and verticals for many years. A neighbor moved in a few doors down and put up a loop antenna. I went over and listened to the "quiet" It is a great antenna if you are really irritated by QRN. He has only used this type of antenna for 20 years since he tried it. I understand why. I have not yet put up one, but will. It is winter here in North Dakota and not a good time for antenna work. Evrery other type of antenna works, but I just love the S/N ratio on a loop. Michael W0EZI "west" wrote in message news:1H3qf.17566$md.3615@tornado.tampabay.rr.com... > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from > Ham > Radio for more than 20 years & would like opinions on what would be the > absolute best omni-directional antenna(s) to buy, for this rig? All > opinions > welcomed. Thank you. > > west > AF4GC > > Article: 220301 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: More BPL rollout. sigh... Date: 21 Dec 2005 21:59:17 GMT Message-ID: References: On Wed, 21 Dec 2005 10:44:35 -0800, Richard Clark wrote: > > Hi Jonesy, > > Did you just move to Pueblo from Gunnison? Gunnison is such a nice > town. Hi Richard. Yep, DM68 has A LOT less WS VHF actvity now. Think of the postage I'll save on QSL cards! HI!HI! How-some-ever, I have to start all over on my 6M WAS. Got all but R.I. with 9.5 watts on 6M from Gunnison. sigh... (There really should be a W49S award! Quite a few folks have that!) > Last time I was in Pueblo was during High School in the 60s. As > we used to say about Tijuana when I was in the Navy: didn't lose > anything there, so there was no reason to go back. Being a contrarian, I selected Pueblo for the move, after my First Wife said she was done being cold in Gunnison. Turns out Pueblo is A Great Place to live -- unless you're trying to raise and educate children, or need to make a living. Luckily I'm not into any of that. > Of course, Colorado Springs has tripled in size since then, and to > no positive gain as far as I can tell. Agreed. We bought a house on the S.E. side of Pueblo -- a little out in the county -- just to stay as far away from C. Spgs. as possible. :-) 73 MC es HNY Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 220302 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: Message-ID: Date: Wed, 21 Dec 2005 22:18:26 GMT John Ferrell wrote: > You can learn to tolerate high SWR's, but I find it worthwhile to try > to keep things matched. The energy has to go somewhere, I prefer it > leave here through the antenna... > John Ferrell W8CCW I assume that you realize there is a high SWR on a standing- wave antenna, like a resonant 1/2WL dipole? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220303 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 18:06:20 -0500 Message-ID: <11qjnt7a2mlskf2@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> I am amazed that this keeps going on. In the early days of radio, the frequencies were low, receivers were not very sensitive, and the antennas were vertical - with some understandable exaggeration. Modern circuit theory - in the sense that things can be calculated - started about 1920. In those early days, the concept of "height" was useful. For a given physical height, one was interested in increasing the "height." Top loading was one major tool. A simple analysis was made based on the reasonable assumption that the current distribution along a short (less than 0.1 WL), thin, rod over a good ground was linearly distributed from a max. at the base to zero at the end. Such an analysis has been made an uncounted number of times since. I found a reference that suggests that Sommerfield might have made the calculation in a paper published in March 1909. The result is always that the assumed antenna has an open circuit voltage between its bottom and ground of no more than 0.5 of the incident, vertically-polarized wave's v/m times the physical length. (An ideal 0.25 WL antenna was expected to have a "height" of 2/pi.) No expert has ever said something to contradict the 0.5 figure. What many have described is a way to visualize E in free space using a one meter wire. That is not the subject. Before Professor Kraus' first edition (1950), "height" had lost most of its utility. Professor Terman in his 1943 edition of -Radio Engineers' Handbook- gives it a definitional footnote on page 841. Directivity and gain had been defined and have been useful ever since. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net Article: 220304 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Wed, 21 Dec 2005 23:11:02 GMT "Cecil Moore" bravely wrote to "All" (21 Dec 05 15:19:51) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:221636 CM> Roy Lewallen wrote: > But voltage isn't energy. Or power. CM> True, but voltage cannot exist without energy. I wouldn't say that. Voltage is kind of like having a big boulder sitting on top of a high cliff. It doesn't do anything so it doesn't expend energy. However, if it rolls off that's splat! Similarly you can have all the electrical potential you want but as long as no charges flow then where is the energy? In an EM wave it is the energy itself that flows in space using voltage and magnetism as a skeleton. A*s*i*m*o*v Article: 220305 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Wed, 21 Dec 2005 23:25:05 GMT Asimov wrote: > Voltage is kind of like having a big boulder > sitting on top of a high cliff. Yep, it is. A big boulder sitting on top of a high cliff contains a lot of potential energy. Voltage is literally potential energy and cannot exist without energy. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220306 of rec.radio.amateur.antenna From: "Bill" Subject: Voyager Hazer ..?? Message-ID: Date: Wed, 21 Dec 2005 18:32:26 -0500 Glen Martin just informed me that they are not making the "Hazer" for the 45G tower anymore.... Anyone know where one is for sale, and does anyone. know of a better or equal "mousetrap"..?? http://www.glenmartin.com/catalog/page12.html TNX, -Bill kc4pe@mindspring.com http://www.kc4pe.com/amateurshack.htm Article: 220307 of rec.radio.amateur.antenna From: "west" References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> <11qjiil4if6ul5c@corp.supernews.com> Subject: Re: 2 or more Ants. needed Message-ID: Date: Thu, 22 Dec 2005 00:28:11 GMT "Michael" wrote in message news:11qjiil4if6ul5c@corp.supernews.com... > If you have the room, a loop antenna is a very good bet. I have used dipoles > and verticals for many years. A neighbor moved in a few doors down and put > up a loop antenna. I went over and listened to the "quiet" It is a great > antenna if you are really irritated by QRN. He has only used this type of > antenna for 20 years since he tried it. I understand why. I have not yet put > up one, but will. It is winter here in North Dakota and not a good time for > antenna work. > Evrery other type of antenna works, but I just love the S/N ratio on a loop. > > Michael > W0EZI > "west" wrote in message > news:1H3qf.17566$md.3615@tornado.tampabay.rr.com... > > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from > > Ham > > Radio for more than 20 years & would like opinions on what would be the > > absolute best omni-directional antenna(s) to buy, for this rig? All > > opinions > > welcomed. Thank you. > > > > west > > AF4GC I agree about the reduction of QRN in a horizontally polarized vs. vertically polarized antenna but what about the gain? I don't have the time to build. I have some property, but not a large amount. Are there commercial loop antennas available and I guess I should concentrate on HF & 6M and worry about VHF/UHF later. Thoughts? Thanks again. west > > > > > > Article: 220308 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: Message-ID: Date: Thu, 22 Dec 2005 00:48:55 GMT Cecil Moore wrote: > > Yep, it is. A big boulder sitting on top of a high cliff > contains a lot of potential energy. Voltage is literally > potential energy and cannot exist without energy. Cecil, Still practicing physics without a license? 8-) Electrical potential energy has units of voltage multiplied by charge. Voltage by itself is not potential energy, literally or otherwise. 73, Gene W4SZ Article: 220309 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Thu, 22 Dec 2005 02:22:43 GMT Gene Fuller wrote: > Electrical potential energy has units of voltage multiplied by charge. > Voltage by itself is not potential energy, literally or otherwise. I didn't mean to imply that voltage and energy are the same thing. But voltage is indeed literally potential energy (per unit charge). -- 73, Cecil http://www.qsl.net/w5dxp Article: 220310 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> Date: Thu, 22 Dec 2005 03:16:17 GMT W. Watson wrote: > A standing wave is the sum of an incident added to the reflective wave. > Isn't it possible to send two incident waves down an xline with > different frequences, and produce two different standing waves by having > some multiplicative relationship between the two incident waves and the > xline length? Sure, it's possible but one wonders about the application. > 2. Matched impedances give ideal power transfer; mismatched > impedances give high SWR and reduced power transfer. A middle ground - Conjugately matched impedances give ideal power transfer in the presence of high SWR. A feedline doesn't have to be flat to be "matched". All that is required is that maximum available power (actually energy) be transferred. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220311 of rec.radio.amateur.antenna From: ehsjr Subject: Re: Still looking for a Tripp Lite PR-25 (or similar) DC power supply References: <43A83F2A.72DD0E2C@psdude.com> Message-ID: Date: Thu, 22 Dec 2005 03:40:24 GMT Paul P wrote: > There are a couple of smoked resistors on the regulator board. I can not > trust the ohm meter reading so I wanted to verify its value. I am trying to > avoid De-engineering the board. Now once the resistors are replace there > may be something else that smoked the resistors too. > > Paul. > Here's a link to an Astron supply: http://www.seits.org/features/pwrsup.htm Assuming a typical 723 ==> pass transistors linear supply, it shouldn't be hard to figure out the values of the cooked resistors. The schematic at the link above serves well as a model for many (most?) of that type of supply. Combined with the LM723 datasheet, you can fix it. Ed > "PS_DUDE" wrote in message > news:43A83F2A.72DD0E2C@psdude.com... > >>hi paul, >> >>Tripp lite makes good supplies but lacks in the >>support side ! >> >>Good thing is the supplies use off the shelf parts >>or easy substituted parts from anywhre, >>http://www.mouser.com etc. >> >>What problem(s) are you having ? >> >>73 ps dude >> > > > Article: 220312 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: <439kq11dj4fh6n7qpe6gm47ded3h9sg302@4ax.com> References: Date: Thu, 22 Dec 2005 04:10:34 GMT I was simply sharing my experiences from the past. If you have followed a few of my earlier posts you are aware I am simply a student who should have been studying this many years ago. I welcome any corrections. I never gave the swr on the radiator any thought. That is a good point. . On Wed, 21 Dec 2005 22:18:26 GMT, Cecil Moore wrote: >John Ferrell wrote: >> You can learn to tolerate high SWR's, but I find it worthwhile to try >> to keep things matched. The energy has to go somewhere, I prefer it >> leave here through the antenna... >> John Ferrell W8CCW > >I assume that you realize there is a high SWR on a standing- >wave antenna, like a resonant 1/2WL dipole? :-) John Ferrell W8CCW Article: 220313 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> Date: Thu, 22 Dec 2005 04:17:11 GMT On Wed, 21 Dec 2005 21:29:37 GMT, Owen Duffy wrote: >On Wed, 21 Dec 2005 20:18:05 GMT, John Ferrell > wrote: > >>On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" >> wrote: >> >> I'm trying to make >>>some sense out of why the emphasis of standing waves. >> >>Here is the short version: >>A matched transmission line behaves like the theory books say it does. >>The rated power from the transmitter goes through the transmission >>line with the lowest possible loss to the antenna where it is radiated >>just like the book says. > >It is true that reducing SWR for a given line does reduce the loss if >the line is long enough. (There are some scenarios where a short line >with high VSWR has less loss than matched line of the same length.) > I will have to take your word for it, I cannot think of any examples. >But is matched line the real goal? > >If low loss is the goal, there are often cost effective lower loss >solutions possible with lower loss line operated at high VSWR. > >>A mismatched transmission just MIGHT work OK. If there is any >>possibility of generating interference, especially TVI, it will. The > >Why? How is TVI "generated" by line mismatch? > >Owen I really don't know why there is more TVI with a high swr. But my experience has been that there is, especially on 6 meters. John Ferrell W8CCW Article: 220314 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 04:30:09 +0000 (UTC) Message-ID: References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> To anybody who may be reading - (1) There's far too much importance attached to standing waves on transmission lines. But see (4). (2) There are colossal standing waves on antennas which are seldom taken any notice of. (3) Anyway, of what use does anybody make of standing waves after taking the trouble to measure them. And the measurements themselves are the most inacurate in the field of radio engineering. (4) And to cap it all, the common or garden SWR meter does NOT measure standing waves on the feedline to the antenna where they might conceivably be of interest. It's all a gigantic hoax! ---- Season's Greetings from Reg, G4FGQ. Article: 220315 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Thanks for antenna help. Date: Thu, 22 Dec 2005 04:43:59 +0000 (UTC) Message-ID: References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> The French should be given full credit for inventing the unit of length by correctly spelling it, the "METRE". Also, this avoids confusion with the frequently used word "METER", a measuring instrument, when they are both mentioned in the same sentence. ========================================== Article: 220316 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Thu, 22 Dec 2005 05:11:05 GMT "Cecil Moore" bravely wrote to "All" (21 Dec 05 23:25:05) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:221661 CM> Asimov wrote: > Voltage is kind of like having a big boulder > sitting on top of a high cliff. CM> Yep, it is. A big boulder sitting on top of a high cliff CM> contains a lot of potential energy. Voltage is literally CM> potential energy and cannot exist without energy. If I can manage to roll the boulder up at the top or at the bottom of the cliff, I will find it weighs about the same. The boulder only picks up energy as it is accelerating towards the foot of the cliff. A*s*i*m*o*v Article: 220317 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> Date: Thu, 22 Dec 2005 06:09:30 GMT On Thu, 22 Dec 2005 04:17:11 GMT, John Ferrell wrote: >>It is true that reducing SWR for a given line does reduce the loss if >>the line is long enough. (There are some scenarios where a short line >>with high VSWR has less loss than matched line of the same length.) >> >I will have to take your word for it, I cannot think of any examples. John, It was really a bit of an aside, a lead into the more important point that followed, however... In most practical lines at HF, loss is dominated by the series resistance. In the regions of a current minimum on a line with high VSWR, the I^2R losses are less than for the same net power on a flat line, and conversely, in the region of a current maximum on a line with high VSWR, the I^2R losses are more than for the same net power on a flat line. Over a half wave of line, the total losses are higher than a flat line, but a short line in the regions of a current minimum may have losses less than the matched line loss. Whilst that is not often to our benefit as we rarely have relatively short lines with high Z loads, the converse is true of the more common situation of a short line with a low Z load. For example, 3m of RG58 with a 5+j0 load (eg mobile antenna) on 3.5MHz has a matched line loss of 0.08dB, and an actual loss of 0.66dB. Many charts and formulas would predict the mismatched loss to be only 0.39dB, but it is worse because the line is short and in the region of a current maximum. >>But is matched line the real goal? >> >>If low loss is the goal, there are often cost effective lower loss >>solutions possible with lower loss line operated at high VSWR. >> >>>A mismatched transmission just MIGHT work OK. If there is any >>>possibility of generating interference, especially TVI, it will. The >> >>Why? How is TVI "generated" by line mismatch? >> >I really don't know why there is more TVI with a high swr. But my >experience has been that there is, especially on 6 meters. If you can't explain the mechanism by which SWR causes TVI, perhaps they correlate by some other cause. For example, an antenna may develop loose oxided connections which both change the load impedance (and hence VSWR), and create intermodulation causing TVI. If VSWR *does* cause TVI, surely someone will be able to explain how? Lots of people operate feedlines at high VSWR by design, and they do not necessarily cause TVI. When you dismiss the TVI myth, you get closer to understanding how the transmission lines work and perform, and that for example, operating a feedline at high VSWR can be part of an efficient and effective multiband HF antenna. Such a solution should not be dismissed out of hand because of high VSWR alone. Owen -- Article: 220318 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Thanks for antenna help. Date: Wed, 21 Dec 2005 22:14:55 -0800 Message-ID: <11qkh31l0humk7e@corp.supernews.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> Reg Edwards wrote: > The French should be given full credit for inventing the unit of > length by correctly spelling it, the "METRE". > > Also, this avoids confusion with the frequently used word "METER", a > measuring instrument, when they are both mentioned in the same > sentence. I'm so glad to hear you're committed to correctness and against confusion. Perhaps you can direct some of your efforts toward your countrymen - the U.K. is the only place I've been where "m" is used as an abbreviation for both metres and miles. Roy Lewallen, W7EL Article: 220319 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Thanks for antenna help. Date: Wed, 21 Dec 2005 22:16:16 -0800 Message-ID: <11qkh5h8if819af@corp.supernews.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135218231.794511.299350@f14g2000cwb.googlegroups.com> The Eternal Squire wrote: > . . . > Noise floor seems to be extremely high for 40 m in the afternoons and > evenings, is this common? Atmospheric noise is usually very low on 40 meters during the day. Sounds like you have some relatively local source of man-made noise. Roy Lewallen, W7EL Article: 220320 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Thanks for antenna help. Message-ID: <1pgkq1pa074foen5ghsfkh5brc7punqnbb@4ax.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> Date: Thu, 22 Dec 2005 06:16:47 GMT