Article: 221901 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Mon, 06 Mar 2006 18:43:22 -0800 Message-ID: <120psqeeu4hiad9@corp.supernews.com> References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> <120pbesgie9bdd3@corp.supernews.com> Gary Schafer wrote: > . . . > The calibration points that Mike did on his receiver should be valid > for any band for his antenna comparisons. An actual signal strength > measurement is not required nor would it be valid between bands. All > that is really needed is the difference measurements between the two > antennas so his calibration between points on the meter scale will be > valid on any band. I'm not sure I fully understand this. The difference from one S meter division to another *is* likely to be different on different bands, since it depends on the gain-vs-voltage characteristics of the controlled stages which can vary with frequency. But I do agree that he can make good comparative antenna measurements without good S meter calibration, because he has a step attenuator. By simply setting the attenuator so he gets the same S-meter reading on both antennas, S-meter calibration is completely irrelevant -- the antenna gain difference is the attenuator setting. I find it useful, however, to be able to see the difference with reasonable accuracy just by looking at my S meter. But that does require calibration for the band in use. >. . . Roy Lewallen, W7EL Article: 221903 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: does doppler systems work only for unmodulated continous wave signals? Message-ID: References: <1141647965.814664.310580@i39g2000cwa.googlegroups.com> Date: Tue, 07 Mar 2006 03:15:26 GMT On 6 Mar 2006 04:26:05 -0800, "mazerom" wrote: >the doppler shift is fundamentally a tone frequency brought about by a >continuous wave source moving in and out. is it possible to have >reliable doppler shift when our source is spread spectrum or say some >form of digital modulation? Back around '57 or so, the beep-beeping of the Sputnik satellite was used to track its orbit by measuring the Doppler effect. bob k5qwg Article: 221904 of rec.radio.amateur.antenna From: stananger < stananger@********.***> Subject: Sun's next 11-year cycle could be 50 pct stronger Message-ID: Date: Tue, 07 Mar 2006 04:50:32 GMT Sun's next 11-year cycle could be 50 pct stronger Mon Mar 6, 2006 3:49 PM ET By Deborah Zabarenko WASHINGTON (Reuters) - Sun-spawned cosmic storms that can play havoc with earthly power grids and orbiting satellites could be 50 percent stronger in the next 11-year solar cycle than in the last one, scientists said on Monday. Using a new model that takes into account what happens under the sun's surface and data about previous solar cycles, astronomers offered a long-range forecast for solar activity that could start as soon as this year or as late as 2008. They offered no specific predictions of solar storms, but they hope to formulate early warnings that will give power companies, satellite operators and others on and around Earth a few days to prepare. "This prediction of an active solar cycle suggests we're potentially looking at more communications disruptions, more satellite failures, possible disruptions of electrical grids and blackouts, more dangerous conditions for astronauts," said Richard Behnke of the Upper Atmosphere Research Section at the National Science Foundation. "Predicting and understanding space weather will soon be even more vital than ever before," Behnke said at a telephone news briefing. The prediction, roughly analogous to the early prediction of a severe hurricane season on Earth, involves the number of sunspots on the solar surface, phenomena that have been monitored for more than a century. TWISTED MAGNETIC FIELDS Every 11 years or so, the sun goes through an active period, with lots of sunspots. This is important, since solar storms -- linked to twisted magnetic fields that can hurl out energetic particles -- tend to occur near sunspots. The sun is in a relatively quiet period now, but is expected to get more active soon, scientists said. However, there is disagreement as to whether the active period will start within months -- late 2006 or early 2007 -- or years, with the first signs in late 2007 or early 2008. Whenever it begins, the new forecasting method shows sunspot activity is likely to be 30 percent to 50 percent stronger than the last active period. The peak of the last cycle was in 2001, the researchers said, but the period of activity can span much of a decade. The strongest solar cycle in recent memory occurred in the late 1950s, when there were few satellites aloft, no astronauts in orbit and less reliance on electrical power grids than there is now. If a similarly active period occurred now, the impact would be hard to predict, according to Joseph Kunches of the National Oceanic & Atmospheric Administration's Space Environment Center in Colorado. "It's pretty uncertain what would happen, which makes this work more relevant," Kunches said. "What we have here is a prediction that the cycle is going to be very active, and what we need and what we're of course working on is to be able to predict individual storms with a couple days or hours in advance so the grids can take the action," Behnke said. Article: 221905 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Re: Current through coils Date: 6 Mar 2006 23:19:04 -0600 Message-ID: References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> >....[snip].... >The measured current at the bottom of a loading coil is primarily >standing wave current. IT IS NOT FLOWING. >....[snip].... My obviously-overloaded must-be-pea-sized brain sure has trouble thinking of current which is NOT flowing, since my basic internal definition of "current" is something like "electrons flowing past a point". I'm enjoying reading this thread, but, what with all the difficulties my brain is having with such subtle points, I'm NOT learning much! -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) Article: 221906 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 7 Mar 2006 05:51:14 +0000 (UTC) Message-ID: References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> A coil inevitably occupies space. In particular, one of its dimensions is length. Therefore it can be, and indeed for accurate modelling always should be, treated as a component having distributed L, C and R. It just makes the mathematics somewhat more complicated. Hyperbolic functions can be involved. Like a transmission line, a coil possesses Zo, phase-shift, attenuation and Q. It is why my coil-loaded antenna programs provide answers in the right ball-park although I havn't a clue about the rules which govern the American ball game. By the way, reflections and standing waves are irrelevant and don't enter the argument. Sorry Cecil! ---- Reg, G4FGQ. Article: 221907 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Vertical vs Horizontal shootout part one Date: Tue, 7 Mar 2006 05:59:50 +0000 (UTC) Message-ID: References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> Roy, you appear to have mislaid your sense of humor. Hope you recover it soon. ;o) ---- Reg. Article: 221908 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Tue, 7 Mar 2006 06:35:30 +0000 (UTC) Message-ID: References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Myron, I'm afraid Cecil has a fixation about standing waves and reflections. He brings them into arguments on every possible occasion. Nevertheless he is very convincing and manages to drag most people in. Give your brain a rest. Visit your nearest barber shop and tune up. You will feel much better. ---- Reg. Article: 221909 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Sun's next 11-year cycle could be 50 pct stronger Date: Tue, 7 Mar 2006 06:49:05 +0000 (UTC) Message-ID: References: Are you sure 'Earth Warming', we hear so much about, has nothing to do with it? Article: 221910 of rec.radio.amateur.antenna From: stananger < stananger@********.***> Subject: Re: Sun's next 11-year cycle could be 50 pct stronger References: Message-ID: <_EaPf.5022$CT.3527@trnddc04> Date: Tue, 07 Mar 2006 07:31:06 GMT Reg Edwards wrote: > Are you sure 'Earth Warming', we hear so much about, has nothing to do > with it? maybe its the sunspots that are causing the so called warming! Article: 221911 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Sun's next 11-year cycle could be 50 pct stronger Date: Tue, 7 Mar 2006 08:03:45 +0000 (UTC) Message-ID: References: <_EaPf.5022$CT.3527@trnddc04> > > Are you sure 'Earth Warming', we hear so much about, has nothing to do > > with it? > > > maybe its the sunspots that are causing the so called warming! ========================================== If its nothing to do with the price of oil perhaps we can recall our troops from the Middle East and release Saddam. Article: 221912 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Tue, 7 Mar 2006 01:59:01 -0600 Message-ID: <16154-440D3D45-967@storefull-3256.bay.webtv.net> References: Myron A. Calhoun wrote: "--I`m not learning much." Alas, I`d wager I don`t have anything new for Professor Calhoun, but >from some of the postings, what I write may be new in part to someone. Current is defined as movement of electrons through a conductor. Obviously, an incomplete definition. As we know, there is beam current in the vacuum of a CRT, and that at r-f, skin-effect forces most electrons to the surface so that most electron movement is on or very near the surface of the conductor rather than "through" it. When currents of equal amplitude and opposite direction meet at various points along a perfect transmission line, as they might after a perfect reflection of the incident wave, one might measure zero amps at cancellation points along the line. These would be distributed periodically as the waves, in fixed phase relation and equal and opposite currents, coincide. The measurement of zero amps occurs because the ammeter is measuring both currents simultaneously. If a directional coupler is used to measure the current in each direction separately, it will be found that the currents traveling in opposite directions are passing through each other without effect. Standing waves are more manifestation than anything else. There was a PBS TV Channel appeal tonight. It Quoted Einstein as saying: "Nothing happens until something moves". Incident and reflected waves move on a transmission line but standing waves are stationary and don`t move. So, it is the incident and reflected waves that make something happen. Not the stationary waves. Circulating energy within a transmission line causes standing waves. Without a reflection, they don`t exist. Energy must be accepted by an antenna to be radiated. It is best if it is accepted on the first pass so that there are no more losses on additional passes. A perfect match at the antenna accepts energy on the first pass. A mismatched antenna produces an SWR. Magnitude of the SWR is an indication of how much mismatch there is. Best regards, Richard Harrison, KB5WZI Article: 221913 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Tue, 07 Mar 2006 09:37:56 GMT mcalhoun@ksu.edu wrote: > My obviously-overloaded must-be-pea-sized brain sure has trouble thinking > of current which is NOT flowing, since my basic internal definition of > "current" is something like "electrons flowing past a point". Forward current is a traveling wave and is flowing. Reflected current is a traveling wave and is flowing. Both can be represented by phasors. But since they are traveling in opposite directions, their phasors are rotating in opposite directions and their superposed sum always add up to the same constant phase angle = zero (in a thin wire). Given a 1/2WL (-90 deg to +90 deg) thin wire dipole fed in the center (at 0 deg) with 1.0 amps, the standing wave current magnitude on the antenna is cos(theta) and the phase angle is a constant zero degrees from end to end. Reference: Figure 14-2, page 464 of "Antennas for All Applications", by Kraus and Marhefka, 3rd edition. If the phasor sum of two currents is not rotating, it is not flowing. Since phasors, by definition, change phase at a rate of (2*pi*f) and the standing wave current doesn't change phase at all, I don't think standing wave current is a phasor. Standing wave current is what we measure on a standing-wave antenna like a 75m mobile center-loaded bugcatcher. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221914 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <16154-440D3D45-967@storefull-3256.bay.webtv.net> Message-ID: <7QcPf.38135$Jd.3617@newssvr25.news.prodigy.net> Date: Tue, 07 Mar 2006 09:59:31 GMT Richard Harrison wrote: > If a directional > coupler is used to measure the current in each direction separately, it > will be found that the currents traveling in opposite directions are > passing through each other without effect. Standing waves are more > manifestation than anything else. And this is equally true of standing wave antennas. Kraus goes as far as assuming the forward and reflected currents on a 1/2 wavelength thin-wire dipole are equal in magnitude so they must be close to equal in magnitude. I have estimated that the magnitude of the reflected current after the round trip to the end of the dipole and back to be in the ballpark of 90% of the forward current at the feedpoint. This entire episode of constant current through a loading coil is the result of thinking standing wave current flows. As you say it is a manifestation of our thinking process and our measurements. It doesn't flow at all. Incidentally, a horizontal dipole above earth can be analyzed as a single-wire transmission line system with the earth being the ground return path. Balanis says, "Standing wave antennas, such as the dipole, can be analyzed as traveling wave antennas with waves propagating in opposite directions (forwards and backwards) and represented by traveling wave currents If and Ib in Figure 10.1(a)." The forward current (If) through a loading coil is very close to constant magnitude. The reflected current (Ib) back through a loading coil is very close to constant magnitude. Their phasor sum is the standing wave current that we measure. There is no physics requirement that the phasor sum of the forward and reflected currents be of equal magnitude on both ends of the loading coil. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221915 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Reflection Loss Message-ID: References: <27174-440CEDDE-994@storefull-3257.bay.webtv.net> Date: Tue, 07 Mar 2006 10:09:35 GMT On Mon, 6 Mar 2006 20:20:14 -0600, richardharrison@webtv.net (Richard Harrison) wrote: >Owen Duffy wrote: >"In formula 4-22b of my copy of Terman, the term on the lhs is |rho| >which is the magnitude of the reflection coefficient." > >In my copy, 4-22b gives the "absolute value" of the reflection >coefficient (it is embraced with bars) which I believe means the >"absolute value" of a number or a symbol without reference to its >algebraic sign. > >(4-22b): >+or- reflection coefficient= >SWR-1 / SWR+1 > Richard, you seem to be dealing with reflection coefficient as a real number when in fact it is a complex number. Your definition of |rho| is inadequate when rho is complex. Terman actually says in the preceding text "The standing wave ratio S is one means of expressing the magnitude of the reflection coefficient; the exact relationship between the two is..." Your statement "On page 99 of Terman`s 1955 edition of "Electronic and Radio Engineering" (my textbook was an earlier edition) is found the formula to convert the reflection coefficient into SWR or vice versa. These two parameters are innexorably locked together by formulas (4-22a) and (4-22b)." is wrong where it says "convert the reflection coefficient into SWR or vice versa" in respect of the "vice-versa" because you ignore the fact that the reflection coefficient is a complex quantity, and that the "magnitude of reflection coefficient" is not the same thing as "reflection coefficient. You cannot calculate the reflection coefficient from the SWR (except of course the special case where SWR=1). You have cited Terman in support of your own loose words, but Terman's words are more carefully chosen and correct, yours are not, and the Terman reference does not support your misconception at all. Owen -- Article: 221916 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> Message-ID: Date: Tue, 07 Mar 2006 10:13:30 GMT Reg Edwards wrote: > By the way, reflections and standing waves are irrelevant and don't > enter the argument. Sorry Cecil! I'm curious, Reg. With traveling wave energy flowing in both directions through a loading coil, how do you analyze it without taking the forward and reflected energy into account? All my reference equations have a term with a positive exponent for forward current and another term with a negative exponent for reflected current. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221917 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: ferrite balun grades References: <5amq02tq3q0lh1ag7d724jbk55j3fj3t5b@4ax.com> Message-ID: Date: Tue, 07 Mar 2006 10:19:23 GMT Mike Newman wrote: > Any advice on which grade of ferrite would be most useful for a > feeedline balun choke effective at 70 cm? #68 material might work although I have never tried it. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221918 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440C75C1-945@storefull-3258.bay.webtv.net> Message-ID: Date: Tue, 07 Mar 2006 13:26:45 GMT Reg Edwards wrote: > I'm afraid Cecil has a fixation about standing waves and reflections. They are part and parcel of a distributed network analysis and are embedded in many transmission line equations. As far as the constant current through the coil goes: Neglecting losses, the forward current through a coil is constant magnitude with changing phase. The reflected current through a coil is constant magnitude with changing phase. Those conditions satisfy the necessary and sufficient conditions of the laws of physics concerning a coil. The laws of physics do not require the phasor sum of the forward current and reflected current to be constant magnitude. In fact, the laws of physics prohibit the standing wave current from being equal magnitude except at equidistant points from a current maximum or minimum. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221919 of rec.radio.amateur.antenna From: "Jerry Martes" References: <5amq02tq3q0lh1ag7d724jbk55j3fj3t5b@4ax.com> Subject: Re: ferrite balun grades Message-ID: Date: Tue, 07 Mar 2006 15:18:33 GMT "Mike Newman" wrote in message news:5amq02tq3q0lh1ag7d724jbk55j3fj3t5b@4ax.com... > Any advice on which grade of ferrite would be most useful for a > feeedline balun choke effective at 70 cm? > Thanks de miken zl1bnb Hi Miken I've been using the tubular, high permeability ferrites designed for RFI suppression slipped over the RG-223 coax for a balun for vhf antennas. I am aware of the high loss with those ferrite tubes. I have been hoping the high permeability would present a high reactance to currents along the outside of the coax. So far, the tubes are working OK for my needs. Your mileage may vary. Jerry Article: 221920 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1141744648.582563.281170@j52g2000cwj.googlegroups.com> Subject: Re: Square cross-section elements? Date: Tue, 7 Mar 2006 10:37:25 -0500 Message-ID: <144cc$440da8b8$471c6203$27512@ALLTEL.NET> As they say, measure with a micrometer, mark with a crayon, and cut with an Ax. From my limited (50 years) experience, your picking fly crap out of pepper! The absolute perfectly modeled antenna will still have to be adjusted in it's environment. The difference between square and round tubing is insignificant unless your into the mental masturbation of caring everything out to 12 decimal places. I am sure that someone will venture forth with an example to show how important this is at some frequency, altitude, temperature, phase of the moon and barometric pressure. Such is the habit of the newsgroups denizens. The reality is YOU have square tubing, use it and enjoy the contacts. wrote in message news:1141744648.582563.281170@j52g2000cwj.googlegroups.com... > Anyone know how to use square rod in modelling programs? > > I'm sure it's a small effect, but I'm interested in the *proper* way to > account for it vs. round rod. > > I've used the mean radius of the inscribed and circumscribed circles > and that turned out fine, > but I don't have much ability to make good gain and F/R measurements. > > It seems that the corners could affect element coupling... > > Should I use the circle that has the same area? Maybe the geometric > mean of the radii of the inscribed and circumscribed circles? > > I've got a bunch of 1/4" square rod that I want to make 435MHz yagis > out of, and pretty much all web searches I could think of on square > antenna elements either get zero hits for being too specific or talk > about quads a lot. > > The square rod is great mechanically; I can slap a piece of PVC pipe on > a milling machine, mill 1/4" slots through very accurately spaced, and > hold the elements in with cable ties. > > Anyway, I'm just going to try the geometric mean and build another > antenna, but I'm interested in any comments on this. > > 73, > Dan > N3OX > www.n3ox.net > Article: 221921 of rec.radio.amateur.antenna From: "Caveat Lector" References: <_EaPf.5022$CT.3527@trnddc04> Subject: Sunspots and "The Little Ice Age" Message-ID: Date: Tue, 7 Mar 2006 08:45:57 -0800 Speaking of sunspots, saw a real eye opener on a TV show the other night about "The Little Ice Age" brrrrrr Some believe a contributing cause was low sunspot activity; See URL: http://en.wikipedia.org/wiki/Little_Ice_Age The impact on humanity was incredible- See URL: http://www2.sunysuffolk.edu/mandias/lia/little_ice_age.html -- CL -- I doubt, therefore I might be ! Article: 221922 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Reflection Loss Date: Tue, 7 Mar 2006 10:55:21 -0600 Message-ID: <4238-440DBAF9-964@storefull-3253.bay.webtv.net> References: Owen Duffy wrote: "Richard, You seem to be dealing with reflection coefficient as a real number when in fact it is a complex number." I plead guilty. Best regards, Richard Harrison, KB5WZI Article: 221923 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: does doppler systems work only for unmodulated continous wave References: <1141647965.814664.310580@i39g2000cwa.googlegroups.com> <2mvtd3-4kv.ln1@p400bob.personal.cox.net> <1141669090.526184.282340@v46g2000cwv.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 10:07:46 -0600 You know I am not quite sure how to answer that.. Doppler shift is a relative thing. If you are travelling at 100kph the signal/carrier whatever relative to you is unaffected. Relative to a RX that is relatively moving either towards or away from you a shift will be apparent. The entire transmitted spectrum will be affected, not just the "carrier". There will of course be a calculable difference in shift over the bandwidth of the signal as the lower end will shift less than the upper one more. Whether it will be a significant amount or not depends on your application. A +- 10MHz wide signal at 2.4GHz for example (100kph) would be close to an extra 1Hz of shift at the signal edges. As your relaitive velocities approach the speed of light other problems crop up. I dont quite remember Einstein's stuff on this. Since though I doubt I'll never get to experiment with it I dont need to go through it again! Is that what you were looking for? Cheers Bob VK2YQA K7ITM wrote: > > Bob wrote, "You'll get about +-200Hz shift with a speed of 100kph." > > Ahem. Care to qualify that as to the carrier or transmitted > frequency?? > Article: 221924 of rec.radio.amateur.antenna From: "Alfred Lorona" Subject: Bend in xmission line Date: Tue, 7 Mar 2006 09:15:06 -0800 Message-ID: <120rfv6k22v7s45@corp.supernews.com> Conventional wisdom cautions against sharp bends in open wire transmission line. What is the practical/quantifiable effect of violating this rule? How does the effect vary with the severity of the bend and does it vary with the distance along the line at which the bend occurs? Tnx es 73, AL. Article: 221925 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: Sun's next 11-year cycle could be 50 pct stronger Date: 7 Mar 2006 17:29:14 GMT Message-ID: References: On Tue, 07 Mar 2006 04:50:32 GMT, stananger wrote: > Sun's next 11-year cycle could be 50 pct stronger <-snip-> > The prediction, roughly analogous to the early prediction of a severe > hurricane season on Earth, .... Translation: Academic Guessing Jonesy Article: 221926 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> <1141748066.033150.267940@v46g2000cwv.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 18:01:18 GMT w8ji@akorn.net wrote: > I NEVER measured a current shift of 60 degrees, and I never said I > measured a current difference of 60 degrees. > > The phase shift I measured was in VOLTAGE. It simply shows the voltage > is out of step with the current. It doesn't indicate current is shifted > 60 degrees between each inductor terminal at all, and I never said it > did. The subject was Kraus' 180 degree current phase shifting coils. Here are you exact words (and all of your words about that measurement) quoted from qrz.com: > By the way, I swept S12 phase with my network analyzer on a 100uH > inductor a few hours ago while working on a phasing system. The > phase shift through that series inductor was about -60 or -70 degrees > on 1 MHz, crossing ZERO phase at self resonance (where loss became very > high) near 18 MHz, and gradually increasing leading phase above 18MHz > reaching 90 degrees and staying there well above resonance. I apologize for missing the small detail that S12 was a voltage measurement rather than a current measurement but I'm sure you can see how that was an honest mistake and easy to make. You didn't mention "voltage" at all in your posting and the context was current. I didn't recall until your objection here today that S12 is a voltage parameter measurement. But that leads to a question. Why were you using voltage measurements to try to disprove Kraus' statement about 180 degree current phase shifting coils. Quoting from: "Antennas for All Applications", Kraus and Marhefka, 3rd edition, page 824: "A coil (or trap) can also act as a 180 deg (current) phase shifter as in the collinear array ... The coil may also be thought of as a coiled-up 1/2WL element." > The current level at each end of the inductor was, as far as I can > measure with test equipment, equal. That sure doesn't make technical sense. If there was no phase shift in the current, then the voltage was lagging the current. But we know the current lags the voltage through an inductor by as much as 90 degrees in the ideal case. If the voltage is delayed by 60 degrees, then the current must necessarily be delayed by 60 degrees plus the lag to satisfy the laws of physics. If you will run the experiment using current probes, I assure you that the current will experience more of a phase shift than the voltage, just as the laws of physics predict. Which means there was more than a 60 deg current phase shift through the coil which makes my argument even stronger. Now, if you are talking only about the magnitude of the current then of course, the current was equal at both ends of the coil because reflected energy was absent for that measurement. IT IS THE PRESENCE OF REFLECTED ENERGY THAT MAKES FALSE YOUR ASSERTION ABOUT NET CURRENT. I think we are in perfect agreement about systems without reflections. > This is another clear case of Cecil taking things out of context ... Not out of context, Tom. The entire quote is just above. The mistake was an honest one and easy to make. I'm only human. :-) > and > mixing them with his idea that an inductor treats current differently, > depending on what direction it "flows" ... Sorry, I never said that. An inductor treats forward waves and reflected waves exactly the same according to the laws of physics. Your statement is more akin to your idea that standing wave current flows into the bottom of a coil and out the top. The coil treats all traveling waves exactly according to the laws of physics and exactly as you and I understand those laws of physics. I accept everything you say about traveling wave current through a coil. My argument with you is that a standing wave current is not a traveling wave current and doesn't behave like a traveling wave current. That seems rather obvious to me. 1. Just as you say, the forward traveling-wave current through a coil is of constant magnitude. Here's what Walter Maxwell says: "If an inductance is in series with a line that has no reflections, the current will be the same at both ends of the inductor." All three of us agree on that statment. 2. As in (1) above and just as you say, the reflected current through a coil is of constant magnitude. 3. There is no law of physics that requires the standing wave current to be equal at the top and bottom of a coil. In fact, such a requirement violates those laws of physics. Here's what Walter Maxwell says: "If an inductance is in series with a line that has reflections, the current will NOT be the same at both ends of the inductor. Consequently, circuit analysis will not work when both forward and reflected currents are present in a lumped circuit. When reflections are present, a current node and a current loop can appear at separate points on an inductor simultaneously." Judging from what he has posted earlier, Richard Harrison agrees with those statements. There's an EZNEC graphic at: http://www.qsl.net/w5dxp/qrzgif35.gif Would you have us believe that 0.1+ amps is flowing into the bottom of the coil and 0.7+ amps is flowing out of the top of the coil? It is your concept that standing wave current flows that is the problem. Please explain how a current with a zero phase angle >from tip to tip on a 1/2WL thin wire dipole can possibly flow without a rotating phase angle. > It is always better to let people directly post what they say, and not > have it run through a "Cecil Moore" filter. I agree, Tom, but you were not posting here so I quoted what I honestly thought you said over on qrz.com. I quoted the same thing on qrz.com over a number of days. You could have pointed out my mistake a lot sooner and saved me from making it here. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221927 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Reflection Loss References: <4238-440DBAF9-964@storefull-3253.bay.webtv.net> Message-ID: <6XjPf.43231$F_3.5267@newssvr29.news.prodigy.net> Date: Tue, 07 Mar 2006 18:04:50 GMT Richard Harrison wrote: > Owen Duffy wrote: > "Richard, You seem to be dealing with reflection coefficient as a real > number when in fact it is a complex number." > > I plead guilty. OTOH, some text I have in my library treats 'rho' as a magnitude and 'gamma' as the complex reflection coefficient. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221928 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Square cross-section elements? Date: Tue, 07 Mar 2006 10:45:27 -0800 Message-ID: <120rl6b4m08af5a@corp.supernews.com> References: <1141744648.582563.281170@j52g2000cwj.googlegroups.com> To model a square conductor with a round wire, use a wire diameter which is 1.18 times the side of the square. Roy Lewallen, W7EL n3ox.dan@gmail.com wrote: > Anyone know how to use square rod in modelling programs? > > I'm sure it's a small effect, but I'm interested in the *proper* way to > account for it vs. round rod. > . . . Article: 221929 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Reflection Loss Message-ID: <0lmr02921e6b36p0udd4l0j21mpl0qc3sh@4ax.com> References: <4238-440DBAF9-964@storefull-3253.bay.webtv.net> <6XjPf.43231$F_3.5267@newssvr29.news.prodigy.net> Date: Tue, 07 Mar 2006 19:15:44 GMT On Tue, 07 Mar 2006 18:04:50 GMT, Cecil Moore wrote: >Richard Harrison wrote: > >> Owen Duffy wrote: >> "Richard, You seem to be dealing with reflection coefficient as a real >> number when in fact it is a complex number." >> >> I plead guilty. > >OTOH, some text I have in my library treats 'rho' as a magnitude >and 'gamma' as the complex reflection coefficient. Irespective of the symbol that may be used, and there are unfortunately many schemes, the reflection coefficient is a complex quantity. Owen -- Article: 221930 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Vertical vs Horizontal shootout part one Date: Tue, 07 Mar 2006 14:18:47 -0500 Message-ID: References: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> Owen Duffy wrote: > On Sun, 05 Mar 2006 19:29:12 -0500, Mike Coslo > wrote: > >> Based on another thread a few weeks back in which Horizontal dipoles >> were being compared to Vertical antennas, and from a little chiding from >> Roy, W7EL, I decided to do some testing on my own personal versions of >> the two. >> > > Mike, this sounds interesting. Sorry for the delay getting back on-line... >> My setup is: >> >> Icom IC-761 >> Antenna 1 - Homebrew OCF dipole at ~ 50 feet. >> Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. >> > > Question, does the magnitude of feedline radiation from the OCF > (presumably predominantly vertical) significantly affect qualification > of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. > Another, are the antennas coupled significantly, eg is one within the > near field zone of the other? It is pretty hard to avoid in a > residential block on the low bands, and it will confuse the results > somewhat. Almost certainly there is some interaction. It isn't a very big yard. >> Part one of this experiment is to calibrate the S-meter. I found that >> trying to calibrate the thing with on-air signals was a nuisance, and >> probably wouldn't be as accurate, so I used a signal generator. >> >> I started out with a +20 signal, then worked my way down. >> >> +20 start >> S9 -18 db >> S8 -23 db >> S7 -26 db >> S6 -29 db >> S5 -32 db >> S4 -35 db >> S3 -37 db >> S2 -39 db >> S1 -41 db > > Not only is the shape of the scale an issue, but the granularity or > resolution, especially with LCD meters, or any meter where there are > discrete steps in the meter current (such as where a D/A converter > drives the meter movement). > > If you want to move beyond S meters, you could try FSM > (www.vk1od.net/fsm) and organise some constant carriers at known > distances / radiation angles that you could make a series of > measurements of and produce summary statistics (median and inter > quartile range) for each antenna type. > >> All in all, I would have to say that the meter tracks very well from S8 >> to S4, and the only place that wasn't that great was from S9 to S8. But >> considering the transient nature of the signals we are receiving, I >> would have to day that the S-meter is of reasonably close accuracy. >> >> With my newly calibrated S-meter I am ready to start looking at what the >> two different antennas are doing for me. I have a coaxial switch to jump >> back and forth between the two. My initial impressions are that there >> are some surprises. The difference in noise levels varies by antenna by >> band. On some bands the vertical is noisier, and on others it is the OCF >> dipole. Especially intriguing is that on PSK mode, where I can see >> several signals at one time, switching between antennas will attenuate >> some signals, while other signals increase in strength. I think that my >> vertical works better than I gave it credit for, but If I definitely >> want *both* antennas. > > I described a technique for assessing the relative performance of > mobile stations by having them transmit known constant carrier, each > station space about 200Hz and turning circles in a carpark near each > other, and to observe them at typical propagation distances with an > audio spectrum analyser, watching the relative strength of the > carriers. > > Your PSK setup is affording you the same type of comparison, and > provides a ready (and recordable) assessment of the relative strength > of the stations under the two antenna scenarios. Be great if you could > orchestrate stations at known distances as part of an organised test. I'll probably be doing the next best thing, which is to do a lookup of the various callsigns as I see them. The more I see of waterfall displays, the more I like them. I would love to see one as standard on an HF rig. - 73 de Mike KB3EIA - Article: 221931 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Vertical vs Horizontal shootout part one Date: Tue, 07 Mar 2006 14:27:23 -0500 Message-ID: References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> Reg Edwards wrote: > Roy says, >>> People who blindly assume the marks on their S-meters are 6 dB > apart >>> should take a good look at your calibration results. > > ======================================= > > The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do > with which antenna produces the stronger received signal. It is purely > a comparison. Just use the same meter throughout the tests. It does allow me to make a stab at comparing those two antennas. As I continue on this test, it would be nice to have something that has some sort of calibration. Otherwise we might as well just go to say "works great" or "doesn't work well for all measurements. - 73 de Mike KB3EIA - Article: 221932 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: OT for Cecil or any other ex RRAPers References: <1141756042.224852.90540@j52g2000cwj.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 19:27:10 GMT an_old_friend wrote: > years ago I remmebr somebody I think it was you cecil (but I have slpet > since then) said something about being to build or modtify some type of > CW kit for some other mode like RTTY etc, looking for the reference > care to help out? It might have been me but I just don't remember, sorry. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221933 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Vertical vs Horizontal shootout part one Date: Tue, 07 Mar 2006 14:44:05 -0500 Message-ID: References: <120ngtl3drs574@corp.supernews.com> <0HZOf.57636$g47.18172@tornado.tampabay.rr.com> <120p1rocfoni584@corp.supernews.com> <440ca00e_5@newsfeed.slurp.net> <120pbesgie9bdd3@corp.supernews.com> <1141684037.607691.234800@p10g2000cwp.googlegroups.com> <120pemmnd5voi9f@corp.supernews.com> Roy Lewallen wrote: > K7ITM wrote: >> I fully agree with Roy's comment about the AGC-derived S-meter output. >> As he says, the AGC characteristics are temperature dependent, and they >> are also dependent on the particular set of active devices (and to some >> extent the passives too) in the signal path. >> >> If you have access to a spectrum analyzer, chances are decent that it >> will have a well-calibrated amplitude readout. The one I use is >> accurate in a relative sense to a fraction of a dB over more than an >> 80dB range, and would certainly be sensitive enough for antenna >> comparisons. I suppose both those would be true of most modern >> spectrum analyzers. In addition, some are quite good at determining >> the total power in a specified frequency range, and if you can find >> such a range with no signals, you can get a better reading on noise >> than you're likely able to do with an S meter, or even a narrow band >> spectral measurement. > > One of the most complex and difficult parts of a spectrum analyzer to > design is the log amp which provides this stable and precisely > logarithmic response over a wide dynamic range. There's an incredible > amount of really ingenious work on the part of some extremely talented > engineers in those circuits. In relatively recent times, Barrie Gilbert > and his folks at Analog Devices have done some equally clever work in > the design of IC log amps. It's not a trivial task by any means. And in this case, it really isn't necessary. I simply need some baseline to start my readings from. Already I have noticed that different stations come in at different strengths - presumably on the basis of propagation differences. There may be some differences over time scales of minutes also. All I need is a meter that allows me to derive a signal strength difference from two different antennas. There was a need to calibrate that. Of course, I would *love* to have a decent analyzer!! - 73 de Mike KB3EIA - Article: 221934 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Vertical vs Horizontal shootout part one Message-ID: <27or02pjdrorgjgqq5bcirbr8tun8pr8kl@4ax.com> References: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> Date: Tue, 07 Mar 2006 19:46:35 GMT On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo wrote: ... >>> My setup is: >>> >>> Icom IC-761 >>> Antenna 1 - Homebrew OCF dipole at ~ 50 feet. >>> Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. >>> >> >> Question, does the magnitude of feedline radiation from the OCF >> (presumably predominantly vertical) significantly affect qualification >> of it as a horizontal antenna? > > There shouldn't be any feedline radiationn, this is oan antenna >running coax to a 4:1 balun at the feedpoint. Mike, I understand that feedline radiation is an un-escapable characteristic of an OCF dipole, caused by the asymmetric feed. Some even claim it as a major advantage (eg Caroline Windom). Whilst no dipole is perfect in that respect, the OCF dipole is less perfect, and it may be worth modelling the thing to comment in your findings on the probably magnitude of the contribution by the feedline. Great project, look forward to follow-ups. Owen -- Article: 221935 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 20:13:14 GMT w8ji@akorn.net wrote: > I think it would be better if Walt represented himself, unless he ASKED > you to post that Cecil. Walt isn't presently posting for reasons of his own. He certainly gave me permission to quote his email. I will ask him if he wants to defend his statements here. > If Walt has something to say, I'm sure he will chime in. I'm sure he will if he feels so inclined. > Drumming up support by writing what we **think** others say or mean > seems pretty desperate. Those were Walt's words, not mine. (Your statement reeks of desperation, i.e. "Please don't quote any authorities who disagree with me.") > All reliable measurements I've seen disagree with Cecil's theory. Simply not true, Tom, proving once again that you don't understand what I am saying. My "theory" explains exactly why neither you nor W7EL could get the current at the ends of the coil to be equal without creating a current maximum point inside the coil. If you would just take time to understand what I am saying, you wouldn't need to utter falsehoods about what I am saying. The standing wave net current at each end of the coil is indeed the same magnitude if a current maximum or current minimum point is located inside the coil. Walter Maxwell says: "When reflections are present, a current node and a current loop can appear at separate points on an inductor simultaneously." Does that sound like constant net current through a coil? Exactly what is it about Walt's statement that you don't understand? > I can't believe anyone with experience in RF systems would think a > physically small inductor (small in terms of wavelength) would have > significantly unequal currents in the inductor or in the terminals of > the inductor, especially any difference caused by "reflected waves". A 75m bugcatcher coil is about 0.2% of a wavelength and so qualifies as "physically small". The current at each end of that coil used with an eight foot whip is nowhere near equal. I cannot believe that anyone with experience in RF systems could utter such nonsense. (That logic is a double-edged sword.) I think you and others simply didn't realize that the current in a 75m mobile bugcatcher system is almost 100% a standing wave current and now you guys are desperately trying to cover up your mistake. Others have stopped responding instead of admitting their mistake. So I ask you again: How do you explain the flow of a current whose phase is unchanging (fixed at zero degrees in a thin wire dipole). Doesn't it take a rotating phasor for current to flow? That's a simple yes/no question. What do you want to bet that it goes unanswered? Incidentally, I posted a little questionaire a couple of days ago. The response to that questionaire has been zero. Why do you reckon all the gurus are afraid to respond? -- 73, Cecil http://www.qsl.net/w5dxp Article: 221936 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 20:38:09 GMT w8ji@akorn.net wrote: > I think it would be better ... I forgot to ask you, Tom, why you trimmed out all the technical content from my posting and whinned about what was left? So I ask you once again: In the graphic at: http://www.qsl.net/w5dxp/qrzgif35.gif do you really expect anyone to believe that 0.1+ amp is flowing into the bottom of that coil and 0.7+ amp is flowing out of the top of the coil. If, as you say, net standing wave current actually flows, then miracles must be possible and the coil is creating energy. If, OTOH, net standing wave current just stands there then such results as reported by EZNEC are just the facts of physics. It is the forward current and reflected current that are doing the flowing and their magnitudes are indeed individually equal through the coil. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221937 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Current through coils References: <120nv3gt1f8gi3a@corp.supernews.com> <16154-440C20D8-847@storefull-3256.bay.webtv.net> <1141748066.033150.267940@v46g2000cwv.googlegroups.com> Message-ID: Date: Tue, 07 Mar 2006 21:07:52 GMT Cecil Moore wrote: [snip] > > I apologize for missing the small detail that S12 was a voltage > measurement rather than a current measurement but I'm sure you can > see how that was an honest mistake and easy to make. You didn't > mention "voltage" at all in your posting and the context was current. > I didn't recall until your objection here today that S12 is a voltage > parameter measurement. > > But that leads to a question. Why were you using voltage measurements > to try to disprove Kraus' statement about 180 degree current phase > shifting coils. Quoting from: "Antennas for All Applications", Kraus > and Marhefka, 3rd edition, page 824: "A coil (or trap) can also act > as a 180 deg (current) phase shifter as in the collinear array ... > The coil may also be thought of as a coiled-up 1/2WL element." Cecil, Interesting, The complete quote from Kraus on page 744 in my copy of his 2nd edition is: "A coil (or trap) can also act as a 180 degree phase shifter as in the collinear array of 4 in-phase lambda/2 elements in Fig. 16.30b. Here the elements present a high impedance to the coil which may be resonated without an external capacitance due to its distributed capacitance. The coil may also be though of as a coiled-up lambda/2 element." * It is possible that Kraus edited the comment in the 3rd edition, but I don't see the word "current" in this quote. It is considered good editorial form to indicate clearly when you have altered the original wording, unless you are trying to make a point, I suppose. * The coil in this case is self-resonant at the frequency of use. Do you use a self-resonant coil for your 80 meter bugcatcher? (Such a coil might be more appropriate for a pterodactyl catcher.) In any case, this has little to do with all of your rantings about loading coils. I suspect even at A&M they must have mentioned something about the characteristics of resonant circuits. * You might have noticed the prominent role of capacitance. I believe that was the item that spurred this thread. 73, Gene W4SZ Article: 221938 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Tue, 7 Mar 2006 16:48:54 -0600 Message-ID: <12478-440E0DD6-1189@storefull-3258.bay.webtv.net> References: Gene, W4SZ wrote: "You might have noted the prominent role of capacitance." Capacitance is one of the factors which include resistance, inductance, conductance and capacitance which determine the velocity factor and other characteristics of a transmission line or antenna. If the load at the end of this line does not match Zo, a reflection from it results. A transmission line can`t be analyzed as a simple series circuit, because the current in the wires is not everywhere the same. Neither is the voltage. To analyze the line, each unit length must be examined. Each unit length produces a phase lag in the current on its wires. The voltage lags too. This can be totaled and the interference between the incident and reflected waves deternined to find the voltage and current at any point on the transmission line, Best regards, Richard Harrison, KB5WZI Article: 221939 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <12478-440E0DD6-1189@storefull-3258.bay.webtv.net> Message-ID: <2CoPf.39509$Jd.37582@newssvr25.news.prodigy.net> Date: Tue, 07 Mar 2006 23:23:42 GMT Richard Harrison wrote: > A transmission line can`t be analyzed as a simple series circuit, > because the current in the wires is not everywhere the same. Neither is > the voltage. To analyze the line, each unit length must be examined. > > Each unit length produces a phase lag in the current on its wires. The > voltage lags too. This can be totaled and the interference between the > incident and reflected waves deternined to find the voltage and current > at any point on the transmission line, Yes, and that also applies to a real-world loading coil installed in an environment of incident (forward) and reflected (backward) waves. Why this is so difficult for some people to understand is puzzling. All one has to do is use the superposition principle. Analyze the forward wave, analyze the reflected wave, and superpose the results. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221940 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: 1n21 diode housing References: <9yJOf.29654$2c4.29425@dukeread11> <2gqm021v4ec7c8t5e05dk0auohtnhv1uqu@4ax.com> Message-ID: Date: Tue, 07 Mar 2006 17:33:05 -0600 Richard Clark wrote: >On Sun, 05 Mar 2006 16:23:37 -0600, Chris W <1qazse4@cox.net> wrote: > > > >>Richard Clark wrote: >> >> >> >>>On Sun, 05 Mar 2006 09:20:20 -0600, Chris W <1qazse4@cox.net> wrote: >>> >>> >>> >>> >>> >>>>Can someone tell me where I can find the housings for a 1n21 crystal >>>>detector diode so I can hook it to some coax and a directional coupler? >>>>I can't seem to fine one anywhere >>>> >>>> >>>> >>>> >>>Try googling with: >>> 1n21 crystal mount >>> >>> >>> >>> >>A google search for that is giving me some links but still no luck >>finding a place I can buy one >> >> > >http://mailgate.supereva.com/misc/misc.industry.electronics.marketplace/msg04490.html >was at the 6th entry. > >http://store.americanmicrosemiconductor.com/1n21.html?gclid=CNbBybHzyIMCFTFZDgodfQQv8A >was at the right as a vendor > >http://www.advancedsemiconductor.com/diodes/1N/1N.shtml >sells the diodes and a call "could" result in leads > >This is a product line that is probably entirely custom design, or >salvage from equipment that is 50 years old. > >73's >Richard Clark, KB7QHC > > I saw no indication on those web sites that they sold the mounts. However, I did call them all and some others that sell the the 1N21 diodes and none sale the mounts or can tell me where to get one. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 221941 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: 1n21 diode housing Message-ID: References: <9yJOf.29654$2c4.29425@dukeread11> <2gqm021v4ec7c8t5e05dk0auohtnhv1uqu@4ax.com> Date: Tue, 07 Mar 2006 23:44:09 GMT On Tue, 07 Mar 2006 17:33:05 -0600, Chris W <1qazse4@cox.net> wrote: >> >I saw no indication on those web sites that they sold the mounts. >However, I did call them all and some others that sell the the 1N21 >diodes and none sale the mounts or can tell me where to get one. I know it is not what you asked for, but a functional replacement might be a HP crystal detector that you frequently see on Ebay for less than $100. The downside is that the consequences of destroying the diode are more expensive. Owen -- Article: 221942 of rec.radio.amateur.antenna From: Jim - NN7K Subject: Re: 1n21 diode housing References: <9yJOf.29654$2c4.29425@dukeread11> <2gqm021v4ec7c8t5e05dk0auohtnhv1uqu@4ax.com> Message-ID: Date: Tue, 07 Mar 2006 23:54:18 GMT Not to mention that - you might locate 1N21-R 's - which are Reverseable, and will leave you with the pin conductors , on BOTH ends, if you leave off the 1/4 inch cover that is swappable for the ends! And, of the mounts I have seen (they used for power out/mixer diode adaptors, for "C" band (6 GHz), they have a "N" male fitting to a "BNC" output female, BUT-- they have a wire in place from the center to the shield of the "N" end! (this for an rf choke, at 6 GHz) which would make then useless (unless you remove that jumper, buried in the male end , delicate surgury, inside the connector)! Lenkurt, Farinon, and several other outfits used these in their comm equipment! Tho, most of the plumbing I saw, had the mounts in waveguide, these MIGHT be an option, if you can locate them-- Jim NN7K Chris W wrote: > Richard Clark wrote: > >> On Sun, 05 Mar 2006 16:23:37 -0600, Chris W <1qazse4@cox.net> wrote: >> >> >> >>> Richard Clark wrote: >>> >>> >>> >>>> On Sun, 05 Mar 2006 09:20:20 -0600, Chris W <1qazse4@cox.net> wrote: >>>> >>>> >>>> >>>> >>>> >>>>> Can someone tell me where I can find the housings for a 1n21 >>>>> crystal detector diode so I can hook it to some coax and a >>>>> directional coupler? I can't seem to fine one anywhere >>>>> >>>>> >>>> >>>> Try googling with: >>>> 1n21 crystal mount >>>> >>>> >>>> >>> >>> A google search for that is giving me some links but still no luck >>> finding a place I can buy one >>> >> >> >> http://mailgate.supereva.com/misc/misc.industry.electronics.marketplace/msg04490.html >> >> was at the 6th entry. >> >> http://store.americanmicrosemiconductor.com/1n21.html?gclid=CNbBybHzyIMCFTFZDgodfQQv8A >> >> was at the right as a vendor >> >> http://www.advancedsemiconductor.com/diodes/1N/1N.shtml >> sells the diodes and a call "could" result in leads >> >> This is a product line that is probably entirely custom design, or >> salvage from equipment that is 50 years old. >> >> 73's >> Richard Clark, KB7QHC >> >> > I saw no indication on those web sites that they sold the mounts. > However, I did call them all and some others that sell the the 1N21 > diodes and none sale the mounts or can tell me where to get one. > Article: 221943 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <21271-440BE4B3-805@storefull-3254.bay.webtv.net> <1141772023.638201.196770@j52g2000cwj.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 00:08:10 GMT w8ji@akorn.net wrote: > What you are missing is the flux inside the coil links all the turns at > light speed. When it does that, current appears at nearly the same > instant of time (light speed over the spatial distance of the inductor) > in all areas that are linked by flux. I am not missing the flux linkage. What you are missing is the known phase lag that the current undergoes compared to the voltage. Whatever voltage phase shift you measured (60 degrees), the lagging current phase shift is likely to be more than double that value. Hint: an ideal inductor forces the current to lag the voltage by 90 degrees. If the current propagates at the speed of light, the voltage propagates much faster than the speed of light so it can lead the current. Please explain that one to us. > The flux coupling also tries to equalize currents throughout every area > of the coil. A well known fact. It applies to the forward current and reflected current, not to the standing wave current which is not flowing into or out of the coil at all. There is no net charge flow in a standing wave and therefore, no net current flow. At any point on a 1/2WL thin wire dipole, the only thing happening is that the energy is migrating between the H-field and the E-field. There is zero energy flow away from that point in either direction. That's why the phase angle of the reflected current is constant and fixed at zero degrees. It is simply not flowing. What is flowing is the forward and reflected component currents which indeed to obey all the rules you have listed here. > Charge conservation also dictates that any current flowing into the > coil has to be equalled by a like current flowing out the other > terminal, less any displacement currents caused by stray capacitance > (electric fields) to the outside world. Absolutely no argument here. Even assuming the coil is lossless, the magnitude of the forward current flowing into the coil is equal to the magnitude of the forward current flowing out of the coil. Likewise for the reflected current. So this part of your argument is somewhat irrelevant. What you seem to be missing is the phase shift in those component currents. > We cannot have a two terminal "black box" with confined fields that > behaves any other way, standing waves or not. If a piece of transmission that is an appreciable percentage of a wavelength is coiled into a coil that is an appreciable percentage of a wavelength, why is it surprising to you that the coil responds somewhat like the piece of wire that it replaces? The answer is that you assumed the proof in your argument. It goes something like this: A lumped inductance doesn't have any magnitude change or phase shift through the coil. A bugcatcher loading coil is a lumped inductance. Therefore, a bugcatcher loading coil doesn't have any magnitude change or phase shift through the coil. The first proof that you offered some months ago was that the lumped inductance modeled in EZNEC didn't show any magnitude change or phase shift. Do you see the fallacy in your thought processes? You assumed the proof in your argument and you are still falling into that logical trap. Is it any surprise that a software program shows no magnitude change or phase shift? Please open up your mind and think the unthinkable. You will be rewarded. > The only flaws in having zero current phase shift and zero current > difference are the less-than-perfect flux coupling and > less-than-perfect confinement of the electric field. There you go, assuming the proof in your argument. A lossless non- radiating transmission line doesn't even obey those rules. Why should you expect a real-world coil made from that transmission line wire to obey those rules? Before you respond with the 2-terminal Vs 4-terminal argument, please realize that a horizontal #14 wire 30 ft. above ground is considered to be a single-wire transmission line with a Z0 of around 600 ohms. Thus, a horizontal dipole is simply a lossy transmission line. If you would like, I can quote Balanis on all of this. > Any deviation from > following perfect two-terminal rules are directly tied to the ratio of > load impedance on the inductor to the stray capacitance to the outside > world, and of course less than perfect flux linkage from end-to-end in > the coil. Assuming the proof again. 1/4WL apart in a lossless, non-radiating transmission line, the standing wave currents are wildly different. Why are you surprised when we take that 1/4WL of wire, wind it into a coil, and achieve a lot of the same conditions? > If you can stay on topic and we process only one point at a tme, I'm > sure you will be able to learn how this works. I'm certainly game for that. We can start by agreeing that the forward current through a loading coil has the same magnitude at each end of the coil but suffers a phase shift through the coil. You measured a voltage phase shift of 60 degrees through a 100uH coil at 1 MHz. Since the current lags the voltage in a coil, the current phase shift has to have been greater than 60 degrees, maybe even 120+ degrees depending upon the Q of the coil. Tom, even I can measure the traveling wave current phase shift in a 75m bugcatcher coil so please don't insult my intelligence by asserting that a phase shift doesn't exist. If a coil could eliminate phase shifts, Intel would be using them in their computer busses. The truth is, a coil in a computer bus increases the phase shift, not decreases it. So please give us a break on that irrational concept. You have been fooled by your model. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221944 of rec.radio.amateur.antenna From: Jim - NN7K Subject: Re: 1n21 diode housing References: <9yJOf.29654$2c4.29425@dukeread11> <2gqm021v4ec7c8t5e05dk0auohtnhv1uqu@4ax.com> Message-ID: Date: Wed, 08 Mar 2006 00:10:24 GMT P.S., might be worth a shot- try :Allied Communications Equipment Supply - (712) 322-2725 - 325 W South Omaha Brg Rd, Council Bluffs, IA 51501 and, inquire about a diode detector for a "LENKURT - MODEL 76 radio", a long shot, I know, but THAT was what was used to alarm low power output, in those units, and other items!! Allied specializeds in communications equipment for commercial users, especially , supplying obsolete equiptment! not cheap, but - at least they have this stuff! Jim NN7K Jim - NN7K wrote: > Not to mention that - you might locate 1N21-R 's - which are > Reverseable, and will leave you with the pin conductors , on BOTH > ends, if you leave off the 1/4 inch cover that is swappable for the > ends! And, of the mounts I have seen (they used for power out/mixer > diode adaptors, for "C" band (6 GHz), they have a "N" male fitting > to a "BNC" output female, BUT-- they have a wire in place from the > center to the shield of the "N" end! (this for an rf choke, at 6 GHz) > which would make then useless (unless you remove that jumper, buried in > the male end , delicate surgury, inside the connector)! Lenkurt, > Farinon, and several other outfits used these in their comm equipment! > Tho, most of the plumbing I saw, had the mounts in waveguide, these > MIGHT be an option, if you can locate them-- Jim NN7K > > > > > Chris W wrote: > >> Richard Clark wrote: >> >>> On Sun, 05 Mar 2006 16:23:37 -0600, Chris W <1qazse4@cox.net> wrote: >>> >>> >>> >>>> Richard Clark wrote: >>>> >>>> >>>> >>>>> On Sun, 05 Mar 2006 09:20:20 -0600, Chris W <1qazse4@cox.net> wrote: >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>> Can someone tell me where I can find the housings for a 1n21 >>>>>> crystal detector diode so I can hook it to some coax and a >>>>>> directional coupler? I can't seem to fine one anywhere >>>>>> >>>>>> >>>>> >>>>> >>>>> Try googling with: >>>>> 1n21 crystal mount >>>>> >>>>> >>>>> >>>> >>>> >>>> A google search for that is giving me some links but still no luck >>>> finding a place I can buy one >>>> >>> >>> >>> >>> http://mailgate.supereva.com/misc/misc.industry.electronics.marketplace/msg04490.html >>> >>> was at the 6th entry. >>> >>> http://store.americanmicrosemiconductor.com/1n21.html?gclid=CNbBybHzyIMCFTFZDgodfQQv8A >>> >>> was at the right as a vendor >>> >>> http://www.advancedsemiconductor.com/diodes/1N/1N.shtml >>> sells the diodes and a call "could" result in leads >>> >>> This is a product line that is probably entirely custom design, or >>> salvage from equipment that is 50 years old. >>> >>> 73's >>> Richard Clark, KB7QHC >>> >>> >> I saw no indication on those web sites that they sold the mounts. >> However, I did call them all and some others that sell the the 1N21 >> diodes and none sale the mounts or can tell me where to get one. >> Article: 221946 of rec.radio.amateur.antenna From: Big Endian Subject: Q. about height of the ends of a doublet Message-ID: Date: Wed, 08 Mar 2006 00:37:20 GMT My center of a 3.8 Mhz doublet is at about 35 feet and am going to drop the ends from 30 feet to about 10 to 15 feet. Just wondering if it will make all that much difference if any? Article: 221947 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141772342.715920.287530@z34g2000cwc.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 01:11:47 GMT w8ji@akorn.net wrote: > That doesn't sound like Walter gave you permission to me. He did give me permission. In a fit of anger, I made a posting that proves that fact. Upon reflection, after cooling down by taking a walk, I should not have made that posting and I have canceled it. Walter Maxwell is my friend and I don't want to drag the great man into your junk yard dog war. I respect him too much for that and regret making that posting. I just hope it didn't make it off my news-server before I canceled it. It is gone from my news-server. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221948 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 01:46:19 GMT w8ji@akorn.net wrote: > All personal issues and insults aside, before anyone does anything with > any of this they would have to have a good feel for how an inductor > behaves. I just asked my dog if she has a good feeling about how an inductor behaves. She wagged her tail in affirmation. Now please explain why feelings are important to this discussion. > Do you agree or disagree with my post about how an inductor behaves? I disagree with you about how an inductor behaves in a standing wave environment. I agree with Walter Maxwell who said: "If an inductance is in series with a line that has reflections, the current will NOT be the same at both ends of the inductor." Sorry about that, but Walt gave me permission to quote him. Note the emphasis on 'NOT' in his statement. A 75m bugcatcher mobile system is a *STANDING WAVE ANTENNA*, so no, I don't agree with you at all as enumerated in my previous posting. Please don't ask me the same question over and over. I am not going to change my mind until you provid valid evidence to the contrary and so far, all you have done is prove your ethics leave something to be desired. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221949 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Current through coils Message-ID: <3res02d1d1ej31mgrj8mti7fpqe4fd6621@4ax.com> References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> Date: Wed, 08 Mar 2006 02:06:31 GMT On Wed, 08 Mar 2006 01:46:19 GMT, Cecil Moore wrote: >w8ji@akorn.net wrote: >> All personal issues and insults aside, before anyone does anything with >> any of this they would have to have a good feel for how an inductor >> behaves. > >I just asked my dog if she has a good feeling about how an inductor >behaves. She wagged her tail in affirmation. ... Oh no Cecil, not another citation! Owen -- Article: 221950 of rec.radio.amateur.antenna Date: Tue, 07 Mar 2006 20:08:39 -0600 From: Tom Ring Subject: Re: Current through coils References: Message-ID: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> Hey folks, they have a word that's used occasionally that I think might be appropriate here, it is "chill". As in chill out. Things are getting more out of hand than normal. Some of you are adults, please start acting that way. Some people have been trying, possibly poorly, to be funny, forgive them. I could say more, but you get the idea. tom K0TAR Article: 221951 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> Message-ID: Date: Wed, 08 Mar 2006 02:43:53 GMT Tom Ring wrote: > Some of you are adults, please start acting that way. Tom, I apologize profusely to everyone for losing my temper. I regret that every time it happens but that time never seems to be the final time. I canceled my posting made in anger. But please note that me losing my temper has absolutely no bearing on objective technical facts and has absolutely no effect at all on the validity of my technical arguments. Galileo probably lost his temper in front of the priests who placed him under house arrest. That made absolutely no difference in the scientific facts that he was asserting at the time. I am presenting my thoughts in front of the internet gurus in much the same manner as Galileo did to the priests. Hopefully, they will listen better than the priests did and not put me under house arrest. (But I have my Colt 45 ready just in case. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 221952 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 1n21 diode housing Date: Tue, 7 Mar 2006 21:12:17 -0600 Message-ID: <21271-440E4B91-1080@storefull-3254.bay.webtv.net> References: Chris W., KE5GIX wrote: "Can somone tell me where O can find the housings hor a 1n21 crystal detector so I can hook it to some coax and a directional coipler?" >From the appearance of the crystal, I`d think a fuse clip and a tube socket pin could be used to make connections. Richard Clark had a good idea to look for ancient military surplus. These diodes were also prevalent in commercial microwave sets which are now long pbsolete. It reminded me I have a military TS-1268/U "Crystal Rectifier Test Set" made to test these crystals in 1945. It`s been stowed away for years, but I broke it out and tested a crystal, It uses a 1.5-volt dry-cell to measure forward and reverse currents on a meter (0-1 ma). The battery was still good and the 1n23 tested OK. It is obviously ddurable so I`m going to keep it. Maybe Fair Radio Sales or some such surplus dealer has exactly what you want. My stock of test diodes comes in lead cylinders. Best rehards, Richard Harrison, KB5WZI Article: 221953 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 1n21 diode housing Date: Tue, 7 Mar 2006 22:07:12 -0600 Message-ID: <21272-440E5870-229@storefull-3254.bay.webtv.net> References: <21271-440E4B91-1080@storefull-3254.bay.webtv.net> CORRECTIION The test set is a TS-268/U. Best regards, Richard Harrison, KB5WZI Article: 221954 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141772342.715920.287530@z34g2000cwc.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 04:34:49 GMT w8ji@akorn.net wrote: > That doesn't sound like Walter gave you permission to me. I have backtracked to try to find out what happened. I asked Walt's permission to post the following: > Walter Maxwell wrote: >> If an inductance is in series with a line that has no reflections, >> the current will be the same at both ends of the inductor. >> >> If an inductance is in series with a line that has reflections, >> the current will NOT be the same at both ends of the inductor. >> >> Consequently, circuit analysis will not work when both forward >> and reflected currents are present in a lumped circuit. He agreed but suggested I also include his fourth statement which followed the above three statements. >> When reflections are present, a current node and a current loop >> can appear at separate points on an inductor simultaneously. When I went back to copy and paste bottom-up from his email in order to include his fourth assertion, I inadvertently copied one too many sentences at the top. It is true that I didn't have Walt's permission to publish that extra first sentence in his email. I regret that accidental mistake and wish I could take it back. And of course, neither Walt nor anyone else in the universe agrees with me 100%. But please note that accidentally including that first sentence doesn't change the technical content of Walt's other four assertions which should be allowed to stand as is until further notice. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221955 of rec.radio.amateur.antenna From: "Sal M. Onella" References: Subject: Re: 3 Monos or a Tribander? Message-ID: Date: Tue, 7 Mar 2006 21:43:22 -0800 "west" wrote in message news:q7pNf.48851$g47.20547@tornado.tampabay.rr.com... > Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was > wondering what I should use for a base antenna that will be over 60ft high > (bet I'll get tons of intermod). One thought is to purchase the best > tri-bander available or, perhaps there is too much compromise with an > all-in-one. Would you use a dual bander and a mono, which band is the dual & > which the mono or 3 monos? Of course with anything other than a tri-bander, > a triplexer will be needed. Oh what trying decisions a ham must make! Any > comments most welcomed. > > 73s > west > AF4GC > > I like j-poles, made of copper pipe. Their appeal to me is their absolute ruggedness and the freedom from any counterpoise. Just last week, I looked at my oldest one (~12 yrs) and it looked good as new except for a light patina. Aluminum would be nearly dust at that age. In addition, I have developed a method of connectorizing a j-pole that is more secure than just a single pop-rivet. On your tower, you can mount two up and one down, with the two up being the 1.25m and the 70 cm. (I think there will be the least interaction between that pair -- just a hunch.) Putting the 2m j-pole down is unlikely to hurt its pattern much; I did some informal experiments with masts near a j-pole and I had to get to less than a two-inch separation distance to affect either transmit or receive. If I can't get 1:1 as my VSWR low point, adding a cap in series with the feed usually fixes it (100pF, or so). You may not need all three antennas. A 2m j-pole is a reasonably good match at 70 cm, although the major 70 cm. lobe is not aimed at the horizon. There is radiation to the horizon, however, evidenced by the fact that I just raised a repeater on Palomar Mountain, about 42 miles to the north, using 0.5W into that durable 12 year-old copper j-pole, cut for 146 MHz. The antenna is only about 20 feet above the ground but I am clear of obstructions to the north, which helps. (At 60 ft, you will be clear of obstructions, too, you lucky devil.) The up-side of using the 2m j-pole as a dual-bander is that you can dispense with the triplexer and run two cables up the mast. The down-side of reading this far is that you now have additional choices -- not what you wanted, eh? 73, John KD6VKW Article: 221956 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: 3 Monos or a Tribander? Message-ID: <89ss02dse89v4fqvvkfmcpos8ad6eiclco@4ax.com> References: Date: Wed, 08 Mar 2006 06:11:41 GMT On Wed, 01 Mar 2006 22:21:10 GMT, "west" wrote: >Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was >wondering what I should use for a base antenna that will be over 60ft high >(bet I'll get tons of intermod). One thought is to purchase the best >tri-bander available or, perhaps there is too much compromise with an >all-in-one. Would you use a dual bander and a mono, which band is the dual & >which the mono or 3 monos? Of course with anything other than a tri-bander, >a triplexer will be needed. Oh what trying decisions a ham must make! Any >comments most welcomed. West, Some thoughts: The economics of feedline(s) might tilt the solution in favour of a single triband antenna with LDF4-50 or better, though you will probably want a very short flylead to the handheld. (Note that the loss in 100' of RG213 at load VSWR=1.5 is 5dB at 70cm, whereas LDF4-50 is 1.5dB, and the loss in a 5' tail of RG58C/U under similar conditions is 0.7dB.) If you only want to work repeaters and your path is good enough, losses might not be an issue. (Remember though that 5W handhelds get really hot on full power.) Is LDF4-50 overkill for a handheld? It might be more appropriate than with a higher powered transmitter. If intermods are an issue (as handhelds have less than adequate front end selectivity), do the repeaters use CTCSS... at least that helps prevent the transceiver breaking mute all day and night. Does the radio have a real rx attenuator that can help with intermods, to you have sufficient rx signal strength to be able to use it? At least you are not intending using a discone. Handhelds rarely work well on external broad antennas (for intermod reasons), and even the multiband antennas can be a challenge for handhelds. Owen -- Article: 221957 of rec.radio.amateur.antenna From: "Jerry Martes" References: <5amq02tq3q0lh1ag7d724jbk55j3fj3t5b@4ax.com> Subject: Re: ferrite balun grades Message-ID: <3EuPf.5356$CT.3859@trnddc04> Date: Wed, 08 Mar 2006 06:15:27 GMT "Mike Newman" wrote in message news:sfis02hfvkc9po1855k2vbjscm0qgosiov@4ax.com... > On Tue, 07 Mar 2006 15:18:33 GMT, "Jerry Martes" > wrote: > >> >>"Mike Newman" wrote in message >>news:5amq02tq3q0lh1ag7d724jbk55j3fj3t5b@4ax.com... >>> Any advice on which grade of ferrite would be most useful for a >>> feeedline balun choke effective at 70 cm? >>> Thanks de miken zl1bnb >> >> Hi Miken >> >> I've been using the tubular, high permeability ferrites designed for RFI >>suppression slipped over the RG-223 coax for a balun for vhf antennas. I >>am >>aware of the high loss with those ferrite tubes. I have been hoping the >>high permeability would present a high reactance to currents along the >>outside of the coax. So far, the tubes are working OK for my needs. >>Your mileage may vary. >> >> Jerry >> > That's exactly what I intended doing, feeding a moxon rectangle in > this case, my win4nec model gives 50+0.1j. > > Given the correct grade of ferrite, it should probably be ok on > UHF. > > But how to to determine the effectiveness? Maybe a small bead with a > couple of turns to pick up voltage nodes on the coax feedline, with > and without the choke balun beads. > > MikeN Hi Mike Since you are acknowledging the existence of 1/10th of an ohm of inductive reactance, at UHF, you are way beyond my level of accuracy in any measurement of effectiveness. But, I once measured the inductance across the ferrite tube by connecting the impedance "meter" to the exposed ends of the coax braid that was threaded thru the center of the ferrite. Then I removed the ferrite and repeated the test with the ferrite removed. Roy Lewallen has an excellant paper written to show how to properly evaluate baluns. I have the paper saved and will be happy to share it with you. It is almost a *must read* since it is so thouough and informative. Jerry Article: 221958 of rec.radio.amateur.antenna From: Big Endian Subject: Re: Q. about height of the ends of a doublet References: <1141779448.549209.64220@j52g2000cwj.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 09:18:40 GMT In article <1141779448.549209.64220@j52g2000cwj.googlegroups.com>, nm5k@wt.net wrote: > It will slightly decrease the performance. I'd keep the ends > as high as possible if you want the max performance. > MK I'd like to but I'm a little concerned about next door, if you know what I mean. The poles are on the lot line and in the front yard, but in the summer they are pretty well shielded by trees, in winter they stand out their naked in the wind. Article: 221959 of rec.radio.amateur.antenna From: Ken C Subject: Impedance with T-connector? Message-ID: Date: Wed, 08 Mar 2006 06:48:29 -0500 If I put a T-connector on my feedline and a 50 ohm dummy load on each leg, does the transmitter see 50 ohms, or 25 ohms? If one leg is not being used, what should be put there (if anything) for the transmitter to see 50 ohms if the impedance of the other leg is 50 ohms? Ken KC2JDY Article: 221960 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Bend in xmission line Date: Wed, 8 Mar 2006 06:56:44 -0600 Message-ID: <9127-440ED48C-13@storefull-3253.bay.webtv.net> References: Alfred Lorona wrote: "Conventional wisdom cautions against sharp bends in open wire transmission line." One does not want to create an impedance bump. Ed Laport shows how to make right-angle turns. See page 396 of "Radio Antenna Engineering". It works fine with 100 KW. Best regards, Richard Harrison, KBB5WZI Article: 221961 of rec.radio.amateur.antenna From: "Dale Parfitt" References: <1141820228.146191.318710@j33g2000cwa.googlegroups.com> Subject: Re: Impedance with T-connector? Message-ID: Date: Wed, 08 Mar 2006 13:17:07 GMT "Jim" wrote in message news:1141820228.146191.318710@j33g2000cwa.googlegroups.com... > > Ken C wrote: >> If I put a T-connector on my feedline and a 50 ohm dummy load on each >> leg, does the transmitter see 50 ohms, or 25 ohms? >> >> If one leg is not being used, what should be put there (if anything) >> for the transmitter to see 50 ohms if the impedance of the other leg >> is 50 ohms? >> >> Ken KC2JDY > > Ken; > > 50 ohms. > > Jim > I'd be interested in seeing your thinking on this. Dale W4OP Article: 221962 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> <1141812993.768076.158930@e56g2000cwe.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 13:36:45 GMT w8ji@akorn.net wrote: > Then we can't go further with this Cecil, ... That's simply not true. We can take this discussion to its logical conclusion if you are not afraid to continue it in logical order at a logical starting point. Starting with coils is like looking for your keys under the street light, instead of where you lost them, because that's where the light is better. Coil theory is not the problem. Standing wave current theory is the problem. Let's discuss the problem. > If you refuse to discuss the behavior or electrical characteristics of > the component you are talking about, there really isn't anything we can > talk about. I'm not refusing to discuss anything as long as it is taken in logical order. Our disagreement extends much farther back into fundamental technical principles than just the subject of coil function. We actually may have no technical disagreement about coils. I believe our basic disagreement involves standing wave current, not coils, so standing wave current should be the topic of this initial discussion. For that, we need to first agree on the 1/2WL thin wire model of a dipole. Let's see what we can agree on. Can we agree on the following pertaining to a 1/2 wavelength thin wire dipole? The net current in a standing wave antenna is a standing wave. The net current displayed by EZNEC for a standing wave antenna is a standing wave. The net standing wave current is the phasor sum of the forward current traveling wave and the reflected current traveling wave. The principle of superposition applies to the two component waves. If we superpose the forward current traveling wave and the reflected current traveling wave, we obtain the net standing wave current. Let's take for instance, that 1/2WL thin wire dipole. The standing wave current distribution and phase appears in Figure 14-2 in Kraus and Figures 1.15 and 4.8 in Balanis. If the current at the feedpoint is 1 amp, the net standing wave current equals cosine(x) where 'x' is the distance in degrees away from the feedpoint. This topic of discussion will most likely reveal that our fundamental point of disagreement is standing wave current and not coils at all. So which points above do you agree/disagree with? References to Kraus are from "Antennas for All Applications", Kraus and Marhefka, 3rd edition. References to Balanis are from "Antenna Theory", Balanis, 2nd edition. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221963 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> <1141812993.768076.158930@e56g2000cwe.googlegroups.com> <6hNpk4NyLsDEFAnW@ifwtech.co.uk> Message-ID: Date: Wed, 08 Mar 2006 13:49:45 GMT Ian White GM3SEK wrote: > And also, if the inductively loaded antenna is designed by the "antenna > as transmission line" method (as used by Boyer and ON4UN for example) it > clearly shows that the loading inductance is simply there to cancel the > net capacitive reactance - in other words, it behaves in exactly the > same way as you would in any other circuit. If that is true, you guys shouldn't have any difficulty proving me wrong and sending me back to the woodshed once and for all. If the above is not entirely true, please don't put me under house arrest until I present the truth as I see it. And certainly, call me on anything that is wrong. If you will keep listening with an open mind, I think I can show you that the words, "clearly", "simply", and "exactly", in your above statement are not entirely correct. -- Ian, no one has explained the antenna currents reported by EZNEC at: http://www.qsl.net/w5dxp/qrzgif35.gif How can 0.1+ amp of current be 'flowing' into the bottom of the coil and 0.7+ amp of current be 'flowing' out of the top of the coil. It's been days now and no one has offered an explanation. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221964 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Non-theoretical, practical and probably stupid question Date: Wed, 08 Mar 2006 09:31:44 -0500 Message-ID: References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> <87u0afnuui.fsf@qmc.ph.msstate.edu> tclay@qmc.ph.msstate.edu wrote: >> It seems necessary to "waste" as much as 60 feet of rope in either >> side. If I support the center insulator, then double that. >> >> Is there a better way? > > I'm not sure what the problem is, yes, it takes a bunch of rope if > you can't climb the tree. > > I usually don't bother with pulleys as I prefer to get the antenna > up as high as possible. You will lose 15-20 feet of height (or more) > using a pulley compared to not. Hi Tor, I don't use pulleys either, but I'm not sure I uunderstand why you would lose height with them. - 73 de Mike KB3EIA - Article: 221965 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Vertical vs Horizontal shootout part one Date: Wed, 08 Mar 2006 09:47:18 -0500 Message-ID: References: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> <818s029289valqofpmkpvp2qghuedqrd83@4ax.com> Richard Clark wrote: > On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo > wrote: > >>> Question, does the magnitude of feedline radiation from the OCF >>> (presumably predominantly vertical) significantly affect qualification >>> of it as a horizontal antenna? >> There shouldn't be any feedline radiationn, this is oan antenna >> running coax to a 4:1 balun at the feedpoint. > > Hi Mike, > > Not all 4:1 BalUns exhibit enough (or sometimes any) common mode Z. Okay. Perhaps I might better characterize my experiment as a comparison of a vertical and an OCF dipole of indeterminate vertical vs horizontal performance. I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". In that case you would feed the antenna with balanced line. Certainly the antenna doesn't seem to be radiating RF >from anywhere but the antenna bits. p.s. forgive the spelling, I am using a beta of Thunderbird for my newsgroups, and it seems to have a few quirks that make it hard to see what I have written!! - 73 de Mike KB3EIA - Article: 221966 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Wed, 8 Mar 2006 15:22:08 +0000 (UTC) Message-ID: References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> Has it ever occurred to you guys that a coil is a coil wherever it is used and always behaves in the same way. Article: 221967 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> Message-ID: <6PDPf.44803$Jd.43007@newssvr25.news.prodigy.net> Date: Wed, 08 Mar 2006 16:41:38 GMT Cecil Moore wrote: > Reg Edwards wrote: >> Has it ever occurred to you guys that a coil is a coil wherever it is >> used and always behaves in the same way. > > The coil always behaves in the same way. Unfortunately, the models > used to explain the operation of the coil don't work in the same > way. Please see: > > http://www.ttr.com/corum/index.htm Dang Reg, I forgot to post the quote from that web page. Here it is: "Lumped element representations for coils require that the current is uniformly distributed along the coil - no wave interference and no standing waves can be present on lumped elements." Therefore, lumped element representations for coil CANNOT be used to analyze standing wave antennas. I wasn't the first to say that. Using a lumped element representation for a coil in a standing wave environment is "assuming the proof". Here's more information along those same lines. http://www.ttr.com/TELSIKS2001-MASTER-1.pdf -- 73, Cecil http://www.qsl.net/w5dxp Article: 221968 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 8 Mar 2006 11:14:18 -0600 Message-ID: <18782-440F10EA-9@storefull-3252.bay.webtv.net> References: Reg Edwards wrote: "Has it ever occurred to you guys that a coil is a coil however it is used and always behaves in the same way?" Yes! But when it is part of an antenna system, the system imposes energy upon the coil in ways which the coil does not control. "The system is the solution", AT&T used to say. John D. Kraus writes on page 176 of his 1950 edition of "Antennas": "The term transmission mode is used to describe the manner in which an electromagnetic wave is propagated along an infinite helix (that`s a coil, right?) as though the helix constituted an infinite transmission line or wave guide." Wave guides and transmission lines are subject to reflections. These produce the standing wave patterns exhibited in many text books. Kraus uses the helix very generally. To him it can collapse to a single loop or be stretched to a straight wire. When a "normal mode" helix (coil) is used as part of a antenna system, It radiates normal to the axis of the coil, similar to the manner it would were it stretched out to a straight wire. A reflection within the antenna system would return energy toward the generator, similar to the manner it would with straight wires. The same sort of interaction between incident and reflected waves must occur. There is no other way. These produce variatiations in both current and voltage in a periodic manner along the helix as described for transmission lines which should be familiar to all. The whole section of helical antennas in Kraus is interesting. Kraus is the inventor of the Axial mode helical antenna. I think he tells the story in his 3rd edition of how he went home and wound one up and tested it after being told by an expert of the times that such an antenna was impossible. Best regards, Richard Harrison, KB5WZI Article: 221969 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Wed, 8 Mar 2006 18:41:58 +0000 (UTC) Message-ID: References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> "Ian White GM3SEK" wrote > Reg Edwards wrote: > >Has it ever occurred to you guys that a coil is a coil wherever it is > >used and always behaves in the same way. > > > > > That is only true if you say it about pure inductance. > ======================================== Ian, old boy, you are no better than the rest of the gaggle ! There's not one of the clever buggers who can design a coil-loaded whip for a given frequency using a pencil, paper and a pocket calculator. They have to copy an already existing, pre-tested, model after searching through the antenna comics. --- Reg. Article: 221970 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> <1141812993.768076.158930@e56g2000cwe.googlegroups.com> <6hNpk4NyLsDEFAnW@ifwtech.co.uk> Message-ID: <3CFPf.26960$2O6.9927@newssvr12.news.prodigy.com> Date: Wed, 08 Mar 2006 18:44:15 GMT Ian White GM3SEK wrote: > There is one typo in that statement: I posted it part-way through > changing from "In other words, you use the inductance in exactly the > same way as you would in any other circuit" to "In other words, it [the > inductance] behaves in exactly the same way as it does in any other > circuit". I stand by both of those statements. Too bad you are standing by false statements. :-) Quoting: http://www.ttr.com/corum/index.htm "... one needs transmission line analysis (or Maxwell's equations) to model these electrically distributed structures. Lumped circuit theory fails because it's a theory whose presuppositions are inadequate. Every EE in the world was warned of this in their first sophomore circuits course." Seems you weren't listening that day, Ian. "Lumped element representations for coils require that the current is uniformly distributed along the coil - no wave interference and no standing waves can be present on lumped elements." > It's because you modeled a real-life coil, whose length and diameter are > each a significant fraction of the size of the whole antenna. A 75m bugcatcher coil is a real-life coil, Ian. Contrary to what W8JI asserts, it is a significant fraction of the size of the whole antenna. It uses 42 feet of wire, for goodness sake. > You are hung up on something far more fundamental. You are > misrepresenting the fundamental electrical properties of inductance to > make them fit your theory. I am using distributed network theory known to work in a standing wave environment. You are using lumped element theory known to fail in a standing wave environment. A 75m bugcatcher mobile antenna is a standing wave environment. So exactly who is "misrepresenting the fundamental electrical properties of inductance to make them fit his theory"? -- 73, Cecil http://www.qsl.net/w5dxp Article: 221971 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: OT for Cecil or any other ex RRAPers References: <1141756042.224852.90540@j52g2000cwj.googlegroups.com> <1141837212.960395.167340@j52g2000cwj.googlegroups.com> Message-ID: Date: Wed, 08 Mar 2006 18:45:27 GMT an_old_friend wrote: > well thanks for responding if you ha[en to remmber (after all I might > have just started your memory moving) :-) My memory moved out a few years ago. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 221972 of rec.radio.amateur.antenna From: "AAA RF Products" Subject: FS: RF Connectors & Adapters Message-ID: <1QFPf.2813$ld2.2727@fed1read11> Date: Wed, 8 Mar 2006 11:00:28 -0800 For your free copy of our new catalog, please email sales@AAARFProducts.com or see www.aaarfproducts.com or call 949 481 3154 (San Clemente, CA) No minimum order. No handling charges. Article: 221973 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> <1141812993.768076.158930@e56g2000cwe.googlegroups.com> <6hNpk4NyLsDEFAnW@ifwtech.co.uk> <7aKdnd_JhqWDjpLZnZ2dnUVZ_smdnZ2d@comcast.com> Message-ID: Date: Wed, 08 Mar 2006 19:04:02 GMT Amos Keag wrote: > I agree with Cecil. Good to hear. > Conclusion: the coil, at 75 degrees of the circuit, has to be treated > differently from DC or LF models. Yes, I just ran an experiment that would support that statement. My 75m bugcatcher coil is mounted on a one foot bottom section on my pickup. I'm sorry but I can't fasten the coil directly to the mount for reasons of clearance. But one foot at 75m is only about 1.5 degrees so let's call it negligible. I have one of those 12 foot telescoping whips from MFJ. It's great for portable operation from my pickup. It is adjustable >from 2 feet to 12 feet. The first measurement I made was with no whip at all, just the bugcatcher sitting on top of a one foot bottom section. I used an MFJ-259B for the measurements connected through a two foot W2DU choke. Here are the results. resonant Stinger frequency 0' 6.7 MHz 2' 5.1 MHz 4' 4.3 MHz 6' 3.8 MHz 8' 3.5 MHz 10' 3.2 MHz 12' 3.0 MHz It's more than obvious that with a stinger length of 0', the coil is very close to 1/4WL and is NOT a lumped inductance. The current at the top of the coil is obviously zero. So moving down the frequency in 2' increments, exactly when does a coil made with 42 feet of wire become a lumped inductance in the presence of standing waves? http://www.ttr.com/corum/index.htm says never. When I get my MFJ current meter, I will actually measure the current at the top and bottom of the coil. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221974 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> Message-ID: <9WFPf.26966$2O6.2887@newssvr12.news.prodigy.com> Date: Wed, 08 Mar 2006 19:05:41 GMT Reg Edwards wrote: > There's not one of the clever buggers who can design a coil-loaded > whip for a given frequency using a pencil, paper and a pocket > calculator. Sure we can, Reg. Just design the coil too big and jumper the un-needed turns. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 221975 of rec.radio.amateur.antenna From: "NA" Subject: Military ships fan antenna Message-ID: <_1GPf.17539$992.17494@tornado.socal.rr.com> Date: Wed, 08 Mar 2006 19:14:02 GMT Can anyone tell me about "fan antennas" like those used on the large navy ships. Thanks Jim N6PJQ Article: 221976 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Vertical vs Horizontal shootout part one Date: Wed, 08 Mar 2006 11:18:28 -0800 Message-ID: <120ubgbo1kpf523@corp.supernews.com> References: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> <818s029289valqofpmkpvp2qghuedqrd83@4ax.com> Michael Coslo wrote: > Okay. Perhaps I might better characterize my experiment as a > comparison of a vertical and an OCF dipole of indeterminate vertical vs > horizontal performance. I was under the impression from the designers of > this flavor of dipole that they were not radiating from the feedline > unless you wanted that "feature". Unfortunately, even if the designers don't intend the feedline to radiate, it's very difficult to avoid. A single balun at the feedpoint is very likely not enough to prevent it. In that case you would feed the > antenna with balanced line. That would make no difference at all in determining whether or not the line would radiate. Certainly the antenna doesn't seem to be > radiating RF from anywhere but the antenna bits. The amount of feedline common mode current and therefore radiation will vary from band to band, probably a great deal. It's easy enough to make up a simple current probe with a clamp-on core and make quantitative measurements if you're interested. They've been described on this newsgroup several times. Roy Lewallen, W7EL Article: 221977 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Impedance with T-connector? Message-ID: References: Date: Wed, 08 Mar 2006 19:35:42 GMT On Wed, 08 Mar 2006 06:48:29 -0500, Ken C wrote: >If I put a T-connector on my feedline and a 50 ohm dummy load on each >leg, does the transmitter see 50 ohms, or 25 ohms? Not necessarily either. The T connects the branches in parallel, so if you have a 50+j0 load and any length of 50 ohm coax connected to each of two branches, the impedance at the T is 25 ohms. If you connect to T to something else (eg a transmitter) with 50 ohm coax, the SWR on that section will result in impedance transformation that depends on the coax (vf), frequency, and length. For example, if you had 3m of RG58C/U at 7MHz, the impedance looking into the cable would be 36+j24. You can solve the transmission line transformation with the calculator at http://www.vk1od.net/tl/tllce.php . >If one leg is not being used, what should be put there (if anything) >for the transmitter to see 50 ohms if the impedance of the other leg >is 50 ohms? You know the answer to that now, the branches of the T are in parallel, leave one branch open circuit. Owen -- Article: 221978 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Vertical vs Horizontal shootout part one Date: Wed, 8 Mar 2006 21:55:42 +0000 (UTC) Message-ID: References: <081n025fa3l0tk3ftnb464ga44sia7h7gh@4ax.com> <818s029289valqofpmkpvp2qghuedqrd83@4ax.com> <120ubgbo1kpf523@corp.supernews.com> Radiation from feedlines is grossly exaggerated. For many purposes, practically it does not occur. When discussing the importance of such radiation one should always crudely estimate its level relative to transmitter or radiated power. If you don't know what its level is then you don't know what you are waffling about. ---- Reg. Article: 221979 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Current through coils Date: Wed, 8 Mar 2006 21:55:42 +0000 (UTC) Message-ID: References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> <9WFPf.26966$2O6.2887@newssvr12.news.prodigy.com> "Cecil Moore" wrote > Reg Edwards wrote: > > There's not one of the clever buggers who can design a coil-loaded > > whip for a given frequency using a pencil, paper and a pocket > > calculator. > > Sure we can, Reg. Just design the coil too big and > jumper the un-needed turns. :-) ========================================== Dear Cecil, you know as well as I do, that pruning the coil is not DESIGN. It is a procedure done by people who are floundering about in the dark. Not by supposedly professionally qualified engineers who are participating in this discussion. Anybody, even a CB-er, can make an antenna with the top of the whip a mile long and then severely prune it until the antenna resonates at the pre-determined frequency, following a score of attempts to use coils of different dimensions and numbers of turns. But even the experimenting CB-er has to understand what he is doing. Not so the so-called professionals. It appears from this discussion the university-educated Ph.D professionals are the ones who are floundering about in the dark. Silly old-wives indeed. As I have said before, the standards of education in Western schools and universities are dropping to bits. Chinese, Japanese, Korean, Iraqian, Iranian, Afganistan, Indian, Pakistan, Vietnam and Indianesian school kids, not forgetting the half-starved sewer-rats of Rio-de-Janerio, are better at arithmetic. And, what is more important, what stems from it! If you are interested I am on Spanish, Valencia Red tonight. It is supposed to minimise cholesterol in the blood stream. ---- Your old pal, Reg. Article: 221980 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <440e3ca7$0$7322$39cecf19@news.twtelecom.net> <1141823025.751401.183670@j33g2000cwa.googlegroups.com> <9WFPf.26966$2O6.2887@newssvr12.news.prodigy.com> Message-ID: <9CIPf.74513$PL5.63379@newssvr11.news.prodigy.com> Date: Wed, 08 Mar 2006 22:09:09 GMT Reg Edwards wrote: > Dear Cecil, you know as well as I do, that pruning the coil is not > DESIGN. I dunno about that, Reg. The Texas Bugcatcher guy made a living off of coils that were designed to require pruning. He even sold a pruning kit. > If you are interested I am on Spanish, Valencia Red tonight. It is > supposed to minimise cholesterol in the blood stream. Muy bueno. California Merlot here. Makes me forget about my cholesterol. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 221981 of rec.radio.amateur.antenna From: Skipp sent this Subject: yahoo rf amplifiers group Date: Wed, 8 Mar 2006 22:25:25 +0000 (UTC) Message-ID: Just a 50 cent plug to let you folks know about the Yahoo RF Amplifiers Group, please feel free to join in if you have an interest in rf and audio amplifiers. Building - construction - operation - design - operation, you get the idea. Hope to see you there... http://groups.yahoo.com/group/rfamplifiers/ cheers, skipp Article: 221982 of rec.radio.amateur.antenna Date: Wed, 08 Mar 2006 16:46:51 -0600 From: Tom Ring Subject: Re: Q. about height of the ends of a doublet References: Message-ID: <440f5f05$0$3762$39cecf19@news.twtelecom.net> Dave Oldridge wrote: > This won't make it into a superior DX antenna but it may allow you to hear > things you missed before. Basically, Bob Heinlein was right. There ain't > any such thing as a free lunch. > TANJ! Tom K0TAR Article: 221983 of rec.radio.amateur.antenna From: rocky Subject: Re: Q. about height of the ends of a doublet References: Message-ID: Date: Wed, 08 Mar 2006 23:23:56 GMT In article , Dave Oldridge wrote: > Big Endian wrote in > news:nospam-3801D8.18373207032006@news-rdr-02.rdc-kc.rr.com: > > > > > My center of a 3.8 Mhz doublet is at about 35 feet and am going to > > drop the ends from 30 feet to about 10 to 15 feet. Just wondering if > > it will make all that much difference if any? > > There will be a marked improvement in the low angle performance in the > direction off the ends of the antenna (the flattop is very poor at this). > This will come at the expense of a sight loss (about .8db) off the > pattern's top (where you can most afford it). You will also experience a > slight deterioration in the SWR (based on 50 ohm coax) from about 1.34 to > 2.05, easily managed by any tuner, including those built into many radios. > You will also find that you need to shorten the antenna very slightly to > maintain the same resonant frequency. > > This won't make it into a superior DX antenna but it may allow you to hear > things you missed before. Basically, Bob Heinlein was right. There ain't > any such thing as a free lunch. What I've read is that when the ends are dropped to an inverted Vee configuration the feedpoint impedance drops closer to 50 ohms, but the Vee bandwidth is more restricted. Hard to believe that lowering the ends by 15 feet from 30 would make all that much difference on 75 meters. Tnx Article: 221984 of rec.radio.amateur.antenna From: "west" Subject: SMA Connector Follow up Message-ID: Date: Thu, 09 Mar 2006 00:04:53 GMT Originally I requested a source for various length of cables with SMA Male on one end to plug into a HT (Kenwood TH-F6A) and the other end a PL-259. Lengthy and comprehensive treads soon made me realize that the PL-259 would be ill advised especially at UHF & higher. So I found some ready made cables with SMA and N connectors. The only problem (if it's really a problem) is those skinny cables they come in. Some claim that they are 50 ohms, another RG-174. I don't know the other types. Do you think it will be alright to use those narrow cables from my HT to an amplifier to my monitoring meter and then use regular RG 8 to the base antenna? Will those skinny cables present some kind of mismatch. You know it's almost impossible to solder a SMA connector to an RG 8. Thoughts, please? Thank you. Cordially, west AF4GC Article: 221985 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: SMA Connector Follow up Date: Thu, 09 Mar 2006 00:47:50 -0000 Message-ID: <120uupmt5ovbdb8@corp.supernews.com> References: In article , west wrote: >Originally I requested a source for various length of cables with SMA Male >on one end to plug into a HT (Kenwood TH-F6A) and the other end a PL-259. >Lengthy and comprehensive treads soon made me realize that the PL-259 would >be ill advised especially at UHF & higher. So I found some ready made cables >with SMA and N connectors. The only problem (if it's really a problem) is >those skinny cables they come in. Some claim that they are 50 ohms, another >RG-174. RG-174 is a 50-ohm cable, just over 1/10" in diameter. It's a decent choice for HT-to-whatever pigtails, at long as the length isn't so great that losses become unacceptable. > I don't know the other types. Do you think it will be alright to use >those narrow cables from my HT to an amplifier to my monitoring meter and >then use regular RG 8 to the base antenna? Almost certainly for short lengths. I wouldn't use it for long runs. The attenuation per 100' of RG-174 is around 13 dB at 146 MHz, and about twice that at 440. Thus, at 440, 10' of the cable would lose you around 2.5 dB, or less than 1/2 of an S-unit at the conventional calibration. This loss would occur for both transmission and reception. There are other cables of this size which are less lossy - LMR-100A has approximately half as much signal loss per foot. Both RG-174 and LMR-100A have solid center conductors, and might not stand up to a very large number of flexing cycles. A cable of similar size with a multistrand center conductor might live longer. > Will those skinny cables present >some kind of mismatch. Not unless the manufacture is seriously botched (e.g. cable not soldered to connector correctly). They're the same impedance as RG-8, but are a lot more lossy. > You know it's almost impossible to solder a SMA >connector to an RG 8. Thoughts, please? Thank you. Go for it. A pigtail of anywhere from 18" to a few feet should act as a perfectly acceptable strain-relief for your HT's SMA connector, and even at 440 its loss should be low enough that you'd be unlikely to notice it. -- 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: 221986 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Current through coils References: <1141757778.043926.115850@i40g2000cwc.googlegroups.com> <1141778806.352135.21840@j52g2000cwj.googlegroups.com> <1141812993.768076.158930@e56g2000cwe.googlegroups.com> <6hNpk4NyLsDEFAnW@ifwtech.co.uk> <7aKdnd_JhqWDjpLZnZ2dnUVZ_smdnZ2d@comcast.com> <1141864325.153022.145680@p10g2000cwp.googlegroups.com> Message-ID: Date: Thu, 09 Mar 2006 02:32:00 GMT w8ji@akorn.net wrote: > Thinking the inductor or loading coil represents 60 degrees of > electrical length is EXACTLY where the big myth is at, and it can > easily be proven to be a myth! Well then do it, Tom. But you are not allowed to use the lumped circuit model. You must use the distributed network model (or Maxwell's equations). I think the distributed network model proves otherwise. Could be you are the one spreading myths after using an invalid model. There's just no getting around it. The forward current undergoes approximately a 90 degree phase shift from the feedpoint to the end of a 75m mobile bugcatcher antenna. It is reflected there (180 degree phase shift) and becomes reflected current which undergoes approximately a 90 degree phase shift from the tip of the antenna back to the feedpoint. So from the start of the forward current wave to the return of the reflected current wave there is approximately a 360 degree shift in order to put the forward current and reflected current in phase so they can superpose constructively. If the straight element part of the antenna is 12 degrees, we can account for 12 + 180 + 12 = 204 degrees without the coil. The coil is the only other thing in the whole system. Where does the other 78+78=156 degrees of total phase shift come from if not from the coil? I've explained all of this to you many times. Might be a good time to start listening. You can prove this for yourself. Using current probes and your o'scope you can measure the traveling wave phase shift through a loading coil. That figure is approximately the electrical length that is replaced by the coil when it is installed in the antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221987 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Current through coils Date: Wed, 8 Mar 2006 23:37:57 -0600 Message-ID: <18782-440FBF35-53@storefull-3252.bay.webtv.net> References: <1141864325.153022.145680@p10g2000cwp.googlegroups.com> Tom, W8JI wrote: "Thinking the inductor or loading coil represents 60 degrees of electrical length is EXACTLY where the big myth is at and it can easily be proven to be a myth!" A vertical antenna is often driven against a reflecting ground system. It is desirable that it be self resonant at nearly 1/4-wavelength (90-degrees), in many instances, to eliminate reactive impedance to current into the antenna, avoid loading coil loss, and avoid bandwidth limitation which comes with high-Q coils. Even with its drawbacks, a base loading coil is often the practical way to resonate a too-short antenna. Suppose the vertical is only 2/3 the height needed for self resonance, or 60-degrees high. The loading coil must replace about 30-degrees of missing antenna to bring the vertical to resonance. 30-degrees is not an inductance value. An inductor is impure because it has resistance and capacitance in addition to inductance. Also, the inductance needed to replace the missing 30-degrees of antenna depends on where it is sited, high, low, or in-between. Siting affects performance as it determines current distribution along the antenna. Where is the myth? Best regards, Richard Harrison, KB5WZI Article: 221988 of rec.radio.amateur.antenna From: SamSvL Subject: Re: FS: RF Connectors & Adapters Date: 9 Mar 2006 09:03:32 GMT Message-ID: References: <1QFPf.2813$ld2.2727@fed1read11> "AAA RF Products" wrote in news:1QFPf.2813 $ld2.2727@fed1read11: > For your free copy of our new catalog, > > please email sales@AAARFProducts.com > > or see www.aaarfproducts.com > > or call 949 481 3154 (San Clemente, CA) > > No minimum order. > > No handling charges. > > No shipping to Europe? Article: 221989 of rec.radio.amateur.antenna From: SamSvL Subject: Re: SMA Connector Follow up Date: 9 Mar 2006 09:06:13 GMT Message-ID: References: You know it's almost impossible to solder a SMA connector to > an RG 8. Thoughts, please? Thank you. > > Cordially, > west > AF4GC > I found on Ebay reasonable priced SMA to N adapters. Might save you from mounting a small connector on a thick cable! sam Article: 221990 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SMA Connector Follow up Message-ID: <2gtv02tb0755vgq9qvr30eaf80pi6cqr91@4ax.com> References: Date: Thu, 09 Mar 2006 09:40:54 GMT On Thu, 09 Mar 2006 00:04:53 GMT, "west" wrote: >Originally I requested a source for various length of cables with SMA Male >on one end to plug into a