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

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


--
Yours truly,
Chuck
 
WA3IAC
FN20la
 
 
 
------=_NextPart_000_0006_01C604C3.C83D9250-- Article: 220230 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: antenna tuner range calculators Date: Mon, 19 Dec 2005 22:53:50 +0000 (UTC) Message-ID: References: <65Epf.1835$RZ6.1473@bignews7.bellsouth.net> Download and run in a few seconds programs T_TUNER and L_TUNER, from website below. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220231 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 23:17:14 +0000 (UTC) Message-ID: References: <43a6b708_3@newsfeed.slurp.net> <11qdvpv9kf3rs80@corp.supernews.com> "Roy Lewallen" wrote > I'd be willing to wager that there are places in Florida which have more > lightning strikes in a single summer than have occurred at your QTH (or > mine) in the past 80 years. ======================================= Roy, your's is a safe bet. Nevertheless, statistically speaking, the good people of Florida should be more scared of dying from gunshot wounds. But it doesn't seem to worry them very much. ---- Reg. Article: 220232 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Mon, 19 Dec 2005 15:17:51 -0800 Message-ID: <11qeft0bpn1590@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> Toni wrote: > > When talking about loop antennas people talk about "capture area". > Whatever that is, this seems to be what makes a ferrite bar antenna > more sensitive than the equivalent simple coil tuned to the same freq. > I know that by using a ferrite bar you are narrowing the pattern, but > I'd think that the main gain does not come from the pattern narrowing > but from "capture area increase" (again, please bear with my ignorance, > these are only my thoughts on what I've read on the Web) Capture area is exactly the same thing as gain, but expressed in different units. There are two ways of increasing the gain or capture area of an antenna: increase its efficiency, or narrow its pattern. The former increases the gain or capture area in all directions; the latter increases it in some directions at the expense of others. A ferrite loop antenna simply has better efficiency than a standard loop of the same physical size. Hence it has better gain or capture area. >>>I know one can not have more than 0 dB with full omni, I just guess the >>>minimalistic antenna in pocketable gps is way below 0 dB and could >>>maybe be improved a little. >> [RL] >>0 dB relative to what? > > > An isotropic antenna; AFAIK a perfect isotropic antenna would have 0 dB > gain dB is a ratio, in this case of gains, or field strengths with a given power input, or capture areas. (All three ratios are the same for a given pair of antennas.) So the reference always must be specified, otherwise a statement of dB gain is meaningless. When using the gain of a free space isotropic antenna as a reference, gain is expressed in dBi, that is, dB relative to isotropic. The gain of a perfectly omnidirectional antenna over an infinite ground plane is 3 dBi, since the same power is concentrated in half the volume as it is for an isotropic free-space radiator. > > [RL] >>Once you get the desired coverage angle, the only way to improve the >>reception of the GPS is to improve the receiver signal/noise ratio. The >>only way you can do that from outside the GPS is to use an external >>antenna with a preamp having a lower noise figure than the GPS's receiver. > > > Please let me doubt that. For a given coverage angle you can't make > better than a perfect antenna, but you can certainly make worst (think > of a T2FD). If by "perfect" you mean "perfectly efficient", I agree. > >>I'm not sure what the "high loss antenna" is. If you mean the GPS >>antenna, it's not high loss at all, but is likely very efficient. If >>it's a patch antenna, you can't model it at all with EZNEC. But even if >>it's a quadrifilar helix, you can't model it with one segment. > > > I dont know how efficient they are, but I do know that normal > commercial patch antennas are noticeably less efficient than helical > ones, and then, for the helicals, I doubt that something aprox 1/10 wl > is anything close to efficient. If this was to be true I'd love to > build an equivalent 6.5 ft. helix to work on 20m! I wasn't aware of that. So if typical GPS patch antennas are indeed significantly inefficient, the reception could be improved without narrowing the pattern. But I don't know if there would be any practical way to do this externally. The civilian GPS frequencies are about 1228 and 1575 MHz. The wavelength in air of the lower frequency is about 9.6 inches. Patch antennas can be made with a side equal to about 0.25 wavelength divided by the square root of the dielectric constant of the material within the patch. So for Teflon dielectric (er ~ 2.3), a patch would have sides of 1.6 inches. If something like alumina is used (very low loss, dielectric constant ~ 10), the side would be 0.76 inches. Some patches have sides twice this long, but alumina would permit even one of those to be used in a typical GPS receiver. The two versions of patches have different patterns, and I don't know right off which would be preferable for GPS use. At any rate, I believe that patches of those dimensions are quite efficient, assuming the dielectic has low loss. Both Teflon and alumina, as well as others, meet this criterion. Maybe someone with a greater knowledge of patch antennas, and GPS antennas in particular, could provide some additional information. Roy Lewallen, W7EL Article: 220233 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Mon, 19 Dec 2005 15:28:13 -0800 Message-ID: <11qeggdrdllf93d@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <1134921266.178997.255510@f14g2000cwb.googlegroups.com> <1134930784.403818.189120@g14g2000cwa.googlegroups.com> Toni wrote: > . . . > There are many classes of helix antennas, and all the "normal" helix > antennas you will find have dimensions comparable to a full wl if not > greater. Quadrifilar helices typically have four twisted half wave elements. The length for 1228 MHz would be somewhat less than 4.8 inches. Twisting would make the assembly less high that that, and fattening the elements or plating them on a dielectric substrate would further shorten them. This is consistent with the antenna of an older GPS unit I had. > My doubting on pocketable GPSs antenna's efficiency is based merely on > their size. They are about 1/10 wl long. The only other antennas of > comparable size I know are loops, isotrons, fractals, CFA, EH and CB > sticks and, except for tuned loops, we know how they are treated > whenever they appear in this forum. It's possible to make an electrically small antenna that's quite efficient. Typical examples are the small transmitting loops made by AEA and MFJ, or the shortened, top loaded verticals described by Jerry Sevick, W2FMI, in a series of articles in the '70s. What you can't make is a short, efficient, broadband antenna. But GPS antennas don't need to be broadband. And for that matter, they don't have to be that electrically small. > > >>The difference is that the helix is quite directional. > > > The ones used in GPS receivers are exactly the opposite. They should > ideally have a "half orange" radiation pattern, as they should be able > to follow a satellite from horizon to horizon all over your head. This describes the approximate pattern of both quadrifilar helix and patch antennas, which is why those are the types which are commonly used. > . . . Roy Lewallen, W7EL Article: 220234 of rec.radio.amateur.antenna From: "Chuck S." References: <1135035213.671636.52820@g14g2000cwa.googlegroups.com> Subject: Re: Z matching of antennas Message-ID: Date: Mon, 19 Dec 2005 23:57:31 GMT Ok Gary, I would like to match a 50 Ohm radio to a 450 Ohm antenna input. I know an "L" network would work, but what I was looking for is if an auto transformer would be as good or use a transformer with a isolated primary winding. wrote in message news:1135035213.671636.52820@g14g2000cwa.googlegroups.com... > Chuck S. wrote: >> With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better >> to use, an autotransformer or a transformer with an isolated primary and >> secondary? I'm looking for the pro's and con's of each. >> >> >> -- >> Yours truly, >> Chuck >> >> WA3IAC >> FN20la >> >> http://www.qsl.net/wa3iac/ > > Hi Chuck, If I read your question correctly, you want to match a 450 > ohm antenna, with no reactive component, to a 50 ohm transmission line. > In this case a 9:1 transformer would do the trick. > If however you are trying to match an antenna fed with a length of > 450 ohm line down to the transmitter, where it will need to be > transformed to 50 ohms, an "L" network or some other impedance matching > network will be required. The impedance seen at the end of the 450 ohm > line, in this instance, will rarely be 450 ohms resistive. > Gary N4AST > Article: 220235 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Mon, 19 Dec 2005 16:02:04 -0800 Message-ID: <11qeiftgbhj3439@corp.supernews.com> References: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> <11q95dgt1j45l93@corp.supernews.com> <11q9kt36n4utv5e@corp.supernews.com> <1134924107.312230.237810@z14g2000cwz.googlegroups.com> <11qbi7i9pegj1db@corp.supernews.com> <11qciqd7vlfm4ec@corp.supernews.com> This has been an interesting discussion, and prompted me to do a tiny bit more research. It seems to me that if there's any nonlinear phenomenon which allows some pressure waves to travel through air faster than the speed of sound, surely a nuclear blast would produce enough pressure to excite it. But it doesn't seem to. From http://www.globalsecurity.org/wmd/intro/nuke-blast.htm: "During the time the blast wave is passing through the superheated atmosphere in the fireball, it travels at supersonic velocities. After it leaves the vicinity of the fireball, it slows down to the normal speed of sound in the atmosphere. As long as the blast wave is expanding radially, its intensity decreases approximately as the square of the distance. When the expanding blast wave from a nuclear air burst strikes the surface of the earth, however, it is reflected, and the reflected wave reinforces and intensifies the primary wave." Roy Lewallen, W7EL Article: 220236 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: MFJ ANTENNA QUESTION References: <43a72aae.7737125@newsgroups.bellsouth.net> Message-ID: Date: Tue, 20 Dec 2005 01:21:44 GMT Steven Fritts wrote: > I wonder if anyone has tried the MFJ collinear dipole that they have > in their new catalog. It is two half waves with a quarter wave length > of 450 ohm ladder line shorted at the bottom hanging down with an > SO 239 connector for the 50 ohn feedline connection. Sounds like a Double Zepp with a J-Pole-like matching stub. The antenna feedpoint impedance is very high. The 1/4WL ladder- line stub is shorted at the bottom. At some point up from the bottom, a 50 ohm point can be achieved, just like on a J-Pole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220237 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Z matching of antennas References: Message-ID: Date: Tue, 20 Dec 2005 01:23:32 GMT Chuck S. wrote: > With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better > to use, an autotransformer or a transformer with an isolated primary and > secondary? I’m looking for the pro’s and con’s of each. Where are you going to find a 450 ohm antenna? -- 73, Cecil http://www.qsl.net/w5dxp Article: 220238 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: One experience with noise References: <1134637337.c857a55f3cab0d38109173525afb1f55@roc.usenetexchange.com> Message-ID: <8kJpf.316866$zb5.87687@bgtnsc04-news.ops.worldnet.att.net> Date: Tue, 20 Dec 2005 01:42:28 GMT Wes, You got that right. Perhaps you are even too kind to cable service. After Hurricane Charley hit us head on last year we saw the following outages. Ordinary phone: 4 days (mostly underground) Electric power: 7 days (extensive pole replacement and rewiring) Cell phones: about 2 weeks (temporary towers brought in) Cable service: one month (cable runs on same poles as electric service) There was no flooding from Charley, but the winds were quite a bit stronger than Katrina and Rita. As soon as we got a temporary generator running we were able to watch regular over-the-air analog TV. 73, Gene W4SZ Wes Stewart wrote: [big snip] > And after a natural disaster cable TV systems will be working about as > well as cell phones have. While the old analog TV and radio will keep > chugging along. Article: 220239 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Passive reradiating antenna Date: Tue, 20 Dec 2005 01:49:41 +0000 (UTC) Message-ID: References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <11qeft0bpn1590@corp.supernews.com> "Roy Lewallen" wrote > A ferrite loop > antenna simply has better efficiency than a standard loop of the same > physical size. Hence it has better gain or capture area. ========================================= It's only a minor point, but when a ferrite core is placed inside a loop the efficiency remains the same. It's the same wire, the same coil dimensions, and hence the same loss in the resistance. If anything happens to efficiency it is reduced due to a loss in the ferrite core material. What happens is that the effective cross-sectional area of the loop increases approximately in proportion to the permeability of the core. For small permeabilities the capture area is much increased. But for larger permeabilities, say above 100, the effect diminishes and the effective core permeability settles down to the order of 20 or 30. It depends on the ratio of length to diameter of the core rather than of the coil. To visualise, it should be remembered most of the magnetic circuit lies in the air between and near the ends of a ferrite rod. There is no point in increasing permeability of rod material beyond a certain amount in an attempt to increase capture area. Capture area depends on the volume of the region of the e.m. field surrounding the core which is distorted by the core. See iron filings sprinkled round a bar magnet. When the reluctance of the rod itself is zero compared with that of the air path the limit of permeability has already been reached. And high values of rod permeability are always associated with high core loss. The moral is obvious. The sensitivity of the coil itself to e.m. waves is calculable. I'll stick out my neck and say the best a ferrite core can do is to increase the effective diameter of the coil by crudely 5 or 6 times. Which means that the gain of your tiny pocket MF transistor radio is much better than your super-dooper transceiver which needs a 260-feet long dipole on the 160 meter band. Just for the sake of argument! ---- Reg. Article: 220240 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? References: <43a6b708_3@newsfeed.slurp.net> <11qdvpv9kf3rs80@corp.supernews.com> Message-ID: Date: Tue, 20 Dec 2005 01:52:10 GMT Reg Edwards wrote: > Nevertheless, statistically speaking, the good people of Florida > should be more scared of dying from gunshot wounds. But it doesn't > seem to worry them very much. Now that so many Floridians are packing, it's the criminals who should be worried. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220241 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> Message-ID: Date: Tue, 20 Dec 2005 01:56:47 GMT Richard, There is no problem with Terman's words, but I believe you are missing his intention. His point in bringing up the magnetic flux is merely to say that one can find "exactly the same voltage" in the one meter long conductor by considered either the electric field directly or by considering the sweep of the magnetic field. It is just a statement of equivalence of the two components of the incident plane wave. This same sort of statement is found in many other textbooks. Terman's conductor is in free space. He discusses the voltage difference between one end of the conductor and the other end of the same conductor. He does not address the question at hand, which is the voltage between a perfect ground plane and the bottom of a short conductor near that ground plane. At least two people have explained why that voltage is not one volt for an incident field strength of one volt per meter. 73, Gene W4SZ Richard Harrison wrote: [snip] > Reg`s question of how much voltage is induced in 1 m of wire in a field > of 1 V/m is answered clearly by Terman in publications which date back > at least to 1932, the earliest copyright date I saw on "Radio > Engineering". So, many competent and critical reviewers have pored over > Terman`s works that it`s almost certain that any errors have been found > and corrected long ago. Everybody makes mistakes, but now Terman is as > close to infallible on the subject of radio as any author I know. Read > page 2 of Terman`s "Electronnic and Radio Engineering" (1955 edition) > for complete details. The same information appears in some other Terman > authored and edited writings (almost word for word). > > Best regards, Richard Harrison, KB5WZI > Article: 220242 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Z matching of antennas Date: Tue, 20 Dec 2005 02:00:10 +0000 (UTC) Message-ID: References: "Chuck S." wrote in message news:KIGpf.10022$aU4.4108@trnddc06... With respects to antenna matching, i.e.: 50 to 450 Ohms, which is better to use, an autotransformer or a transformer with an isolated primary and secondary? I'm looking for the pro's and con's of each. ========================================== It all depends on what you want the transformer to do besides perform an impedance matching function. Otherwise there's little to choose between them. The autotransformer will have slightly less loss. More details please. ---- Reg. Article: 220243 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 02:52:28 +0000 (UTC) Message-ID: References: <12711-43A6F12A-56@storefull-3253.bay.webtv.net> <11qeglddhokhvbf@corp.supernews.com> "Roy Lewallen" wrote > Hm. Have my postings gone unread? Or just unbelieved? > ================================== Or, am I trying to find somebody else who believes you ? Terman, Kraus and Balanis and some computer programs are of no help! ;o) ---- Reg. Article: 220244 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 23:16:41 -0600 Message-ID: <26465-43A793B9-961@storefull-3254.bay.webtv.net> References: Gene Fuller wrote: "There is no problem with Terman`s words, but I believe you are missing his intention." I parsed Terman`s words carefully trying to avoid misinterpretation. There is a RCA FM Coverage Calculator (special slide rule) pictured and described on the internet. Text accompanies the rule. This text says the range of the rule is for a radius of urban coverage of 1000 microvolts per meter and a radius of rural coverage of 50 microvolts per meter. They obviously anticipate a much higher urban noise level than found in rural areas. The rule has distance scales of 4 to 100 miles, and 16 to 143 miles.. The text says: "If you hold up 1 meter of wire at exactly the right angle, this is exactly how many millionths of a volt are generated between its ends. If you assume that 50 microvolts per meter in the country gives an acceptable quality signal at the receiver, you`ll be able to calculate how far away you can reach." There is much more text dealing with transmitter powers, broadcast antenna types, and antenna heights. Accuracy is said to be within 10%.. I`ve never seen one of these special slide rules myself, but maybe Walter Maxwell, Richard Fry, or someone else has and can elaborate. I quoted the text because it contained in effect the simple statement that 1 microvolt is generated betweens the ends of a well placed 1 meter long wire when immersed in a 1 microvolt electromagnetic field. I certainly never expected to see that fact debated. Best regards, Richard Harrison, KB5WZI Article: 220245 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Mon, 19 Dec 2005 23:33:58 -0600 Message-ID: <26465-43A797C6-962@storefull-3254.bay.webtv.net> References: Gene, W4SZ wrote: "At least two people have explained why that voltage is not one volt per meter." Here are Terman`s exact words again: "The strength of the wave measured in terms of microvolts per meter of stress in space is also exactly the same voltage that the magnetic flux of the wave induces in a conductor 1 m long when sweeping across this conductor with the velocity of light." I see Gene`s statemennt as a contradiction within itself. Definition of field strength is the volts it will generate in a wire 1 meter long. There is no contradiction in Terman`s statement. Best regards, Richard Harrison, KB5WZI Article: 220246 of rec.radio.amateur.antenna Message-ID: <43A80523.E3A51346@shaw.ca> From: Irv Finkleman Subject: Re: Thanks for antenna help. References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 13:20:17 GMT The Eternal Squire wrote: > > All, > > I'm finally back on the air! Thanks for the antenna help, everyone. I > found on the net a 30m collapsible fiberglass pole. I applied copper > tape to one side as the radiator. I used layers of duct tape to > reinforce every joint. I have the ground side tied to the ground rod > of the trailer electrical system. No counterpoise yet. I worked a few > stations tonight on 40m CW. > > I am grateful for all the help, even to those who thought I wasn't > listening at first. > > The Eternal Squire My experience with duct tape is that it doesn't hold up well due to weathering. I'm not sure if it was the cold, the sun, or what, but it gradually let go and fell apart. I have no recommendations for a substitute but someone on the group might. Irv VE6BP -- -------------------------------------- Diagnosed Type II Diabetes March 5 2001 Beating it with diet and exercise! 297/215/210 (to be revised lower) 58"/43"(!)/44" (already lower too!) -------------------------------------- Visit my HomePage at http://members.shaw.ca/finkirv/index.html Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm -------------------- Irv Finkleman, Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP Calgary, Alberta, Canada Article: 220247 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Identify Old HF Vertical Message-ID: References: <173eq1li33s526o0f2j5s77t82f7sp2vhs@4ax.com> Date: Tue, 20 Dec 2005 13:22:02 GMT On Mon, 19 Dec 2005 20:39:38 -0600, "gb" wrote: > >John - > >This antenna model is almost identical to one that my brother was given in >the 1970s. I see you used a torch (scorch marks)..... the corrosion can be >removed with naval jelly or an electrolysis process (described in >boatanchors newsgroup). > >You should be able to wind a proper coil and have a 1/4 or 1/2 wave vertical >for 15 or 17 meters. You could use schedule 40 electrical conduit (gray >PVC) for new cover of coil. > >w9gb > I used a paint stripper gun to loosen the PVC. After I discovered that It would not be difficult to replace the sleeve I lost interest in trying to save it. On the next trip to town I will get some naval jelly for clean up. The bracket hardware needs it as well. My current plan for this project is to experiment with short 80 and 160 meter verticals. This is pretty early in the project, I have not constructed the radial system yet. The focus will be on matching methods, I feel the EZNEC software answers most of my other questions. This is an academic pursuit! John Ferrell W8CCW Article: 220248 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Identify Old HF Vertical Message-ID: References: Date: Tue, 20 Dec 2005 13:27:43 GMT On Mon, 19 Dec 2005 16:59:58 -0500, LarryLurker wrote: >What you have there is a Super Magnum CB antenna, vintage mid-60's. >The Magnum model had 4 foot radials and no top hat. The Super Magnum >has 9 foot radials with the top hat. By rewinding, or retapping the >coil, you can make a great 10 meter vertical. .... or it may be >simpler to change the length of the vertical section. I did the coil >thing in the mid-80's and used it to work all states and 130 >countries. > >LL > That is a pretty impressive testimony! John Ferrell W8CCW Article: 220249 of rec.radio.amateur.antenna From: "Richard Fry" Subject: Antenna Factor Date: Tue, 20 Dec 2005 07:48:03 -0600 Message-ID: <43a80ad7$1_4@newsfeed.slurp.net> With all the earlier/ongoing posts here about the voltage across a receive antenna immersed in a known field, it may be appropriate to recall the affect that "antenna factor" has on these measured values. Here is a website with background on this: http://www.djmelectronics.com/articles/emc-antenna-parameters-p3.html The measured field strength using commercial VHF/UHF field intensity meters needs to be adjusted based on antenna factor to determine the real value of the incident field, using charts included with the test system documentation. RF Article: 220250 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Thanks for antenna help. Message-ID: References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 13:51:07 GMT On 19 Dec 2005 22:55:39 -0800, "The Eternal Squire" wrote: >All, > >I'm finally back on the air! Thanks for the antenna help, everyone. I >found on the net a 30m collapsible fiberglass pole. I applied copper >tape to one side as the radiator. I used layers of duct tape to >reinforce every joint. I have the ground side tied to the ground rod >of the trailer electrical system. No counterpoise yet. I worked a few >stations tonight on 40m CW. > >I am grateful for all the help, even to those who thought I wasn't >listening at first. > >The Eternal Squire I have to ask: Do you really mean 30 feet rather than 30 meters? John Ferrell W8CCW Article: 220251 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Thanks for antenna help. References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <43A80523.E3A51346@shaw.ca> Message-ID: <36Upf.44214$Zv5.21586@newssvr25.news.prodigy.net> Date: Tue, 20 Dec 2005 13:58:23 GMT Irv Finkleman wrote: > My experience with duct tape is that it doesn't hold up well due > to weathering. I'm not sure if it was the cold, the sun, or what, but > it gradually let go and fell apart. I have no recommendations for > a substitute but someone on the group might. Automotive rated duct tape is of a higher quality than air-conditioning duct tape - also more expensive. A coating of clear Krylon also helps. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220252 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <26465-43A797C6-962@storefull-3254.bay.webtv.net> Message-ID: Date: Tue, 20 Dec 2005 14:16:17 GMT Richard, Not only are you misunderstanding Terman, you have twisted my words as well. I said, "At least two people have explained why that voltage is not one volt for an incident field strength of one volt per meter." You removed some of my words and completely changed the meaning. Once more, Terman is undoubtedly correct with his statement. I agree completely. However, the configuration described by Terman is NOT the subject at hand. 73, Gene W4SZ Richard Harrison wrote: > Gene, W4SZ wrote: > "At least two people have explained why that voltage is not one volt per > meter." > > Here are Terman`s exact words again: > "The strength of the wave measured in terms of microvolts per meter of > stress in space is also exactly the same voltage that the magnetic flux > of the wave induces in a conductor 1 m long when sweeping across this > conductor with the velocity of light." > > I see Gene`s statemennt as a contradiction within itself. Definition of > field strength is the volts it will generate in a wire 1 meter long. > There is no contradiction in Terman`s statement. > > Best regards, Richard Harrison, KB5WZI > Article: 220253 of rec.radio.amateur.antenna From: Andy Cowley Subject: Re: Antenna reception theory Message-ID: References: <26465-43A793B9-961@storefull-3254.bay.webtv.net> Date: Tue, 20 Dec 2005 14:40:14 GMT Richard Harrison wrote: > Gene Fuller wrote: > "There is no problem with Terman`s words, but I believe you are missing > his intention." > > I parsed Terman`s words carefully trying to avoid misinterpretation. > > There is a RCA FM Coverage Calculator (special slide rule) pictured and > described on the internet. Text accompanies the rule. This text says the > range of the rule is for a radius of urban coverage of 1000 microvolts > per meter and a radius of rural coverage of 50 microvolts per meter. > They obviously anticipate a much higher urban noise level than found in > rural areas. > > The rule has distance scales of 4 to 100 miles, and 16 to 143 miles.. > > The text says: "If you hold up 1 meter of wire at exactly the right > angle, this is exactly how many millionths of a volt are generated > between its ends. > And just how are you going to measure that voltage without getting an opposite voltage in your voltmeter leads. Or alternatively how can you present that voltage at the input to a receiver? You can't. So the above tells us zip about the question Reg asked. Roy answered the question correctly and you haven't even attempted it. Why is that? Andy Article: 220254 of rec.radio.amateur.antenna Date: Tue, 20 Dec 2005 08:17:49 -0700 From: sjt Subject: grounding Message-ID: I am installing a short tower. The soil is very dry, mostly volcanic ash and low conductivity. I had the backhoe operator dirll several holes 4 feet deep for grounding. It is impossible to drive a ground rod deeper than 4 feet due to bedrock. What should I use to fill the holes after the ground rods are installed? Article: 220255 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 09:38:02 -0600 Message-ID: <25358-43A8255A-47@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "Terman, Kraus, and Balanis and some computer programs are of no help!" My dictionary defines "field strength" as: "3. The strength of radio waves at a distance from the transmitting antenna, usually expressed in microvolts-per-meter. This is not the same as the strength of a radio signal at the antenna terminals of the receiver." The definition looks OK to me. The reason the signal is not the same as the microvolts-per-meter even when the antenna is a 1-meter length of wire with just the right slant is because the induced voltage gets divided between the antenna and its load (the receiver). Maybe Cecil`s IEEE dictionary has something to say about field strength. Best regards, Richard Harrison, KB5WZI Article: 220256 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Message-ID: <%ZVpf.37084$q%.36663@newssvr12.news.prodigy.com> Date: Tue, 20 Dec 2005 16:06:19 GMT Richard Harrison wrote: > Maybe Cecil`s IEEE dictionary has something to say about field strength. magnitude of the electric field vector in volts per meter, or magnitude of the magnetic field vector in amps (or ampere-turns) per meter, or power flux density P in watts per square meter. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220258 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Device insertion loss References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> Message-ID: Date: Tue, 20 Dec 2005 18:28:31 GMT Ron J wrote: > I was curious. If a matching network was designed to make the SWR at a > band of frequency less than 1.4 to 1, then what would happen if I > inserted a power sensor on the line with a rated SWR of 1.05 to 1 at > this frequency band? > > Would that make my overall system SWR 1.4 + .05 = 1.45 to 1? SWRs, like power, cannot be superposed. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220259 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> Subject: Re: Device insertion loss Message-ID: Date: Tue, 20 Dec 2005 18:32:38 GMT "Ron J" wrote in message news:1135102701.893263.244550@o13g2000cwo.googlegroups.com... > Hello, > > I was curious. If a matching network was designed to make the SWR at a > band of frequency less than 1.4 to 1, then what would happen if I > inserted a power sensor on the line with a rated SWR of 1.05 to 1 at > this frequency band? > > Would that make my overall system SWR 1.4 + .05 = 1.45 to 1? > No, SWR does not do a simple addition. If it is a power sensor that uses a short piece of transmission line then you have to know the frequency , the length in wavelengths, the inpedance of the line, and then do some calculations. It could be slightly beter or worse than it was to start with. Probably not enough to show on a simple swr meter. Article: 220260 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Device insertion loss References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> <1135104134.083886.169140@g14g2000cwa.googlegroups.com> Message-ID: <7lYpf.44262$Zv5.18745@newssvr25.news.prodigy.net> Date: Tue, 20 Dec 2005 18:47:31 GMT Ron J wrote: > My main concern is that at the band of design > frequency the transmitter is only designed to handle 1.5 SWR max. I'm > afraid that I might break it since our matching network already changes > the SWR to a peak 1.40 to 1 at certain frequencies on the band. > > I may have other idea. If I add the return loss of the devices, would > that allow me to somehow find the SWR? Measure the impedance of the system (using low power). That's the only way to know for sure. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220261 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Device insertion loss Date: Tue, 20 Dec 2005 20:38:33 +0000 (UTC) Message-ID: References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> I note the subject matter of this thread is "Insertion Loss" Insertion loss is the ratio of power delivered to a load, to the power delivered to the same load when a network is inserted between the load and the same generator. With insertion of a passive network, such as a tuner, the insertion loss can even be a gain. Calculation or measurement of insertion loss ALWAYS involves or implies knowledge of the generator impedance. In the present context the generator is the transmitter. As nobody knows the internal impedance of the transmitter this thread will rapidly degenerate into nonsensical argument if it hasn't already done so. You have been warned! ---- Reg, G4FGQ Article: 220262 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Device insertion loss Message-ID: References: <1135102701.893263.244550@o13g2000cwo.googlegroups.com> <1135104134.083886.169140@g14g2000cwa.googlegroups.com> Date: Tue, 20 Dec 2005 21:00:03 GMT On 20 Dec 2005 10:42:14 -0800, "Ron J" wrote: >Hi Cecil, > >Thanks! I try to explain the affect of the power sensor even if it is >ideally very minimal. My main concern is that at the band of design >frequency the transmitter is only designed to handle 1.5 SWR max. I'm >afraid that I might break it since our matching network already changes >the SWR to a peak 1.40 to 1 at certain frequencies on the band. > >I may have other idea. If I add the return loss of the devices, would >that allow me to somehow find the SWR? As others have told you, no, the system isn't analysed as simply as you suggest. Some thoughts: - your concern that your transmitter will suddenly degrade at VSWR=1.5 is probably unfounded; - if your power sensor is intended for inline monitoring, it should be designed to "monitor" with insignificant impact on the load presented to the transmitter. You didn't tell us enough to give you a definitive answer, but it is likely that you are unnecessarily worried about the sensitivity of the transmitter to VSWR, and the cumulative effect of the monitoring sensor which should be insignificantly small in the real world with suitable / practical components. Owen -- Article: 220263 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 21:22:56 +0000 (UTC) Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <43a18d37.137420350@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> What is the proportion of Black amateur radio licencees to Whites? How does it correspond to the same proportion in the population as a whole? =========================================== Article: 220264 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 15:33:50 -0600 Message-ID: <27842-43A878BE-1151@storefull-3251.bay.webtv.net> References: Andy wrote: "So the above told us zip about the question Reg asked. Roy answered the question correctly and you haven`t even attempted it." I assumed the definition of "field strength" correctly answered Reg`s question and his descrepancy lay elswhere. Field strength of an electromagnetic wave is expressed in microvolts per meter. It is defined as the number of microvolts which would be induced in a properly placed piece of wire one meter long. If a field strength of one microvolt per meter does not induce one microvolt into a piece of wire one meter long, why not? I`ve been looking for an explanation and found a possible answer in Figure 2-9-1 on page 31 of Kraus` 3rd edition of "Antennas". The possible explanation is called the "effective height" in meters of an antenna. It is a "factor", which when multiplied by the microvolts per meter of the field strength, gives the volts induced in the antenna at its terminals. According to Kraus` figure, h is a function of current distribution in the antenna. The text says that for a dipole 0.1 lambda long, h = 0.5X the length of the antenna. Reg did not specify a frequency or wavelength for his antenna, as I recall, and he did specify a ground mounted vertical whip 1 m long for his receiving antenna. For a dipole 0.5 lambda long, Kraus gives (h) as 0.64X the length of the antenna. For all I know, there is a vertical antenna length in terms of wavelength for which h=1. If so, the volts between the antenna base and the ground directly under it would numerically exactly equal the microvolts per meter of the field strength. All we need to do is pick the right frequency. The applicable Formula is (1) on page 30. I suspect that in most cases, h is determined experimentally. I regret I`ve not had a copy of Kraus nearly as long as I`ve had a copy of Terman. I`m still using an edition I`ve had for 58 years. It shows lots of wear and tear. Best regards, Richard Harrison, KB5WZI Article: 220265 of rec.radio.amateur.antenna From: "The Magnum" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 22:06:20 -0000 Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> "Amos Keag" wrote in message news:DNGdncHNgZZj5zXeRVn-hg@comcast.com... > Reg Edwards wrote: > > What is the proportion of Black amateur radio licencees to Whites? > > > > How does it correspond to the same proportion in the population as a > > whole? > > =========================================== > > > > > > I don't believe that information is required on an application. > Therefore it should be un-obtainable. That percentage must be rising now thanks to the M3/CB'ers licence as so many Hams class it. Before I would say it was very low as it doesn't involve shooting people, stealing mugging or raping. Now it takes no effort there will be plenty of them using the radios to co-ordinate robberies and gangland shootings... yeeee haaaaah good buddy....... So what's wrong with being racist? Why let your neighbourhood turn into a shithole.......... Article: 220266 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 22:06:56 +0000 (UTC) Message-ID: References: <26465-43A793B9-961@storefull-3254.bay.webtv.net> <52hgq1trg07spm2fpm3g515f6nllimpjg1@4ax.com> "Richard Clark" wrote > You make a loop. ====================================== I normally reply, if I reply at all to your idiotic statements, with "Phooey". But on this occasion, to protect innocent, bystanding, novices from your deliberate, inexcusible, misleading statement, it should be said that the voltage induced in a circular loop is altogether different and very much smaller from that induced in a straight wire of the same length. You disgust me! A disgrace to amateur radio! Have a miserable Christmas! ---- Reg, G4FGQ. Article: 220267 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 23:19:48 +0000 (UTC) Message-ID: References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> "Amos Keag" wrote - > Reg Edwards wrote: > > What is the proportion of Black amateur radio licencees to Whites? > > > > How does it correspond to the same proportion in the population as a > > whole? > > =========================================== > I don't believe that information is required on an application. > Therefore it should be un-obtainable. > =========================================== Indeed it is. But you can always have a guess and think about what it means. --- Reg. Article: 220268 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 17:11:21 -0600 Message-ID: <25358-43A88F99-94@storefull-3257.bay.webtv.net> References: Reg, G4FGQ wrote: "Have a miserable Christmas!" In the cinema, "The Grinch Who Stole Christmas", the Grinch turned into a kind, green, Santa Claus. Let`s hope Reg has a change of heart too! Merry Christmas, Richard Harrison, KB5WZI Article: 220269 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 17:27:28 -0600 Message-ID: <25358-43A89360-96@storefull-3257.bay.webtv.net> References: Richard Clark wrote: "You make a loop." There is a difference. The small whip has a high capacitive reactance. The small loop has a high inductive reacvtance. Both have low radiation resistance. But, the loop is more often used to determine EM field strength. You just need the right "fudge factor" to convert antenna voltage tto field strength or vice versa. Best regards, Richard Harrison, KB5WZI Article: 220271 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 00:30:31 +0000 (UTC) Message-ID: References: <25358-43A89360-96@storefull-3257.bay.webtv.net> "Richard Harrison" wrote in message news:25358-43A89360-96@storefull-3257.bay.webtv.net... > Richard Clark wrote: > "You make a loop." > > There is a difference. The small whip has a high capacitive reactance. > The small loop has a high inductive reacvtance. Both have low radiation > resistance. But, the loop is more often used to determine EM field > strength. You just need the right "fudge factor" to convert antenna > voltage tto field strength or vice versa. > > Best regards, Richard Harrison, KB5WZI ===================================== For the very last time I will repeat my question :- "What is the voltage measured between the bottom end of a 1 metre vertical antenna and ground when the field strength is 1 volt per metre. The height (length) of the antenna is much less than 1/4-wavelength. The bottom end of the antenna is immediately above the ground. The ground is assumed perfect. The field is vertically polarised. Frequency, loops, reactance, radiation resistance do not enter into the argument. No other information is needed. Terman, Kraus and Balanis' bibles provide answers to a different question in which I am not interested. Mere mention of these learned gentlemen only confuses the issue. The answer is entirely fundamental to e.m. radiation and reception. All I need is a number of volts. What is it please? ---- Reg, G4FGQ. Article: 220272 of rec.radio.amateur.antenna From: "Richard Fry" References: <25358-43A89360-96@storefull-3257.bay.webtv.net> Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 19:10:49 -0600 Message-ID: <43a8aade_2@newsfeed.slurp.net> "Reg Edwards" wrote > For the very last time I will repeat my question :- Pray it so... > "What is the voltage measured between the bottom end of a 1 metre > vertical antenna and ground when the field strength is 1 volt per > metre." Of what relevance is this to anyone but (apparently) you? Please elaborate. RF Article: 220273 of rec.radio.amateur.antenna From: "Dave Pitzer" Subject: Geo coordinates -- didtance Date: Tue, 20 Dec 2005 20:31:56 -0500 Message-ID: <43a8b08c$0$58074$742ec2ed@news.sonic.net> I'm looking for a way to enter two pairs of geographic coordinates (point X and point Y) and have the over-ground distance between them returned. Any help? Dave P Article: 220274 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Geo coordinates -- didtance References: <43a8b08c$0$58074$742ec2ed@news.sonic.net> Message-ID: Date: Wed, 21 Dec 2005 01:46:11 GMT Dave Pitzer wrote: > I'm looking for a way to enter two pairs of geographic coordinates (point X > and point Y) and have the over-ground distance between them returned. > > Any help? > > Dave P The standard formula for the great circle distance is: d=arccos[sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(long1-long2)] There is no magic here; this is simply spherical geometry and trigonometry at work. Of course if you don't care about the great circle distance, the answer can be anything you wish. 73, Gene W4SZ Article: 220275 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 18:12:02 -0800 Message-ID: <11qhefipinecp86@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Richard Harrison wrote: > Reg, G4FGQ wrote: > "Terman, Kraus, and Balanis and some computer programs are of no help!" > > My dictionary defines "field strength" as: > "3. The strength of radio waves at a distance from the transmitting > antenna, usually expressed in microvolts-per-meter. This is not the same > as the strength of a radio signal at the antenna terminals of the > receiver." > > The definition looks OK to me. The reason the signal is not the same as > the microvolts-per-meter even when the antenna is a 1-meter length of > wire with just the right slant is because the induced voltage gets > divided between the antenna and its load (the receiver). > No, that's not why. The terminal voltage of an open circuited 1 meter (electrically short) dipole is 1/2 the field strength in volts/meter. The terminal voltage when terminated with a conjugately matched load can be well over a thousand volts (in the theoretical lossless case). But it's pointless to keep repeating this. Reg keeps asking the same question, and you keep responding with the same incorrect answers. I believe I've gotten through to everyone who really wants to know the answers, so I'll let this be my last repetition. Roy Lewallen, W7EL Article: 220276 of rec.radio.amateur.antenna From: "Joel Kolstad" Subject: Re: One experience with noise Date: Tue, 20 Dec 2005 18:12:55 -0800 Message-ID: <11qhejvjtj1ak38@corp.supernews.com> References: <1134637337.c857a55f3cab0d38109173525afb1f55@roc.usenetexchange.com> "Wes Stewart" wrote in message news:m4keq1tmlrevv8fm3gih3266obcdh725ba@4ax.com... > On Thu, 15 Dec 2005 09:02:17 +0000, Paul Johnson > wrote: > And after a natural disaster cable TV systems will be working about as > well as cell phones have. Only as long as the emergency broadcast system is kept alive. There's no particular reason the funding for it couldn't be shut off/expanded to include cable/switch only to cable/whatever. In fact, one could argue that during a natural disaster cable TV could actually be more reliable in that its infrastructure is somewhat more protected than a huge antenna ever could be. (I seem to recall from Hurricane Katrina that some of the first phone calls getting out -- barring folks with satellite phones -- were VOIP calls over wired Internet connections.) >>4:3 aspect was a technical limitation that really should have died long >>before my birth, much less now. Good riddance. > > What "technical limitation"? Aspect ratios are arbitrary. Not true. In the 'early days' of TV, the glass for CRTs couldn't be blown into such arbitrary aspect ratios; hence 4:3 was chosen as a reasonably compromise between producibility and "well, at least it's not square...!" :-) Presumably 16:9 is a closer match to human vision than 4:3, and for viewing a movie it would seem to make sense to try to match that since you're trying to encompass the viewer. ---Joel Article: 220277 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: One experience with noise Message-ID: References: Date: Wed, 21 Dec 2005 02:34:12 GMT On Sat, 10 Dec 2005 08:06:58 -0700, Wes Stewart wrote: >On Tue, 06 Dec 2005 23:28:15 GMT, Owen Duffy wrote: > >> >>Don't you have digital television? Best thing since sliced bread. >> >>I don't know if you can receive analog television beyond the digital >>coverage ranges, but you probably wouldn't want to watch it. >> >>Digital TV makes weak signals most watchable, DVD quality at weak >>signals. >> >>I use it and I am only 4km from the transmitter, but that is another >>situation where it works a treat, ghost free pictures close to the >>tranmitter in the presence of local reflections (hills, water towers >>etc). > >I suppose you have the Coded Orthogonal Frequency Division >Multiplexing (COFDM) standard there. Yes. I saw STBs in the supermarket this morning for A$69 or about US$55. Owen -- Article: 220278 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 02:41:28 +0000 (UTC) Message-ID: References: <25358-43A89360-96@storefull-3257.bay.webtv.net> <43a8aade_2@newsfeed.slurp.net> "Richard Fry" wrote in message news:43a8aade_2@newsfeed.slurp.net... > "Reg Edwards" wrote > > For the very last time I will repeat my question :- > > Pray it so... > > > "What is the voltage measured between the bottom end of a 1 metre > > vertical antenna and ground when the field strength is 1 volt per > > metre." > > Of what relevance is this to anyone but (apparently) you? Please elaborate. > > RF ========================================= For starters, Have you never heard of field strength measurements? Have you ever designed the input stage of a radio receiver? The topic is fundamental to an understanding of e.m. radiation and reception. Can YOU answer the simple question? Or are you entirely dependent on your gospel faith in 'Bibles'. On this occasion at least, the Bibles are letting dependent people down. The immediate relevance to me is that I have a program which has been reported to have a calculating error. It was reported by a person who is not dependent on bibles. He stated that the conventional/traditional calculating method used in my program was incorrect. I was not entirely convinced so I posed a related question on this newsgroup to which only one person has replied with a number. And he was wrong first time. Other persons who replied, after consulting their bibles, were unable even to answer the question, either rightly or wrongly. They just generated more confusion. The program concerned is GRNDWAV4 which I think, but not absolutely certain, has now been corrected. Why not download it, input a very few standard values, and tell me whether or not it provides the correct answer to receiver power input? You may, of course, prefer not to commit yourself. Is that enough elaboration for you? ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220279 of rec.radio.amateur.antenna From: "west" References: <1135099145.094973.160920@f14g2000cwb.googlegroups.com> Subject: Re: grounding Message-ID: Date: Wed, 21 Dec 2005 02:59:28 GMT wrote in message news:1135099145.094973.160920@f14g2000cwb.googlegroups.com... > You are lucky to have 4 feet. I have 8 inches or less around my house. > Zero behind the garage. > > Is this going to be an antenna or just a tower for an antenna? Is the > area irrigated/watered for grass? If an antenna, you will need to > install a bunch of radials on or just under the ground surface. If you > are trying to ground the tower for lightening protection, I guess I > would mix a bunch of granular commercial fertilizer in with the soil as > I packed it around the ground rods. Then lots of water on the area. > > Did you also have holes placed for guy wire anchors? > > Paul, KD7HB I believe the aim is to get more conductivity from the soil. That being the case, I would pour rock salt in the holes. west > Article: 220280 of rec.radio.amateur.antenna From: "DrDeath" Subject: Re: more stevei lies Date: Tue, 20 Dec 2005 21:10:21 -0600 Message-ID: <11qhhsrql5700ef@corp.supernews.com> References: <439dccd3.22632213@news.blueyonder.co.uk> <11q4003qm1ndb7f@corp.supernews.com> <11q97mfbt474cda@corp.supernews.com> <11qbi9ao07pnuf7@corp.supernews.com> <1135060280.562026.114430@g49g2000cwa.googlegroups.com> <1135079937.604256.291980@g49g2000cwa.googlegroups.com> <1135104221.580690.175130@g44g2000cwa.googlegroups.com> <1135104427.270844.31240@o13g2000cwo.googlegroups.com> <1135104638.521121.181110@g49g2000cwa.googlegroups.com> <1135104876.950374.195170@g49g2000cwa.googlegroups.com> <1135105162.280236.230030@g14g2000cwa.googlegroups.com> <1135107988.588191.76590@g44g2000cwa.googlegroups.com> <1135111967.356035.112600@z14g2000cwz.googlegroups.com> wrote in message news:do9v67$el4$1@news7.svr.pol.co.uk... > "Amos Keag" wrote in message > news:DNGdncHNgZZj5zXeRVn-hg@comcast.com... >> Reg Edwards wrote: >> > What is the proportion of Black amateur radio licencees to Whites? >> > >> > How does it correspond to the same proportion in the population as a >> > whole? >> > =========================================== >> > >> > >> >> I don't believe that information is required on an application. >> Therefore it should be un-obtainable. > > That percentage must be rising now thanks to the M3/CB'ers licence as so > many Hams class it. Before I would say it was very low as it doesn't > involve > shooting people, stealing mugging or raping. Now it takes no effort there > will be plenty of them using the radios to co-ordinate robberies and > gangland shootings... yeeee haaaaah good buddy....... > > So what's wrong with being racist? Why let your neighbourhood turn into a > shithole.......... > > > > Drug dealers already use FRS and scanners for surveillance. Article: 220281 of rec.radio.amateur.antenna From: "west" Subject: 2 or more Ants. needed Message-ID: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> Date: Wed, 21 Dec 2005 03:08:45 GMT I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from Ham Radio for more than 20 years & would like opinions on what would be the absolute best omni-directional antenna(s) to buy, for this rig? All opinions welcomed. Thank you. west AF4GC Article: 220282 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 22:08:44 -0600 Message-ID: <3647-43A8D54C-984@storefull-3258.bay.webtv.net> References: Reg, G4FGQ wrote: "All I need is a number of volts." I`ll guess, because Reg asked, not because I know aanything. I`ve now discovered Kraus` effective antenna height which may be related to an Icelandic connection. Reg hasn`t told us everything he knows. One reason we don`t know is because the effective antenna height is related to the antenna`s length in terms of wavelength according to Kraus. One of the examples given by Kraus is a dipole of 1/10 of a wavelength. Kraus tells us the effective height of this length gives a factor of 0.5. According to Equation (1) on page 30 of the 3rd edition of "Antennas", Voltage at the terminals of the antenna = effective height X field strength. If we guess that a short whip might have the same effective height as a short dipole, then with a 1 volt per meter field strength X 0.5 as an effective height factor, their product would be 0.5 volts. I`ll assume rms because that`s the convention for expression. I don`t have much confidence in the number because I think you must determine the effective height experimentally. Terman says on page 991 of his 1943 "Radio Enginneers` Handbook: "If an antenna other than a loop is used, the effective height must be determined experimentally. Maybe someone has worked this out since 1943. Best regards, Richard Harrison, KB5WZI Article: 220283 of rec.radio.amateur.antenna Message-ID: <43A8E22D.6070208@bogus.net> Date: Tue, 20 Dec 2005 22:03:41 -0700 From: hayseed Subject: Re: grounding References: I saw a group of reps from MITRE solve a radar grounding issue by tying the ground line to a 4'X8' copper plate and burying the plate in a 6' deep pit filled with copper sulfate crystals. Threw in water, waited and, viola, decent ground in granite rock mountain top. -Bob Article: 220284 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 21 Dec 2005 06:31:44 GMT K7ITM wrote: > There are several possible reasons for being interested in standing > waves (on transmission lines). Some are valid, some are not, and > you'll even get plenty of, um, discussion about what's valid and what > isn't. > > If your goal is to get maximum power delivered to a load, then it's > good to minimize standing waves on the line delivering power to that > load, because a line delivering a particular amount of power to a load > will have greater power lost in the line with greater standing waves. > If the line is being used near its maximum power or voltage rating, > standing waves are a concern because for a given power delivered to the > load, the rms current at current nodes and the peak voltage at voltage > nodes both increase with increased standing waves. And a high standing > wave ratio on a line which is long compared with a wavelength suggests > that the input impedance to the line will vary rapidly with frequency, > whereas a line with low standing wave ratio will present a relatively > constant impedance to the driving source, assuming the load is > reasonably "flat" with frequency. > > As an example of this last point, a 30 meter (~100 foot) 50 ohm line > with 0.8 velocity factor and very low loss, delivering power to a 50 > ohm load at 450MHz, will present a 50 ohm load to the driving source. > But delivering power to a 200 ohm load, the source will "see" almost > 200 ohms at frequencies where the line is an integer number of > electrical half-waves long, and it will "see" just over 12.5 ohms > midway between those frequencies. You get 200 ohms at 440MHz, 12.5 > ohms at 442MHz--and reactive in between. > > It's possible to use stubs and series line sections to effect an > impedance match between a load and a line. For example, the right > length and impedance series section will give you a match at one > particular frequency, at least, and multiple sections can give you a > "perfect" match at multiple frequencies, with (perhaps) quite > acceptable match over a range of frequencies. > > There are lists of analogs among electrical, mechanical, acoustic, and > other media. "electrical hydraulic impedance analog" in a Google > search will give you many hits. > > Cheers, > Tom > Thanks for your reply. I have a few questions. When you say "standing waves", I take it that one can have more than one on the line? I follow your example, but I may come back to it once I've done the calcs. How does one know they want to improve their impedance match? Why doesn't there seem to be a need for this (probably through a balun) on a standard AM radio with a 1/2 wave line antenna or even some ferrite coil? Is there some auto-balun that works this all out? Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet "He who laughs, lasts." -- Mary Pettibone Poole -- Web Page: Article: 220285 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: VHF/UHF Antenna Date: Wed, 21 Dec 2005 06:42:59 -0000 Message-ID: <11qhubj9sg5tm24@corp.supernews.com> References: <1135142322.762859.121600@g44g2000cwa.googlegroups.com> >I'm not sure if this is the correct newsgroup for this type of question >- sorry if I've posted in the wrong newsgroup. I want to ditch my cable >and go with an antenna. I'm trying to figure out what would be the best >type for my location. > >All the channels thatI want to pick up are less than or equal to 25 >miles from my home, except for one. The one that is the greatest >distance away, FOX, is 30 miles away from my home. > >All of the channels that are less than or equal to 25 miles are between >12 o'clock and 1 o'clock. They consist of a mixture of VHF and UHF >channels. FOX (30 miles away) is at my 2 o'clock and is a UHF channel. > >Antennaweb.org says I need a large directional with pre-amp antenna in >order to pick up FOX, but I can't get something that big to put on the >side of my house. My wife will scream bloody murder if I did that. I >have no obstructions of the sky in the directions that the antenna will >have to point. > >What type of antenna would be best for my circumstance? I would prefer >something that is small and not very noticeable (maybe something that >could pass for a DirecTV dish). Also, I would prefer to have it point >in a fixed direction so that I do not have to turn it in order to view >different channels. I'm planning on getting a HDTV in the near future. >Do I need a special type of antenna in order to view a TV program in HD >or will any antenna work? I'd say that AntennaWeb is giving you pretty decent advice. It's perhaps a bit conservative but not excessively so. I'm operating under similar circumstances - I'm near the south of the San Francisco peninsula about 35-40 miles away from the transmitters in San Francisco. We get a good, clean picture using a "medium fringe" UHF/VHF antenna (log-periodic plus corner reflector), mounted on a 18' mast on the roof (antenna height above ground is somewhere around 30'). We do have an amplifier for our indoor signal distribution, but could probably get away without one if we were only driving one or two TVs/tuners. We don't need to use the rotator, since all but one of the stations are north of us. The one exception is a San Jose station, which is right "off the back" of the main antenna. We *would* need to use the rotator, but I built a separate single-channel Yagi antenna and pointed it at San Jose and used a combiner. Most people around here who have roof antennas, have ones which are in roughly the same ballpark as ours... some higher, some not quite so high. The height helps a lot - an antenna down at roof level is going to "see" its horizon only about half as far away as an antenna with an extra 15' of height, and that's enough to make the difference between a clean ghost-free signal and one that's pretty noisy or ghosty. Most TV antennas have a relatively broad forward beamwidth. Your "noon to 2 o'clock" antenna pattern is about 60 degrees, which is probably going to be workable for a standard medium-fringe log-periodic antenna design if you've got the antenna up high enough. If you don't have enough height, then you're going to have a substantially weaker signal hitting the antenna, which would mean you'd need more antenna gain, which means a longer and more obvious antenna and a narrower beam-width, which might require a rotator. A small, roof-mounted, non-obvious antenna which might pass itself off as a satellite dish is likely to be nearly omnidirectional, having little or no gain, and in your situation it won't "get a good look" at the transmitters (they may be over the horizon), and you won't get a good signal. The requirements for digital TV (hi-def or standard-def) are not all that different from the requirements for NTSC analog. If you have a non-snowy, non-ghosty analog TV picture, you'll likely get a good digital-TV signal from any digital TV transmitter operating at full power. However, since most DTV transmitters today seem to be running at reduced power to avoid interference with nearby analog-TV frequencies, you can't necessarily count on getting a good digital signal lock. If your analog TV signal is noisy or ghosty, receiving digital TV properly is likely to be a problem. Unfortunately, there's no real substitute for a good antenna, up on a mast, clear of trees and buildings and other obstructions, pointed in the correct direction. Any compromise you make from that, will probably compromise the signal to some extent. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 220286 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Date: Wed, 21 Dec 2005 07:01:17 GMT "Richard Harrison" bravely wrote to "All" (20 Dec 05 09:38:02) --- on the heady topic of "Re: Antenna reception theory" RH> From: richardharrison@webtv.net (Richard Harrison) RH> Xref: core-easynews rec.radio.amateur.antenna:221565 RH> Reg, G4FGQ wrote: RH> "Terman, Kraus, and Balanis and some computer programs are of no RH> help!" RH> My dictionary defines "field strength" as: RH> "3. The strength of radio waves at a distance from the transmitting RH> antenna, usually expressed in microvolts-per-meter. This is not the RH> same as the strength of a radio signal at the antenna terminals of the RH> receiver." RH> The definition looks OK to me. The reason the signal is not the same RH> as the microvolts-per-meter even when the antenna is a 1-meter length RH> of wire with just the right slant is because the induced voltage gets RH> divided between the antenna and its load (the receiver). Not only that, but also this: the antenna rebroadcasts half of the intercepted energy. A*s*i*m*o*v Article: 220287 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 20 Dec 2005 23:18:36 -0800 Message-ID: <11qi0ecphael065@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> Asimov wrote: > . . . > RH> The definition looks OK to me. The reason the signal is not the same > RH> as the microvolts-per-meter even when the antenna is a 1-meter length > RH> of wire with just the right slant is because the induced voltage gets > RH> divided between the antenna and its load (the receiver). > > > Not only that, but also this: the antenna rebroadcasts half of the > intercepted energy. But voltage isn't energy. Or power. Roy Lewallen, W7EL Article: 220288 of rec.radio.amateur.antenna From: "Dave Pitzer" References: <43a8b08c$0$58074$742ec2ed@news.sonic.net> Subject: Re: Geo coordinates -- didtance Date: Wed, 21 Dec 2005 08:23:16 -0500 Message-ID: <43a95747$0$58051$742ec2ed@news.sonic.net> Gene: Thanks. And for those who wish to enter the coordinates of two points and have the distance returned (my original request), this is a Web site that does the caluculation for you: http://www.indo.com/distance/ Dave P. "Gene Fuller" wrote in message news:Dt2qf.175939$qk4.31863@bgtnsc05-news.ops.worldnet.att.net... > Dave Pitzer wrote: > > I'm looking for a way to enter two pairs of geographic coordinates (point X > > and point Y) and have the over-ground distance between them returned. > > > > Any help? > > > > Dave P > > The standard formula for the great circle distance is: > > d=arccos[sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(long1-long2)] > > There is no magic here; this is simply spherical geometry and > trigonometry at work. > > Of course if you don't care about the great circle distance, the answer > can be anything you wish. > > 73, > Gene > W4SZ Article: 220289 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 07:22:58 -0600 Message-ID: <27216-43A95732-40@storefull-3253.bay.webtv.net> References: <4l1iq1h3c85qklsplq3i8d3mndk6r3f7m6@4ax.com> Richard Clark, KB7QHC wrote: "In land stations the actual effective height is from 50 to 90% of the measured height." If the effective height is 50%, volts at the antenna terminals are no more than 50% numericcally of the volts per meter in the field strength when all else is optimum. This could account for Reg`s 2 to 1 discrepancy. I wonder what the speculations of Reg and his Icelandic correspondent are? Do they have a formula to predict effective height? Does Roy have such a formula? It`s a factor which won`t go away, even when ignored.. Best regards, Richard Harrison, KB5WZI Article: 220290 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: Date: Wed, 21 Dec 2005 15:17:50 GMT W. Watson wrote: > Thanks for your reply. I have a few questions. When you say "standing > waves", I take it that one can have more than one on the line? Standing waves are created by two coherent traveling waves moving in opposite directions in a transmission line. In a conventional system of source, transmission line, and load, one of the traveling waves moves from the source toward the load and is called the forward wave. The other traveling wave moves from the load toward the source as a reverse or reflected wave. The reflected wave is usually the result of a load being mismatched to a transmission line. If no mismatch exists, no standing waves are created and the system is considered to be "flat", i.e. one forward traveling wave. > How does one know they want to improve their impedance match? For a transmitted signal, we establish a Z0-match to our transmitter often at the input of an antenna tuner. When reflected energy is eliminated on the coax between the tuner and transmitter, we know we have a Z0-match by the SWR meter reading of 1:1. We also use our antenna tuners to tune for maximum received signal on our S-meters. At the Z0-match point, maximum available energy is transferred. If you know the input impedance to a receiver, you can match your antenna system to it to achieve maximum available energy transfer >from the antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220291 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> Message-ID: Date: Wed, 21 Dec 2005 15:19:51 GMT Roy Lewallen wrote: > But voltage isn't energy. Or power. True, but voltage cannot exist without energy. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220292 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> Message-ID: Date: Wed, 21 Dec 2005 15:47:38 GMT dansawyeror wrote: > Be carefully, that is not exactly true. Voltage cannot be created > without energy, it is a force. Dan, Stop now, before you further embarrass yourself. 73, Gene W4SZ Article: 220293 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: 2 or more Ants. needed Date: Wed, 21 Dec 2005 11:03:13 -0500 Message-ID: References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> west wrote: > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from Ham > Radio for more than 20 years & would like opinions on what would be the > absolute best omni-directional antenna(s) to buy, for this rig? All opinions > welcomed. Thank you. Ain't no such beast! Anyhow, if you are looking for omni-directional, I guess you are looking at a vertical antenna. Of course it is hard to call most verticals "absolute best". If I had to have only one antenna, it would be a dipole What are you planning on doing, how much land do you have, and are you under any restrictions? And are you going to buy or make? - 73 de Mike KB3EIA - Article: 220294 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> Message-ID: Date: Wed, 21 Dec 2005 16:26:46 GMT dansawyeror wrote: > Be careful, that is not exactly true. Voltage cannot be created > without energy, it is a force. However once it is 'in place' it requires > no energy to sustain. A voltage cannot be sustained without energy. The joule of energy used to create a voltage on a capacitor is stored in the capacitor until something changes. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220295 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: More BPL rollout. sigh... Date: 21 Dec 2005 18:22:46 GMT Message-ID: http://biz.yahoo.com/bizj/051221/1205323.html?.v=4 Under the deal, Current will design, build and operate the "smart grid," which will cover the majority of the TXU Electric Delivery service area -- about 2 million homes and businesses in Dallas-Fort Worth and other communities in Texas. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 220296 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Sloper Questions Date: Wed, 21 Dec 2005 18:47:19 +0000 (UTC) Message-ID: References: For practical receiving purposes, a sloping wire, in the midst of buildings, can be considered to be omi-directional, even isotropic. Any variations in directivity, in either the vertical or horizontal planes, although they exist, are not measurable or noticeable. The random effect of the presence of a nearby building or buildings is greater than the direction in which the wire may or may not slope. Sensitivity is frequency dependent. It falls of rapidly when the length of the antenna is less than 1/6th wavelength at the lowest frequency of interest. Of at least as great importance is the grounding system. With ordinary garden soil you will need at least 5 or 6 shallow buried wires under the antenna, radiating from a common point in random directions. Ground wire length need be no longer than 1/12th wavelengths at the lowest frequency of interest. Lengths and numbers are very non-critical. A sloping wire or inverted-L is the best general-purpose antenna you can get. Just erect something, not forgetting the ground. ---- Reg, G4FGQ. Article: 220297 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL rollout. sigh... Date: Wed, 21 Dec 2005 18:41:04 +0000 (UTC) Message-ID: References: Allodoxaphobia wrote: > Under the deal, Current will design, build and operate the "smart grid," > which will cover the majority of the TXU Electric Delivery service area > -- about 2 million homes and businesses in Dallas-Fort Worth and other > communities in Texas. All because you refused to boycott Google............ Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 You should have boycotted Google while you could, now Google supported BPL is in action. Time is running out on worldwide radio communication. Article: 220298 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: References: Date: Wed, 21 Dec 2005 20:18:05 GMT On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" wrote: I'm trying to make >some sense out of why the emphasis of standing waves. Here is the short version: A matched transmission line behaves like the theory books say it does. The rated power from the transmitter goes through the transmission line with the lowest possible loss to the antenna where it is radiated just like the book says. A mismatched transmission just MIGHT work OK. If there is any possibility of generating interference, especially TVI, it will. The currents and voltages on a mismatched line are extreme... There MIGHT even be some sparks. Power loss will be at its worst for a given line. RF finds its way every where. Getting zapped once in a while eventually grows old to everyone. I remember the good old days when desk mikes were the only way to go. If you got too close, you got an RF zap on your lip. Solid state rigs don't tolerate a high SWR. They either protect themselves by reducing power or they require a lot of maintenance. You can learn to tolerate high SWR's, but I find it worthwhile to try to keep things matched. The energy has to go somewhere, I prefer it leave here through the antenna... John Ferrell W8CCW Article: 220299 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> References: Date: Wed, 21 Dec 2005 21:29:37 GMT On Wed, 21 Dec 2005 20:18:05 GMT, John Ferrell wrote: >On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" > wrote: > > I'm trying to make >>some sense out of why the emphasis of standing waves. > >Here is the short version: >A matched transmission line behaves like the theory books say it does. >The rated power from the transmitter goes through the transmission >line with the lowest possible loss to the antenna where it is radiated >just like the book says. It is true that reducing SWR for a given line does reduce the loss if the line is long enough. (There are some scenarios where a short line with high VSWR has less loss than matched line of the same length.) But is matched line the real goal? If low loss is the goal, there are often cost effective lower loss solutions possible with lower loss line operated at high VSWR. >A mismatched transmission just MIGHT work OK. If there is any >possibility of generating interference, especially TVI, it will. The Why? How is TVI "generated" by line mismatch? Owen -- Article: 220300 of rec.radio.amateur.antenna From: "Michael" Subject: Re: 2 or more Ants. needed Date: Thu, 22 Dec 2005 11:33:12 -0800 Message-ID: <11qjiil4if6ul5c@corp.supernews.com> References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> If you have the room, a loop antenna is a very good bet. I have used dipoles and verticals for many years. A neighbor moved in a few doors down and put up a loop antenna. I went over and listened to the "quiet" It is a great antenna if you are really irritated by QRN. He has only used this type of antenna for 20 years since he tried it. I understand why. I have not yet put up one, but will. It is winter here in North Dakota and not a good time for antenna work. Evrery other type of antenna works, but I just love the S/N ratio on a loop. Michael W0EZI "west" wrote in message news:1H3qf.17566$md.3615@tornado.tampabay.rr.com... > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from > Ham > Radio for more than 20 years & would like opinions on what would be the > absolute best omni-directional antenna(s) to buy, for this rig? All > opinions > welcomed. Thank you. > > west > AF4GC > > Article: 220301 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: More BPL rollout. sigh... Date: 21 Dec 2005 21:59:17 GMT Message-ID: References: On Wed, 21 Dec 2005 10:44:35 -0800, Richard Clark wrote: > > Hi Jonesy, > > Did you just move to Pueblo from Gunnison? Gunnison is such a nice > town. Hi Richard. Yep, DM68 has A LOT less WS VHF actvity now. Think of the postage I'll save on QSL cards! HI!HI! How-some-ever, I have to start all over on my 6M WAS. Got all but R.I. with 9.5 watts on 6M from Gunnison. sigh... (There really should be a W49S award! Quite a few folks have that!) > Last time I was in Pueblo was during High School in the 60s. As > we used to say about Tijuana when I was in the Navy: didn't lose > anything there, so there was no reason to go back. Being a contrarian, I selected Pueblo for the move, after my First Wife said she was done being cold in Gunnison. Turns out Pueblo is A Great Place to live -- unless you're trying to raise and educate children, or need to make a living. Luckily I'm not into any of that. > Of course, Colorado Springs has tripled in size since then, and to > no positive gain as far as I can tell. Agreed. We bought a house on the S.E. side of Pueblo -- a little out in the county -- just to stay as far away from C. Spgs. as possible. :-) 73 MC es HNY Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 220302 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: Message-ID: Date: Wed, 21 Dec 2005 22:18:26 GMT John Ferrell wrote: > You can learn to tolerate high SWR's, but I find it worthwhile to try > to keep things matched. The energy has to go somewhere, I prefer it > leave here through the antenna... > John Ferrell W8CCW I assume that you realize there is a high SWR on a standing- wave antenna, like a resonant 1/2WL dipole? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220303 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Antenna reception theory Date: Wed, 21 Dec 2005 18:06:20 -0500 Message-ID: <11qjnt7a2mlskf2@corp.supernews.com> References: <25358-43A8255A-47@storefull-3257.bay.webtv.net> <11qi0ecphael065@corp.supernews.com> <43A9748C.9050808@comcast.net> I am amazed that this keeps going on. In the early days of radio, the frequencies were low, receivers were not very sensitive, and the antennas were vertical - with some understandable exaggeration. Modern circuit theory - in the sense that things can be calculated - started about 1920. In those early days, the concept of "height" was useful. For a given physical height, one was interested in increasing the "height." Top loading was one major tool. A simple analysis was made based on the reasonable assumption that the current distribution along a short (less than 0.1 WL), thin, rod over a good ground was linearly distributed from a max. at the base to zero at the end. Such an analysis has been made an uncounted number of times since. I found a reference that suggests that Sommerfield might have made the calculation in a paper published in March 1909. The result is always that the assumed antenna has an open circuit voltage between its bottom and ground of no more than 0.5 of the incident, vertically-polarized wave's v/m times the physical length. (An ideal 0.25 WL antenna was expected to have a "height" of 2/pi.) No expert has ever said something to contradict the 0.5 figure. What many have described is a way to visualize E in free space using a one meter wire. That is not the subject. Before Professor Kraus' first edition (1950), "height" had lost most of its utility. Professor Terman in his 1943 edition of -Radio Engineers' Handbook- gives it a definitional footnote on page 841. Directivity and gain had been defined and have been useful ever since. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net Article: 220304 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Wed, 21 Dec 2005 23:11:02 GMT "Cecil Moore" bravely wrote to "All" (21 Dec 05 15:19:51) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:221636 CM> Roy Lewallen wrote: > But voltage isn't energy. Or power. CM> True, but voltage cannot exist without energy. I wouldn't say that. Voltage is kind of like having a big boulder sitting on top of a high cliff. It doesn't do anything so it doesn't expend energy. However, if it rolls off that's splat! Similarly you can have all the electrical potential you want but as long as no charges flow then where is the energy? In an EM wave it is the energy itself that flows in space using voltage and magnetism as a skeleton. A*s*i*m*o*v Article: 220305 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Wed, 21 Dec 2005 23:25:05 GMT Asimov wrote: > Voltage is kind of like having a big boulder > sitting on top of a high cliff. Yep, it is. A big boulder sitting on top of a high cliff contains a lot of potential energy. Voltage is literally potential energy and cannot exist without energy. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220306 of rec.radio.amateur.antenna From: "Bill" Subject: Voyager Hazer ..?? Message-ID: Date: Wed, 21 Dec 2005 18:32:26 -0500 Glen Martin just informed me that they are not making the "Hazer" for the 45G tower anymore.... Anyone know where one is for sale, and does anyone. know of a better or equal "mousetrap"..?? http://www.glenmartin.com/catalog/page12.html TNX, -Bill kc4pe@mindspring.com http://www.kc4pe.com/amateurshack.htm Article: 220307 of rec.radio.amateur.antenna From: "west" References: <1H3qf.17566$md.3615@tornado.tampabay.rr.com> <11qjiil4if6ul5c@corp.supernews.com> Subject: Re: 2 or more Ants. needed Message-ID: Date: Thu, 22 Dec 2005 00:28:11 GMT "Michael" wrote in message news:11qjiil4if6ul5c@corp.supernews.com... > If you have the room, a loop antenna is a very good bet. I have used dipoles > and verticals for many years. A neighbor moved in a few doors down and put > up a loop antenna. I went over and listened to the "quiet" It is a great > antenna if you are really irritated by QRN. He has only used this type of > antenna for 20 years since he tried it. I understand why. I have not yet put > up one, but will. It is winter here in North Dakota and not a good time for > antenna work. > Evrery other type of antenna works, but I just love the S/N ratio on a loop. > > Michael > W0EZI > "west" wrote in message > news:1H3qf.17566$md.3615@tornado.tampabay.rr.com... > > I'm ready to buy a Yaesu FT-857D (160-6m) & (2, 440). I been away from > > Ham > > Radio for more than 20 years & would like opinions on what would be the > > absolute best omni-directional antenna(s) to buy, for this rig? All > > opinions > > welcomed. Thank you. > > > > west > > AF4GC I agree about the reduction of QRN in a horizontally polarized vs. vertically polarized antenna but what about the gain? I don't have the time to build. I have some property, but not a large amount. Are there commercial loop antennas available and I guess I should concentrate on HF & 6M and worry about VHF/UHF later. Thoughts? Thanks again. west > > > > > > Article: 220308 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Antenna reception theory References: Message-ID: Date: Thu, 22 Dec 2005 00:48:55 GMT Cecil Moore wrote: > > Yep, it is. A big boulder sitting on top of a high cliff > contains a lot of potential energy. Voltage is literally > potential energy and cannot exist without energy. Cecil, Still practicing physics without a license? 8-) Electrical potential energy has units of voltage multiplied by charge. Voltage by itself is not potential energy, literally or otherwise. 73, Gene W4SZ Article: 220309 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Thu, 22 Dec 2005 02:22:43 GMT Gene Fuller wrote: > Electrical potential energy has units of voltage multiplied by charge. > Voltage by itself is not potential energy, literally or otherwise. I didn't mean to imply that voltage and energy are the same thing. But voltage is indeed literally potential energy (per unit charge). -- 73, Cecil http://www.qsl.net/w5dxp Article: 220310 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> Message-ID: <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> Date: Thu, 22 Dec 2005 03:16:17 GMT W. Watson wrote: > A standing wave is the sum of an incident added to the reflective wave. > Isn't it possible to send two incident waves down an xline with > different frequences, and produce two different standing waves by having > some multiplicative relationship between the two incident waves and the > xline length? Sure, it's possible but one wonders about the application. > 2. Matched impedances give ideal power transfer; mismatched > impedances give high SWR and reduced power transfer. A middle ground - Conjugately matched impedances give ideal power transfer in the presence of high SWR. A feedline doesn't have to be flat to be "matched". All that is required is that maximum available power (actually energy) be transferred. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220311 of rec.radio.amateur.antenna From: ehsjr Subject: Re: Still looking for a Tripp Lite PR-25 (or similar) DC power supply References: <43A83F2A.72DD0E2C@psdude.com> Message-ID: Date: Thu, 22 Dec 2005 03:40:24 GMT Paul P wrote: > There are a couple of smoked resistors on the regulator board. I can not > trust the ohm meter reading so I wanted to verify its value. I am trying to > avoid De-engineering the board. Now once the resistors are replace there > may be something else that smoked the resistors too. > > Paul. > Here's a link to an Astron supply: http://www.seits.org/features/pwrsup.htm Assuming a typical 723 ==> pass transistors linear supply, it shouldn't be hard to figure out the values of the cooked resistors. The schematic at the link above serves well as a model for many (most?) of that type of supply. Combined with the LM723 datasheet, you can fix it. Ed > "PS_DUDE" wrote in message > news:43A83F2A.72DD0E2C@psdude.com... > >>hi paul, >> >>Tripp lite makes good supplies but lacks in the >>support side ! >> >>Good thing is the supplies use off the shelf parts >>or easy substituted parts from anywhre, >>http://www.mouser.com etc. >> >>What problem(s) are you having ? >> >>73 ps dude >> > > > Article: 220312 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: <439kq11dj4fh6n7qpe6gm47ded3h9sg302@4ax.com> References: Date: Thu, 22 Dec 2005 04:10:34 GMT I was simply sharing my experiences from the past. If you have followed a few of my earlier posts you are aware I am simply a student who should have been studying this many years ago. I welcome any corrections. I never gave the swr on the radiator any thought. That is a good point. . On Wed, 21 Dec 2005 22:18:26 GMT, Cecil Moore wrote: >John Ferrell wrote: >> You can learn to tolerate high SWR's, but I find it worthwhile to try >> to keep things matched. The energy has to go somewhere, I prefer it >> leave here through the antenna... >> John Ferrell W8CCW > >I assume that you realize there is a high SWR on a standing- >wave antenna, like a resonant 1/2WL dipole? :-) John Ferrell W8CCW Article: 220313 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> Date: Thu, 22 Dec 2005 04:17:11 GMT On Wed, 21 Dec 2005 21:29:37 GMT, Owen Duffy wrote: >On Wed, 21 Dec 2005 20:18:05 GMT, John Ferrell > wrote: > >>On Tue, 20 Dec 2005 03:41:41 GMT, "W. Watson" >> wrote: >> >> I'm trying to make >>>some sense out of why the emphasis of standing waves. >> >>Here is the short version: >>A matched transmission line behaves like the theory books say it does. >>The rated power from the transmitter goes through the transmission >>line with the lowest possible loss to the antenna where it is radiated >>just like the book says. > >It is true that reducing SWR for a given line does reduce the loss if >the line is long enough. (There are some scenarios where a short line >with high VSWR has less loss than matched line of the same length.) > I will have to take your word for it, I cannot think of any examples. >But is matched line the real goal? > >If low loss is the goal, there are often cost effective lower loss >solutions possible with lower loss line operated at high VSWR. > >>A mismatched transmission just MIGHT work OK. If there is any >>possibility of generating interference, especially TVI, it will. The > >Why? How is TVI "generated" by line mismatch? > >Owen I really don't know why there is more TVI with a high swr. But my experience has been that there is, especially on 6 meters. John Ferrell W8CCW Article: 220314 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 04:30:09 +0000 (UTC) Message-ID: References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> To anybody who may be reading - (1) There's far too much importance attached to standing waves on transmission lines. But see (4). (2) There are colossal standing waves on antennas which are seldom taken any notice of. (3) Anyway, of what use does anybody make of standing waves after taking the trouble to measure them. And the measurements themselves are the most inacurate in the field of radio engineering. (4) And to cap it all, the common or garden SWR meter does NOT measure standing waves on the feedline to the antenna where they might conceivably be of interest. It's all a gigantic hoax! ---- Season's Greetings from Reg, G4FGQ. Article: 220315 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Thanks for antenna help. Date: Thu, 22 Dec 2005 04:43:59 +0000 (UTC) Message-ID: References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> The French should be given full credit for inventing the unit of length by correctly spelling it, the "METRE". Also, this avoids confusion with the frequently used word "METER", a measuring instrument, when they are both mentioned in the same sentence. ========================================== Article: 220316 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Thu, 22 Dec 2005 05:11:05 GMT "Cecil Moore" bravely wrote to "All" (21 Dec 05 23:25:05) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:221661 CM> Asimov wrote: > Voltage is kind of like having a big boulder > sitting on top of a high cliff. CM> Yep, it is. A big boulder sitting on top of a high cliff CM> contains a lot of potential energy. Voltage is literally CM> potential energy and cannot exist without energy. If I can manage to roll the boulder up at the top or at the bottom of the cliff, I will find it weighs about the same. The boulder only picks up energy as it is accelerating towards the foot of the cliff. A*s*i*m*o*v Article: 220317 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> Date: Thu, 22 Dec 2005 06:09:30 GMT On Thu, 22 Dec 2005 04:17:11 GMT, John Ferrell wrote: >>It is true that reducing SWR for a given line does reduce the loss if >>the line is long enough. (There are some scenarios where a short line >>with high VSWR has less loss than matched line of the same length.) >> >I will have to take your word for it, I cannot think of any examples. John, It was really a bit of an aside, a lead into the more important point that followed, however... In most practical lines at HF, loss is dominated by the series resistance. In the regions of a current minimum on a line with high VSWR, the I^2R losses are less than for the same net power on a flat line, and conversely, in the region of a current maximum on a line with high VSWR, the I^2R losses are more than for the same net power on a flat line. Over a half wave of line, the total losses are higher than a flat line, but a short line in the regions of a current minimum may have losses less than the matched line loss. Whilst that is not often to our benefit as we rarely have relatively short lines with high Z loads, the converse is true of the more common situation of a short line with a low Z load. For example, 3m of RG58 with a 5+j0 load (eg mobile antenna) on 3.5MHz has a matched line loss of 0.08dB, and an actual loss of 0.66dB. Many charts and formulas would predict the mismatched loss to be only 0.39dB, but it is worse because the line is short and in the region of a current maximum. >>But is matched line the real goal? >> >>If low loss is the goal, there are often cost effective lower loss >>solutions possible with lower loss line operated at high VSWR. >> >>>A mismatched transmission just MIGHT work OK. If there is any >>>possibility of generating interference, especially TVI, it will. The >> >>Why? How is TVI "generated" by line mismatch? >> >I really don't know why there is more TVI with a high swr. But my >experience has been that there is, especially on 6 meters. If you can't explain the mechanism by which SWR causes TVI, perhaps they correlate by some other cause. For example, an antenna may develop loose oxided connections which both change the load impedance (and hence VSWR), and create intermodulation causing TVI. If VSWR *does* cause TVI, surely someone will be able to explain how? Lots of people operate feedlines at high VSWR by design, and they do not necessarily cause TVI. When you dismiss the TVI myth, you get closer to understanding how the transmission lines work and perform, and that for example, operating a feedline at high VSWR can be part of an efficient and effective multiband HF antenna. Such a solution should not be dismissed out of hand because of high VSWR alone. Owen -- Article: 220318 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Thanks for antenna help. Date: Wed, 21 Dec 2005 22:14:55 -0800 Message-ID: <11qkh31l0humk7e@corp.supernews.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> Reg Edwards wrote: > The French should be given full credit for inventing the unit of > length by correctly spelling it, the "METRE". > > Also, this avoids confusion with the frequently used word "METER", a > measuring instrument, when they are both mentioned in the same > sentence. I'm so glad to hear you're committed to correctness and against confusion. Perhaps you can direct some of your efforts toward your countrymen - the U.K. is the only place I've been where "m" is used as an abbreviation for both metres and miles. Roy Lewallen, W7EL Article: 220319 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Thanks for antenna help. Date: Wed, 21 Dec 2005 22:16:16 -0800 Message-ID: <11qkh5h8if819af@corp.supernews.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135218231.794511.299350@f14g2000cwb.googlegroups.com> The Eternal Squire wrote: > . . . > Noise floor seems to be extremely high for 40 m in the afternoons and > evenings, is this common? Atmospheric noise is usually very low on 40 meters during the day. Sounds like you have some relatively local source of man-made noise. Roy Lewallen, W7EL Article: 220320 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Thanks for antenna help. Message-ID: <1pgkq1pa074foen5ghsfkh5brc7punqnbb@4ax.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> Date: Thu, 22 Dec 2005 06:16:47 GMT On Thu, 22 Dec 2005 04:43:59 +0000 (UTC), "Reg Edwards" wrote: > >The French should be given full credit for inventing the unit of >length by correctly spelling it, the "METRE". Reg, I think the US was one of the relatively early signatories to the metre convention, but reserved the position to spell "metre" as "meter". I can't recall when the UK signed the convention, my recollection is that we in VK signed it much later than both, however we metricated earlier than the UK, and the US hasn't metricated (metericated???) in the true sense of the word. I don't miss the days of rods roods poles perches chains etc, without mentioning other dimensional units. > >Also, this avoids confusion with the frequently used word "METER", a >measuring instrument, when they are both mentioned in the same >sentence. >========================================== > > Oh well. Give some people 25.4mm and they will take 16,609.344m! (Lost something in the translation I suspect!) Owen -- Article: 220321 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Wed, 21 Dec 2005 22:18:36 -0800 Message-ID: <11qkh9tkmvoehff@corp.supernews.com> References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> John Ferrell wrote: > . . . > I really don't know why there is more TVI with a high swr. But my > experience has been that there is, especially on 6 meters. > John Ferrell W8CCW It might be that the same phenomenon, or related ones, have caused both the high SWR and the TVI. But high SWR doesn't cause TVI. Or feedline radiation, which is another mistaken idea. Roy Lewallen, W7EL Article: 220322 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Wed, 21 Dec 2005 22:38:09 -0800 Message-ID: <11qkiej4csr8i4e@corp.supernews.com> References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> W. Watson wrote: > . . . > Not a bad explanation from Wikipedia: > > SWR has a number of implications that are directly applicable to radio use. > > 1. SWR is an indicator of reflected waves bouncing back and forth > within the transmission line, and as such, an increase in SWR > corresponds to an increase in power in the line beyond the actual > transmitted power. This increased power will increase RF losses, as > increased voltage increases dielectric losses, and increased current > increases resistive losses. I go along with that. > 2. Matched impedances give ideal power transfer; mismatched > impedances give high SWR and reduced power transfer. That's oversimplified and a misapplication of the rule of maximum power transfer. Suppose I have a 50 ohm source connected to a 50 ohm load and adjust the source so it puts 100 watts into the load. Then I put a half wavelength of 300 ohm line between the source and the load. The transmission line will have a 6:1 SWR. There will be a 6:1 impedance mismatch at the transmission line-load junction. Yet -- The load power will be 100 watts as before. -- The power produced by the source will be 100 watts as before. -- The system efficiency will be the same as it was before. -- 100 watts will be transferred from the source to the line. -- 100 watts will be transferred from the line to the load. So in no way did the high SWR result in reduced power transfer. Now change the load impedance to 300 ohms. -- There is now a 6:1 mismatch between the source and the line. -- The line SWR is now 1:1. -- The load power will be reduced. The mismatch between source and line didn't cause a high SWR on the line. In fact, changing the line impedance degraded the match at the same time it improved the SWR. > 3. Higher power in the transmission line also leaks back into the > radio, which causes it to heat up. That's demonstrably false. For some examples and explanations, see http://www.eznec.com/misc/food_for_thought/Food%20for%20thought%20-%20Forward%20and%20Reverse%20Power.txt. (You might have to splice this URL back together if your browser splits it.) > 4. The higher voltages associated with a sufficiently high SWR could > damage the transmitter. Solid state radios which have a lower tolerance > for high voltages may automatically reduce output power to prevent > damage. Tube radios may arc. The high voltages may also cause > transmission line dielectric to break down and/or burn. That's true. Some transmitters can be damaged from a number of causes when the load impedance isn't approximately what the transmitter was designed for. Only one of those possible causes is increased voltage. Of course, a high SWR can also cause the voltage at the transmitter to be lower than it otherwise would have been. > Abnormally high > voltages in the antenna system increase the chance of accidental > radiation burn if someone touches the antenna during transmission. But the antenna doesn't have an SWR, the transmission line does. If you do have an open wire transmission line, it's best not to touch the line regardless of the SWR. But if you have a high line SWR, there's just a good of a chance that the voltage at the point you touch is lower due to the high SWR than it is than the voltage is higher. I'll bet if you search the web you can find just about any kind of possible misinformation about SWR, just as you can about any other topic. Roy Lewallen, W7EL Article: 220323 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Wed, 21 Dec 2005 22:45:20 -0800 Message-ID: <11qkis2gk7qad60@corp.supernews.com> References: John Ferrell wrote: > > Here is the short version: > A matched transmission line behaves like the theory books say it does. > The rated power from the transmitter goes through the transmission > line with the lowest possible loss to the antenna where it is radiated > just like the book says. Mismatched transmission lines also behave like the theory books say. The rated power from the transmitter goes through the transmission line to the antenna where it is radiated just like the book says. I deleted only "with the lowest possible loss" because increased SWR does increase line loss. But if the line loss is low when matched, the increased loss due to high SWR is often negligible. >. . . Roy Lewallen, W7EL Article: 220324 of rec.radio.amateur.antenna Message-ID: <43AA4CDA.46CD92EB@nobplforme.com> From: bpl_just_say_NO Subject: Re: More BPL rollout. sigh... References: Date: Thu, 22 Dec 2005 06:51:08 GMT 150 Million for ten years. that is a lot of money for nothing. DQE will also have a pilot program in Monroeville PA http://biz.yahoo.com/prnews/051215/cgth037.html?.v=44 I don't think they can compete with the newer intel and motorola technology for wireless. Article: 220325 of rec.radio.amateur.antenna From: "Super DX" Subject: website Message-ID: Date: Thu, 22 Dec 2005 13:23:21 +0100 Hi all, here is a new ham website : http://superdx.free.fr 73's and Merry Xmas ! Vince Article: 220326 of rec.radio.amateur.antenna From: Jim Higgins Subject: Re: More BPL rollout. sigh... Message-ID: References: <43AA4CDA.46CD92EB@nobplforme.com> Date: Thu, 22 Dec 2005 13:57:06 GMT On Thu, 22 Dec 2005 06:51:08 GMT, bpl_just_say_NO wrote: >150 Million for ten years. that is a lot of money for nothing. > >DQE will also have a pilot program in Monroeville PA > >http://biz.yahoo.com/prnews/051215/cgth037.html?.v=44 > >I don't think they can compete with the newer intel and >motorola technology for wireless. If the common folk play their cards right BPL can't compete with anyone anywhere. If rollout is inevitable it's time (past time actually) to go to the PUC and ask that everything related to BPL only be paid for from revenue gained from BPL. No shifting of revenue from power sales to support BPL - strictly separate. Also ask that service be provided promptly to anyone asking for it and everyone at the same price regardless of whether in a large city or one with a population of 22 at the end of 150 miles of dead-end power line. After all, BPL promises high speed Internet access to EVERYONE and you can be sure that at some point that was said. Hold them to it now, not 20 years >from now. The result? BPL economics absolutely cannot support the promises made for it. If they have to fulfill the promises it's dead before it starts. Article: 220327 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> Date: Thu, 22 Dec 2005 14:09:38 GMT I am glad I chose to display my ignorance, I have learned a lot. I will modify my earlier position that High SWR causes TVI to Roy's better explanation that they seem to have the same causes. I have noted that other people seem to get along with High SWR's and Non resonant antennas. Neither has worked well for me in the past. I used to operate ATV on 440mhz with a 48 element collinear antenna. (I did not do the initial construction) It was basically a collection of dipoles and reflectors tied together with open wire phasing harnesses. I could never quite figure out what the harness might be losing. The antenna seemed to be worth about 21db with very primitive measuring schemes. I speculated that it had a theoretical potential of 48db. I always felt that the phasing harness was the major contributor to the losses. With each driven element being resonant, some measure of success was assured with each one. At 440, feed line losses get critical in a hurry. The transmitter final was a military surplus cavity with a 4CX250 that had been "stuffed" to get it up to 440. As a side effect the output Z was determined to be pretty low by trying several home brew quarter wave coaxial matching sections. When a good match was made, a lot of problems went away. Not only was I managing a better signal, but the polyethylene cooling ducting was taking a longer time to melt down. Hence, my position that SWR IS important. Please note: I am not here to pick an argument, I recently took W4RNL's antenna course, bought Roy's EZNEC+ program, downloaded (still studying) Reg's many programs and have taken note that Cecil is a motorcycle fan like my Dad was. When I provoke an argument, I am trying to learn something. BTW, I do have a pretty good library of reference books but you guys explain it better in terms I can grasp! On Wed, 21 Dec 2005 22:45:20 -0800, Roy Lewallen wrote: >John Ferrell wrote: >> >> Here is the short version: >> A matched transmission line behaves like the theory books say it does. >> The rated power from the transmitter goes through the transmission >> line with the lowest possible loss to the antenna where it is radiated >> just like the book says. > >Mismatched transmission lines also behave like the theory books say. The >rated power from the transmitter goes through the transmission line to >the antenna where it is radiated just like the book says. > >I deleted only "with the lowest possible loss" because increased SWR >does increase line loss. But if the line loss is low when matched, the >increased loss due to high SWR is often negligible. > > >. . . > >Roy Lewallen, W7EL John Ferrell W8CCW Article: 220328 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <439kq11dj4fh6n7qpe6gm47ded3h9sg302@4ax.com> Message-ID: <3xyqf.33646$BZ5.10034@newssvr13.news.prodigy.com> Date: Thu, 22 Dec 2005 14:14:23 GMT John Ferrell wrote: > I never gave the swr on the radiator any thought. That is a good > point. Hi John, it was supposed to be humorous. I find it amusing that someone will say, "I hate high SWRs.", while running a resonant dipole with an SWR of 20:1 (or whatever) on the radiating elements. Superposition and interference between the forward waves and reflected waves on the radiating elements is what brings the feedpoint impedance of a 1/2WL dipole down to 50 ohms (or whatever). If it were not for standing waves on a 1/2WL dipole, the feedpoint impedance would be in the neighborhood of 1200 ohms, similiar to an infinite dipole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220329 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> Message-ID: Date: Thu, 22 Dec 2005 14:27:59 GMT John Ferrell wrote: > I really don't know why there is more TVI with a high swr. But my > experience has been that there is, especially on 6 meters. SWR can have an indirect effect on common-mode currents by causing a malfunction of the balun. For an SWR of 1:1, the balun is probably functioning in the impedance environment for which it was designed. That balun may cease to choke properly when exposed to the impedances present in an SWR >> 1:1 environment and allow more common-mode signals to develop and radiate. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220330 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Thu, 22 Dec 2005 14:47:46 GMT Asimov wrote: > If I can manage to roll the boulder up at the top or at the bottom of > the cliff, I will find it weighs about the same. The boulder only > picks up energy as it is accelerating towards the foot of the cliff. Energy cannot be created or destroyed. The kinetic energy gained as it accelerates is exactly balanced by the loss in potential energy that it had at the top of the cliff. Consider a pendulum. When it stops at the limit of its swing, it possesses potential energy. When it is moving at its fastest at the bottom of its swing, it possesses kinetic energy. When it finishes the swing to the other limit, it possesses potential energy. Neglecting losses, potential energy at the top of the swing is converted into an equal magnitude of kinetic energy at the bottom of the swing and back to potential energy at the top of the swing. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220331 of rec.radio.amateur.antenna From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: More BPL rollout. sigh... Date: Thu, 22 Dec 2005 14:41:03 +0000 (UTC) Message-ID: References: <43AA4CDA.46CD92EB@nobplforme.com> Jim Higgins wrote: >The result? BPL economics absolutely cannot support the > promises made for it. If they have to fulfill the promises it's dead > before it starts. The flaw in your logic is that Google invested $100,000,000 on Current Communications. If the trial flops economicaly, they can just keep pouring money into it until they corner the market. The way I figure it is they just raised $4b in a stock offering. If the $3b left over after buying part of AOL isn't enough, they will just sell more stock. Every time you click on an "ads by google", you are supporting BPL. Every time you vist a web site with "ads by google" you are supporting BPL. If you bought Google stock, or invested in a mutual fund that did, you are supporting BPL. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 The trouble with being a futurist is that when people get around to believing you, it's too late. We lost. Google 2,000,000:Hams 0. Article: 220332 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> Message-ID: <5jzqf.33656$BZ5.28225@newssvr13.news.prodigy.com> Date: Thu, 22 Dec 2005 15:07:45 GMT Owen Duffy wrote: > Lots of people operate feedlines at high VSWR by design, and they do > not necessarily cause TVI. Here's one example where a high VSWR might cause more TVI. XMTR--tuner--12:1 balun--5.25 WL 600 ohm feedline--600 ohm load XMTR--tuner--12:1 balun--5.25 WL 600 ohm feedline--50 ohm load The 600 ohm SWR is 1:1 in the first case. The balun sees the impedance for which it was designed and functions to choke off common mode currents with its 3000 ohms of choking impedance. The 600 ohm SWR is 12:1 in the second case. Neglecting losses, the balun sees 7200 ohms, 12 times higher than that for which it was designed. Its 3000 ohm choking impedance may allow much more common mode current to flow and radiate to the TV than in the first case. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220333 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Thanks for antenna help. References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> Message-ID: Date: Thu, 22 Dec 2005 15:11:26 GMT Reg Edwards wrote: > The French should be given full credit for inventing the unit of > length by correctly spelling it, the "METRE". > > Also, this avoids confusion with the frequently used word "METER", a > measuring instrument, when they are both mentioned in the same > sentence. The accident investigation crews here have a device that meters distances. I assume that in the UK, it is calibrated in metres. Do you guys call that device a "metre meter"? -- 73, Cecil http://www.qsl.net/w5dxp Article: 220334 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Standing Waves (and Impedance) References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> <11qkiej4csr8i4e@corp.supernews.com> Message-ID: Date: Thu, 22 Dec 2005 15:16:03 GMT Roy Lewallen wrote: > But the antenna doesn't have an SWR, ... Actually it does, if it is a standing-wave antenna like a 1/2WL resonant dipole. The reflections from the ends of the dipole are what lowers the virtual feedpoint impedance so that coax is a good match. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220335 of rec.radio.amateur.antenna From: Michael Gardner Subject: Re: More BPL rollout. sigh... Date: Thu, 22 Dec 2005 13:20:29 -0600 Message-ID: References: <43AA4CDA.46CD92EB@nobplforme.com> In article , Jim Higgins wrote: > On Thu, 22 Dec 2005 06:51:08 GMT, bpl_just_say_NO > wrote: > > >150 Million for ten years. that is a lot of money for nothing. > > > >DQE will also have a pilot program in Monroeville PA > > > >http://biz.yahoo.com/prnews/051215/cgth037.html?.v=44 > > > >I don't think they can compete with the newer intel and > >motorola technology for wireless. > > If the common folk play their cards right BPL can't compete with > anyone anywhere. If rollout is inevitable it's time (past time > actually) to go to the PUC and ask that everything related to BPL only > be paid for from revenue gained from BPL. No shifting of revenue from > power sales to support BPL - strictly separate. Also ask that service > be provided promptly to anyone asking for it and everyone at the same > price regardless of whether in a large city or one with a population > of 22 at the end of 150 miles of dead-end power line. After all, BPL > promises high speed Internet access to EVERYONE and you can be sure > that at some point that was said. Hold them to it now, not 20 years > from now. The result? BPL economics absolutely cannot support the > promises made for it. If they have to fulfill the promises it's dead > before it starts. What's worse is that capital should be spent on beefing up the distribution system - adding more monitoring, controls and redundancy. They are looking for a pot of gold - and will find nothing but a bunch of BPL gear rotting in the warehouses that have no power. -- sig goes here Article: 220336 of rec.radio.amateur.antenna From: "RB" Subject: ant tuner question Message-ID: Date: Thu, 22 Dec 2005 13:25:15 -0600 Got one for you gurus and mavens. I'm runnning an unbalanced roller T tuner through a balun to ladderline. I want to set up a chart of mid band tune points so I can QSY reasonably quickly and with minimum fuss of knob twiddling. I have a small antenna analyzer. Can I just put this on the rig side of the tuner, and use it to find matchpoints? Would I set it on 50 ohms, and then adjust the tuner controls until I get that? Article: 220337 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Re: grounding Date: 22 Dec 2005 13:53:30 -0600 Message-ID: References: >I am installing a short tower. The soil is very dry, mostly volcanic ash >and low conductivity. I had the backhoe operator drill several holes 4 >feet deep for grounding. It is impossible to drive a ground rod deeper >than 4 feet due to bedrock. What should I use to fill the holes after >the ground rods are installed? Do a web-search for "bentonite" and "ground", and you'll learn lots! Although I've never used it (but I'm going to start!), "bentonite" is the appropriate stuff to use. When wet, it expands inward to squeeze the ground rod and outward to press firmly against the soil, thereby resulting in (effectively) a very large-diameter ground well-connected to the soil. Clumping-type kitty-litter is supposedly bentonite (a clay material), so it should be relatively cheap. -- --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: 220338 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: ant tuner question Date: Thu, 22 Dec 2005 20:14:25 -0000 Message-ID: <11qm2912at2nlcc@corp.supernews.com> References: In article , RB wrote: >Got one for you gurus and mavens. > >I'm runnning an unbalanced roller T tuner through a balun to ladderline. > >I want to set up a chart of mid band tune points so I can QSY reasonably >quickly and with minimum fuss of knob twiddling. > >I have a small antenna analyzer. Can I just put this on the rig side of the >tuner, and use it to find matchpoints? Would I set it on 50 ohms, and then >adjust the tuner controls until I get that? That will work fairly well, as long as there isn't enough strong-signal energy hitting the antenna to confuse the antenna analyzer and cause false readings. For example, trying to use an MFJ analyzer to tune up an 80-meter antenna in an urban area can (I understand) be quite an exercise in frustration, because the strong signals from local AM broadcast stations are enough to cause the analyzer to mis-indicate the antenna system's SWR. I'd say, go right ahead and make these measurements... but make 'em in pencil, and plan on verifying them using your transmitter (at low power) and an in-line forward/reflected-power SWR meter. -- 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: 220339 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 12:23:42 -0800 Message-ID: <11qm2qgbn0p7g0d@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> John Ferrell wrote: > . . . > The transmitter final was a military surplus cavity with a 4CX250 that > had been "stuffed" to get it up to 440. As a side effect the output Z > was determined to be pretty low by trying several home brew quarter > wave coaxial matching sections. When a good match was made, a lot of > problems went away. Not only was I managing a better signal, but the > polyethylene cooling ducting was taking a longer time to melt down. > > Hence, my position that SWR IS important. > . . . All this demonstrates is that impedance match is important to the transmitter final. The quality of impedance match is often indicated as SWR on an SWR meter when in fact the meter reading often has little or nothing to do with the SWR on any transmission line. Even when it does, the problems with the transmitter are due solely to the poor impedance match and not at all due to the SWR on connected transmission lines. Let me give an example. Connect your transmitter through a half wavelength of 300 ohm transmission line to a 50 ohm (resistive) load. The transmitter sees 50 ohms, so an SWR meter at the transmitter will read 1:1, even though the SWR on the line is in fact 6:1. The transmitter can't tell the difference between this setup, a direct connection to the 50 ohm load, or connection to it through a half wavelength of cable with any impedance and therefore having any SWR. In all cases, the transmitter sees 50 ohms, which is all that matters. The line's SWR makes no difference at all. If for some reason you were really interested in finding the SWR on the 300 ohm line, you'd have to insert a 300 ohm SWR meter at the transmitter-line junction. It would correctly read 6:1. Roy Lewallen, W7EL Article: 220340 of rec.radio.amateur.antenna From: "RB" Subject: anothr ant tuner question Message-ID: Date: Thu, 22 Dec 2005 14:45:18 -0600 Geee-----we're on a roll! Thanks for good info on my previous query. Now, a new one: Just put a small MFJ -949E tuner into my antenna system. Thing works great. The only weird thing is I notice the tuning is extremely "tight" and "goosey". The slightest movement of the variable caps produces jumps in meter readings. Having said that, I can still manage with it. Years ago, this kind of tuning effect was from hand capacity, when just about everything in the shack was RF hot. However, this isn't what we're dealing with here. Once my controls are set, touching around the tuner anywhere doesn't alter anything. So, it's not hand capacity/coupling. What is this effect indicative of? Just curious. Article: 220341 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Thu, 22 Dec 2005 21:04:03 GMT "Cecil Moore" bravely wrote to "All" (22 Dec 05 14:47:46) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:221698 CM> Asimov wrote: > If I can manage to roll the boulder up at the top or at the bottom of > the cliff, I will find it weighs about the same. The boulder only > picks up energy as it is accelerating towards the foot of the cliff. CM> Energy cannot be created or destroyed. The kinetic energy gained CM> as it accelerates is exactly balanced by the loss in potential CM> energy that it had at the top of the cliff. CM> Consider a pendulum. When it stops at the limit of its swing, CM> it possesses potential energy. When it is moving at its fastest CM> at the bottom of its swing, it possesses kinetic energy. When CM> it finishes the swing to the other limit, it possesses potential CM> energy. Neglecting losses, potential energy at the top of the CM> swing is converted into an equal magnitude of kinetic energy at CM> the bottom of the swing and back to potential energy at the top CM> of the swing. Consider the Earth-Moon system, they interact via the oceans on Earth. The water level bulges can be considered as the pendulum in your example. The result of the tide is that gravitational energy is being transfered to the Moon and it is gradually accelerating away from the Earth. So in your example the pendulum doesn't have any energy except that which it borrows and returns to the Earth's pull of gravity. If we were to follow your logic the Moon should fall to the Earth instead. Assuming frictionless bearings and zero drag your pendulum should go on forever because it has no energy of its own. A*s*i*m*o*v Article: 220342 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: anothr ant tuner question Date: Thu, 22 Dec 2005 21:06:18 -0000 Message-ID: <11qm5aalocl83f@corp.supernews.com> References: In article , RB wrote: >Geee-----we're on a roll! Thanks for good info on my previous query. Now, >a new one: > >Just put a small MFJ -949E tuner into my antenna system. > >Thing works great. The only weird thing is I notice the tuning is extremely >"tight" and "goosey". The slightest movement of the variable caps produces >jumps in meter readings. Having said that, I can still manage with it. > >Years ago, this kind of tuning effect was from hand capacity, when just >about everything in the shack was RF hot. > >However, this isn't what we're dealing with here. Once my controls are set, >touching around the tuner anywhere doesn't alter anything. So, it's not >hand capacity/coupling. > >What is this effect indicative of? Just curious. Any of several things. This could indicate that your caps have noisy (dirty or oxidized or burned) sliding contacts to the stator. It could indicate that the caps have a somewhat "sticky" bearing arrangement, which is subject to both stiction and some amount of backlash and overshoot. It could indicate that you are attempting to tune a highly reactive or otherwise-difficult load, and have one or both of the caps set to a low-mesh (and thus high-reactance) setting. If the rotor and stator plates in those caps have the same radius throughout (I can't tell >from the picture), then when the caps are mostly un-meshed, a very small change in the position of the rotor can make a proportionally- large change in capacitance and change the reactance (and thus the matching) quite a lot. There can be a definite advantage to using air-variable caps which have plates (on either the rotor or stator) which are tapered in radius, from one end of the rotation to the other... it makes the adjustments at the mostly-unmeshed, low-capacitance end rather less critical. Take a look at a typical "broadcast variable" capacitor >from an older AM radio set, and you'll probably see this sort of construction. With a C-L-C T-match tuner, it's usually possible to achieve a match at several different settings of the controls. If you've achieved a match, and find that both of the caps are set up to a fairly-far- unmeshed setting, try switching the inductor down to the next-lower inductance setting, and then tweaking both caps in the direction of greater mesh (more capacitance, lower reactance). This may boost your tuner's electrical efficiency, and may also make the tuning less critical and "jumpy". -- 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: 220343 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: References: <8dhjq19tqdj6mpc9pl1jgv4l4dluhc259a@4ax.com> <00akq1tpd63d6p90lspuju1k4joa6m1gtj@4ax.com> <5jzqf.33656$BZ5.28225@newssvr13.news.prodigy.com> Date: Thu, 22 Dec 2005 21:33:54 GMT On Thu, 22 Dec 2005 15:07:45 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Lots of people operate feedlines at high VSWR by design, and they do >> not necessarily cause TVI. > >Here's one example where a high VSWR might cause more TVI. > Your example suggests a simplified method of analysing the effectiveness of a balun in reducing common mode current under two different load scenarios (that happen to have a transmission line operating at different VSWR). If the line length of your example was an even number of quarter waves, then by your own analysis method, in the second case, the balun with 50 ohm load and "3000 ohm choking impedance" would be more effective at 12:1 VSWR than the flat line? So that goes to the meaning of "high VSWR *might* cause more TVI". Perhaps there is some other factor, and perhaps VSWR is not a root cause at all. There is nothing in what you have said that suggests to me that VSWR is the cause of TVI (or feedline radiation in the more general case). Owen -- Article: 220344 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 21:49:47 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> Roy, you are, at least, on the right track. To measure SWR on the feedline, it is necessary to climb up the mast or a ladder and insert an SWR meter, of the correcct impedance, between the antenna and the feedline? Then you have to come down safely to ground level, switch on the transmitter, and view the meter reading through an astronomical telescope, bearing in mind that the field of view with an astronomical telescope is inverted with respect to normal. In its usual position the SWR meter does not measure SWR on any line. It merely indicates whether or not the transmitter is correctly loaded with a resistive 50 ohms. Which is all anyone may wish to know. After 50 years or more of ignorance, it is about time this hoax was exposed to the world. Then, all that is necessary to prevent the instrument from telling lies, is to leave it where it is and change its name to TLI (Transmitter Loading Indicator). ---- Reg, G4FGQ. Article: 220345 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 14:24:14 -0800 Message-ID: <11qm9slee4e1kf2@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> Reg Edwards wrote: > Roy, you are, at least, on the right track. > > To measure SWR on the feedline, it is necessary to climb up the mast > or a ladder and insert an SWR meter, of the correcct impedance, > between the antenna and the feedline? No. You can insert the SWR meter of the correct impedance at the input end of the feedline. Stay inside, nice and warm. Of course, if your line has a significant amount of loss, the SWR will vary along the line, so you'll have to put the meter at the point where you want to know the SWR. > Then you have to come down safely to ground level, switch on the > transmitter, and view the meter reading through an astronomical > telescope, bearing in mind that the field of view with an astronomical > telescope is inverted with respect to normal. That's surely a novel way of doing it, although unnecessary. On the one hand, that method might seem more plausible after finishing off a bottle of wine. On the other, that would be a bad time to be climbing the mast. > In its usual position the SWR meter does not measure SWR on any line. > It merely indicates whether or not the transmitter is correctly loaded > with a resistive 50 ohms. Which is all anyone may wish to know. > > After 50 years or more of ignorance, it is about time this hoax was > exposed to the world. > > Then, all that is necessary to prevent the instrument from telling > lies, is to leave it where it is and change its name to TLI > (Transmitter Loading Indicator). Have you had any luck in selling Agilent (HP), Narda, Anritsu, and those other ignorant companies into not specifying the input impedances of their precision RF measurement equipment, terminations, and other components in terms of SWR? Once you get them to see the light, hams will surely enlist in your jihad. Otherwise, we'll have postings from hams that go something like this: "My TLI says my precision termination resistor has an impedance of 1.02 Reggies. But the manufacturer specifies a maximum SWR of 1.05:1. Is it ok? Reg says there are 6 dB in an S-Unit, so are there 6 SWRs to a Reggie?" Roy Lewallen, W7EL Article: 220346 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 22:42:36 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> "Reg Edwards" wrote > Then, all that is necessary to prevent the instrument from telling > lies, is to leave it where it is and change its name to TLI > (Transmitter Loading Indicator). ========================================== This will have the effect of reducing SWR on the line to a more appropriate and realistic level of importance. Who cares what is the SWR on the transmission line provided the transmitter is loaded with its correct load resistance? ---- Reg, G4FGQ. Article: 220347 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Thu, 22 Dec 2005 14:47:08 -0800 Message-ID: <11qmb7efhmg451d@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <11qeft0bpn1590@corp.supernews.com> Reg Edwards wrote: > "Roy Lewallen" wrote > >>A ferrite loop >>antenna simply has better efficiency than a standard loop of the > > same > >>physical size. Hence it has better gain or capture area. > > ========================================= > > It's only a minor point, but when a ferrite core is placed inside a > loop the efficiency remains the same. It's the same wire, the same > coil dimensions, and hence the same loss in the resistance. > > If anything happens to efficiency it is reduced due to a loss in the > ferrite core material. > Sorry, that's not true. When the ferrite core is inserted, the loss resistance stays the same, as you say. But the radiation resistance increases, resulting in increased efficiency. > What happens is that the effective cross-sectional area of the loop > increases approximately in proportion to the permeability of the core. > For small permeabilities the capture area is much increased. This is a good illustration of why I don't like using "capture area" for antennas of small dimensions -- even Reg gets the mistaken idea that physical or effective physical area is directly related to capture area. For some antennas, like horns and ones with a parabolic reflector, it is. But for simple, small antennas, it isn't. The effective aperture (capture area) of a small loop is 3 * lambda^2 / (8 * pi) where lambda is the wavelength, for a loop of any size as long as it's electrically small enough to have essentially uniform current. Notice that the capture area doesn't increase as the loop size increases as long as the current is essentially uniform. This is, in fact, exactly the same thing that happens for a short dipole. Making a loop larger (or short dipole longer) decreases the radiation resistance which in the presence of inevitable loss, increases the efficiency. But if you could make a lossless loop or dipole, you couldn't get any more power out of it by increasing its size, again with the restriction that the current remains essentially uniform, or for a dipole that the length is very short compared to a wavelength. (The above discussion assumes that effective aperture and capture area don't include the effect of loss. This is the assumption commonly used in texts.) > But for > larger permeabilities, say above 100, the effect diminishes and the > effective core permeability settles down to the order of 20 or 30. It > depends on the ratio of length to diameter of the core rather than of > the coil. > > To visualise, it should be remembered most of the magnetic circuit > lies in the air between and near the ends of a ferrite rod. There is > no point in increasing permeability of rod material beyond a certain > amount in an attempt to increase capture area. Again, adding the ferrite improves efficiency by reducing radiation resistance, not by increasing capture area. > . . . Roy Lewallen, W7EL Article: 220348 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna - correction Date: Thu, 22 Dec 2005 15:19:14 -0800 Message-ID: <11qmd3kko2j6j84@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> <11q7as26ibspr8e@corp.supernews.com> <1134912638.780711.72140@g43g2000cwa.googlegroups.com> <11qeft0bpn1590@corp.supernews.com> <11qmb7efhmg451d@corp.supernews.com> Roy Lewallen wrote: > . . . > Making a loop larger (or short dipole > longer) decreases the radiation resistance which in the presence of > inevitable loss, increases the efficiency. . . That should be *increases* rather than decreases. Roy Lewallen, W7EL Article: 220349 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 23:25:42 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> Your reply was very fast. You didn't have time to think about it. The only way to "measure" SWR is to place the meter at the antenna end of the line. You know that as well as I do. The SWR does not apply to any particular point on the line. It applies to the WHOLE line. ---- Reg, G4FGQ. Article: 220350 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 16:07:56 -0800 Message-ID: <11qmfuvged5rf16@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> Reg Edwards wrote: >. . . > The only way to "measure" SWR is to place the meter at the antenna end > of the line. You know that as well as I do. > > The SWR does not apply to any particular point on the line. It applies > to the WHOLE line. I disagree with both of those statements, and both can be shown to be incorrect. If a line is lossless, the SWR is the same all along the line. An SWR meter of the line's impedance will measure the SWR correctly when placed anywhere along the line, including at either end. If a line has loss, the SWR varies along the line, being the greatest at the load and decreasing toward the source. (The concept of SWR at a single point is well understood and widely used and accepted, even though it deviates from the original literal definition.) In that case, the meter will correctly read the SWR at the position where it's placed. That position can be anywhere along the line including either end. Roy Lewallen, W7EL Article: 220351 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Standing Waves (and Impedance) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> <11qmfuvged5rf16@corp.supernews.com> Date: Fri, 23 Dec 2005 00:38:07 GMT On Thu, 22 Dec 2005 16:07:56 -0800, Roy Lewallen wrote: >If a line has loss, the SWR varies along the line, being the greatest at >the load and decreasing toward the source. (The concept of SWR at a >single point is well understood and widely used and accepted, even >though it deviates from the original literal definition.) In that case, >the meter will correctly read the SWR at the position where it's placed. >That position can be anywhere along the line including either end. ... and for most practical purposes, with knowledge of the matched line loss, the VSWR at any other point on that line can be estimated with reasonable accuracy from the measurement at a point on the line. Owen -- Article: 220352 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: Thanks for antenna help. Date: Thu, 22 Dec 2005 21:53:17 -0500 Message-ID: <11qmpin540olsbe@corp.supernews.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> <1pgkq1pa074foen5ghsfkh5brc7punqnbb@4ax.com> Dear Owen: As I recall, very early in The Republic's life, the use of the metric system was made legal. Rods, chains, links, feet, inches, and degrees are bound to legal descriptions of land here in The Republic in a manner that is likely to be permanent. Some land descriptions sound like this: The east half of the NE quarter of section 24, T16N, R8W. This describes 80 acres in the corner of a specific section (one mile on each side) in the 16th township north of a reference and the eighth west of a reference. An ideal township is 36 square miles (6 by 6 miles). Out East, some descriptions reference objects that have not been seen for a few hundred years. Precision GPS and its required antennas will, with time and care, change the some properties are described. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net "Owen Duffy" > > Reg, I think the US was one of the relatively early signatories to the > metre convention, but reserved the position to spell "metre" as > "meter". > > I can't recall when the UK signed the convention, my recollection is > that we in VK signed it much later than both, however we metricated > earlier than the UK, and the US hasn't metricated (metericated???) in > the true sense of the word. > > I don't miss the days of rods roods poles perches chains etc, without > mentioning other dimensional units. > > Owen > -- Article: 220353 of rec.radio.amateur.antenna From: Russ Subject: Re: grounding Message-ID: References: Date: Fri, 23 Dec 2005 03:24:56 GMT On 22 Dec 2005 13:53:30 -0600, mcalhoun@ksu.edu wrote: >>I am installing a short tower. The soil is very dry, mostly volcanic ash >>and low conductivity. I had the backhoe operator drill several holes 4 >>feet deep for grounding. It is impossible to drive a ground rod deeper >>than 4 feet due to bedrock. What should I use to fill the holes after >>the ground rods are installed? > >Do a web-search for "bentonite" and "ground", and you'll learn lots! > >Although I've never used it (but I'm going to start!), "bentonite" is >the appropriate stuff to use. When wet, it expands inward to squeeze >the ground rod and outward to press firmly against the soil, thereby >resulting in (effectively) a very large-diameter ground well-connected >to the soil. > >Clumping-type kitty-litter is supposedly bentonite (a clay material), >so it should be relatively cheap. Hi Myron, how are you these days? If I recall, bentonite is used in the oil patch as a slurry to seal the drill hole. It is called drilling mud in that context. It should be pretty cheap! Russ Article: 220354 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> <1135306044.877301.21990@g44g2000cwa.googlegroups.com> Subject: Re: Thanks for antenna help. Date: Thu, 22 Dec 2005 23:08:51 -0500 Message-ID: I would consider 33[m]=3.3[km] is even more slipshod... "The Eternal Squire" wrote in message news:1135306044.877301.21990@g44g2000cwa.googlegroups.com... > Oh, come on.... > > In engineering literature an SI measurement is generally given as a > number followed by the abbreviated unit in braces: 330 [cm] = 33 [m] > = 3.3 [km] > > Sorry for being slipshod and forgetting the braces. > > The Eternal Squire > > P.S. Why Santa got pulled over: 3E8 [km/s], not just a good idea, its > the LAW!!!! > Article: 220355 of rec.radio.amateur.antenna From: "Crazy George" References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> Subject: Re: Standing Waves (and Impedance) Date: Thu, 22 Dec 2005 22:16:31 -0600 Message-ID: <43ab7ab2@kcnews01> . "Cecil Moore" wrote in message news:5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com... > W. Watson wrote: >> A standing wave is the sum of an incident added to the reflective wave. >> Isn't it possible to send two incident waves down an xline with different >> frequences, and produce two different standing waves by having some >> multiplicative relationship between the two incident waves and the xline >> length? > > Sure, it's possible but one wonders about the application. Cecil: Think about a 6 MHz wide analog TV channel. Those antennas aren't flat, and there are 2 transmitters, visual and aural. Putting an analog TV station on the air the first time, particularly low VHF, is a real interesting exercise. Or at least it was back in the stone (vacuum tube) age, the last time I did one. 73, George W5VPQ My real address is my ham call ARRL.NET The ATTGlobal is a SPAM trap > Article: 220356 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <1135102751.103538.224970@g47g2000cwa.googlegroups.com> <5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com> Subject: Re: Standing Waves (and Impedance) Message-ID: Date: Fri, 23 Dec 2005 04:34:00 GMT "Cecil Moore" wrote in message news:5Uoqf.43886$6e1.2147@newssvr14.news.prodigy.com... > W. Watson wrote: > > A standing wave is the sum of an incident added to the reflective wave. > > Isn't it possible to send two incident waves down an xline with > > different frequences, and produce two different standing waves by having > > some multiplicative relationship between the two incident waves and the > > xline length? > > Sure, it's possible but one wonders about the application. > Some repeaters use one antenna for two repeaters on 144 and 440 mhz. Comercial transmitters do this all the time. Usually the transmitters are in the same band. Article: 220357 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Thanks for antenna help. Message-ID: References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> <1pgkq1pa074foen5ghsfkh5brc7punqnbb@4ax.com> Date: Fri, 23 Dec 2005 04:40:30 GMT On Thu, 22 Dec 2005 06:56:50 -0500, Amos Keag wrote: >Owen Duffy wrote: > >> SNIPPED > >> >> >> Give some people 25.4mm and they will take 16,609.344m! (Lost >> something in the translation I suspect!) >> >> Owen >> -- > >Hmmm ... 16,609.344m = 10 miles does it not?? No, it is not. The mistake is the repeated 6, it should have been 1,609.344m. Apologies... Owen -- Article: 220358 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Thanks for antenna help. Message-ID: <010nq15qf7prillnbd1sdcqsgv3vt5hs6l@4ax.com> References: <1135061739.857569.44630@g43g2000cwa.googlegroups.com> <1135136632.653994.293680@g43g2000cwa.googlegroups.com> <1135306044.877301.21990@g44g2000cwa.googlegroups.com> Date: Fri, 23 Dec 2005 04:44:05 GMT On 22 Dec 2005 18:47:24 -0800, "The Eternal Squire" wrote: >P.S. Why Santa got pulled over: 3E8 [km/s], not just a good idea, its >the LAW!!!! Wow, that is 1000 times the speed of light! -- Article: 220359 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Crimp, Clamp or Solder? Message-ID: Date: Fri, 23 Dec 2005 01:05:36 -0600 I am new in ham radio and want to get set up to make the coax assemblies I will inevitably be needing in the future. I am planing on using only LMR style coax 240, 400, 600 and maybe some 900 if I get into the 1.2ghz stuff. So is it better to use the crimp, clamp or solder on connectors. In the case of the center conductor, there are some where that is solder and the outer is crimp or clamp so is crimp and or clamp ok for the outer conductor and solder better for the inner? I welcome all points of view on this. Thanks for you input. -- 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: 220360 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Program GRNDWAV4 Date: Fri, 23 Dec 2005 02:06:33 -0800 Message-ID: <11qnj1btnnk8ie7@corp.supernews.com> References: <11q7a46jtvo9jf9@corp.supernews.com> <6Hfpf.12069$wg4.4975@edtnps84> Frank wrote: > > Not sure I really understand what is going on, but have been aware of your > previous postings, also on the NEC-list. What I should have said is that > the above program agrees with Reg's previous assumption -- but not with his > new program "grndwav4.exe". In any case, just to satisfy my curiosity, I > ran the following code, which is, in essence, almost identical to your > NEC-list post with 5.555.... kW input producing 1V/m peak at 1000m. The > following agrees exactly with Reg's new program. > > CM Short Monopoles > CE > GW 1 50 0 0 1 0 0 0 0.000814 > GW 2 50 1000 0 1 1000 0 0 0.000814 > GS 0 0 1 > GE 1 > GN 1 > EX 0 1 50 00 65698.12106 0.00000 > LD 4 2 50 50 1.747 823.796 > FR 0 3 0 0 19.9 0.1 > RP 1 1 360 0000 0 0 1.00000 1.00000 1000 > RP 0 181 1 1000 -90 45 1 1 > EN > > Noting the comments by others, obviously familiar with ATR measurement > techniques, this exercise with NEC is purely academic. There is no way you > could experimentally prove these results. Since I have never made > measurements on an "Open-air" test site it will be interesting to verify > Mac's assumptions, which I am sure are correct. > > The confusions I have are now related to the fact that NEC results depend on > how the incident E-field is generated. I will check all previous posting by > Roy to see if I can figure out this anomaly. For some reason I have not > received any update concerning the NEC list postings. > I've just now finally gotten around to posting a response to the NEC-list. It might help clarify things for you. The essential point is that when you specify a plane wave source, it acts like a plane wave of the specified amplitude coming from the specified direction. That wave interacts with the ground plane just as any other field would. When a ground plane is specified, the result is a field strength -- and polarization -- which isn't generally the same as that of the original wave. You can illustrate this by specifying a plane wave which originates at an angle of 45 degrees above the horizon, and looking at the current induced in a short circuited vertical wire or the base voltage of an open circuited wire (the latter simulated by putting a high impedance load at the base). Begin with the wire vertical, then tilt the wire so the direction of the plane wave source is broadside to the wire, and again so the direction of the source is in line with the wire. You'll get the same result from the last two tests, and the induced current or voltage in those two is less (by about 1/sqrt(2)) than when the wire is vertical. This shows that the field is purely vertically polarized (normal to the ground plane) at the location of the wire. (I think there's actually a small horizontal component except exactly at the ground plane surface.) It does show conclusively that the orientation of the field isn't the same as it was when it left the source -- otherwise the induced current or voltage would be greatest when the wire was tilted broadside to the plane wave source and zero when tilted in the source direction. So the interaction of the plane wave source's field with the ground plane alters both the amplitude and the polarization of the field. When the source is in the horizontal direction and the ground plane is perfect, the field strength just above the ground plane is exactly twice the amplitude of the plane wave source. So a 1 V/m plane wave source at zero elevation angle (90 degree zenith angle) produces 2 V/m just above the ground plane, which induces 1 V at the base of an open circuited electrically short 1 m vertical wire. Roy Lewallen, W7EL Article: 220361 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Crimp, Clamp or Solder? References: Message-ID: Date: Fri, 23 Dec 2005 11:22:03 GMT Chris, Solder. 'Doc Article: 220362 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: To Reg Edwards et al: Questions On Inverted L Message-ID: References: Date: Fri, 23 Dec 2005 12:06:58 GMT On Thu, 22 Dec 2005 07:27:19 -0500, "Robert11" wrote: >Hello, and aHappy Holidays, > >Thanks for taking the time to reply to my questions re Slopers. >Am pretty new at this, and find antennas a fascinating, and quite confusing, >subject. >Lots to learn, but fun doing so. > >Have a JRC 545 which I really love, but obviously am not using to its full >potential. >Just have a random length wire running around my attic. >Do listening only, from 30 MHz on down. Would really want something very >close to omni for antenna. > >Once it warms up a bit, I plan on putting up outside either a PAR SWL-EFL >end fed in an Inverted-L configuration, >or possibly an Alpha Delta, or similar, Sloper. About 15 years ago, I put up the Alpha Delta swl sloper, hooked to a JRC NRD 525. That was an excellent combination; strong signals. This particular antenna is quite heavy duty, and may be a good choice for your snowy conditions. Have a happy... bob k5qwg > >My thinking right now is for the PAR as an Inverted-L. > >Would like to ask if you have any thoughts on the PAR ? > >a. e.g., in practice, is it also omni, or should I try and orient it ? >If so, is it most sensitive perpendicular to the horiz. wire axis ? > >b. what would be the best ratio between the horiz. and vert. legs ? > >c. I guess the end of the vertical leg should be very, very close to the >Balun and ground >bar I'll be putting in. But, how does one handle 4' snow drifts getting >over the Balun, etc. Is this Coax Sealer product good enough ? >Or, should I just raise the end about 4' and run some braid from the Balun >to the ground bar ? > >You seem very knowledgeable on all of this "black magic" so any other hints >or opinions >re the PAR, or mtg and using it, would be most appreciated. > >Thanks, and best regards, >Bob >------------------ >For practical receiving purposes, a sloping wire, in the midst of >buildings, can be considered to be omi-directional, even isotropic. >Any variations in directivity, in either the vertical or horizontal >planes, although they exist, are not measurable or noticeable. The >random effect of the presence of a nearby building or buildings is >greater than the direction in which the wire may or may not slope > Article: 220363 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Crimp, Clamp or Solder? Message-ID: <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com> References: Date: Fri, 23 Dec 2005 12:12:20 GMT On Fri, 23 Dec 2005 01:05:36 -0600, Chris W <1qazse4@cox.net> wrote: >I am new in ham radio and want to get set up to make the coax assemblies >I will inevitably be needing in the future. I am planing on using only >LMR style coax 240, 400, 600 and maybe some 900 if I get into the 1.2ghz >stuff. So is it better to use the crimp, clamp or solder on >connectors. In the case of the center conductor, there are some where >that is solder and the outer is crimp or clamp so is crimp and or clamp >ok for the outer conductor and solder better for the inner? I welcome >all points of view on this. Thanks for you input. As Doc said, solder. Get a Weller SP-120 soldering iron. It's 120 watts. About $46. You can typically find it by Googling. You'll need that kind of heat to solder coax connector outer shells to the braid. Get the ARRL Handbook, and look at their pages on soldering coax connectors. Bob k5qwg Article: 220364 of rec.radio.amateur.antenna From: "Chuck S." References: Subject: Re: Crimp, Clamp or Solder? Message-ID: Date: Fri, 23 Dec 2005 13:51:42 GMT Clamp types have cause me problems over the years, stay away from them. Crimp type work ok in the shack but not out side for a long time. Solder it by far the best way to go. Another type that works good outside is compression clamps. The ones meant to be used with hard line. They cost more, but unless you like climbing up a 60 foot tower in a contest, they are worth the cost! Chuck WA3IAC "Chris W" <1qazse4@cox.net> wrote in message news:SkNqf.41400$ih5.2551@dukeread11... >I am new in ham radio and want to get set up to make the coax assemblies I >will inevitably be needing in the future. I am planing on using only LMR >style coax 240, 400, 600 and maybe some 900 if I get into the 1.2ghz stuff. >So is it better to use the crimp, clamp or solder on connectors. In the >case of the center conductor, there are some where that is solder and the >outer is crimp or clamp so is crimp and or clamp ok for the outer conductor >and solder better for the inner? I welcome all points of view on this. >Thanks for you input. > > > -- > 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: 220365 of rec.radio.amateur.antenna Message-ID: <43AC1B1F.33D66325@pl259.com> From: Luke Subject: Re: Crimp, Clamp or Solder? References: Date: Fri, 23 Dec 2005 15:43:29 GMT hi Chris, Welmcome to ham radio, I am sure you will enjoy it as much as the rest of us have ! Since you are starting out, to solder you just need the iron, 100-120 watts with chisel tip is just fine, don't attempt with the lower wattage units, you end up damaging the coax dielectric and have more problems. Crimps have their place, but, you will need to buy or borrow the crimp frame tool along with the correct dies for the connectors you want to crimp. This is a lot more expensive then the solder iron. Be sure to buy and use name brand connectors, quality is worth the price, you buy it once. You can get a bag of the cheap ones to practice with and then use the good Amphenol or other brands. http://www.amphenolrf.com/products/assemblyInstructions/274.pdf The above pdf has installation instructions. 73 Luke Article: 220366 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Passive reradiating antenna Date: Fri, 23 Dec 2005 09:44:12 -0600 Message-ID: <13158-43AC1B4C-464@storefull-3254.bay.webtv.net> References: Reg,G4FGQ wrote: "---when a ferrite core is placed inside a loop the efficiency remains the same. Its the same wire, the same coil dimensions, and hence the same loss in resistance." Not if the coil is doing the same job. Remember the permeability tuned coils? You insert the core farther into the coil to increase its inductance. The powdered-iron core has a much higher permeability than air. The powdered-iron core gathers and concentrates lines of flux inside the coil. If the iron-cored coil is to resonate at the same frequency as the air-cored coil does, the iron-cored coil must have many fewer turns, and thus it has much less loss. Good design requires a ferrite with low-loss at the frequency. For a ferrite loopstick antenna, sensitivity is proportional to the length of the ferrite rod and best placement of the coil is squarely in the middle of the ferrite rod. Best regards, Richard Harrison, KB5WZI Article: 220367 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 16:19:19 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> Roy, you surprise me. Try a jug of Moonshine. Placing the SWR meter at the start of the feed-line terminated by the antenna, will tell you NOTHING about the SWR on that line. It is the antenna input impedance which determines the SWR on the line, and the meter doesn't have the foggiest idea what THAT is. The unknown antenna impedance is at the other end of a line of unknown length, unknown impedance and unknown loss. Unknown, that is, to the meter. YOU might have that knowledge. But then you can CALCULATE what the SWR is on the line. Meter readings having been discarded as useless. I repeat - the meter tells you only whether or not the transmitter is loaded with a resistive 50 ohms. No more and no less. If it is not 50 ohms the ambiguous meter will not even tell you the actual value of Z. Intoxicated or not, if you insist on a meter reading, there is no alternative to climbing the antenna mast. ---- Reg, G4FGQ. PS. The use of SWR by American plug and socket manufacturers to describe unrelated characteristics of their products is a small indication of the abysmal depths to which engineering has descended. Technical specifications are reduced to Camm's Comics. But they look good to the uninitiated. ---- Reg. ========================================== Article: 220368 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: To Reg Edwards et al: Questions On Inverted L Date: Fri, 23 Dec 2005 10:36:43 -0600 Message-ID: <10106-43AC279B-352@storefull-3252.bay.webtv.net> References: Bob wrote: "What would be the best ratio between horiz. and vert. legs?" Short answer: Zero. All the wire should be vertical for best results. Try to borrow a copy of ON4UN`s "Low-Band DXing" published by ARRL. Look at page 9-48 for the radiation resistance (good) for an inverted-L with various ratios of horizontal and vertical portions. Mistly, this is a vertical antenna with the forizontal section providing top-loading. Best regards, Richard Harrison, KB5WZI Article: 220369 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Standing Waves (and Impedance) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> <11qmfuvged5rf16@corp.supernews.com> Date: Fri, 23 Dec 2005 16:59:15 GMT On Thu, 22 Dec 2005 16:07:56 -0800, Roy Lewallen wrote: >Reg Edwards wrote: > > >. . . > >> The only way to "measure" SWR is to place the meter at the antenna end >> of the line. You know that as well as I do. >> >> The SWR does not apply to any particular point on the line. It applies >> to the WHOLE line. > >I disagree with both of those statements, and both can be shown to be >incorrect. > >If a line is lossless, the SWR is the same all along the line. An SWR >meter of the line's impedance will measure the SWR correctly when placed >anywhere along the line, including at either end. > >If a line has loss, the SWR varies along the line, being the greatest at >the load and decreasing toward the source. (The concept of SWR at a >single point is well understood and widely used and accepted, even >though it deviates from the original literal definition.) In that case, >the meter will correctly read the SWR at the position where it's placed. >That position can be anywhere along the line including either end. > >Roy Lewallen, W7EL I am absorbing this, but slowly. I have understood that a "matched line" would indicate the same SWR at every point you might measure it with a directional coupler. The Swr we are discussing is that which we can measure with a directional coupler, is it not? The SWR on a mis-matched line will vary with the position you choose to measure it. This can be indicated by varying the transmission line length to get an acceptable match for the system. This will satisfy the need to match a transmitter for a given frequency. A directional coupler placed at different places on the line will still indicate a non uniform SWR. Any feed line losses due to insulation or radiation are effectively hidden from the transmitter end. This is why I have gone to the antenna/feed line to measure the power level and the SWR. If your feed line has become an effective dummy load or a better radiator than your antenna it would nice to know. I don't have an answer as to how to measure the instruments insertion effects. Please tell me where I am in error! John Ferrell W8CCW Article: 220370 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 17:10:05 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> To all and sundry, The length and directions and off-shoots of this and other threads, the resulting arguments, confusion and misunderstandings prove my basic point - The SWR meter is grossely mis-named. It leads old-timers, novices, CB-ers and professional engineers severely astray. It overstretches imaginations. Dis-educational! ---- Reg. Article: 220371 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 18:34:15 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> "Reg Edwards" wrote > Technical specifications are reduced to Camm's Comics. But they look > good to the uninitiated. > ========================================== Insert between "they look good" and "to the uninitiated" - "and sell". ---- Reg. Article: 220372 of rec.radio.amateur.antenna Subject: Re: Crimp, Clamp or Solder? From: Ed References: Message-ID: Date: 23 Dec 2005 18:35:44 GMT Crimp connectors work just fine when done properly, but I would not use them on anything above 2M. You will find the compression type fittings for larger coax and heliax superior to anything else for microwave work. But most will probably suggest generally a good soldered connector the best for most apps. If you have the money, the best iron for soldering coax connectors would be one such as made by American Beauty..... but very pricey. A hefty Weller gun will suffice if funds are limited. Ed K7AAT Article: 220373 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Crimp, Clamp or Solder? Date: Fri, 23 Dec 2005 18:39:51 -0000 Message-ID: <11qoh3nq5cvi92@corp.supernews.com> References: <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com> In article <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com>, Bob Miller wrote: >Get a Weller SP-120 soldering iron. It's 120 watts. About $46. You can >typically find it by Googling. > >You'll need that kind of heat to solder coax connector outer shells to >the braid. Get the ARRL Handbook, and look at their pages on soldering >coax connectors. Another trick: it's usually possible to solder the outer shells into place with a lower-wattage gun, if you first pre-heat the whole assembly with a hot air gun (hair dryer might work). This can be gentler on the coax (and its meltable internal insulation) than just hitting the shell with a soldering iron and waiting for the shell to soak up enough heat to allow the solder to melt. -- 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: 220374 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Message-ID: References: Date: Fri, 16 Dec 2005 22:55:09 GMT On Fri, 16 Dec 2005 11:20:53 -0500, "Robert11" wrote: >Hello: > >Have been reading up on lightning a bit, and it certainly >is a confusing subject. > >Let's say I have an Inverted-L or a Sloper in the yard (receiving only). > >If a lightning storm is in the vicinity, obviously the best protection >possible is to just disconnect the radio from the antenna. No differences >of opinion here, I would imagine. > >But, as a more or less theoretical question, to minimize the possibility of >lightning hitting the antenna at all, or inducing large voltages in it, is >it better to just leave the now "floating" antenna alone, or is it better to >ground one end of it ? > >Why ? You have to think carefully about what you are trying to protect. It seems to me that in the event of a lightning stroke in the near vicinity of your antenna, large voltages will be induced in the antenna wrt "ground", whether or not your antenna or its support structure features as a streamer, or takes the current from a leader. That voltage may be sufficient for insulation breakdown, and charge will flow to ground via some path, not necessarily of your choosing. Substantial physical damage may occur where insulation breaks down, the path of the side-flash current may result in further damage to persons or equipment. If you make a substantial connection from the feedline to some thing, you have some degree of control over the path that the discharge current flows. Properly chosen and implemented, that might be better than doing nothing, but if poorly designed or implemented, it could be worse than doing nothing. Side-flash can still occur where you have provided a path to ground. Very often, the target of effective lighting protection of radio installations is minimisation of voltage drops or potential differences internal to an installation as a result of lightning discharge current rather than trying to minimise the voltage to "ground" resulting from the current. Owen -- Article: 220375 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: Crimp, Clamp or Solder? References: <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com> Message-ID: Date: Fri, 23 Dec 2005 14:01:08 -0600 Bob Miller wrote: >As Doc said, solder. > >Get a Weller SP-120 soldering iron. It's 120 watts. About $46. You can >typically find it by Googling. > > Thanks for the suggestion on the iron, I found it for $40 which isn't too bad. >You'll need that kind of heat to solder coax connector outer shells to >the braid. Get the ARRL Handbook, and look at their pages on soldering >coax connectors. > > I guess the book you are talking about isn't the antenna book, I can't find much on soldering in there. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 220376 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: Crimp, Clamp or Solder? References: <43AC1B1F.33D66325@pl259.com> Message-ID: <9fZqf.41426$ih5.7094@dukeread11> Date: Fri, 23 Dec 2005 14:38:42 -0600 Luke wrote: >hi Chris, > >Welmcome to ham radio, I am sure you will enjoy it >as much as the rest of us have ! > >Since you are starting out, to solder you just need >the iron, 100-120 watts with chisel tip is just fine, >don't attempt with the lower wattage units, you end >up damaging the coax dielectric and have more problems. > >Crimps have their place, but, you will need to buy or >borrow the crimp frame tool along with the correct >dies for the connectors you want to crimp. >This is a lot more expensive then the solder iron. > >Be sure to buy and use name brand connectors, >quality is worth the price, you buy it once. >You can get a bag of the cheap ones to practice >with and then use the good Amphenol or other brands. > >http://www.amphenolrf.com/products/assemblyInstructions/274.pdf > > Actually I plan on going out of my way to avoid UHF connectors. I plan on doing a fair amount at 400+ mhz and the UHF connectors don't do well up there. So about the only place I will be using UHF is at the radio if I can't find a radio with N connectors. My watt meter has N connectors and so do my antennas. I'm not sure why anyone would want to use UHF on anything outside. The only way to protect a UHF from the weather is with some coax wrap but the N has a seal built in, of course some kind of wrap as additional protection isn't a bad idea either if it is done right. In some cases I may even replace the UHF connector in the radio with an N but only if it is an old radio no longer under warranty. -- 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: 220377 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Program GRNDWAV4 Date: Fri, 16 Dec 2005 19:46:31 -0800 Message-ID: <11q72gqq39466d9@corp.supernews.com> References: Hopefully my recent posting on the "Antenna reception theory" thread will clarify things a bit. Roy Lewallen, W7EL Reg Edwards wrote: > > Frank, > > The situation changes by the hour so I suggest you don't spend a great > deal of time trying to sort things out. Either the program is in error > or you have entered incorrect data. Or (see below) both you and I have > the correct answer in the first place. > > From the situation at present we have :- > > It seems the numerous Bibles written by learned professors don't agree > on the subject. > > Computer programs, whose results are falsely taken as being gospel > truths, don't agree on the subject. > > The 'experts' who contribute to this newsgroup can't agree on the > subject. But, from the frequency of arguments which result. this is > perfectly normal. > > I remain as an innocent, neutral bystander, in danger of being > unjustly accused of being a troll, whereas - > > All I need is an answer to my simple but essentially fundamental and > practical question - > > "What is the voltage measured between the bottom end of a 1 metre high > vertical antenna and ground, when the field strength is 1 volt per > metre?" > > It goes without saying, a perfect ground is assumed, the antenna > height is less than 1/4-wavelength and the radio wave is vertically > polarised. > > Is the measured voltage 1 volt or is it 0.5 volts? > > There's a simple factor of 2 involved somewhere. Should I take a > statistical average of the replies if there are any? > > What happens on an isolated dipole is irrevalant. It is just a > time-wasting diversion. > > I don't have access to the 'learned Bibles' or to computer programs > (except my own). So there is no point in referring to them. But I > don't consider this to be any handicap. Short, logical, convincing > explanations in plain English and perhaps a little arithmetic would be > welcome of course. > ---- > Reg, G4FGQ. > > Article: 220378 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: Crimp, Clamp or Solder? References: Message-ID: Date: Fri, 23 Dec 2005 14:48:35 -0600 Ed wrote: > Crimp connectors work just fine when done properly, but I would not use >them on anything above 2M. > Then why is it that Times Microwave only shows how to put on crimp and clamp connectors on their cables on their web site. On their larger cables (LMR 900 and up) they only have clamp connectors. >You will find the compression type fittings >for larger coax and heliax superior to anything else for microwave work. > > Like I already mentioned, I think that is all you can put on the LMR 900 and up size coax. > But most will probably suggest generally a good soldered connector the >best for most apps. > > If you have the money, the best iron for soldering coax connectors >would be one such as made by American Beauty..... but very pricey. > I found an 150 watt one for $115, that doesn't seem too bad to me if it is that much better than others. http://www.hmcelectronics.com/cgi-bin/scripts/product/0400-0027 One thing I forgot to mention in my first post, where you have to use a UHF, it seems that for LMR 400, the only option is solder, I could be looking in the wrong places, but I haven't seen any crimp or clamp on UHF connectors for LMR 400 only solder. About the only time I plan on using anything smaller than LMR 400 is for a jumper to hook my hand held to the big antenna, for that I am going to get some LMR 240 ultra flex. -- 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: 220379 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: Crimp, Clamp or Solder? References: Message-ID: Date: Fri, 23 Dec 2005 14:56:06 -0600 Chuck S. wrote: >Clamp types have cause me problems over the years, stay away from them. >Crimp type work ok in the shack but not out side for a long time. > If you are going to crimp and use it outside you certainly need to use some good adhesive lined shrink tube to seal it up. I'm curious why no one seems to like crimp. Other than the cost of the tools to do it right it seems like a much easier way to go. Crimping works great for other types of connections. Also I did a lot of browsing on Times Microwave's web site and about all they talk about are crimp and clamp on connectors, for the big cables it is clamp only, I think part of the reason for that is you would probably need a hydraulic crimping tool for those big cables :) >Solder it >by far the best way to go. Another type that works good outside is >compression clamps. The ones meant to be used with hard line. They cost >more, but unless you like climbing up a 60 foot tower in a contest, they are worth the cost! > > I like those, the only connectors I have put on so far is a solder/clamp N and a solder UHF, the N was a solder on pin, which was pretty easy and then the clamp on outer shell. The only hard part was getting the cable striped cleanly but a good coax stripper should fix that. That is the next thing I plan on buying, I just need to find a good 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: 220380 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 12:58:14 -0800 Message-ID: <11qop79kg3qr274@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> <11qmfuvged5rf16@corp.supernews.com> John Ferrell wrote: > > I am absorbing this, but slowly. > > I have understood that a "matched line" would indicate the same SWR at > every point you might measure it with a directional coupler. A matched line is one which is terminated with its characteristic impedance. The SWR on a matched line is 1:1 at all points along the line. > The Swr > we are discussing is that which we can measure with a directional > coupler, is it not? Yes and no. To measure the SWR requires an SWR meter or directional coupler which is designed for the particular characteristic impedance of the line. If a directional coupler is the proper impedance, it can be used to calculate the SWR from the forward and reverse powers. If it isn't, it can't. > The SWR on a mis-matched line will vary with the position you choose > to measure it. No, it won't, unless it has loss. If it has loss, the SWR will be greatest at the load and will monotonically decrease toward the source. > This can be indicated by varying the transmission line > length to get an acceptable match for the system. This will satisfy > the need to match a transmitter for a given frequency. A directional > coupler placed at different places on the line will still indicate a > non uniform SWR. Any feed line losses due to insulation or radiation > are effectively hidden from the transmitter end. It appears that you're assuming that what you measure with an SWR meter or calculate from directional coupler readings is the SWR. Unless the coupler or meter is designed for the Z0 of the line, it isn't. If the coupler or meter isn't of the proper impedance for the line, you'll get different readings as you move along the line. Those readings aren't, however, the line's SWR. >. . . Roy Lewallen, W7EL Article: 220381 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: Crimp, Clamp or Solder? References: Message-ID: Date: Fri, 23 Dec 2005 14:59:21 -0600 I forgot to bring up resistive soldering, does any one use one of those? I guess if I get a big iron that will work good. I used a 140 watt gun for the UHF connector I did first, I hear the big irons work better because of the larger thermal mass, I may try the heat gun trick too. I have a small heat gun that will get up to 200 and something F or so. -- 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: 220382 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Passive reradiating antenna Date: Fri, 16 Dec 2005 22:09:02 -0800 Message-ID: <11q7as26ibspr8e@corp.supernews.com> References: <1134765387.519872.236400@g47g2000cwa.googlegroups.com> Toni wrote: > Hi, > > I've seen here before suggestions about using a tuned loop to increase > the gain of radio controlled clocks. Do you think this could also be > used to increase the gain of a gps receiver? No. If you were to increase the gain of your GPS antenna, either by redesign of the antenna or by an external parasitic structure of some sort, it would have to result in a narrower pattern. So you'd reduce the reception in some directions. > I guess that loop should be 1wl circumference, or about 2 1/2 inch > diameter, easy enought to cary in a pocket and play with. > > I know one can not have more than 0 dB with full omni, I just guess the > minimalistic antenna in pocketable gps is way below 0 dB and could > maybe be improved a little. 0 dB relative to what? Once you get the desired coverage angle, the only way to improve the reception of the GPS is to improve the receiver signal/noise ratio. The only way you can do that from outside the GPS is to use an external antenna with a preamp having a lower noise figure than the GPS's receiver. > Could this be modeled in EZNEC, one segment with some series resitance > for high loss antenna and the other 19 to simulate the loop? I'm not sure what the "high loss antenna" is. If you mean the GPS antenna, it's not high loss at all, but is likely very efficient. If it's a patch antenna, you can't model it at all with EZNEC. But even if it's a quadrifilar helix, you can't model it with one segment. Roy Lewallen, W7EL Article: 220383 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Sat, 17 Dec 2005 00:49:52 -0600 Message-ID: <23342-43A3B510-367@storefull-3252.bay.webtv.net> References: Reg, G4FGQ wrote: "What do photons have to do with winning a contest?" I don`t know. But, B.Whitfield Griffith, Jr. has some observations in "Rado-Eledtronic Transmission Fundamentals" that may be a useful check on your computations. I expect he checked, rechecked, then checked again before publication. He put a transmitter on an elemental antenna but it would work the same in reverse. From page 325: "An Elemental Antenna Since the length of an antenna is commonly expressed in electrical degrees and since this allows the convenient use of trigonometric tables in computing the ratios of currents in various parts of an antenna, let us choose as our elemental antenna a piece of wire which is 1-degree in length and in which the current is constant from one end to the other.We shall first assume that this elemental antenna is located far out in space, so that its field is not disturbed by reflections from the surface of the earth or from any other object. This, of course, is a most improbable set of conditions, but we can certainly imagine that we have a situation such as this and compute from the field equations its electromagnetic result. These computations will show, first of all, that the maximum field intensity will be produced in the directions which are at right angles to the direction of current flow. This is a reasonable result, since the magnetic field which is produced by the current surrounds the wire in concentric rings and thus gives rise to a radiation field which moves outward at right angles to the wire. As a matter of fact, the field intensity, measured according to our standard procedure at a distance of 1 mile in any direction from the radiating element, will be found to be proportional to the sine of the angle between the direction of the current flow and the direction in which the measurement is taken. If we represent the field intensity at 1 mile in any direction by the length of a vector starting at the center of the element and extending in that direction, the tips of the vectors will mark out the radiation pattern of the antenna element. A cross section of the entire radiation pattern of this element is shown in Fig. 39-2; the entire pattern would be obtained by rotating the figure about the axis of the antenna element. But this pattern tells us only the relative signal strength in various directions; it is a normalized pattern, with the intensity in the direction of maximum radiation being considered simply as unity. We need much more information than this; we must know the relationship between the current and the actual value of the field it produces. Further computation from the field equations gives this relalationship; we find that a current of 1 amp flowing in the antnna element will produce a field intensity of 0.3253 mv/m at a distance of 1 mile iin the direction of maximum radiation. We have said nothing about the frequency, and we do not need to; as long as the wavelength is shorter than 1 mile, so that there are no serious induction-ffield effects to upset our calculations, this figure will be correct at any frequencyfor which the length of the element is 1/360 wavelength. The field intensity of the elemental antenna is directly proportional to the current. Therefore, if the current in the element is 15 amp, the field intensity will be 15 X 0.3253, or 4.8795, mv/m at 1 mile. Similarly, the field intensity is directly proportional to the length of the element; an element which is 2-degrees in length, carrying a current of 1 amp, will thus produce a maximum field intensity of 0.6506 mv/m at 1 mile. Best regards, Richard Harrison, KB5WZI Article: 220384 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 13:13:40 -0800 Message-ID: <11qoq46qkkfco08@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> This is pretty strange. Suppose Reg has a 50 ohm line of some length connected to an antenna whose impedance is 100 + j0 ohms. After putting away his evening's bottle of wine, he climbs the tower and inserts a 50 ohm SWR meter at the antenna. He climbs back down, gets out his vintage brass telescope and keys the transmitter. Then, steadying himself, he peers through the telescope and sees that the SWR meter reads 2:1. (Being a clever person, he mounted the meter upside down so it would be right side up in the telescope, obviating the need for the added challenge of mental inversion.) I have an identical antenna, feedline, and SWR meter. I sit in my warm shack sipping my moonshine, connect the SWR meter to the input end of the line, hit the key, and note that the meter reads 2:1. Or perhaps slightly less if the line is noticeably lossy. Reg says: > Placing the SWR meter at the start of the feed-line terminated by the > antenna, will tell you NOTHING about the SWR on that line. I guess the 2:1 reading from the meter at the input end of the line is telling Reg nothing, while the 2:1 reading at the antenna is. Strange. The fact is that it's the SWR on the line, and it can be measured at any point along the line. I like my method better, but each to his own. Roy Lewallen, W7EL Reg Edwards wrote: > Roy, you surprise me. Try a jug of Moonshine. > > Placing the SWR meter at the start of the feed-line terminated by the > antenna, will tell you NOTHING about the SWR on that line. > > It is the antenna input impedance which determines the SWR on the > line, and the meter doesn't have the foggiest idea what THAT is. > > The unknown antenna impedance is at the other end of a line of unknown > length, unknown impedance and unknown loss. Unknown, that is, to the > meter. > > YOU might have that knowledge. But then you can CALCULATE what the SWR > is on the line. Meter readings having been discarded as useless. > > I repeat - the meter tells you only whether or not the transmitter is > loaded with a resistive 50 ohms. No more and no less. If it is not > 50 ohms the ambiguous meter will not even tell you the actual value of > Z. > > Intoxicated or not, if you insist on a meter reading, there is no > alternative to climbing the antenna mast. > ---- > Reg, G4FGQ. > > PS. The use of SWR by American plug and socket manufacturers to > describe unrelated characteristics of their products is a small > indication of the abysmal depths to which engineering has descended. > Technical specifications are reduced to Camm's Comics. But they look > good to the uninitiated. > ---- > Reg. > ========================================== > > Article: 220385 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Fri, 16 Dec 2005 23:52:47 -0800 Message-ID: <11q7gujb3kps066@corp.supernews.com> References: <23342-43A3B510-367@storefull-3252.bay.webtv.net> Richard Harrison wrote: > > I don`t know. But, B.Whitfield Griffith, Jr. has some observations in > "Rado-Eledtronic Transmission Fundamentals" that may be a useful check > on your computations. I expect he checked, rechecked, then checked again > before publication. He put a transmitter on an elemental antenna but it > would work the same in reverse. From page 325: Yes, it should. > . . . > . . . We need > much more information than this; we must know the relationship between > the current and the actual value of the field it produces. Further > computation from the field equations gives this relalationship; we find > that a current of 1 amp flowing in the antnna element will produce a > field intensity of 0.3253 mv/m at a distance of 1 mile iin the direction > of maximum radiation. . . > > The field intensity of the elemental antenna is directly proportional to > the current. Therefore, if the current in the element is 15 amp, the > field intensity will be 15 X 0.3253, or 4.8795, mv/m at 1 mile. > Similarly, the field intensity is directly proportional to the length of > the element; an element which is 2-degrees in length, carrying a current > of 1 amp, will thus produce a maximum field intensity of 0.6506 mv/m at > 1 mile. A short dipole antenna with 1 amp of current at the center has an average of 0.5 amp of current along the whole length. So it should be obvious from the above analysis that the field from a dipole is half the field from the elemental antenna with uniform current which the author is discussing. Or, instead of just taking the average, you can integrate I * delta L to get the same result. Roy Lewallen, W7EL Article: 220386 of rec.radio.amateur.antenna From: "Chuck S." References: Subject: Re: Crimp, Clamp or Solder? Message-ID: Date: Fri, 23 Dec 2005 21:36:10 GMT One thing I should have said was that I use ONLY "N" connectors from 144 to 1296. I read, maybe in this group, that UHF connectors are ok to 500MHz. Like I said, I don't use them above 144MHz. and I know some hams that don't use UHF connectors on 6 meter. Above 2304 I use SMA's and WG on 24GHz. I'm getting off track, solder is the best way to go for UHF, or use whatever "N" connector Time recommends for their cables. "Chris W" <1qazse4@cox.net> wrote in message news:tvZqf.41428$ih5.4963@dukeread11... > Chuck S. wrote: > >>Clamp types have cause me problems over the years, stay away from them. >>Crimp type work ok in the shack but not out side for a long time. > If you are going to crimp and use it outside you certainly need to use > some good adhesive lined shrink tube to seal it up. I'm curious why no > one seems to like crimp. Other than the cost of the tools to do it right > it seems like a much easier way to go. Crimping works great for other > types of connections. Also I did a lot of browsing on Times Microwave's > web site and about all they talk about are crimp and clamp on connectors, > for the big cables it is clamp only, I think part of the reason for that > is you would probably need a hydraulic crimping tool for those big cables > :) > >>Solder it by far the best way to go. Another type that works good outside >>is compression clamps. The ones meant to be used with hard line. They cost >>more, but unless you like climbing up a 60 foot tower in a contest, they >>are worth the cost! >> > > I like those, the only connectors I have put on so far is a solder/clamp N > and a solder UHF, the N was a solder on pin, which was pretty easy and > then the clamp on outer shell. The only hard part was getting the cable > striped cleanly but a good coax stripper should fix that. That is the > next thing I plan on buying, I just need to find a good 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: 220387 of rec.radio.amateur.antenna From: Bill Turner Subject: Re: Crimp, Clamp or Solder? Date: Fri, 23 Dec 2005 14:31:03 -0800 Message-ID: References: <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com> <-8CdnVyNb5_FrTHeRVn-ig@comcast.com> ORIGINAL MESSAGE: On Fri, 23 Dec 2005 12:14:19 -0500, "Tam/WB2TT" wrote: >A ~200W soldering gun from Radio Shack or Home Depot will also work fine. > >Tam/WB2TT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ That's my preference too. Weller makes a 250 watt gun that works great for PL-259s. Heats up in a few seconds, unlike an iron, and cools down quickly. Be sure you get the 250 watt version, not the 125 watt. 73, Bill W6WRT Article: 220388 of rec.radio.amateur.antenna From: Bill Turner Subject: Re: Ground Or Not To Ground Receiving Antenna In Storm ? Date: Sat, 17 Dec 2005 09:49:13 -0800 Message-ID: <3hj8q19qtonh9l08563ec3c2j23btla05u@4ax.com> References: On Sat, 17 Dec 2005 01:48:24 -0600, " hillbilly3302" wrote: >I always tell new Hams to ground everything they can.... but if they get a >direct hit then they will be too busy fighting fire to worry about the >antenna... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This summer my 80 foot tower took a direct hit, the first in my 48 years of hamming. The tower was grounded and there was no fire, but it tripped a circuit breaker in my house and damaged a radio connected to it. My point is that fire is not an automatic consequence. Incidentally, the sound of thunder from a hit that close is remarkably different from a hit some distance away. First, you hear the clap from the nearest part of the bolt and then from parts successively farther away, a long, rolling sound that continues much longer than one at a distance. If I don't ever hear it again, that will be ok by me. :-) 73, Bill W6WRT Article: 220389 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Sat, 24 Dec 2005 00:05:45 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> In this day and age, there is only one meter on or associated with a transmitter. It is the misnamed SWR meter. Consequently and unavoidably, with nothing else left to talk about, the importance attached to SWR becomes exaggerated. It is perfectly natural, for CB-ers and professional engineers alike, to imagine the indicated SWR applies to the one and only transmission line in the system. That is along the line from the transmitter/tuner to the antenna. But the meter does not indicate SWR on any line. It merely indicates whether or not the load on the transmitter is 50 ohms. Which is nice to know. But, nevertheless, you have been fooled! After half a century of being unwittingly misled, it is admittedly difficult to have to suddenly switch one's ideas about what is thought to be an important subject. Carry on arguing! ---- Reg. Article: 220390 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: reciprocity and program zl_zin ?? Date: Fri, 23 Dec 2005 16:10:01 -0800 Message-ID: <11qp4esifj10vdc@corp.supernews.com> References: dansawyeror wrote: > The program zl_zin calculates a Zload from a known Zin. It would seem > that given a symmetrical feedline that Zin and Zload should be mirrors. > Why is that not so? I'm not sure what you mean by "mirrors". But the relationship between Zin and Zload is dictated by the way transmission lines transform impedances. A better question is, why should it be anything else? A series inductor is symmetrical, is it not? Suppose you have a series inductor with impedance +j10 ohms in a box. Connect it to a load of 50 + j0 ohms. Looking into the input of the series inductor, you see 50 + j10 ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0. Are you saying you expect to see 50 + j0 at the input? Why? > Is there a program that will calculate Zin from a known Zload? Hopefully someone else will be able to answer that. Roy Lewallen, W7EL Article: 220391 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: reciprocity and program zl_zin ?? Message-ID: <944pq1piql55o77t7b1gevfb7dn81mpun2@4ax.com> References: Date: Sat, 24 Dec 2005 00:14:18 GMT On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror wrote: >The program zl_zin calculates a Zload from a known Zin. It would seem that given >a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? Line loss. > >Is there a program that will calculate Zin from a known Zload? http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload, and Zload from Zin. Owen > >Thanks - Dan kb0qil -- Article: 220392 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 16:20:25 -0800 Message-ID: <11qp52bhjttf12f@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qm9slee4e1kf2@corp.supernews.com> <11qoq46qkkfco08@corp.supernews.com> <43AC8FCE.4060806@comcast.net> dansawyeror wrote: > Roy, > > Plot this on a smith chart program. You are correct, your meter reads > close to 2:1, however you know nothing about the phase or resonance of > the antenna. It does not tell you if you have a tuned antenna and a poor > R match or if your antenna is way out of tune. (Of course neither does > the telescope) What you say is true, but I don't understand what it has to do with the discussion at hand. No one has mentioned phase, resonance, tuning, or R match. An SWR meter isn't a suitable tool for measuring any of these, except that it'll usually indicate the resonant frequency fairly closely for most typical antennas. Roy Lewallen, W7EL Article: 220393 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Standing Waves (and Impedance) Date: Fri, 23 Dec 2005 16:38:26 -0800 Message-ID: <11qp645e3gts080@corp.supernews.com> References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> Reg Edwards wrote: > . . . > But the meter does not indicate SWR on any line. It merely indicates > whether or not the load on the transmitter is 50 ohms. Which is nice > to know. But, nevertheless, you have been fooled! > . . . Let's not be fooled by these contrived misstatements. An SWR meter tells us the SWR on a transmission line to which it's connected, providing that the line and meter impedances are the same. This can easily be verified with a couple of simple experiments. So it does indeed indicate the SWR on a line. It will, of course, still give a reading under other conditions, such as when the line and meter Z0 are different or when there's no line at all, in which cases it means only what Reg says(*). But I'm afraid that the effort to leave a legacy of a new TLA (three letter acronym) for SWR meters is causing Reg to adopt an increasingly distorted view of what SWR meters can and can't indicate. (*) Any kind of test equipment can be misused or the results misinterpreted. For example, anyone using a 1000 ohm/volt voltmeter to read voltage in a high-impedance circuit will not see the voltage which is there when the meter is disconnected. Likewise, measuring high frequency waveforms with a 10 pF scope probe, even at moderate impedances. The list is endless. But this doesn't justify renaming each of those pieces of test equipment to accommodate the most naive user. Roy Lewallen, W7EL Article: 220394 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: reciprocity and program zl_zin ?? Message-ID: References: Date: Sat, 24 Dec 2005 00:40:49 GMT On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror wrote: >The program zl_zin calculates a Zload from a known Zin. It would seem that given >a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so? Line loss (if I understand your question correctly) > >Is there a program that will calculate Zin from a known Zload? http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload, and Zload from Zin. Owen > >Thanks - Dan kb0qil -- Article: 220395 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: reciprocity and program zl_zin ?? Date: Sat, 24 Dec 2005 00:47:23 +0000 (UTC) Message-ID: References: > Is there a program that will calculate Zin from a known Zload? > ========================================== Yes, from the same place you obtained program ZL_ZIN. For coax lines use program COAXPAIR. For balanced twin lines use programs RJELINE3 or 4. These programs are to professional standards, 1% accuracy or better, covering the frequency range from audio to UHF. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220396 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: reciprocity and program zl_zin ?? Message-ID: References: <11qp4esifj10vdc@corp.supernews.com> Date: Sat, 24 Dec 2005 01:35:01 GMT On Fri, 23 Dec 2005 16:10:01 -0800, Roy Lewallen wrote: >dansawyeror wrote: >> The program zl_zin calculates a Zload from a known Zin. It would seem >> that given a symmetrical feedline that Zin and Zload should be mirrors. >> Why is that not so? > >I'm not sure what you mean by "mirrors". But the relationship between >Zin and Zload is dictated by the way transmission lines transform >impedances. A better question is, why should it be anything else? Roy, I also wasn't quite sure of the concept of *symmetry* and *mirror* as used by Dan. I made the assumption (perhaps incorrectly) that the transformation is symmetrical for an integral number of half waves of lossless transmission line. Impedances might be seen to "mirror" (if mirror means an exact copy) for an integral number of half waves of lossless line. Having made that assumption, loss introduces errors to the "mirroring", and line lengths other than an integral number of quarter waves aren't symmetrical in that sense. Having read Dan's further comments, it seems he thought any length of real line was symmetric as an impedance transformer. It might be that you can swap A and B ends in a circuit and obtain the same behaviour, but you can't swap Zload and Zin in the general case. Dan, the terms you have used don't have common usage in this context, and confuse the issue. Owen -- Article: 220397 of rec.radio.amateur.antenna Message-ID: <43ACB14C.338A26D9@alex.com> From: alex Subject: Re: Crimp, Clamp or Solder? References: Date: Sat, 24 Dec 2005 02:24:14 GMT Crimp is also very common in aerospace and military. Article: 220398 of rec.radio.amateur.antenna Message-ID: <43ACB1B7.B5CA6B5B@alex.com> From: alex Subject: Re: Crimp, Clamp or Solder? References: <43AC1B1F.33D66325@pl259.com> <9fZqf.41426$ih5.7094@dukeread11> Date: Sat, 24 Dec 2005 02:26:01 GMT You only need low power iron to attach the center conductor to the pin, the N connectors are clamp types. No tools needed. Chris W wrote: > Luke wrote: > > >hi Chris, > > > >Welmcome to ham radio, I am sure you will enjoy it > >as much as the rest of us have ! > > > >Since you are starting out, to solder you just need > >the iron, 100-120 watts with chisel tip is just fine, > >don't attempt with the lower wattage units, you end > >up damaging the coax dielectric and have more problems. > > > >Crimps have their place, but, you will need to buy or > >borrow the crimp frame tool along with the correct > >dies for the connectors you want to crimp. > >This is a lot more expensive then the solder iron. > > > >Be sure to buy and use name brand connectors, > >quality is worth the price, you buy it once. > >You can get a bag of the cheap ones to practice > >with and then use the good Amphenol or other brands. > > > >http://www.amphenolrf.com/products/assemblyInstructions/274.pdf > > > > > Actually I plan on going out of my way to avoid UHF connectors. I plan > on doing a fair amount at 400+ mhz and the UHF connectors don't do well > up there. So about the only place I will be using UHF is at the radio > if I can't find a radio with N connectors. My watt meter has N > connectors and so do my antennas. I'm not sure why anyone would want to > use UHF on anything outside. The only way to protect a UHF from the > weather is with some coax wrap but the N has a seal built in, of course > some kind of wrap as additional protection isn't a bad idea either if it > is done right. In some cases I may even replace the UHF connector in > the radio with an N but only if it is an old radio no longer under warranty. > > -- > 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: 220399 of rec.radio.amateur.antenna Message-ID: <43ACB25C.47D8E6DA@alex.com> From: alex Subject: Re: Crimp, Clamp or Solder? References: Date: Sat, 24 Dec 2005 02:28:46 GMT Yes, the 3/8" chisel tip is great. 100w or higher 700 deg. autotemp weller. many used on the forsale forums and ebay. Big difference between a heat sink and heat source ! Chris W wrote: > I forgot to bring up resistive soldering, does any one use one of > those? I guess if I get a big iron that will work good. I used a 140 > watt gun for the UHF connector I did first, I hear the big irons work > better because of the larger thermal mass, I may try the heat gun trick > too. I have a small heat gun that will get up to 200 and something F or so. > > -- > 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: 220400 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Connect coax shield to pipe when dipole is at top of pipe? Date: 23 Dec 2005 20:29:01 -0600 Message-ID: I've long used an end-to-end pair of same-band hamsticks on a metal bracket at the top of a push-up pole for a quick-and-dirty expedient dipole. My support pole is usually wood, but when I put the dipole on top of a metal pipe I realized there are two ways to do it: The hamstick that is connected to the coax center wire is always insulated from the pole, and the hamstick that is connected to the coax shield could EITHER be INSULATED or "GROUNDED" to the pole. QUESTIONS: Which should it be? Should/Would it make any difference? -- --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: 220401 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: reciprocity and program zl_zin ?? Date: Fri, 23 Dec 2005 18:57:10 -0800 Message-ID: <11qpe89h8o2em3c@corp.supernews.com> References: <11qp4esifj10vdc@corp.supernews.com> <6pidnW3uJb7eCzHeRVn-sg@comcast.com> dansawyeror wrote: > Roy, > > Well the intuition was correct, however the problem is one level more > complex. The Smith chart shows the following approximate 'mirror' > relationships for j=0: > > Load Input Measurement > 20 125 > 25 100 > 35 71 > 10 250 > 50 50 > > It is a "log" mirror centered on 50 Ohms. The mirror relationship holds > for j /= 0, however the calculation is more complex. - Dan Well, yes, you can find specific relationships for various special cases of load impedance and line length, particularly if you assume zero loss. But only the appropriate equations, derived from basic principles, will give you the correct relationship in the general case. Be wary of oversimplification. Roy Lewallen, W7EL Article: 220402 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: reciprocity and program zl_zin ?? Message-ID: <65gpq15iaqpqm0k48neuuptn5jmh6b6rl5@4ax.com> References: <11qp4esifj10vdc@corp.supernews.com> Date: Sat, 24 Dec 2005 03:31:07 GMT On Sat, 24 Dec 2005 01:35:01 GMT, Owen Duffy wrote: >I made the assumption (perhaps incorrectly) that the transformation is >symmetrical for an integral number of half waves of lossless >transmission line. Impedances might be seen to "mirror" (if mirror >means an exact copy) for an integral number of half waves of lossless >line. > That should have read: I made the assumption (perhaps incorrectly) that the transformation is symmetrical for an integral number of *quarter* waves of lossless transmission line. Impedances might be seen to "mirror" (if mirror means an exact copy) for an integral number of half waves of lossless line. Owen -- Article: 220403 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Crimp, Clamp or Solder? Message-ID: <8lgpq15vmilr6s06v3io3b2sho0u10gac2@4ax.com> References: <46qnq1lgk6o72105goronkk8lo8pkttv22@4ax.com> Date: Sat, 24 Dec 2005 03:43:17 GMT On Fri, 23 Dec 2005 14:01:08 -0600, Chris W <1qazse4@cox.net> wrote: >Bob Miller wrote: > >>As Doc said, solder. >> >>Get a Weller SP-120 soldering iron. It's 120 watts. About $46. You can >>typically find it by Googling. >> >> >Thanks for the suggestion on the iron, I found it for $40 which isn't >too bad. > >>You'll need that kind of heat to solder coax connector outer shells to >>the braid. Get the ARRL Handbook, and look at their pages on soldering >>coax connectors. >> >> >I guess the book you are talking about isn't the antenna book, I can't >find much on soldering in there. If you have the ARRL Antenna Book (I have the 19th edition) page 24-21 talks about PL-259 assembly, and explains how to prepare the coax and solder it to the connector. This is in the chapter labled "Transmission Lines" if you have another edition of the book. bob k5qwg Article: 220404 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Crimp, Clamp or Solder? Message-ID: References: Date: Sat, 24 Dec 2005 04:12:04 GMT On Fri, 23 Dec 2005 01:05:36 -0600, Chris W <1qazse4@cox.net> wrote: >I am new in ham radio and want to get set up to make the coax assemblies >I will inevitably be needing in the future. I am planing on using only >LMR style coax 240, 400, 600 and maybe some 900 if I get into the 1.2ghz >stuff. So is it better to use the crimp, clamp or solder on >connectors. In the case of the center conductor, there are some where >that is solder and the outer is crimp or clamp so is crimp and or clamp >ok for the outer conductor and solder better for the inner? I welcome >all points of view on this. Thanks for you input. You should not dismiss crimp connectors as inferior to soldered connections. Crimp connectors, properly executed with correct fitting dies, produce a very good result, they are good electrically, and they often have superior strength compared to "field serviceable" connectors (the solder / braid clamp) type. For my own use, I: - avoid PL-259 type connectors (that is not to mean UHF); - prefer N type for thicker cables and all outdoors (whether or not in the weather); - on Heliax, prefer the connectors that are sealed by injection of silicone into the backshell, ambivalent about whether the centre pin is soldered or spring contact (which are usually cheaper and quicker); - prefer BNC on thin patch cables and fly leads; - prefer crimped connectors to "field serviceable" connectors in indoors applications; - prefer sealed connectors for all outdoors applications, and question whether most sealed crimp connectors are actually effective through life; - keep a pair of multigrips handy for times when UHF connectors must be used. If you are choosing to use LMR cables, you might want to look at LMR195 (I think) which is dimensionally similar to RG58 and can use low cost RG58 crimp connectors. If you use BNC (or TNC for that matter), look at whether the connectors you buy locate / retain the centre pin independently of the wire connection. Owen -- Article: 220405 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Standing Waves (and Impedance) Date: Sat, 24 Dec 2005 04:33:16 +0000 (UTC) Message-ID: References: <11qkis2gk7qad60@corp.supernews.com> <11qm2qgbn0p7g0d@corp.supernews.com> <11qp645e3gts080@corp.supernews.com> The so-called SWR meter is just a resistance (not impedance) bridge. The bridge is at balance and indicates SWR = 1:1 when a resistance of precisely 50 ohms is connected to its output terminals. It is arranged within the meter that this 50-ohm resistance, or whatever is connected to the output terminals, is the transmitter load. With the meter in its normal location, the load is the input impedance of the transmission line to the antenna. So when the input impedance of the line, as determined by Zo of the line and the antenna input impedance, is 50 ohms then the meter indicates SWR = 1:1 regardless of Zo, line length and antenna impedance. As Roy says, in the special case of line Zo being precisely 50 ohms it so happens that the meter will correctly indicate SWR along the line. For any other value of line Zo the meter will indicate varying degrees of nonsense. At HF, line Zo is frequently anywhere between 50 and 600 ohms and a tuner is used to transform line input impedance, either up or down, to the 50 ohms required by the transmitter. But Zo is not affected and the SWR meter indications remain in error. Whatever Zo and antenna impedance may be, the meter always indicates whether or not the transmitter is correctly loaded with a resistive 50 ohms. Note that the circuit operates independently of transmitter internal impedance whatever that may be. ---- Reg. Article: 220406 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Crimp, Clamp or Solder? Message-ID: References: Date: Sat, 24 Dec 2005 05:11:03 GMT "'Doc" bravely wrote to "All" (23 Dec 05 11:22:03) --- on the heady topic of "Re: Crimp, Clamp or Solder?" 'D> From: 'Doc 'D> Xref: core-easynews rec.radio.amateur.antenna:221739 'D> Chris, 'D> Solder. 'D> 'Doc Spot weld. Makes great thermocouple joints. A*s*i*m*o*v Article: 220407 of rec.radio.amateur.antenna From: Bill Turner Subject: Re: Connect coax shield to pipe when dipole is at top of pipe? Date: Fri, 23 Dec 2005 21:25:52 -0800 Message-ID: <4jmpq15behsrkodtfb3dgpp8smiuplf0b3@4ax.com> References: ORIGINAL MESSAGE: On 23 Dec 2005 20:29:01 -0600, mcalhoun@ksu.edu wrote: > The hamstick that is connected to the coax center wire > is always insulated from the pole, and the hamstick > that is connected to the coax shield could EITHER be > INSULATED or "GROUNDED" to the pole. > >QUESTIONS: Which should it be? Should/Would it make any difference? >-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ What would be the point of "grounding" it to the pole? Do you want some of your RF to flow into the pole and thereby have the pole radiate? I wouldn't. The HamSticks are your antenna. Don't add something else unless you have a specific reason. The 1:1 balun mentioned by someone else is a good idea. It will keep all the RF in the antenna and prevent any from flowing on the outside of the coax. If you choose to not use it, it's not a major deal but that would distort the antenna pattern a small amount. 73, Bill W6WRT Article: 220408 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <1135422926.082522.168780@o13g2000cwo.googlegroups.com> Subject: Re: If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ? Message-ID: Date: Sat, 24 Dec 2005 13:03:37 GMT "tomerbr" wrote in message news:1135422926.082522.168780@o13g2000cwo.googlegroups.com... > this was a qustion from my instractor in college > As Dave said, there is no ideal length for an antenna. The 1/4 wave antenna will have a radiation patern that sends much of the signal at high angles from it. Not usually good for cell phones where they are usually on short towers (if you call a couple of hundred feet short). The longer (in wavelengths) antennas tend to put the signal more to the horizon and not overhead. By modifying the radiation patern to put it more where it is needed instead of where it is not needed you get gain in that direction and hopefully longer range. Article: 220409 of rec.radio.amateur.antenna From: "harrogate2" References: <1135422926.082522.168780@o13g2000cwo.googlegroups.com> Subject: Re: If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ? Message-ID: Date: Sat, 24 Dec 2005 15:06:10 GMT "Ralph Mowery" wrote in message news:JGbrf.9795$nm.1327@newsread2.news.atl.earthlink.net... > > "tomerbr" wrote in message > news:1135422926.082522.168780@o13g2000cwo.googlegroups.com... > > this was a qustion from my instractor in college > > > > As Dave said, there is no ideal length for an antenna. > > The 1/4 wave antenna will have a radiation patern that sends much of the > signal at high angles from it. Not usually good for cell phones where they > are usually on short towers (if you call a couple of hundred feet short). > The longer (in wavelengths) antennas tend to put the signal more to the > horizon and not overhead. By modifying the radiation patern to put it > more where it is needed instead of where it is not needed you get gain in > that direction and hopefully longer range. > > What an absolute load of blx. The reason that car cellular antennae are longer than a 1/4 wavelength is that almost all of them are centre loaded dual antennas or are 5/8 or 7/8 co-linears. The very short ones are often a little longer as they are coupled through glass and have to be matched. The wavelength of a signal and it's aerial have nothing to do with the propagation pattern. A simple VHF or UHF folded dipole for the same mounting and wavelength related structure spacing radiates the same shape of pattern irrespective of frequency - roughly apple-shaped in cross-section. What you are getting mixed up with is the panel aerials used on most base station sites. These are almost all multiple stacked element arrays which are designed to project the signal more outwards and not down/close in, and they amost always are spaced within the package to make them directional after a fashion. Many of them have 5 deg or 10 deg of electrical downtilt to give the close-in coverage, hence why you sometimes see the 'rabbit ears' tilted backwards where range is important for that particular location. -- Woody harrogate2 at ntlworld dot com Article: 220410 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: reciprocity and program zl_zin ?? Date: Sat, 24 Dec 2005 15:51:11 +0000 (UTC) Message-ID: References: <43ACD4E4.6080304@comcast.net> "dansawyeror" wrote in message news:43ACD4E4.6080304@comcast.net... > Thanks, > > Can you explain "transmission performance". Is it as measured and the source, > Zin? What is the range of Reflection Coeff? Is it a percentage? Is refl. coeff. > angle measured at Input? > =================================== "Transmission performance" is just a descriptive term relating to how well a line works compared with what is expected from it. It is not measurable. It is a way of referring to the very many different characteristics / properties / attributes of anything which performs. It can be good, poor, better, worse, etc., etc. The "reflection coefficient" is a dimension-less ratio, the mathematical relationship between line Zo and the line terminating impedance Zt. RC = ( Zt - Zo ) / ( Zt + Zo ). In general, both Zt and Zo are complex quantities and therefore RC possesses both magnitude and a phase angle. The magnitude can be anywhere between 0 and 1+Sqrt(2) although only in very exceptional circumstances will it exceed 1.0 It is never expressed as a percentage. The phase angle can lie in any of the 4 quadrants of a circle. i.e., it can have an angle anywhere between 0 and 360 degrees. When performing calculations it is more comvenient to refer to the angle as lying between -180 and +180 degrees. It can be referred to any point along a line. The angle, as in a vector, rotates as the reference point moves away from the termination towards the generator. As you are probably aware, RC is closely related to SWR. SWR can be calculated from RC. But RC cannot be calculated from SWR. This is because RC conveys twice the amount of information as SWR. When calculating SWR from RC half the information is lost. The angle of SWR disappears. SWR is the end of the line! Whether SWR is measured or calculated you can't go much further. But SWR / RC is a fascinating subject. ---- Reg, G4FGQ. Article: 220411 of rec.radio.amateur.antenna From: "Richard Fry" Subject: Effective Height of Vertical Antenna Date: Sat, 24 Dec 2005 10:58:53 -0600 Message-ID: <43ad7d96_3@newsfeed.slurp.net> Recently I bought a used copy of "Reference Data for Radio Engineers" published by Howard Sams in 1975. On page 27-6 the following applies to this topic: QUOTE The effective height of a grounded vertical antenna is equivalent to the height of a vertical wire producing the same field along the horizontal as the actual antenna, provided the vertical wire carries a current that is constant along its entire length and of the same value as at the base of the actual antenna. Effective height depends upon the geometry of the antenna and varies slowly with wavelength. For types of antennas normally used at low and medium frequencies, it is roughly 1/2 to 2/3 the actual height of the antenna. For certain antenna configurations, effective height can be calculated by the following equations. Straight Vertical Antenna: h =< 1/4 lambda Effective Height = [lambda/pi*sin(2*pi*h/lambda)]*sin^2(pi*h/lambda) where h = actual height END QUOTE This may be useful toward the earlier thread started here by Reg ("Back to fundamentals"), that went off in several directions. RF