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Current in antenna loading coils controversy (*sigh*)
I really begrudge the necessity of posting once more on this newsgroup,
and particularly on this thread. However, I'm dismayed and disgusted by postings being made by Yuri and Cecil in other forums in which they're claiming that measurements I made agree with theories and predictions they allegedly made, and that my measurements therefore validate their theories. (A quick scan of this thread shows that they even made the false claims here, after I had quit posting.) One of the postings is the following, made by Yuri on the eHam TowerTalk group, Nov. 21, topic "Trap Resonance": "Why don't you mention what W5DXP came up as explanation for Tom's errors, why don't you mention what W7EL measured and that it was what I predicted based on available information and was right on - the 5% difference for the base loading coil?" and this one, posted by Yuri on the EHam.net forum topic " Current in Antenna Loading Coils" on Jan. 7: "I will leave it here, as the rest of it. W7EL, author of EZNEC measured toroid coil and found that it HAS different current at its ends, roughly proportional to the part of antenna that it replaces." and this one, posted by Cecil on that same group on Jan. 12: "Roy's data clearly illustrates the phase shift through the coil. ARCCOS(Iout/Iin) gives an estimate of the phase shift (assuming forward current and reflected current are of equal magnitude). In Roy's experiment, Iout/Iin was about 0.95. ARCCOS(0.95) equals 18 degrees, an approximation for the phase shift through the coil." As you'll see below (or by looking up the original thread), the first of my two measurements, for an antenna shortened an equivalent of about 18 degrees, resulted in 3% current attenuation across the coil (not 5%), and zero phase shift (not 18 degrees). The second test, where the antenna was shortened more than 33 degrees, measured 5% current reduction and no phase shift. The method used in the above quote predicts more than 16% amplitude reduction and 33 degrees of phase shift for the second test. There's no way my data "clearly illustrates" Cecil's explanation. To say that it does is a pure fabrication. I feel compelled to respond to these fabrications, and put the record straight. I'll do it here, since this is where my measurements were originally posted. I made two sets of measurements of the current into and out of a toroidal inductor at the base of a vertical antenna. The details of the measurement method and the measurement results were posted here, on this newsgroup, on this thread. Pictures of the setup were posted on my web site, with a link posted here. Before I posted each set of measurements, I asked for predictions of the results, so that alternate theories could be tested. (I was criticized for doing this -- it seems that the preferred method of testing a theory is to look at the results first, then adjust the theory to fit.) Yuri made a prediction (actually, two different ones) for the first set of measurements that didn't accurately predict the results. When I calculated the predicted result for the second set of measurements using the same method he had used for the first prediction, he retracted any claim that the method would be valid. (Exact quotes are below.) He didn't make any prediction at all for the second set of measurements. Cecil made a number of vague predictions which he later contradicted or retracted. At the time the second set of measurements were posted, he had made no prediction at all. Perhaps Yuri and Cecil have, after the measurements were posted, developed theories to explain the results. As of the time the measurements were posted, they hadn't. I highly recommend that anyone considering their alternative theories to find where they have calculated the results which agree with my measurements (particularly the second one, which was designed to produce a testable difference), and how they derived the equations used for the calculation. Following is a summary of some of the exchanges between Yuri and me on this thread last November. The entire thread, " Current in antenna loading coils controversy" and variants, is available for viewing at groups.google.com. ------ Summary ------ Here's what really happened. The following quotes are directly from the google archives of the rraa thread. I made two sets of measurements. The first had the inductor connected at the base of a 33 foot vertical. But the vertical was mounted about 1/4" from a four foot pipe, which reduced the base reactance. Here, I was asking for predictions for my FIRST measurement -- the one with the vertical mounted on the pipe. Yuri posted on Nov. 9: "In that case, If the feedpoint current was at 0 deg of the radiator length, and coil replaces 18 deg of wire, the cos 18 deg = 0.951 which should make difference, drop in the coil current 5% (or half, 2.5 deg?) Providing current maximum is exactly at the bottom end of the coil." and later on Nov. 9: "Incidentally, I take it that your prediction for the setup I did measure includes an 18 degree phase shift of current from input to output of the inductor? Roy Lewallen, W7EL Yes, I used Cecil estimate/calculation and taking cos 18 = 0.951056516 which is 4.8943483%" So now we have his prediction, using the "cosine rule". The measurement I made showed about 3% current reduction from input to output, but with about 2% (the same amount within measurement error) also occurring when the antenna was replaced by a series resistor and capacitor -- that is, no antenna at all. So the 5% prediction was wrong. His prediction of 18 degrees phase shift, which wasn't present, was also wrong. When asked for the justification for the "cosine rule", he never offered any, so its origin remains obscure. However, I saw that the value was too small to be convincing, which is why I devised the second test. The second test used a more ideal antenna, with more of the antenna being "replaced" by the inductor. The "cosine rule" would predict more than 16% reduction, and more than 33 degrees of phase shift. Before I gave the results from the second measurement, I posted the predictions which had been made, as I understood them. Since Yuri had invoked the "cosine rule" for the first test, I naturally assumed it would also apply to the second. (This is simply applying the equation Yuri used in his Nov. 9 posting to the second antenna setup. It's also the equation now being used by Cecil, as shown in his quote from the eHam group.) So in my posting I said: (Quote from my posting on Nov. 11): "**Yuri's method predicts a reduction of output current magnitude of 16.5% and a phase shift of 33 degrees." to which Yuri responded, also on Nov. 11: "It is not my theory. My argument with W8JI and his followers: is the current in typical loading coil in quarter wave radiator same at both ends or does it drop with distance from the feedpoint. I have made temperature observations, W9UCW measured the difference, W5DXP provided some explanation. Based on Cecils analysis of data you provided, and on my understanding of the phenomena I guestimated drop in current in your setup. No theory, no mathematical procedure (yet) just attempt (using degrees replaced by coil in a radiator) at explanation of what is happening. I will measure things myself, try to verify previous measurements and then come up with conclusions and "theory". So far Cecils (and ON4UN book) theory seems to be closest to the truth. . . " So now, Yuri has disclaimed the "cosine rule". /He made no other prediction of the results of the second test./ In summary, Yuri first stated that the "cosine rule" can be used to calculate the current drop. That would have predicted over 16% current reduction in the second test. Then he retracted his claim that that theory would work, before the results from the second test were posted, and never made any other prediction. He never predicted the 5% result which was measured, as he's now claiming. And if you can find a numerical prediction anywhere in the thread which Cecil made and stayed with, my hat's off to you. $100 goes to the first person who can point to any prediction made by either Yuri or Cecil before the second measurement results were posted that predicted second measurement results of 5% magnitude and zero phase shift. (In the case of Cecil, this would have to be a prediction that wasn't later modified or retracted before the second set of results were posted.) My measurement results are consistent with the fact that the currents into and out of a physically small inductor are equal. The small magnitude difference I measured can be explained by stray capacitance on the order of 7 pF from the output to ground and/or the probe -- not an unreasonable amount to expect. In no way do my measurements support the odd theories being proposed by Cecil and Yuri, and any statement that they do is completely false. Roy Lewallen, W7EL |
Roy Lewallen wrote:
The second test, where the antenna was shortened more than 33 degrees, measured 5% current reduction and no phase shift. There's no way my data "clearly illustrates" Cecil's explanation. Roy, you obviously don't understand what that phase shift is all about. It is NOT a phase shift in the net current. It is a calculated phase shift in the forward current and reflected current components through the coil based on the net current ratios. And your data indeed does "clearly illustrate" my explanation. Please stop making false statements about what I said. You did NOT measure the phase angle about which I was talking. You apparently don't even know what I was talking about. The forward current into the coil and the reflected current out of the coil can be assumed to be in phase at resonance. So we have Ifwd at 0 deg superposed with Iref at 0 deg to obtain the net current into the coil. The forward current out of the coil lags the forward current into the coil by some phase angle (PA). The reflected current out of the coil lags the reflected current into the coil by the same phase angle (PA). PA is the phase angle I was talking about. You did NOT measure it! The net current into the coil is Ifwd at 0 deg plus Iref at 0 deg. The net current out of the coil is Ifwd at -PA plus Iref at +PA Assuming the net current distribution is a cosine, the phase angle by which the forward current and reflected current is shifted is ArcCos(Iout/Iin). For a 5% current reduction that would be ArcCos(0.95) = ~18 degrees. You did NOT even attempt to measure that phase angle. There is almost no phase shift in the net current through the coil which is exactly what you measured. I feel compelled to respond to these fabrications, and put the record straight. I'll do it here, since this is where my measurements were originally posted. How can you possibly set the record straight when you didn't even comprehend what I was saying? Here's what I have said: The net current is the sum of the forward current and reflected current. Both the forward current and reflected current undergo a phase shift through the coil. Assuming the forward current and reflected current are in phase on one side of the coil, that phase shift can be calculated using ArcCos(Iout/Iin) where those currents are the measured net currents. A 5% reduction in current is equivalent to an 18 degree phase shift. A 3% reduction in current is equivalent to a 14 degree phase shift. Your data matches my explanation exactly! The only data that doesn't match my explanation is Tom's toroidal coil which he asserts doesn't have any delay through it at all. I suspect his currents are of equal magnitude and opposite phase thus indicating a delay but confusing his magnitude data. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Roy Lewallen wrote:
$100 goes to the first person who can point to any prediction made by either Yuri or Cecil before the second measurement results were posted that predicted second measurement results of 5% magnitude and zero phase shift. Send it to my QSL.NET address. Yuri predicted the 18 degree phase shift which is calculated from the 5% magnitude, ArcCos(Iout/Iin). The phase shift measurement that you made is irrelevant and not the phase shift that was being discussed at the time. The net current phase shift that you measured can always be assumed to be close to zero since the forward current and reflected current are approximately equal and rotating in opposite phase directions. I explained all this and posted the information to my web page many weeks ago yet you still don't understand it. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil,
I've learned that there is no point in arguing with you. When confronted, you dodge, reverse your position, twist words, misquote, and, if all fails, insult. (An experienced reader of this group will recognize that this statement isn't itself an insult, but a statement of fact.) My statements stand. Let the readers review what you and I have written and decide. Your claim that my measurements support your odd theory is entirely false, and you are irresponsible if not delusional in claiming they do. I meant the $100 offer. I'll have a crisp bill in the mail to the first person that shows that you correctly predicted the results of my tests. Now, I'm finished wasting my time and energy on you. Roy Lewallen, W7EL |
Roy Lewallen wrote:
Your claim that my measurements support your odd theory is entirely false, and you are irresponsible if not delusional in claiming they do. Can Gurus just lie and get away with it? Your measurements support my "odd theory" 100%. With a current ratio of 0.95 to 1.0, ArcCos(0.95) = ~18 degrees of phase shift through the coil which is what I predicted. You didn't measure the correct phase shift. The one I asked you to measure was the phase shift through the coil *WITH NO REFLECTIONS PRESENT*. My "odd theory", residing on my web page for weeks now, clearly predicts that the net current will have the same phase angle at both ends of the coil. Your measurements of that phase angle proves that I was right. Based on my "odd theory", I predicted a 5% reduction in the current. Your measurements proves that I was right given the accuracy of your measurements. My "odd theory" is nothing but standard accepted physics. The net current equals the superposed sum of the forward current and reflected current according to Kraus and Balanis. It's hard to believe that you disagree. I meant the $100 offer. I'll have a crisp bill in the mail to the first person that shows that you correctly predicted the results of my tests. I predicted the 0.95 to 1.0 ratio. Yuri posted it. The calculated phase shift through the coil is 18 degrees. Pay up. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
No, Cecil, I'll give the money to anyone who _shows_ that Yuri made the
correct prediction, not someone who just says he did. The result of the first test (about 18 degrees equivalent antenna "replacement") was 3.1% reduction, with no phase shift, output to input. For that test, Yuri predicted 5% or 2.5% with 18 degrees of phase shift. See the direct quotes I just posted for evidence. For the second test, with 33 degrees of a more ideal antenna "replaced", Yuri made no prediction, and the result was 5.4% and no phase shift. The "theory" you and Yuri are fond of, and which you thoughtfully again show in your posting, predicts 16+%. Do you really think we're dumb enough not to notice you're using the "replacement" length from the first test to calculate the result from the second test, then crying "Aha!"? That you're completely ignoring the results from the second test and what your favorite equation would predict? Only a fool or an idiot would try to engage in a rational discussion with you, with your creative distortion and juggling of figures to suit your purposes. So I'm afraid I'm a bit of both -- but I'm trying to improve. Present evidence (you do understand the concept, don't you?) that Yuri -- or you -- correctly predicted the result of either test before the test result was posted, by giving the date and quote, and the money's yours. I'll be out of here unless the evidence is presented. I'm not holding my breath. Roy Lewallen, W7EL Cecil Moore wrote: Roy Lewallen wrote: $100 goes to the first person who can point to any prediction made by either Yuri or Cecil before the second measurement results were posted that predicted second measurement results of 5% magnitude and zero phase shift. Send it to my QSL.NET address. Yuri predicted the 18 degree phase shift which is calculated from the 5% magnitude, ArcCos(Iout/Iin). The phase shift measurement that you made is irrelevant and not the phase shift that was being discussed at the time. The net current phase shift that you measured can always be assumed to be close to zero since the forward current and reflected current are approximately equal and rotating in opposite phase directions. I explained all this and posted the information to my web page many weeks ago yet you still don't understand it. |
Roy Lewallen wrote:
No, Cecil, I'll give the money to anyone who _shows_ that Yuri made the correct prediction, not someone who just says he did. That 5% prediction was within your measurement accuracy which you quoted earlier. The result of the first test (about 18 degrees equivalent antenna "replacement") was 3.1% reduction, with no phase shift, output to input. You keep talking about the phase shift of the NET current. That is NOT what was being discussed. The phase shift that Yuri and I were talking about is the phase shift of the component forward and reflected waves. Because of your lack of comprehension, YOU MEASURED THE WRONG FRIGGIN' CURRENT!!! You cannot be allowed to make a stupid mistake like that and then try to turn it into an advantage for you. It is a no- brainer to predict that there's no phase shift in the NET current since the forward and reflected currents are approximately the same magnitude and rotating in opposite directions. My web page explains it all. For that test, Yuri predicted 5% or 2.5% with 18 degrees of phase shift. See the direct quotes I just posted for evidence. For the second test, with 33 degrees of a more ideal antenna "replaced", Yuri made no prediction, and the result was 5.4% and no phase shift. The "theory" you and Yuri are fond of, and which you thoughtfully again show in your posting, predicts 16+%. 5% equals a phase shift of 18 degrees. 3% equals a phase shift of 14 degrees. Why can't you get that through your head? Our predictions were, no doubt, within your measurement accuracy. ArcCos(0.95) = 18 degrees ArcCos(0.97) = 14 degrees Do you really think we're dumb enough not to notice you're using the "replacement" length from the first test to calculate the result from the second test, then crying "Aha!"? That you're completely ignoring the results from the second test and what your favorite equation would predict? You obviously still don't comprehend. The phase shift is a *calculated* value based on the current ratio. If you had bothered to read my web page, you wouldn't be so ignorant of what I have been saying. "Replacement" length does not appear anywhere in my equations and is irrelevant to those equations. You remind me of the guy who got extremely angry when he thought someone had stolen his expensive sunglasses only to discover them on his own head. When (and if) you comprehend the error of your ways, I expect an apology. A predicted current difference of 5% equals a phase shift of 18 degrees in both the forward and reflected currents. According to the laws of physics, it cannot be anything else, given the assumptions. You cannot have a current difference of 5% and zero phase shift in the forward current. That's technically impossible but you didn't even recognize it. A predicted current difference of 3% equals a phase shift of 14 degrees in both the forward and reflected currents. Present evidence (you do understand the concept, don't you?) that Yuri -- or you -- correctly predicted the result of either test before the test result was posted, by giving the date and quote, and the money's yours. You have already admitted the estimate was close. A 5% prediction corresponds to a phase shift of 18 degrees. A 3% prediction corresponds to a phase shift of 14 degrees. Your lack of comprehension is no excuse for you welching on your bet. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Tue, 13 Jan 2004 01:23:33 -0600, Cecil Moore
wrote: Roy Lewallen wrote: Do you really think we're dumb enough not to notice snip Your lack of comprehension is no excuse (*sigh*) indeed. You boys need to get a room and do this in private. |
Richard Clark wrote:
You boys need to get a room and do this in private. Bottom line - The original question was: Is the current at the bottom of a real-world mobile bugcatcher coil equal to the current into the stinger. The answer is NO! -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Why would that be? I find it fascinating.
Do you mean you can understand the tripe? |
Roy, W7EL wrote:
"When asked for the justification of the "cosine rule", he never offered any, so its origin remains obscure." It comes from the similarity of a standing wave antenna to a transmission line. It isn`t a prominent feature of antenna texts because energy isn`t confined to an antenna as it is to a transmission line. Antenna behavior is more complicated. Terman refers the reader to his transmission line section to explain standing wave antenna action innstead of making a detailled explanation in his antenna section. Maybe he was limited in number of pages. The explanation is available from a collection of sources. From "Transmission Lines, Antennas, and Wave Guides" by King, Mimno, and Wing, page 93: "---the distribution of current in antennas with h=WL/4 and with a wide range of radii can be represented quite accurately by: Iz = Io cos beta(z) beta(z) is the distance from the antenna input in degrees. It is obvious that the current must reverse directions at the open circuit end of the antenna. This results in a total of forward and reflected current of nearly zero while 1/4-wave back from the open circuit, a current maximum results. Kraus says that at the center of a 1/2-wavelength dipole, the effect of wave cancellation is least and radiation is maximum perpendicular to the wire at the center of the dipole, or words to that effect. The same is true of the 1/4-wave vertical which along with its reflection in a ground plane constitutes a 1/2-wavelength dipole. Kraus also says that the tip cancellation accounts for the dipole radiation pattern shaped as a doughnut impaled at the center of a dipole. Again, these are my interpretations of Kraus` words as I remember them. Best regards, Richard Harrison, KB5WZI |
Richard Harrison wrote: Roy, W7EL wrote: "When asked for the justification of the "cosine rule", he never offered any, so its origin remains obscure." It comes from the similarity of a standing wave antenna to a transmission line. It isn`t a prominent feature of antenna texts because energy isn`t confined to an antenna as it is to a transmission line. Antenna behavior is more complicated. Terman refers the reader to his transmission line section to explain standing wave antenna action innstead of making a detailled explanation in his antenna section. Maybe he was limited in number of pages. The explanation is available from a collection of sources. From "Transmission Lines, Antennas, and Wave Guides" by King, Mimno, and Wing, page 93: "---the distribution of current in antennas with h=WL/4 and with a wide range of radii can be represented quite accurately by: Iz = Io cos beta(z) beta(z) is the distance from the antenna input in degrees. It is obvious that the current must reverse directions at the open circuit end of the antenna. This results in a total of forward and reflected current of nearly zero while 1/4-wave back from the open circuit, a current maximum results. Excellent. Roy is telling us that beta(z) at one end of the coil is essentially equal to beta(z) at the other end of the coil. And Reg might have us believe it's the length of the bobbin that matters in this regard. 73, Jim AC6XG |
Cecil Moore wrote: Jim Kelley wrote: Richard Harrison wrote: Iz = Io cos beta(z) Excellent. Roy is telling us that beta(z) at one end of the coil is essentially equal to beta(z) at the other end of the coil. Which requires a lossless, non-radiating coil with zero capacitance. Just out of curiosity, to which of those characteristics do you attribute the phase delay? 73, Jim AC6XG |
Richard Harrison wrote:
Roy, W7EL wrote: "When asked for the justification of the "cosine rule", he never offered any, so its origin remains obscure." Roy, I posted a reference for the cosine rule weeks ago. Perhaps you missed it. If you had read it, you wouldn't have wasted your time measuring the phase angle of the net current through a loading coil. My "odd theory" is based on Kraus' treatment of the cosine rule. See below: It comes from the similarity of a standing wave antenna to a transmission line. It isn`t a prominent feature of antenna texts because energy isn`t confined to an antenna as it is to a transmission line. Kraus says that at the center of a 1/2-wavelength dipole, the effect of wave cancellation is least and radiation is maximum perpendicular to the wire at the center of the dipole, or words to that effect. The reference for the cosine rule is from _Antennas_For_All_Applications_, by Kraus & Marhefka, 3rd edition, pages 463-465, section 14-3, Current Distributions, Figure 14-2, Relative current amplitude and phase along a center-fed 1/2WL cylindrical antenna. This is where my "odd theory" comes from. Kraus says: "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, and that the phase is constant over a 1/2WL interval, changing abruptly by 180 degrees between intervals." Kraus is making the assumption that the forward current is equal to the reflected current such that their superposition sum has constant phase. Setting the center of the dipole as the origin and normalizing the feedpoint current to 1.0, the current at any point on the dipole can be calculated as the cosine of 'x' where 'x' is degrees away from the center. Thus, if one knows the normalized current at any point on the dipole, one can calculate the number of degrees one is away from center using ArcCos(I). This is how I calculate the number of degrees associated with a loading coil. Assuming the input current is 1.0 and the output current is 0.95, ArcCos(0.95) = 18 degrees. All this "odd theory" is based on Kraus. I suggest anyone who thinks this is "odd theory" take time out and read Kraus. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Jim Kelley wrote:
Richard Harrison wrote: Iz = Io cos beta(z) Excellent. Roy is telling us that beta(z) at one end of the coil is essentially equal to beta(z) at the other end of the coil. Which requires a lossless, non-radiating coil with zero capacitance. Where can I get one of those? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Jim Kelley wrote:
Cecil Moore wrote: Which requires a lossless, non-radiating coil with zero capacitance. Just out of curiosity, to which of those characteristics do you attribute the phase delay? Speed of light? :-) Seems the primary cause of the phase delay would be the capacitance. In many ways, this discussion has become ridiculous. On 440 MHz, one inch of wire is ~13 degrees. Some gurus would have us believe that a physically small one inch coil is zero degrees?????? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: Which requires a lossless, non-radiating coil with zero capacitance. Just out of curiosity, to which of those characteristics do you attribute the phase delay? Speed of light? :-) The finite speed of light though a finite length of wire, yes. Seems the primary cause of the phase delay would be the capacitance. With regard to coils, I think inductance is probably the more relevant parameter. It's proportional to the number of turns and the length of each turn of wire, and inversely proportional to the length of the bobbin. 73, Jim AC6XG |
Jim Kelley wrote:
With regard to coils, I think inductance is probably the more relevant parameter. It's proportional to the number of turns and the length of each turn of wire, and inversely proportional to the length of the bobbin. Is that "bobbin" a part of a coil winding machine? Coil form? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil Moore wrote:
Jim Kelley wrote: With regard to coils, I think inductance is probably the more relevant parameter. It's proportional to the number of turns and the length of each turn of wire, and inversely proportional to the length of the bobbin. Is that "bobbin" a part of a coil winding machine? Coil form? It's a spool-like object used to constrain the length and diameter of a coil of wire to prescribed values. 73, Jim AC6XG |
Esteemed Antenna Gentlemen.
I am sorry I could not participate in the heated discussions and do experiments and measurements in the past few weeks. I was QRL, weather was lousy and I caught the nasty flu that I hope to shake off in the South next few days. It looks to me like some made statements (contrary to facts) and now are defending them or going all out to prove they are right. Rather than concentrating on the original question, is the current in the antenna loading coil in typical mobile quarter wave whip same or different on its ends, we are drifting to side shows like how precisely you measured it, what is your guess, theory, toroids etc. To recap, W9UCW measured, I witnessed and new that bottom of the coils get hotter than top ergo, more current at the bottom. W8JI attacked that it can't be, he stated it HAS to be equal, Kirchoff, bla, bla. (Now it is maybe not so equal, length of coil, stray capacitance, phase of moon, but it is the same, even when it isn't. Go figure.) W8JI also proved that he lied when stated that he measured thousands of (what?) coils and they all had equal current. Now he posted some measurements and proved that he was wrong, he measured differences. He doesn't describe his setup, and as Cecil explained, one can rig the coils to have the same current, but in a center loaded resonant quarter wave vertical - no way. Now we drifted to ferrites, we guessed Roy's difference and he measured it, THERE WAS A DIFFERENCE 5% at the base. Is difference not a difference? The first experiment I will do is the "thermal test" - I will take Hustler 80m coil, I have two fishing tank LCD strip thermometers ($2.50 in any pet store) I will stick them on the coil at the bottom, at the top, or in between. I will fire TX to it and video tape the change in temperature with timer running. Really smart gurus should be able to calculate the power and currents from that. If gurus object that thermometers are disturbing the coil. Then the thermal test No2 will be done. I will put higher power to it and see the coil unshrink the tubing from the bottom up. I have done it before and it made me true believer in the phenomena. Next test will be with thermocouple ammeters and next with current probe similar (but better) as W8JI used on his tests and showed on the web page. Then we will try to correlate it with our "obscure theories", then we will write the nice, detailed article that hopefully will help to understand the thing for the other side of the fence gurus. The proof is in reality, W9UCW done it, but that CAN'T BE? Thanks Cecil and others for Herculean task and effort in digging out references and trying to 'splain it. Looks like Krause and others are wrong, but old Belrose error perpetuated in ARRL Antenna Book is right, oh and EZNEC modeling 0 size coil and loading stub differently is right too. W8JI used it as a proof that current can be increasing from the base up to the coil. How come that straight piece of wire (as antenna) can exhibit different current along its length (where is Kirchoff) but when you insert the coil and retune it, that coil "refuses" for current to taper? Take the coaxial wound chokes, coil wound of coax at the antenna terminals can reduce the current flowing in the shield. We know that, or are we going to deny that? How is that COIL different that it has different RF current at its ends? That you can check even with MFJ current meter. I hope that weather gets better, flu goes away and life gives me more time. In the mean time, if you are contemplating to get TenTec Orion, read my first part of review on my web www.K3BU.us 73 Yuri |
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Richard Clark wrote:
What does that prove except you are having either a rough time, or delusions of accuracy - take your pick as it seems both side of this argument are looking through the bottom of the same glass. When measuring only current magnitude, to detect a 5 degree phase shift through a base loading coil requires differentiation between 1 amp of RF on one end and 0.996 amps of RF on the other end. Are you saying that the measured 1 amp at both ends might be suspect? :-) -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Bill:
[snip] No, at my level of understanding they both sound compelling. It's the human interaction I find interesting. There's something about highly educated people getting down in the mud and rasslin' with each other... :-) -- Bill, W6WRT [snip] What are you thinkin man! Who wants to watch to old codgers like Roy and Cec rasslin in the mud? We all wanna see Britney and Madonna doing that, not Roy and Cec! -- Peter K1PO Indialantic By-the-Sea, FL |
Peter O. Brackett wrote:
We all wanna see Britney and Madonna doing that, not Roy and Cec! Cec agrees. Probably, so does Roy. Where can I buy tickets? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Richard Clark wrote in message . ..
On 14 Jan 2004 03:13:25 GMT, oUsama (Yuri Blanarovich) wrote: How come that straight piece of wire (as antenna) can exhibit different current along its length (where is Kirchoff) Sheesh², Kirchhoff is explicitly violated by employing his laws at wavelength scales. Kirchhoff NEVER said anything about current into/out-of a device (which by necessity is of some obvious dimension). Rather, his current law speaks of a POINT (which is dimensionless). In failing to have come to terms with this simple issue, the entire course of, what, 600 postings yields little more than white noise. If you want to talk Kirchhoff and nets, get your definitions right. It is his voltage law that describes in terms of devices (across a resistor, between two points, what have you). 73's Richard Clark, KB7QHC Check out this gentlemen: http://www.scientia.org/cadonline/Ph.../kirchoffq.ASP Yeah, it's very simple, isn't it? But if you consider that dQ/dt=I AT A SPECIFIC POINT, then it's all about conserving Coulombs, it seems to me. Kirchoff's current law applies when you have a junction between multiple current-carrying paths, and it applies more to a DC current situation. The law isn't violated when you consider the AC current running through a capacitor, otherwise you would demand that there be a current running through the dielectric, which there is clearly not (the coulombs never travel across it). Likewise, an antenna can store coulombs, more at the ends of the radials, and can therefore have a different AC current distribution at the different points on the antenna. So Kirchoff's law stands the test of conserving coulombs, but is easier to understand in a DC situation. Slick |
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