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Current across the antenna loading coil - from scratch
John Popelish wrote:
Cecil Moore wrote: What does it mean to the E-fields and H-fields to say the voltage is leading the current? It means that the current at both ends of the coil was delayed (relative to its phase if the coil had not been there). It means that there was a voltage difference across the ends of the coil that drove that current through the coil. In order to avoid any delay through the coil, you propose a delay in the one inch of wire at the bottom of the coil? Does that really make sense to you? How is this magic delay accomplished? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Gene Fuller wrote:
You spent a lot of time developing the "10 degree" model for the bugcatcher coil. Yes, it was a waste of time since I didn't accomplish the goal of eliminating reflections. The phase angle between the source voltage and source current is 71 degrees. That proves that I failed to eliminate reflections. You keep referring everyone to the now famous gif image on your web page. The question becomes why is EZNEC correct in supporting your position at some times and incorrect when it does not support your position at other times? EZNEC doesn't differentiate between standing waves and traveling waves. The user has to ensure there are no reflected waves. I failed in that task. It's no big deal. I fail quite often. My position is technical facts and accuracy. What is your position? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
K7ITM wrote:
Like I posted earlier today, Tom, all of this provides an interesting window into Cecil's mind. Tom, I find it strange that you are defending your violation of newnews attribution guidelines. What other unethical activities do you defend? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: What does it mean to the E-fields and H-fields to say the voltage is leading the current? It means that the current at both ends of the coil was delayed (relative to its phase if the coil had not been there). It means that there was a voltage difference across the ends of the coil that drove that current through the coil. In order to avoid any delay through the coil, you propose a delay in the one inch of wire at the bottom of the coil? Does that really make sense to you? How is this magic delay accomplished? Exactly the way it is accomplished if you apply AC to an LC "L" low pass filter that droves a resistor load. The short antenna acts as the capacitor (in parallel with losses and radiation) in the circuit. It is resonated with the series inductor so both the inductance and capacitance cancel, so the source drives only the losses and radiation. Power factor corrected. If you don't believe me, simulate it with EZNEC. Connect a source to a parallel combination of C and R. Record the phase of the current with respect to the voltage (the current will lead). Then add a series inductance that cancels the capacitance, and the current will be delayed till it matches the phase of the applied voltage. Power factor corrected. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote: Yuri Blanarovich wrote: What we are saying that the loading coil appears to replace "missing" electrical degrees of the radiator in order to make it resonant, ... W8JI says we are correcting the power factor. Every EE knows that correcting the power factor involves shifting the phase, i.e. the coil cannot correct the power factor without providing a phase shift. This is another area where you fall right square on your face. An inductance changes the relationship between phase of voltage and current, NOT current through the inductance from terminal to terminal. You either know that and are intentionally avoiding it to save face, or you need to brush up on basic theory. The whole controversy is that "gurus" claim current doesn't drop across the coil, while we say that it does, ... Yuri again distorts fact. What everyone is saying is there can be a current change, but it is not caused by standing waves or missing antenna area. It is caused by displacement current, and so can have a wide range of change in a given antenna. Please write that down Yuri, and keep it in front of you so you don't forget again! 73 Tom |
Current across the antenna loading coil - from scratch
On Wed, 12 Apr 2006 21:01:25 GMT, Cecil Moore
wrote: Richard Clark wrote: Cecil Moore wrote: It doesn't cost anything to be paranoid. :-) You must have a Xerox bulk copy rate. I got a free printer with my new Dell computer. Now you need a free scanner, and you are truly paranoid by your own tally. |
Current across the antenna loading coil - from scratch
"Roy Lewallen" wrote in message ... Yuri Blanarovich wrote: Oooops, carefull here. As far as I know, nobody has claimed that inserted loading coil replaces the "missing" degrees of the radiator in terms of providing magical properties that would look like that "replaced" portion of the antenna, or make the antenna act like 90 degree full size physical radiator. Agreed, it's not quite stated as such. Here are some statements which were made: From your web page http://www.k3bu.us/loadingcoils.htm, in bold type: "In summary: The current in a typical loading coil in the shortened antennas drops across the coil roughly corresponding to the segment of the radiator it replaces." By Cecil, on March 5, on this newsgroup: "A loading coil thread is climaxing over on qrz.com. I have used EZNEC to generate a graphic which shows a 3/4WL vertical and a similar 1/2WL vertical with a ~1/4WL loading coil. The loading coil is a wire helical coil containing (surprise) roughly 1/4WL of wire. The coil does a good (not perfect) job of replacing 1/4WL of wire. Many things can be gathered from observation of the current reported by EZNEC for the two antennas. The coil occupies roughly the same number of degrees of the antenna as the wire it replaces. The current at the top and bottom of the coil is roughly the same as the current at the two ends of the wire it replaces. Is the coil an exact replacement? Of course not." What we are saying that the loading coil appears to replace "missing" electrical degrees of the radiator in order to make it resonant, that is back to 90 electrical degrees (has to be in order to resonant), which rest of the existing "straight" radiator forces it to do (+/-). It's getting muddier and muddier just what you mean by "replace". Nobody has questioned that a loading coil makes the antenna resonant; that's its purpose. But that's simply an impedance transformation property which can be accomplished well away from the antenna by many different methods. Roy, the above are the attempts to illustrate and add some more to understanding and reasoning why the current across (alonng) the loading coil, roughly half way or 2/3 up the resonant quarter wave radiator is larger at the bottom and drops about 40 - 60% at the top. While one side argues that it is (almost) the same, we argue that it drops. That is the argument and not detours to degrees, phasors, and rest of the mud that was rehashed here. Radiation properties and efficiency of the loaded antenna is proportional to the area under the current curve. It is obvious to anyone comparing the area under the current curve of full size quarter wave radiator vs. loaded radiator that there is huge difference in area under the curve and performance, efficiency, which is known and been verified by numerous measurements. HOW the current curve is modified by different loadings and position along the radiator is important in knowing how the current distribution curve along the radiator is modified. I agree with all this. I'm glad you've clarified this for the benefit of posters like the one to whom my recent posting was directed. The whole controversy is that "gurus" claim current doesn't drop across the coil, while we say that it does, therefore making the area under current curve above the coil smaller and effciency of loaded antenna worse than they believe and insist on. I don't think you'll have any trouble winning your arguments against your imaginary "gurus", whomever and whatever they might be. Over two years ago I made careful measurements which showed a current difference between the top and bottom of a loading coil. Cecil posted an EZNEC model on his web site showing a substantial difference. I've commented on it several times, explaining the reason for the difference, and modifying the model to illustrate the explanation. If I remember correctly you inserted the coil at the base and I am not sure if it was resonant quarter wave radiator. Can you describe the setup, length and frequencies used? You should try to use quarter wave resonant radiator with coil about 1/2 to 2/3 up the mast and tell us what the current values are. W9UCW has pictures and data measured, we should try to emulate this situation, that is the object of controversy. Cecil mentioned cases when current can be the same, or lower at the top, or bottom, depending where the same coil is placed in relation to the standing wave and current distribution on the radiator. Are you denying that this is the case or something wrong with W9UCW test setup and results? The controversy is in the explanation of the difference. It simply doesn't require Cecil's theories. I've never been able to tell exactly what your theory is, if you indeed have one. The controversy is about the claims that the current at the ends of the typical loading coil is the same or different in range of 40 -60% drop. Its not my theory, it is the reality that we are trying to bring forth and correct misconceptions that are obviously floating around since 1953. My approximation and explanation (latest) I mentioned is in one of my posts in reply to W8JI "arguments" (to do with impedances). Again, when applied in modeling programs, wrong assumption will produce erroneous results, which will be magnified in multielement antenna designs. So the "gurus" basically ignore behavior of coil in the standing wave environment along the loaded radiator, where the current drops from max at base to zero at the tip, but coil would magicaly resist that, because, bla, bla, bla.... (see their "reasons") Would you name these "gurus" so we can read their postings and see what you're talking about? Mostly the "equal current camp". So while everyone knows (?) that standing wave current drops acros (along) the wire (all the antenna books show that), but it is "impossible" to drop along the coiled wire (real inductance - coil, loading stub). Reality and measurments prove that, but according to them "it can't be so". I am already gathering necessary hardware to do more experiments, measurements to show what is really happening, and will prepare articles how to model and apply it to antenna design. I would challenge the "unbelievers" to join me and repeat the tests, to see wasaaaap. You'll be surprised when everyone agrees that there's a current difference between the top and bottom of the coil. Unless your "gurus" show up, whomever they are. I've already made a test and posted the results, over a year ago. When it failed to show a current difference anywhere near the number of degrees it "replaced", your complaint was that I was using an inductor which was too small physically. So obviously your theory works only on certain size inductors. Once you or Cecil has the theory fully worked out, it should be able to not only tell us what the current difference between top and bottom should be, but also how physically large an inductor must be before the theory works. And why it doesn't work for physically small inductors. I have not verified it, but W9UCW claims using ferite inductor and got very similar results. I believe your test, you used coil near the base. I will run test with different inductors from bugcatcher type, "no good" Hustler, to ferite and in different positions. Those of us stuck with old fashioned conventional theory can explain the drop for small as well as large coils, so you folks have a bit of catching up to do. Looks like the size of the coil has small effect on current variation (unless high resistance). Position of the coil in relation to current distribution along the radiator would cause equal (special case), less on the top of coil or more, depending where on the standing wave curve coils is located. In our case we are arguing about 2/3 up the resonant radiator. I think a lot of the experimental work can be done by modeling. I'd be interested in hearing of any cases where measured results differ significantly from EZNEC results. Incidentally, your web page is a bit outdated in that respect, apparently being written before EZNEC v. 4.0 was available with its automated helix creation feature. Now with solenoid generation in EZNEC 4.0 it helps to get away from the lumped inductance and it shows that there is current drop, reflecting situations in question. Also the loading stub produces similar results. Cecil showed the cases and with different positions along the current curve, demonstrated in EZNEC huge differences in current at the ends of the coil. But this is getting strangely ignored and instead we get all kinds of "reasons" why it can't be. I am sorry I dropped out of this due to AOL dropping NG, and I thought that reality would be understood by now. Only when Cecil told me that subject flared up again and nothing changed, I rejoined the discussions. I think really at this point, it is beating the dead horse. I will do the tests and write it up. I will try to corellate the tests with modeling in EZNEC. If someone denies the reality, that's their choice. I will post the progress on my web page. I can't stomach W8JI "exchanges" any more. No answer to questions or following the points, just twist and jive. Roy Lewallen, W7EL I didn't look it up, but is there way in EZNEC to know or calculate the inductance of modeled solenoid? Or better, specify the inductance and let the EZNEC "make" the coil of prescribed diameter and TPI? 73, Yuri Blanarovich, K3BU |
Current across the antenna loading coil - from scratch
David G. Nagel wrote:
Wes Stewart wrote: Responding to no one in particular. This is starting to make me miss the shorter Fractenna threads. Phil, comeonback good buddy. They certainly made more sense. Dave N Although there is a large difference - this is an arument over how soemthing that works works. The other was about _whether_ the thing works. tom K0TAR |
Current across the antenna loading coil - from scratch
John Popelish wrote:
If you don't believe me, simulate it with EZNEC. Connect a source to a parallel combination of C and R. Record the phase of the current with respect to the voltage (the current will lead). Then add a series inductance that cancels the capacitance, and the current will be delayed till it matches the phase of the applied voltage. Power factor corrected. The "current will be delayed"? That cannot be, according to W8JI and W7EL. They say there is no more delay through a 6" coil than through a 6" wire. That's what the argument is all about. Instead of the current being delayed, their voltage jumps ahead in time at greater than the speed of light in order to correct that power factor. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: If you don't believe me, simulate it with EZNEC. Connect a source to a parallel combination of C and R. Record the phase of the current with respect to the voltage (the current will lead). Then add a series inductance that cancels the capacitance, and the current will be delayed till it matches the phase of the applied voltage. Power factor corrected. The "current will be delayed"? Compared to the phase of the current without the inductor being in series." That cannot be, according to W8JI and W7EL. They say there is no more delay through a 6" coil than through a 6" wire. You are talking about delay from one end of the coil to the other. I am talking about delay, compared to the same circuit without the inductor in place. See the difference? That's what the argument is all about. Not from where I am watching. Instead of the current being delayed, their voltage jumps ahead in time at greater than the speed of light in order to correct that power factor. Good one. Pull the other. |
Current across the antenna loading coil - from scratch
Yuri Blanarovich wrote:
Roy, the above are the attempts to illustrate and add some more to understanding and reasoning why the current across (alonng) the loading coil, roughly half way or 2/3 up the resonant quarter wave radiator is larger at the bottom and drops about 40 - 60% at the top. While one side argues that it is (almost) the same, we argue that it drops. That is the argument and not detours to degrees, phasors, and rest of the mud that was rehashed here. You still haven't told us who this "side" is that argues that the current is the same at the bottom and top. I assume it's those unnamed "gurus" who you haven't identified. It shouldn't be a problem to show that the other "side" is wrong if it doesn't exist. If I remember correctly you inserted the coil at the base and I am not sure if it was resonant quarter wave radiator. Can you describe the setup, length and frequencies used? You should try to use quarter wave resonant radiator with coil about 1/2 to 2/3 up the mast and tell us what the current values are. W9UCW has pictures and data measured, we should try to emulate this situation, that is the object of controversy. Cecil mentioned cases when current can be the same, or lower at the top, or bottom, depending where the same coil is placed in relation to the standing wave and current distribution on the radiator. Are you denying that this is the case or something wrong with W9UCW test setup and results? You can find my earlier postings at groups.google.com. The results you're asking about were posted on Nov. 11, 2003. You can find your own comments about my measurements there also, on the same date. I'm sorry, but I don't have time to try and model or carefully analyze W9UCW's results. The results for a toroid show more current difference than I'd expect, and suspect that's due to the shunt capacitance of the physically large meters he was using. Before, you complained because the coil wasn't physically long enough. Now you want it placed somewhere else along the radiator. Sorry, after the reaction I got to my previous test, I have no interest at all in making additional ones. The controversy is about the claims that the current at the ends of the typical loading coil is the same or different in range of 40 -60% drop. Its not my theory, it is the reality that we are trying to bring forth and correct misconceptions that are obviously floating around since 1953. My approximation and explanation (latest) I mentioned is in one of my posts in reply to W8JI "arguments" (to do with impedances). The only posting I see that fits that description is your posting on this thread on April 7. As I read it, you say that as you put a coil higher and higher in an antenna, the inductance required to maintain resonance increases, and the difference in current between the bottom and top of the coil increases as the coil is made larger. I don't see any values or way of calculating them, but don't have any disagreement with the qualitative statements you made there. [Yuri wrote:] Again, when applied in modeling programs, wrong assumption will produce erroneous results, which will be magnified in multielement antenna designs. So the "gurus" basically ignore behavior of coil in the standing wave environment along the loaded radiator, where the current drops from max at base to zero at the tip, but coil would magicaly resist that, because, bla, bla, bla.... (see their "reasons") [I wrote:] Would you name these "gurus" so we can read their postings and see what you're talking about? [Yuri wrote:] Mostly the "equal current camp". I take that as a "no", you can't name the "gurus". The advantage of arguing against imaginary "gurus" is that you can have them claim anything you want. It shouldn't have taken you so many postings to prove them wrong. I have not verified it, but W9UCW claims using ferite inductor and got very similar results. I believe your test, you used coil near the base. I will run test with different inductors from bugcatcher type, "no good" Hustler, to ferite and in different positions. Then you and Cecil have quite different theories, it seems. His doesn't predict the drop I measured. Those of us who are tired of the endless arguments should sit back and let you and Cecil go at it until you come to an agreement. Looks like the size of the coil has small effect on current variation (unless high resistance). Position of the coil in relation to current distribution along the radiator would cause equal (special case), less on the top of coil or more, depending where on the standing wave curve coils is located. In our case we are arguing about 2/3 up the resonant radiator. I don't know who "we" is. The technical theory I subscribe to doesn't require any particular placement of the coil. Now with solenoid generation in EZNEC 4.0 it helps to get away from the lumped inductance and it shows that there is current drop, reflecting situations in question. Also the loading stub produces similar results. Cecil showed the cases and with different positions along the current curve, demonstrated in EZNEC huge differences in current at the ends of the coil. But this is getting strangely ignored and instead we get all kinds of "reasons" why it can't be. I replaced the whip in one of Cecil's models with a lumped RC and got the same result. Then I eliminated the ground and reduced the current drop to near zero. I've commented on that on several occasions. That certainly doesn't constitute "strangely ignoring" Cecil's model. I am sorry I dropped out of this due to AOL dropping NG, and I thought that reality would be understood by now. Only when Cecil told me that subject flared up again and nothing changed, I rejoined the discussions. I think really at this point, it is beating the dead horse. I will do the tests and write it up. I will try to corellate the tests with modeling in EZNEC. If someone denies the reality, that's their choice. I will post the progress on my web page. Let us know when it's available. Hopefully it'll actually happen this time. Again, I'll be interested in knowing of any significant difference between modeling and measurement results. I can't stomach W8JI "exchanges" any more. No answer to questions or following the points, just twist and jive. Funny, that's just the way most of your postings appear to me and, I'm sure, to Tom. I didn't look it up, but is there way in EZNEC to know or calculate the inductance of modeled solenoid? Or better, specify the inductance and let the EZNEC "make" the coil of prescribed diameter and TPI? The answer to your second question is no. To your first, yes. What I've done is model the inductor in free space with ends extended to the helix axis (an option when creating it). Put a wire end-to-end down the center of the coil with a source in the middle. Src Data will show you the reactance, from which you can get the inductance. This seems to work reasonably well provided that the frequency is low enough that the coil is well below self resonance and low enough that it doesn't radiate much but high enough that NEC-2 doesn't have trouble with the loop size. If it shows good results in the Average Gain test, it's probably ok. Roy Lewallen, W7EL |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
Mike Coslo wrote: Yuri Blanarovich wrote: Check my article that describes the controversy, shows some proof of reality and then efforts of the "gurus" to deny it and "reason" why it can't be so. http://www.k3bu.us/loadingcoils.htm The problem is that back in 1953 in QST article there was erroneous conclusion/statement made, which propagated through the books, until W9UCW measured the current across the loading coils and found that there is significant drop from one end to the other, and the rest is (ongoing) history Hmm, certainly it would seem to make sense that: The current in a typical loading coil in the shortened antennas drops across the coil roughly corresponding to the segment of the radiator it replaces. Quote from your page. I would not expect anything else. If the loading coil is making the antenna act like a physically longer antenna, other "qualities" of that simulation are likely to be similar. Is there a reason why the coil would *not* do this? Yes, many, and they've been discussed here at length. Okay. Seems like a more constructive use of bits than most of this thread 8^) That this concept is wrong can and has been shown by theory, modeling, and measurement. I made and posted measurements on this newsgroup in November 2003 which demonstrated clearly that the presumption is false. Okay. It looks like we have at least some measurements that differ. Any idea why that would be? Do you remember the name of the thread? The loading coil isn't making the antenna act like a physically longer antenna. In the extreme case of a physically short inductor at the feedpoint, it's simply modifying the feedpoint impedance and has no effect whatever on the antenna's radiation. Would the inductor then be best right past the feedpoint? Certainly having the inductor at the far end, or in the middle seems like a bad place for it. (not talking about trap antennas) As the inductor gets longer, it does become some part of the antenna, but adding an inductor which resonates, say, a 45 degree physical radiator doesn't make the antenna act like a 90 degree physical radiator. - 73 de Mike KB3EIA - |
Current across the antenna loading coil - from scratch
"Roy Lewallen" wrote K3BU wrote: I can't stomach W8JI "exchanges" any more. No answer to questions or following the points, just twist and jive. Funny, that's just the way most of your postings appear to me and, I'm sure, to Tom. Then there is your answer to who is "gurus" and who is "we". "Gurus" know that current in loading coil is the same. "We" know, measured it properly and argue that that is significantly different. I am sorry, you are wrong. I tried to follow some stepts to get to the point, Tom ignores my points and jumps to lecture how, bla, bla... I am really done here, you guys can believe what you want. Just that reality doesn't jive with your "can't be". 73 Yuri |
Current across the antenna loading coil - from scratch
Mike Coslo wrote:
Roy Lewallen wrote: That this concept is wrong can and has been shown by theory, modeling, and measurement. I made and posted measurements on this newsgroup in November 2003 which demonstrated clearly that the presumption is false. Okay. It looks like we have at least some measurements that differ. Any idea why that would be? The amount the magnitude of the current drops across an inductor is determined primarily by the amount of inductance and the capacitance from the inductor to ground or the other half of the antenna. This is easily explained by simple lumped constant circuit theory. There's also some variation due to radiation and imperfect coupling between turns. In the extreme case of a very loose helix, coupling is poor and radiation is high, so the helix acts more like a wire than an inductance. This requires a more complex analysis, but that's also in the realm of well known phenomena. With this wide variation in physical possibilities, different results can't be avoided. What some of us have tried to do is explain why the results occur. I don't know of differing results from the same physical setup, but it could surely happen. Making good measurements isn't a trivial task. Do you remember the name of the thread? Current in antenna loading coils controversy (long). I made two sets of measurements. The second was posted on Nov. 11, 2003 and the first a few days earlier. The loading coil isn't making the antenna act like a physically longer antenna. In the extreme case of a physically short inductor at the feedpoint, it's simply modifying the feedpoint impedance and has no effect whatever on the antenna's radiation. Would the inductor then be best right past the feedpoint? Certainly having the inductor at the far end, or in the middle seems like a bad place for it. (not talking about trap antennas) Generally not, but it depends on several factors. Moving the coil upward increases the radiation resistance of the system, which improves efficiency in the presence of ground loss. However, it also requires a larger coil, so the coil's resistance is greater. But the current at the location of the coil is lower, so overall I^R loss of the coil is often less with the coil somewhere around halfway up. The relative amount of coil and ground loss, as well as the amount of top loading if any, are all factors in determining which position is best. This is really a separate question, and I don't have varied enough experience with HF mobile setups to be anywhere near an expert. Tom, W8JI, is though. You can take what he says on the subject to the bank. Roy Lewallen, W7EL |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
Then you and Cecil have quite different theories, it seems. His doesn't predict the drop I measured. The current can be a DROP or a RISE or EQUAL depending upon where it is installed in the standing wave environment. That certainly doesn't constitute "strangely ignoring" Cecil's model. You have completely ignored the EZNEC results posted at: http://www.qsl.net/test316.GIF where the current at the top of the coil is greater than the current at the bottom of the coil. How would your theory handle a current RISE through a coil? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Mike Coslo wrote:
Would the inductor then be best right past the feedpoint? Certainly having the inductor at the far end, or in the middle seems like a bad place for it. (not talking about trap antennas) Here's a graphic that might help: http://www.qsl.net/w5dxp/1WLDIP.GIF The coil can have a current DROP, a current RISE, or equal currents depending upon where it is placed in the standing wave system. Most of the discussion has been about base-loaded mobile antennas. Everyone have a nice Easter. I'll be away from my computer until Monday. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil,
I gave you a very specific reference to demonstrate your supposition was incorrect. You came back with nothing but, "Because I say so." You have not offered one shred of backing for your constant Vf argument. And it is up to ME to further prove something? I don't think so. 73, Gene W4SZ Cecil Moore wrote: Gene Fuller wrote: I will retain the entire message below, so that I am not accused of misattribution. Gene, to the best of my knowledge, you have never misattributed anything. Where did you get this idea that the velocity factor is constant? The equation for velocity factor includes coil diameter, turns per inch, and wavelength. Keeping the coil diameter constant, the turns per inch constant, and the wavelength constant should ensure that the velocity factor is constant. Specifically, why is the velocity factor of a resonant coil the same as the velocity factor of a significantly shorter coil? It is pretty well accepted that the inductance of coils does not scale linearly with the length of the coil. Therefore any arguments about based on direct calculation of Vf from L and C would seem to fail to support your model. You are obviously mistaken. If you increase the L by lengthening the coil, you have also increased the C by the same percentage. The L and C for any unit length are the same no matter how long the coil or transmission line is. " . . . an approximation for M has been determined by Kandoian and Sichak which is appropriate **for quarter-wave resonance** and is valid for helices . . ." Yes, but if one doesn't change the frequency or the diameter or the turns per inch, the approximation should hold since nothing in the VF equation changes by shortening the coil. One should be able to shorten or lengthen the coil andmaintain the same VF. Seems it is up to you to prove what you are saying. Please prove that the ratio of L to C ratio of a coil changes with length. That should be an interesting proof. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
You have completely ignored the EZNEC results posted at: http://www.qsl.net/test316.GIF where the current at the top of the coil is greater than the current at the bottom of the coil. How would your theory handle a current RISE through a coil? Cecil, Do you suppose that maybe the displacement current can actually work in either direction? Did someone put a diode in the aether? 73, Gene W4SZ |
Current across the antenna loading coil - from scratch
Gene Fuller wrote: .... Cecil, Do you suppose that maybe the displacement current can actually work in either direction? Did someone put a diode in the aether? 73, Gene W4SZ Yes, some time earlier today than that exchange, I posted elsewhere in this thread a specific circuit, complete with values, how the same thing is easily accomplished with the infamous ideal lumped components. No standing waves need apply. But of course if one used distributed reactances, one could easily get the same effect, and the analysis can easily be done w/o any reference to standing or travelling waves. Cheers, Tom |
Current across the antenna loading coil - from scratch
On Wed, 12 Apr 2006 23:07:20 -0400, "Yuri Blanarovich"
wrote: I am really done here Hope triumphs over experience. |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote: That this concept is wrong can and has been shown by theory, modeling, and measurement. I made and posted measurements on this newsgroup in November 2003 which demonstrated clearly that the presumption is false. Mike Coslo wrote: Okay. It looks like we have at least some measurements that differ. Any idea why that would be? Yes, because the physical construction of the coil and the antenna changes the capacitance from the inductor to the outside world and the impedance loading the coil. It is the ratio of capaciatnce of the coil to the outside world to the load impedance presented by the whip above the coil that causes or allows any phase difference in current or current level at each end of the coil. It isn't standing waves, it is missing electrical degrees. I can take a resonant mobile antenna of basically the same height and construction, change only the coil while maintaining resonance, and have difference of current and phase of current change all over the place. Try reading: http://www.w8ji.com/mobile_and_loaded_antenna.htm there is a link to actual measurements in that text. The loading coil isn't making the antenna act like a physically longer antenna. In the extreme case of a physically short inductor at the feedpoint, it's simply modifying the feedpoint impedance and has no effect whatever on the antenna's radiation. Would the inductor then be best right past the feedpoint? Certainly having the inductor at the far end, or in the middle seems like a bad place for it. (not talking about trap antennas) No. The current in the antenna below the loading coil (or a top hat of sufficent capacitance)is essentially uniform. This increases radiation resistance. Increased radiation resistance can increase efficiency. See: http://www.w8ji.com/radiation_resistance.htm 73 Tom |
Current across the antenna loading coil - from scratch
"Richard Clark" wrote in message ... On Wed, 12 Apr 2006 23:07:20 -0400, "Yuri Blanarovich" wrote: I am really done here Hope triumphs over experience. yep, "hope" with pictures, measurements and descriptions (no good) vs. "experience" = it can't be, but, but, but... ("proof") how does the coil have higher current at the top if it loses radiation through capacitance to W8JI? "Experienced" silencio!!! There is your sign! Richard, keep up sticking needles, that really sheds light on the subject Happy Easter to everyone, even unbelievers! Yuri da BUm |
Current across the antenna loading coil - from scratch
On Thu, 13 Apr 2006 09:42:35 -0400, "Yuri Blanarovich"
wrote: Happy Easter to everyone, even unbelievers! Hi Yuri, I was at Seder last night. Are you calling me an unbeliever? 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
Yuri Blanarovich wrote: .... yep, "hope" with pictures, measurements and descriptions (no good) vs. "experience" = it can't be, but, but, but... ("proof") how does the coil have higher current at the top if it loses radiation through capacitance to W8JI? "Experienced" silencio!!! There is your sign! .... Yuri da BUm Hi Yuri, Yesterday I posted in this thread a very simple ideal lumped-circuit specific example of how it happens. Have a look for that. Consider the capacitance in that lumped circuit to be part and parcel of the coil in the distributed case, so you can't in the distributed case separate its current from the coil current; all you see is the current going in the "input" terminal (1.3 amps, per Cec's request) and the current coming out the "output" terminal (2.1 amps) into a load impedance. If you don't overconstrain the problem (that is, if you don't specify anything beyond reasonable input and output currents and load impedance) I can show you a lumped circuit with only series inductance, series resistance to represent loss if you wish, and shunt capacitance, that will do the same thing with respect to terminal currents. It really is not a stretch at all to get more current coming out than going in. It WOULD be a stretch to have more power dissipated in the load than you put in the network, but that's not what's happening, of course. Is that all specific enough for you, or would you like to give me a challenge with a different set of input and output currents and load impedance (which agrees with what you might actually observe in an antenna-with-loading-coil situation, and not some ridiculous impossible set)? I'll even embed the capacitance in the circuit so you won't be able to say you could measure its current separately from that of the coil. It's a somewhat pointless exercise, but good mental stimulation, like working a crossword puzzle, so I'm up for it. (I trust you didn't really mean that the coil loses radiation _directly_ to W8JI in your posting quoted above! If every loading coil in the world did that, poor Tom would be getting pretty warm, I suppose. In any event, PLEASE UNDERSTAND THIS: the displacement current from the coil is mostly NOT losing power to the outside world. Like current in more tangible capacitors, it represents stored energy that's put into an electric field in part of the cycle, only to be almost all returned in another part.) Cheers, Tom |
Current across the antenna loading coil - from scratch
Tom, W8JI wrote:
"It isn`t standing waves, it is missing electrical degrees." That could be sarcasm because it certainly could be standing waves. In a coil the RF signal travels as a surface wave around the turns of the coil (helix) at about the velocity of light. Hopper`s rule says this is about one foot in a billionth of a second (one nanosecond). Self inductance can`t magically induce the signal in one end of a coil instantaneously into the opposite end of the coil. Here`s why. Current in the coil induces voltage and current lags the applied voltage by 90-degrees (1/4 of the time required for a complete cyclr). That`s a delay. Antenna systems produce a reflection from the open-circuit at the tip of an antenna. The incident wave reaching the tip reverses its direction becoming the reflected wave, traveling in the opposite direction from the incident wave. You likely have seen the interference pattern produced by incident and reflected waves on a transmission line in a book. The same pattern starts at the tip of an antenna not terminated in its Zo. At certain points on the signal path the voltages in the two waves will be in phase and will add, while at other points they will be out of phase and subtract. The points along the path where the two voltages are in phase are points of maximum voltage and minimum current and are spaced one-half wavelength apart. The points along the path where the two voltages are 180-degrees out of phase are points of minimum voltage and maximum current and are also spaced one-half wavelength apart. The distance between alternate points is one-quarter wavelength. Coil, wire, free-space, whever you have an incident wave and its reflection on a path, you will get this interference pattern on a conductor. So, a loading coil is going to have variations of voltage and current caused by an energy reflection with or without coupling to the rest of the universe. Best regards, Richard Harrison, KB5WZI |
Current across the antenna loading coil - from scratch
Yuri Blanarovich wrote: vs. "experience" = it can't be, but, but, but... ("proof") how does the coil have higher current at the top if it loses radiation through capacitance to W8JI? "Experienced" silencio!!! There is your sign! Yuri da BUm Yuri, It is so obvious to anyone experienced with antenna tuners how that can happen I really dodn't think it requires an answer at all. It is possible to build a "current step up network", or a "current step down network" with two or more reactances, one in series and one in shunt. What it is NOT possible to do is make a coil change current without that third path to the outside world. Standing waves will not do it, missing antenna degrees will not do it. Look at a simple L network when you have time, or more closely an L/C/L T network. You will find all laws of charge conservation are met. The current at any junction of one source path into two other branches always totals zero (current in balances currents out). The antenna is no different. The loading coil in a normal antenna mode might have a somewhat large phase shift in current of the coil has considerable shunt capacitance to the outside world or it might have almost none. This has NOTHING to do with standing waves causing the difference, or missing antenna degrees causing the difference. There isn't anything mystical or magical about any of this. The only problem is Cecil's theory, Barry's theory, and your idea doesn't fit all systems, and the models and workings presented by Reg, Roy, Tom, Ian, Gener, and others does work in **every** situation. I can make a mobile antenna that is resonant, change nothing but the coil, and have a mobile antenna that is exactly the same size and still resonant with different currents and phase of currents at both ends of the loading coil. I can do this simply by changing the coil's capacitance to the outside world. I can prove this. 73 Tom |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Thu, 13 Apr 2006 09:42:35 -0400, "Yuri Blanarovich" wrote: Happy Easter to everyone, even unbelievers! Hi Yuri, I was at Seder last night. Are you calling me an unbeliever? 73's Richard Clark, KB7QHC Unfortunately Richard, to many, including some I am acquainted with, you would be considered much worse than that. Minnesota is not as broad minded as they like to pretend. Religious hangings weren't that long ago here. And, as the grandson of Polish Jews who, for some unknown reason, hid their ancestry to the point where I was raised Catholic, I am obviously conflicted! ;) tom K0TAR |
Current across the antenna loading coil - from scratch
(Continuing the basenote drift, since the basenote thread is pretty
much a mess anyway...) So it's not clear to me who might be calling whom an unbeliever. Both Christians and Jews celebrate seder. Maybe it would be those of some other faith? It's interesting to me--and sad--that so many whose religion teaches that God is all-powerful and too great to be known fully by any person are intolerant of others whose religions teach just the same thing. The intolerance seems as common between sects of nominally the same religion as between religions. If you can't ever fully know your god, who are you to say it's not the same god as the one someone else worships differently, or as someone else worships as a set of gods? Hey, we might as well be discussing religion as loading coils... Ducking, Tom Tom Ring wrote: Richard Clark wrote: On Thu, 13 Apr 2006 09:42:35 -0400, "Yuri Blanarovich" wrote: Happy Easter to everyone, even unbelievers! Hi Yuri, I was at Seder last night. Are you calling me an unbeliever? 73's Richard Clark, KB7QHC Unfortunately Richard, to many, including some I am acquainted with, you would be considered much worse than that. Minnesota is not as broad minded as they like to pretend. Religious hangings weren't that long ago here. And, as the grandson of Polish Jews who, for some unknown reason, hid their ancestry to the point where I was raised Catholic, I am obviously conflicted! ;) tom K0TAR |
Current across the antenna loading coil - from scratch
Wot's seder?
Can one drink wine to excess? If so, can I join the club? ---- Reg |
Current across the antenna loading coil - from scratch
Oh, dear, Reg. We've driven you to drink, eh?
Can you continue to talk (reasonably coherently) after you've been drinking to excess?? ;-/ one of the Toms may break out some Merlot shortly... |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Mon, 10 Apr 2006 16:04:56 -0400, Michael Coslo wrote: Not that I could fan the flames any more anyhow, but just what was the original discussion about anyhow? Hmmm, Mike, I bet you didn't find a pony in that pile of "responses" did you? I learned something. Not exactly what I was asking about tho' - 73 de Mike KB3EIA - |
Current across the antenna loading coil - from scratch
Tom Donaly wrote:
Reg Edwards wrote: "K7ITM" wrote W8JI-Tom, Tom Donaly, Ian White, Roy Lewallen, Gene Fuller, Reg Edwards, I, and others I can think of are NOT, repeat NOT, absolutely NOT, most definitely NOT, talking about a lumped-circuit model. ========================================== I do wish you would't take my name in vain about what I might have said or not said. I have in fact said little or nothing about lumped circuits or anything else in this stupid, ridiculous argument. Please don't drag me down to your level. ---- Reg Edwards. If the argument is that ridiculous, why do you continue to read it? Morbid curiosity is what keeps me reading it! This thread reminds me of the time at lunch in school, I put $5 in the jukebox in the lunchroom. I continually pushed the buttons to play "On the Cover of the Rolling Stone", the goofy song by Dr. Hook and the Medicine show. After the 5th repeat, the kids would alternately groan and laugh with each successive play. But most of them stuck around to see just how many times the idiot would play the same song. (turns out 50 - at a dime a pop) Some of us are now the students, listening to other people sing a different version of "On the Cover of the Rolling Stone". - 73 de Mike KB3EIA - |
Current across the antenna loading coil - from scratch
On Fri, 14 Apr 2006 00:59:37 +0100, "Reg Edwards"
wrote: Wot's seder? Can one drink wine to excess? At least four times. Get to act and sing too. If so, can I join the club? I was asked. Weren't you? |
Current across the antenna loading coil - from scratch
K7ITM wrote:
(Continuing the basenote drift, since the basenote thread is pretty much a mess anyway...) So it's not clear to me who might be calling whom an unbeliever. Both Christians and Jews celebrate seder. Maybe it would be those of some other faith? It's interesting to me--and sad--that so many whose religion teaches that God is all-powerful and too great to be known fully by any person are intolerant of others whose religions teach just the same thing. The intolerance seems as common between sects of nominally the same religion as between religions. If you can't ever fully know your god, who are you to say it's not the same god as the one someone else worships differently, or as someone else worships as a set of gods? Hey, we might as well be discussing religion as loading coils... Ducking, Tom No, it's just that certain groups of Xians, not a majority but getting too populous for my taste, seem to think they are the be all end all, and everyone else is going to HELL, even other Xians, especially Catholics. And those that aren't Xian, fuggetaboutit, they are all damned even if they are Good Samaritans and kinder than Mother Theresa, because they don't belive in the RIGHT THINGS. tom K0TAR |
Current across the antenna loading coil - from scratch
Richard Clark wrote:
On Thu, 13 Apr 2006 09:42:35 -0400, "Yuri Blanarovich" wrote: Happy Easter to everyone, even unbelievers! Hi Yuri, I was at Seder last night. Are you calling me an unbeliever? 73's Richard Clark, KB7QHC I would hope not!! Here in NH the Jewish community invites the Christian, including Catholic, Community to share the SEDER with them. The SEDER is served in the meeting room at the local synagogue. About 200 non Jewish people, meaning Christian, from the City of Manchester attend. It is an annual event. The Jewish Community is REFORMED. I do not imagine such an invitation would occur from an Orthodox or Conservative Community. I respect their practice. In the recent past I have been invited to pray in the congregation with a Conservative Community in Massachusetts. I am humbled. The Rabbi is a holy man. /S/ W1MCE, AKA Deacon Dave [Reverend Mr.] |
Current across the antenna loading coil - from scratch
wrote:
Roy Lewallen wrote: That this concept is wrong can and has been shown by theory, modeling, and measurement. I made and posted measurements on this newsgroup in November 2003 which demonstrated clearly that the presumption is false. Mike Coslo wrote: Okay. It looks like we have at least some measurements that differ. Any idea why that would be? Yes, because the physical construction of the coil and the antenna changes the capacitance from the inductor to the outside world and the impedance loading the coil. It is the ratio of capaciatnce of the coil to the outside world to the load impedance presented by the whip above the coil that causes or allows any phase difference in current or current level at each end of the coil. It isn't standing waves, it is missing electrical degrees. I can take a resonant mobile antenna of basically the same height and construction, change only the coil while maintaining resonance, and have difference of current and phase of current change all over the place. Try reading: http://www.w8ji.com/mobile_and_loaded_antenna.htm there is a link to actual measurements in that text. The loading coil isn't making the antenna act like a physically longer antenna. In the extreme case of a physically short inductor at the feedpoint, it's simply modifying the feedpoint impedance and has no effect whatever on the antenna's radiation. Would the inductor then be best right past the feedpoint? Certainly having the inductor at the far end, or in the middle seems like a bad place for it. (not talking about trap antennas) No. The current in the antenna below the loading coil (or a top hat of sufficent capacitance)is essentially uniform. This increases radiation resistance. Increased radiation resistance can increase efficiency. See: http://www.w8ji.com/radiation_resistance.htm Wow, good pages, Tom. Okay now. Your results are pretty compelling, and thanks for the understandable treatment too. I note differing measurements, and a reason for those measurements I'm still reading the pages, but wanted to respond before you thought I was ignoring you. For the next question, which is directed toward Yuri and/or Cecil, is are your measurements at all related to what Tom reports? Do the numbers correlate? - 73 de Mike KB3EIA - |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
The amount the magnitude of the current drops across an inductor is determined primarily by the amount of inductance and the capacitance from the inductor to ground or the other half of the antenna. This is easily explained by simple lumped constant circuit theory. How does lumped constand circuit theory handle the phase shift through the inductance? It is certainly NOT zero as your measured. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Gene Fuller wrote:
I gave you a very specific reference to demonstrate your supposition was incorrect. You came back with nothing but, "Because I say so." You have not offered one shred of backing for your constant Vf argument. Good Grief, Gene, can't I have a 6 day motorcycle in piece without you saying something that is not true? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Gene Fuller wrote:
Do you suppose that maybe the displacement current can actually work in either direction? I guess magical thinking works in any directions. -- 73, Cecil http://www.qsl.net/w5dxp |
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