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#311
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Jim, it sounds like you're firmly in the camp that believes that a phase
and/or magnitude shift will occur from one terminal to the other of a physically very small inductor. Your participation in the predictions will be welcome. Perhaps you can also propose an inductor I can put at the base of a short antenna that would guarantee a large phase shift which would be large and easily seen in a measurement. Roy Lewallen, W7EL Jim Kelley wrote: "Roy Lewallen" wrote in message ... I did read what you said. You said that it wouldn't exhibit a phase shift if placed at a current maximum. The current at the base of a short vertical antenna is at its maximum there. So now if you're saying that it *won't* exhibit a phase shift if placed at the base of a short antenna, let's try this. Naturally, the inductance of the coil and the resistance of the circuit determine how much of a phase shift there will be. But the amount of resulting change in current magnitude will depend on where on the cosine curve this shift occurs. A 10 degree phase shift from 40 to 50 degrees generates almost an order of magnitude greater change in current that it does shifting from 0 to 10 degrees. Obviously, the closer the center of the coil is to zero (or 180) degrees, the smaller the resulting differential in current across the coil. 73, Jim AC6XG |
#312
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Yes, I did measure it. But how much difference in your prediction would,
say, +/- 10 ohms of reactance make -- I can't guarantee my measurements any closer than that in any case. So why not make your predictions for 35 - j2 and 35 + j18, and let's see just how much difference it makes. Roy Lewallen, W7EL Cecil Moore wrote: Roy Lewallen wrote: So, you've retracted your prediction. What's your new one, then? No, you misunderstood my prediction. I cannot make an accurate prediction until you tell us the feedpoint impedance of the antenna including the coil. Is it 34.6+j8 or what? You have told us the feedpoint impedance of the antenna without the coil and the impedance of the coil but we still don't have an accurate measurement for the feedpoint impedance of the antenna including the coil. Did you measure it? If not, any estimate is not going to be very accurate. -- 73, Cecil, W5DXP |
#313
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Cecil Moore wrote in message ...
Roy Lewallen wrote: I did read what you said. You said that it wouldn't exhibit a phase shift if placed at a current maximum. I'm sorry, there is a misunderstanding that is my fault. When I say "current is the same.", I'm implying magnitude only. That's a convention left over from my college days and may not be a convention any longer. If I said anything at all about phase, I used the word, "phase", in my posting. So I will stop omitting the word, "magnitude", when I am talking about magnitude. So do a system reset on what you think I said. There is always a phase shift through a real-world inductor. Whether it can be measured accurately is another matter. When I said: "If the current maximum point is located in the middle of a coil, the current (implied magnitude) in and out of a coil will be equal.", I was implying current magnitude only. I didn't imply or say anything about phase unless I used the word, "phase" in the sentence. I also have not said anything about the phase of the currents into and out of your toroidal inductance except to say it replaces approximately 18 degrees of antenna. The current at the base of a short vertical antenna is at its maximum there. So now if you're saying that it *won't* exhibit a phase shift if placed at the base of a short antenna, let's try this. As you can see above, I never said anything like that. Suppose I remount my antenna to eliminate the shunting effect of the mounting, and do my measurements at 3.8 MHz as before. Suppose the base input Z is, say, 35 -j380. You choose any inductor value you'd like, that will best illustrate your method, and tell me what output to input current ratio to expect. I am still leery about your ability to separate small phase shifts from noise. We need to make the inductor large enough to ensure the phase shift measurements are above the noise level. I have no disagreement that a "bugcatcher" coil, or any coil of physically significant size, will exhibit a phase shift and magnitude change of current from one end to the other. Huh?????? I thought that was what the argument was all about. What triggered this whole discussion was W8JI's alleged assertion that a loading coil like a bugcatcher doesn't affect the current at all. Where we disagree is that you believe that a physically very small inductor will also exhibit this. I don't. The effect of a very small inductor may be too small to measure in the presence of strong fields and noise. Ask yourself, at exactly what value of inductor does the phase shift completely disappear? +j1? +j10? +j100? +j1000? What is the crossover point from some phase shift to zero phase shift? Can you measure a phase shift of 0.1 degree at HF? Zero phase implies faster than light propagation through the coil. Cecil Is not the group straying somewhat from the initial discussion on E ham? That discussion that started all this was with regard to a whip antenna and the coil on it. Why has the discussion been pulled away from the original coil to a torroid of all things ? The basic discussion was on a inductor of length which can be considered a major part of the antennas length. It is this situation that Yuri stated that he measured a current difference at the inductors end, to which Tom replied that it was probably capacitive coupling to ground, so even Tom did not dispute the possibility of a current drop per Yuri's measurements ! Maneuvering to to a toroid style of inductance is placing darkness over the original statement, probably to prevent the application of light by others. Now the playing on words is intruding again ( phase ) so I suggest that in that atmosphere one should relate to a inductive network to prevent the accusation of a 'pure' inductance which is a whole different ball game as conditions imposed in the solution of such a network is certainly not the same. Best regards and have fun. Please do not pull into the discussion the root of minus one or all the answers given by the application of a quadratic equation since many will go crazy by taking them to the lab and measuring them. Grin Art |
#314
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Roy Lewallen wrote:
So what's your new, more precise prediction of the output:input current ratio (magnitude and phase) for the system I did measure? I don't see any way to make a precise prediction given that the antenna doesn't exhibit the expected characteristics of a 33' vertical on 75m. I don't see that your experiment makes a lot of difference now that you have said that a 75m bugcatcher coil causes a current magnitude change and a phase shift. That was the original argument. -- 73, Cecil, W5DXP |
#315
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Art Unwin KB9MZ wrote:
Is not the group straying somewhat from the initial discussion on E ham? That discussion that started all this was with regard to a whip antenna and the coil on it. Why has the discussion been pulled away from the original coil to a torroid of all things ? Because someone can't stand to be wrong? -- 73, Cecil, W5DXP |
#316
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So your math is good only for an ideal antenna? That's a sad state of
affairs. Ok, let's suppose I build an ideal antenna that's about 33 feet high, with a feedpoint impedance of 35 - j370 ohms at 3.8 MHz. Choose an inductor value and let me know what the output:input current ratio would be for that inductor at the base of the antenna. Assume that the inductor is physically very small. You have such a clear understanding of what's happening, it should be a simple calculation. Then I'll do my best to build the antenna and make the measurement. Or you can. Roy Lewallen, W7EL Cecil Moore wrote: Roy Lewallen wrote: So what's your new, more precise prediction of the output:input current ratio (magnitude and phase) for the system I did measure? I don't see any way to make a precise prediction given that the antenna doesn't exhibit the expected characteristics of a 33' vertical on 75m. I don't see that your experiment makes a lot of difference now that you have said that a 75m bugcatcher coil causes a current magnitude change and a phase shift. That was the original argument. -- 73, Cecil, W5DXP |
#317
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Chuckle.
I'm continually amazed at how different our backgrounds are. Whenever I've encountered a complex system I don't understand, I try to begin with a simple system, to make sure I understand it first. Only after I know how a simple one will behave do I have a chance of understanding the more complex one. This is the method adopted by virtually all the capable engineers I've had the pleasure to work with over the years. In contrast, complexity is embraced by people who have a need to conceal a lack of understanding. By resisting simplification and constantly pleading that the system is too complex to analyze, fundamental understanding isn't required, and one can never be shown to be wrong. If the best you can do in any case is to give vague answers and wave hands, it doesn't really make any difference whether you understand it or not -- it's impossible to tell. On the other hand, if it's necessary to actually calculate values (as I've had to do for years as a design engineer) and truly understand what's happening, there's no way I'll be able to do it for a complex system if I can't even do it for a simple one. As for standing to be wrong, I'm willing to post my measurements and my predictions, and be wrong. So far, only Yuri has joined me. And, Art, I'm surprised at your objecting to my bringing up the dreaded complexity of -- gasp -- phase. You should rejoice, because it gives me twice the opportunity to show just how wrong I am. If the small inductor shows a measureable phase shift from input to output, I'll be just as wrong as I'll be if it shows a magnitude change. So I've doubled the odds I'll fall on my face. At the same time, it puts Cecil at no extra risk at all, since he won't venture a prediction of either magnitude or phase, and I feel confident in my assumption that you won't, either. I'm the only one (except Yuri, who has bravely given a range of magnitude values at least) who *can* be wrong, and including phase makes it all the more likely. Surely, that should cheer you up a bit. Roy Lewallen, W7EL Cecil Moore wrote: Art Unwin KB9MZ wrote: Is not the group straying somewhat from the initial discussion on E ham? That discussion that started all this was with regard to a whip antenna and the coil on it. Why has the discussion been pulled away from the original coil to a torroid of all things ? Because someone can't stand to be wrong? -- 73, Cecil, W5DXP |
#318
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Roy Lewallen wrote:
So your math is good only for an ideal antenna? That's a sad state of affairs. Heck, I'll just supply you with ten dimensions and virtual photons and see just how well your math works. :-) This discussion has very little to do with math equations. The orbits of the planets got along just fine before man ever walked the earth and came up with the math to explain them. Reality rules! Here's what Einstein said: "One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike ..." Ok, let's suppose I build an ideal antenna that's about 33 feet high, with a feedpoint impedance of 35 - j370 ohms at 3.8 MHz. Choose an inductor value and let me know what the output:input current ratio would be for that inductor at the base of the antenna. Assume that the inductor is physically very small. Why? The argument is/was about bugcatcher coils which are NOT small. Who uses a physically small toroid in his center-loaded mobile antenna? Not that it wouldn't be an interesting experiment. Roy, it appears to me that you are trying to win the last battle after the war is over, like the South did weeks after Lee surrendered. Please feel free to proceed with whatever mission that you are trying to complete. Whatever it is, it is a diversion from the original argument based on W8JI's alleged assertion that the current magnitude and phase doesn't change through an HF mobile antenna's loading coil. That argument has been lost. It appeared that you jumped in and defended W8JI and called everyone who disagreed, "ignorant engineers", or something to that effect. The issue between you and me was settled when you posted that you had no argument with current magnitude and phase changes through HF mobile antenna loading coils. (Now if we can just get W8JI to agree with you.) -- 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! =----- |
#319
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Roy Lewallen wrote in message ...
Chuckle. I'm continually amazed at how different our backgrounds are. Whenever I've encountered a complex system I don't understand, I try to begin with a simple system, to make sure I understand it first. Only after I know how a simple one will behave do I have a chance of understanding the more complex one. This is the method adopted by virtually all the capable engineers I've had the pleasure to work with over the years. In contrast, complexity is embraced by people who have a need to conceal a lack of understanding. By resisting simplification and constantly pleading that the system is too complex to analyze, fundamental understanding isn't required, and one can never be shown to be wrong. If the best you can do in any case is to give vague answers and wave hands, it doesn't really make any difference whether you understand it or not -- it's impossible to tell. On the other hand, if it's necessary to actually calculate values (as I've had to do for years as a design engineer) and truly understand what's happening, there's no way I'll be able to do it for a complex system if I can't even do it for a simple one. As for standing to be wrong, I'm willing to post my measurements and my predictions, and be wrong. So far, only Yuri has joined me. And, Art, I'm surprised at your objecting to my bringing up the dreaded complexity of -- gasp -- phase. You should rejoice, because it gives me twice the opportunity to show just how wrong I am. From my point of view you are rarely wrong and should be admired on how knoweledgable you have become despite insurmountable hardships that make mine a a Sunday morning walk despite the war. I agreed with your posting regarding an inductance but then realised that Yuri was talking about what is really a network and thus he could take measurements. Now I am hoping that Yuri will get a true explanation of what he has observed which in the real world is a circuit containing capacitance,resistance and inductance and where he is unable to separate the parts as you are doing on paper. From an engineering stand point I am not willing to discard fundamentals as you would suggest as their use provides solutions even to one such as I who wasted my younger year by not going to school. My point is that you are playing with Yuri because he used the term inductance instead of a circuit which would then prevented your present tack. For some reason you take offense at that suggestion given in the starting post nd I really do not know why until you come up with an explosive point.. Regards Art If the small inductor shows a measureable phase shift from input to output, I'll be just as wrong as I'll be if it shows a magnitude change. So I've doubled the odds I'll fall on my face. At the same time, it puts Cecil at no extra risk at all, since he won't venture a prediction of either magnitude or phase, and I feel confident in my assumption that you won't, either. I'm the only one (except Yuri, who has bravely given a range of magnitude values at least) who *can* be wrong, and including phase makes it all the more likely. Surely, that should cheer you up a bit. Roy Lewallen, W7EL Cecil Moore wrote: Art Unwin KB9MZ wrote: Is not the group straying somewhat from the initial discussion on E ham? That discussion that started all this was with regard to a whip antenna and the coil on it. Why has the discussion been pulled away from the original coil to a torroid of all things ? Because someone can't stand to be wrong? -- 73, Cecil, W5DXP |
#320
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Roy Lewallen wrote:
If the small inductor shows a measureable phase shift from input to output, I'll be just as wrong as I'll be if it shows a magnitude change. And if the small inductor shows a phase shift too small to be measured, you will have invented faster than light transmission because inches per nanosecond is easy to measure nowadays. Heck, my old bench scope will display two nanoseconds per division. -- 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! =----- |
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