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Roy Lewallen wrote:
Egad. Of course I reject the notion that there's "phase information in the standing wave current magnitude". I should have provided a reference in my earlier posting. Your above statement disagrees with Kraus. On page 464 of "Antennas for All Applications", 3rd edition, Kraus shows the relative current amplitude for a 1/2WL thin-wire dipole. He says on that page that the magnitude is a sinusoidal function. Would you care to explain how a sinusoidal magnitude function is NOT associated with phase? For everyone else: Roy had ploinked me so he never sees my references. Therefore, he disagrees with Kraus over and over and over. -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
Roy Lewallen wrote: Egad. Of course I reject the notion that there's "phase information in the standing wave current magnitude". I should have provided a reference in my earlier posting. Your above statement disagrees with Kraus. On page 464 of "Antennas for All Applications", 3rd edition, Kraus shows the relative current amplitude for a 1/2WL thin-wire dipole. He says on that page that the magnitude is a sinusoidal function. Would you care to explain how a sinusoidal magnitude function is NOT associated with phase? For everyone else: Roy had ploinked me so he never sees my references. Therefore, he disagrees with Kraus over and over and over. What is a "sinusoidal magnitude function," Cecil? I don't have Kraus, so I'll take your word for it that he wrote that the current on a 1/2 WL thin wire dipole can be represented as a sine function. Good. I can now throw away my EZNEC. I doubt very much if any of the people who disagree with you really write anything that contradicts Kraus or any of the other textbook writers. Selective quoting is another low trick you like to play, Cecil. You must have learned it in Bible class. 73, Tom Donaly, KA6RUH |
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Tom Donaly wrote:
What is a "sinusoidal magnitude function," Cecil? Y = sin(X) The magnitude 'Y' is equal to the sine of an angle, 'X', in degrees. Wouldn't you agree with me that it is ridiculously ignorant to assert that the magnitude 'Y' has nothing to do with the phase angle 'X', i.e. that there's no "phase information in the ... magnitude". -- 73, Cecil http://www.qsl.net/w5dxp |
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Tom Donaly wrote:
Cecil Moore wrote: For everyone else: Roy had ploinked me so he never sees my references. Therefore, he disagrees with Kraus over and over and over. I don't recall ever having disagreed with anything I've read in Kraus. I do, however, frequently disagree with the misinterpretations and misquotations of Kraus and many other references which Cecil has made. His frequent claims of "If you disagree with me, you disagree with [Kraus, Maxwell, Balanis, Hecht, Heaviside, Terman, God, whoever] are total baloney (to use a much kinder term than it deserves). Yes, I plonked Cecil a couple of years ago. Seeing only the occasional text quoted by others of his bizarre ramblings is more than enough. Those which I do see reinforce my belief that I'm certainly not missing anything of technical or educational merit. Roy Lewallen, W7EL |
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Roy Lewallen wrote:
I don't recall ever having disagreed with anything I've read in Kraus. Your posting below disagrees with the information on page 464 of "Antennas for all Applications", 3rd edition. Of course I reject the notion that there's "phase information in the standing wave current magnitude". The standing wave current magnitude is sinusoidal, according to Kraus. How can you possibly have a sinusoidal wave without an associated phase angle? For a 1/2WL thin-wire dipole: If the source current is 1.0 at 0 deg at t=0, the magnitude of the standing wave current is cos(X) where X is the number of degrees from the source. Your statement that there is no phase information in a cosine function is absolutely false. In fact, in the above example the arc-cosine of the standing wave magnitude is the phase angle of the reflected current. The negative of that angle is the phase angle of the forward current. -- 73, Cecil http://www.qsl.net/w5dxp |
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Well,
It looks like Dave successfully excited some natural frequencies in the group for some weekend entertainment. Congratulations. 73, Glenn AC7ZN |
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Oh, and by the way, natural frequencies cannot exist without forward,
and reflected... :- |
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Cecil Moore wrote:
Tom Donaly wrote: What is a "sinusoidal magnitude function," Cecil? Y = sin(X) The magnitude 'Y' is equal to the sine of an angle, 'X', in degrees. Wouldn't you agree with me that it is ridiculously ignorant to assert that the magnitude 'Y' has nothing to do with the phase angle 'X', i.e. that there's no "phase information in the ... magnitude". Actually, I don't think it's "ridiculously ignorant" at all. If all you have is the value of current at one point, you can't possibly tell anything about the phase. You need to compare it to something - itself even - somewhere or sometime else in order to have an idea of phase. Here's what I mean: suppose I have a piece of wire of unknown length, excited by an unknown frequency, and picking a random point on the wire I measure 1.73 amps. What is the phase? You're trying to square the circle and hear the sound of one hand clapping at one and the same time, Cecil. Of course, in your case, you know the length of the wire, the frequency of the wave and its wavelength, and you think you know the current distribution on the wire (a half wavelength dipole) so you don't need anything but a ruler to find what you're looking for. Of course, you have to decide what you mean by the term "phase." Try not to get a permanent headache thinking about it. 73, Tom Donaly, KA6RUH |
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wrote in message oups.com... Oh, and by the way, natural frequencies cannot exist without forward, and reflected... :- If there is reflector (impedance bump) in their way. If W8JI waves are not reflected or opposed, then they would propagate merrily into the ethernity and become the law of the RF jungle and other pagan believers would worship them and praise the radio guru. Waves have frequencies and sines/cosines, so this is related to antennas, unless, of course there are those who "know better" :-) Jus' stirring the pot... Yuri da BUm |
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Roy Lewallen wrote:
Tom Donaly wrote: Cecil Moore wrote: For everyone else: Roy had ploinked me so he never sees my references. Therefore, he disagrees with Kraus over and over and over. I don't recall ever having disagreed with anything I've read in Kraus. I do, however, frequently disagree with the misinterpretations and misquotations of Kraus and many other references which Cecil has made. His frequent claims of "If you disagree with me, you disagree with [Kraus, Maxwell, Balanis, Hecht, Heaviside, Terman, God, whoever] are total baloney (to use a much kinder term than it deserves). Yes, I plonked Cecil a couple of years ago. Seeing only the occasional text quoted by others of his bizarre ramblings is more than enough. Those which I do see reinforce my belief that I'm certainly not missing anything of technical or educational merit. Roy Lewallen, W7EL For someone like me, Cecil can be (but usually isn't) a very useful crackpot. I can be pretty sure he's wrong, but the process of educating myself into turning that hunch into a dead certainty that I can prove to everyone (except him) can be enlightening. 73, Tom Donaly, KA6RUH |
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Cecil Moore wrote:
Gene Fuller wrote: I do not disagree with anything you have said. Please answer this question. Does the amplitude of the standing wave current contain any phase information? You have previously asserted that it does. Roy says it doesn't. Time to chose between technical fact and agreeing with your friend (who is technically incorrect). Cecil, You win! You have now set the new world record in misquoting. You might want to give a call to the fine folks at Guinness. 73, Gene W4SZ |
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Tom Donaly wrote:
If all you have is the value of current at one point, you can't possibly tell anything about the phase. But the value of current at one point is *NOT* all we have so your supposition is irrelevant. After a century of theory by some of the most brilliant human minds, we know virtually everything there is to know about a 1/2WL thin-wire dipole. We know there *IS* indeed phase information in the standing wave current magnitude just Kraus graphed it in his book. You need to compare it to something - itself even - somewhere or sometime else in order to have an idea of phase. The standard thing to compare it to is the feedpoint current, e.g. provided by EZNEC, usually 1.0 amps at 0 degrees. Here's what I mean: suppose I have a piece of wire of unknown length, excited by an unknown frequency, and picking a random point on the wire I measure 1.73 amps. What is the phase? You're trying to square the circle and hear the sound of one hand clapping at one and the same time, Cecil. First, you insult me with irrelevant ad hominem attacks ... Of course, in your case, you know the length of the wire, the frequency of the wave and its wavelength, and you think you know the current distribution on the wire (a half wavelength dipole) so you don't need anything but a ruler to find what you're looking for. And second, you agree with Kraus and me ... Here is a chart regarding Kraus' 1/2WL thin-wire dipole copied from my other posting. Please tell us what is wrong with it and exactly why the standing wave current magnitude doesn't tell us how many degrees away the feedpoint is for the formula I = Io*cos(X). X degrees away standing wave arc-cosine of the from feedpoint current magnitude current magnitude 0 1.000 amps 0 deg 30 0.866 amps 30 deg 45 0.707 amps 45 deg 60 0.500 amps 60 deg 90 0.000 amps 90 deg Do you really think it is a mere coincidence that column 1 and column 3 are identical??? -- 73, Cecil http://www.qsl.net/w5dxp |
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Tom Donaly wrote:
For someone like me, Cecil can be (but usually isn't) a very useful crackpot. I can be pretty sure he's wrong, but the process of educating myself into turning that hunch into a dead certainty that I can prove to everyone (except him) can be enlightening. Now's your chance to enlighten us, Tom. Please explain again how the standing wave current magnitude on a 1/2WL thin-wire dipole doesn't depend upon how many degrees it is away from the feed point, i.e. doesn't contain any phase information. While you are at it, please explain exactly how Kraus is mistaken about this antenna when he plots the standing wave current as I = cos(X) where X is the number of degrees away from the feedpoint and feedpoint current equals 1 amp at 0 degrees. -- 73, Cecil http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
Cecil Moore wrote: Please answer this question. Does the amplitude of the standing wave current contain any phase information? You have previously asserted that it does. Roy says it doesn't. Time to chose between technical fact and agreeing with your friend (who is technically incorrect). Cecil, You win! You have now set the new world record in misquoting. You might want to give a call to the fine folks at Guinness. It was a simple yes/no question, Gene. That you refuse to answer speaks volumes so I will ask it once again, copying from a previous posting that you ignored. Just insert an 'X' for the one you agree with. If you don't respond, I will add this to a long list of questions that I have asked that the "experts" are afraid to answer. _____ Standing wave current magnitude contains some phase information. _____ Standing wave current magnitude contains zero phase information. -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
Tom Donaly wrote: If all you have is the value of current at one point, you can't possibly tell anything about the phase. But the value of current at one point is *NOT* all we have so your supposition is irrelevant. After a century of theory by some of the most brilliant human minds, we know virtually everything there is to know about a 1/2WL thin-wire dipole. We know there *IS* indeed phase information in the standing wave current magnitude just Kraus graphed it in his book. You need to compare it to something - itself even - somewhere or sometime else in order to have an idea of phase. The standard thing to compare it to is the feedpoint current, e.g. provided by EZNEC, usually 1.0 amps at 0 degrees. Here's what I mean: suppose I have a piece of wire of unknown length, excited by an unknown frequency, and picking a random point on the wire I measure 1.73 amps. What is the phase? You're trying to square the circle and hear the sound of one hand clapping at one and the same time, Cecil. First, you insult me with irrelevant ad hominem attacks ... Of course, in your case, you know the length of the wire, the frequency of the wave and its wavelength, and you think you know the current distribution on the wire (a half wavelength dipole) so you don't need anything but a ruler to find what you're looking for. And second, you agree with Kraus and me ... Here is a chart regarding Kraus' 1/2WL thin-wire dipole copied from my other posting. Please tell us what is wrong with it and exactly why the standing wave current magnitude doesn't tell us how many degrees away the feedpoint is for the formula I = Io*cos(X). X degrees away standing wave arc-cosine of the from feedpoint current magnitude current magnitude 0 1.000 amps 0 deg 30 0.866 amps 30 deg 45 0.707 amps 45 deg 60 0.500 amps 60 deg 90 0.000 amps 90 deg Do you really think it is a mere coincidence that column 1 and column 3 are identical??? Cecil, you can always know something you already know. Knowing that your antenna is 1/2 wavelength long gives you all the information you need for your definition of phase. By the way, where did you get that table, from EZNEC? 73, Tom Donaly, KA6RUH |
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Cecil Moore wrote:
Tom Donaly wrote: For someone like me, Cecil can be (but usually isn't) a very useful crackpot. I can be pretty sure he's wrong, but the process of educating myself into turning that hunch into a dead certainty that I can prove to everyone (except him) can be enlightening. Now's your chance to enlighten us, Tom. Please explain again how the standing wave current magnitude on a 1/2WL thin-wire dipole doesn't depend upon how many degrees it is away from the feed point, i.e. doesn't contain any phase information. While you are at it, please explain exactly how Kraus is mistaken about this antenna when he plots the standing wave current as I = cos(X) where X is the number of degrees away from the feedpoint and feedpoint current equals 1 amp at 0 degrees. I didn't say that the value of the standing wave current on a 1/2 wavelength dipole doesn't vary with length. I did say that just measuring the value at some point doesn't give you all the information you need to calculate the phase. Of course, you already know the phase, because you defined the antenna as 1/2 wavelength, so finding any kl is trivial. Secondly, even if you're right about the current in your antenna being a sine function, in order to use that information, you have to measure the current input at the current maximum - which you've already defined to be the center of the antenna - in order to compare it with the current at the point of interest in order to get your result. In short, you still have to know the current at two points in order to get an answer. The information isn't contained in just one measurement. So let me turn it around and ask you to tell me again why you think you can get some "phase" information from measuring a single point on an antenna without knowing anything else about it. I haven't read Kraus, but I expect he was talking about an idealized, infinitely thin antenna. Add thickness to the wire, and a feedpoint gap, and you may come up with something slightly more complicated. 73, Tom Donaly, KA6RUH |
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Cecil Moore wrote:
Gene Fuller wrote: Cecil Moore wrote: Please answer this question. Does the amplitude of the standing wave current contain any phase information? You have previously asserted that it does. Roy says it doesn't. Time to chose between technical fact and agreeing with your friend (who is technically incorrect). Cecil, You win! You have now set the new world record in misquoting. You might want to give a call to the fine folks at Guinness. It was a simple yes/no question, Gene. That you refuse to answer speaks volumes so I will ask it once again, copying from a previous posting that you ignored. Just insert an 'X' for the one you agree with. If you don't respond, I will add this to a long list of questions that I have asked that the "experts" are afraid to answer. _____ Standing wave current magnitude contains some phase information. _____ Standing wave current magnitude contains zero phase information. If a magnitude can, by itself, contain phase information, why do we have to specify the angle in a phasor? 73, Tom Donaly, KA6RUH |
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Tom Donaly wrote:
Cecil, you can always know something you already know. Knowing that your antenna is 1/2 wavelength long gives you all the information you need for your definition of phase. Apparently that knowledge is not enough for W7EL who said regarding the current distribution in a 1/2WL thin-wire dipole: W7EL wrote: Of course I reject the notion that there's "phase information in the standing wave current magnitude". This in the face of technical evidence that the standing wave current magnitude is a cosine function of the number of degrees the referenced point is away from the feedpoint. Also contradicting Gene Fuller who said: The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. By the way, where did you get that table, from EZNEC? From page 464 of "Antennas for all Applications", 3rd Edition, by Kraus and Marhefka. Where Kraus presents the independent variable in fractions of a wavelength, I simply converted it to degrees. Most knowledgeable people comprehend that there are 360 degrees per sinusoidal cycle, i.e. per one wavelength. -- 73, Cecil http://www.qsl.net/w5dxp |
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On Mon, 15 May 2006 17:12:58 GMT, "Tom Donaly"
wrote: _____ Standing wave current magnitude contains some phase information. _____ Standing wave current magnitude contains zero phase information. If a magnitude can, by itself, contain phase information, why do we have to specify the angle in a phasor? Hi Tom, Cecil probably doesn't understand that both options give both current magnitude AND phase as choices. Rather makes the "question" pointless, but nothing new in the correspondence from our Xerox philosopher. For the record: ____X____ Standing wave current magnitude contains NO phase information. 73's Richard Clark, KB7QHC |
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Tom Donaly wrote:
I didn't say that the value of the standing wave current on a 1/2 wavelength dipole doesn't vary with length. I did say that just measuring the value at some point doesn't give you all the information you need to calculate the phase. The subject is a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees as illustrated by Kraus on page 464 of "Antennas for All Applications", 3rd Edition. That's about the sixth time I have stated those boundary conditions. The information isn't contained in just one measurement. For a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees, as illustrated by Kraus, all the phase information one needs to know is indeed "contained in just one measurement". I haven't read Kraus, but I expect he was talking about an idealized, infinitely thin antenna. I have been very careful about specifying Kraus' 1/2WL thin-wire dipole as the subject of this discussion. It is easiest to understand because it has the least number of variables. What is the agenda in trying to divert the subject away from something easy to understand to something that is difficult to understand? -- 73, Cecil http://www.qsl.net/w5dxp |
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Tom Donaly wrote:
If a magnitude can, by itself, contain phase information, why do we have to specify the angle in a phasor? The subject is the standing wave current phasor on a 1/2WL thin-wire dipole, not phasors in general. The point is that we do *NOT* have to specify the angle for the standing wave current phasor on a 1/2WL thin-wire dipole. The standing wave current phase angle at any point up and down the antenna is already known to be EXACTLY the same as the angle of the source current at any particular time. That's why W7EL's phase measurements were meaningless and his conclusions false. Note he has refused to discuss the subject with me here or over private email. If the source current is 1 amp at 0 degrees, the standing wave current magnitude equals cos(X) and the standing wave current phase equals zero degrees. That you guys disagree indicates ignorance of the assertions of Kraus, Balanis, and others. This is what the argument is all about. The phase angle for the standing wave current is known to be zero degrees and unchanging with respect to the source current phasor. The standing wave magnitude is known to be the cosine of the number of degrees away from the feedpoint. That same number of degrees is the absolute value of the phase angle of the forward current and reflected current phasors. The magnitude of the standing wave current on a 1/2WL thin-wire dipole, fed with 1 amp at 0 degrees as illustrated by Kraus, indeed does contain all the phase information that anyone could ever need or want. -- 73, Cecil http://www.qsl.net/w5dxp |
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Richard Clark wrote:
For the record: ____X____ Standing wave current magnitude contains NO phase information. Remember the context is the 1/2WL thin-wire dipole fed by 1 amp at 0 degrees on page 464 in Kraus' "Antennas For All Applications", 3rd Edition where the standing wave current magnitude EQUALS cos(X) where X is the number of degrees away from the feedpoint. The arc-cosine of the standing wave current magnitude *IS* the phase. One other point. At least one expert has said that nothing is lost in the superposition process. We know that the forward traveling wave has phase and the reverse traveling wave has phase. If the superposed standing wave current magnitude contains no phase information, then something was lost in the superposition process because the standing wave current phase certainly contains no phase information as illustrated at: http://www.qsl.net/w5dxp/travstnd.GIF -- 73, Cecil http://www.qsl.net/w5dxp |
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On Mon, 15 May 2006 18:18:43 GMT, Cecil Moore
wrote: Richard Clark wrote: For the record: ____X____ Standing wave current magnitude contains NO phase information. Remember the context is the 1/2WL thin-wire dipole fed Context schmomtext, Nothing said is nothing said. This is the problem that comes of a Xerox education. |
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Richard Clark wrote:
On Mon, 15 May 2006 18:18:43 GMT, Cecil Moore wrote: Richard Clark wrote: For the record: ____X____ Standing wave current magnitude contains NO phase information. Remember the context is the 1/2WL thin-wire dipole fed Context schmomtext, Nothing said is nothing said. This is the problem that comes of a Xerox education. Hi Richard, all Cecil's information is in the schmomtext. 73, Tom Donaly, KA6RUH |
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Based on my reading, it appears that Kraus did not say anything closely
resembling Cecil's comments. Cecil is "interpreting" a very simple picture in Kraus. All of the math appears to arise from Cecil's imagination. Cecil is so good at quoting that he should have no problem with providing the exact unedited words from Kraus that support the arc-cosine analysis. 73, Gene W4SZ |
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Tom Donaly wrote:
If a magnitude can, by itself, contain phase information, why do we have to specify the angle in a phasor? It looks like Cecil is trying to use "phase" as a function of position, of the envelope of a standing wave rather than the time phase of the total voltage or current which brings about the standing wave. This makes it possible to keep the simple topic suitably muddled and enhances the opportunity to misquote. As I pointed out some time ago, the envelope of a standing wave isn't in general sinusoidally shaped. At the one extreme of a matched load, the total current or voltage vs position function is a straight line, and there is no standing wave. At the other extreme where there's a complete reflection, the function is sinusoidally shaped. The current on an antenna falls into neither category, although the distribution on a thin antenna is nearly sinusoidal. In between the two extremes, the shape of the total current or voltage vs position function (that is, the envelope of the standing wave) is neither straight nor sinusoidal, but can be described with hyperbolic trig functions. You can of course divide the period of any periodic function into 360 degrees or two pi radians and call the point along it a "phase" relative to some arbitrary reference. In the case of a standing wave's envelope, doing so doesn't generally accomplish anything useful. But it seems to be providing fodder for imagining great and wonderful insights about physics. And it certainly is useful in keeping a meaningless argument going by interpreting "phase" to mean either time phase or the positional "phase" of a standing wave envelope as necessary to keep the discussion from proceeding on a linear and logical track. Roy Lewallen, W7EL |
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"Cecil Moore" wrote in message . com... Tom Donaly wrote: I didn't say that the value of the standing wave current on a 1/2 wavelength dipole doesn't vary with length. I did say that just measuring the value at some point doesn't give you all the information you need to calculate the phase. The subject is a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees as illustrated by Kraus on page 464 of "Antennas for All Applications", 3rd Edition. That's about the sixth time I have stated those boundary conditions. The information isn't contained in just one measurement. For a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees, as illustrated by Kraus, all the phase information one needs to know is indeed "contained in just one measurement". I haven't read Kraus, but I expect he was talking about an idealized, infinitely thin antenna. I have been very careful about specifying Kraus' 1/2WL thin-wire dipole as the subject of this discussion. It is easiest to understand because it has the least number of variables. What is the agenda in trying to divert the subject away from something easy to understand to something that is difficult to understand? -- 73, Cecil http://www.qsl.net/w5dxp The AGENDA is to get you guys fighting! boy, sure didn't take much, even in a thread that was obviously a troll with no technical question to start it of! you guys are just fighting over your own statements since there was no initial technical question or statement that started this thread... i love it, kept me amused through a whole rainy weekend and now on a rainy monday... supposed to rain more this week, think you guys can keep going a bit longer?? |
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Dave wrote:
"Cecil Moore" wrote in message . com... Tom Donaly wrote: I didn't say that the value of the standing wave current on a 1/2 wavelength dipole doesn't vary with length. I did say that just measuring the value at some point doesn't give you all the information you need to calculate the phase. The subject is a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees as illustrated by Kraus on page 464 of "Antennas for All Applications", 3rd Edition. That's about the sixth time I have stated those boundary conditions. The information isn't contained in just one measurement. For a 1/2WL thin-wire dipole with a feedpoint current of 1 amp at 0 degrees, as illustrated by Kraus, all the phase information one needs to know is indeed "contained in just one measurement". I haven't read Kraus, but I expect he was talking about an idealized, infinitely thin antenna. I have been very careful about specifying Kraus' 1/2WL thin-wire dipole as the subject of this discussion. It is easiest to understand because it has the least number of variables. What is the agenda in trying to divert the subject away from something easy to understand to something that is difficult to understand? -- 73, Cecil http://www.qsl.net/w5dxp The AGENDA is to get you guys fighting! boy, sure didn't take much, even in a thread that was obviously a troll with no technical question to start it of! you guys are just fighting over your own statements since there was no initial technical question or statement that started this thread... i love it, kept me amused through a whole rainy weekend and now on a rainy monday... supposed to rain more this week, think you guys can keep going a bit longer?? You're welcome, Dave. Glad to oblige. 73, Tom Donaly, KA6RUH |
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Gene Fuller wrote:
Cecil is so good at quoting that he should have no problem with providing the exact unedited words from Kraus that support the arc-cosine analysis. "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, ..." Simply look at Kraus' graph in Figure 14-2. A sinusoid with current amplitude equal to 1.0 at the center and current amplitude equal to zero at the end is obviously a cosine wave. Since the magnitude varies from 1.0 at the center to zero at the end, taking the arc-cosine of the magnitude yields the distance from the center in degrees. -- 73, Cecil http://www.qsl.net/w5dxp |
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Roy Lewallen wrote:
It looks like Cecil is trying to use "phase" as a function of position, Referenced to the source current, the phase of the forward traveling wave current *IS* directly proportional to position along the dipole. Any competent engineer knows that. So is the phase of the rearward traveling wave current. That is obvious from the equations for those two currents. Those are simply facts of physics that you probably should try to comprehend instead of dismissing them. Inet = Io*cos(X)*cos(wt) = Ifor*cos(-X+wt) + Iref*cos(X-wt) Inet is the standing wave current. X is the distance in degrees from the feedpoint. If the source current is 1.0 amps at 0 degrees, e.g. from EZNEC, at t=0 Inet = Io*cos(X) = Ifor*cos(-X) + Iref*cos(X) As I pointed out some time ago, the envelope of a standing wave isn't in general sinusoidally shaped. Balanis says: "If the diameter of each wire is very small (d lamda) the ideal standing wave pattern of the current along the arms of the dipole is sinusoidal with a null at the end." Kraus says: "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal,..." d lamda for an 80m dipole made out of #18 wire. I'm sorry to hear that you disagree with both Balanis and Kraus. -- 73, Cecil http://www.qsl.net/w5dxp |
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Dave wrote:
you guys are just fighting over your own statements since there was no initial technical question or statement that started this thread... Doesn't have to be. This is a continuation of earlier threads. And I'm not fighting - I'm simply stating the laws of physics as asserted by Balanis, Kraus, and Hecht. -- 73, Cecil http://www.qsl.net/w5dxp |
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Cecil Moore wrote:
Gene Fuller wrote: Cecil is so good at quoting that he should have no problem with providing the exact unedited words from Kraus that support the arc-cosine analysis. "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, ..." Simply look at Kraus' graph in Figure 14-2. A sinusoid with current amplitude equal to 1.0 at the center and current amplitude equal to zero at the end is obviously a cosine wave. Since the magnitude varies from 1.0 at the center to zero at the end, taking the arc-cosine of the magnitude yields the distance from the center in degrees. The key words are "infinitesimally thin," and "generally assumed." With you, Cecil those words become just "thin," and "dead certain." I'm glad you clarified that for us. I was beginning to wonder about Kraus. Now I know it's just Kraus' message suffering from Cecil distortion. 73, Tom Donaly, KA6RUH |
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Cecil Moore wrote:
Gene Fuller wrote: Cecil is so good at quoting that he should have no problem with providing the exact unedited words from Kraus that support the arc-cosine analysis. "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, ..." Simply look at Kraus' graph in Figure 14-2. A sinusoid with current amplitude equal to 1.0 at the center and current amplitude equal to zero at the end is obviously a cosine wave. Since the magnitude varies from 1.0 at the center to zero at the end, taking the arc-cosine of the magnitude yields the distance from the center in degrees. Cecil, Sorry, I missed the comments that Kraus made about the phase of a standing wave. Is that the concept that is represented by the " ..." in your quote above? 73, Gene W4SZ |
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Tom Donaly wrote:
The key words are "infinitesimally thin," and "generally assumed." With you, Cecil those words become just "thin," and "dead certain." Kraus is using author-speak as most technical authors do to avoid nit-picking from people like you. Balanis uses the words, "very small" for the wire diameter. I'm glad you clarified that for us. I was beginning to wonder about Kraus. Now I know it's just Kraus' message suffering from Cecil distortion. It is true for infinitesimally thin wire *AND* anything close to that condition, i.e. also true for d lamda, according to Balanis who says: "If the diameter of each wire is very small (d lamda), the ideal standing wave pattern of the current along the arms of the dipole is sinusoidal with a null at the end." The diameter of #18 wire is certainly very small compared to a wavelength at 80m (0.003' 246') ensuring that the standing wave current distribution on the real world dipole is sinusoidal within a certain degree of real world accuracy. If you want to see the sinusoidal current waveform for yourself, observe the current distribution reported by EZNEC for a G5RV used on 20m. Anyone with EZNEC, presumably including W7EL, can observe that sinusoidal standing wave current pattern. -- 73, Cecil http://www.qsl.net/w5dxp |
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Gene Fuller wrote:
Sorry, I missed the comments that Kraus made about the phase of a standing wave. Quoting: "Figure 14-2 Relative current amplitude AND PHASE along a center-fed 1/2WL cylindrical antenna." Emphasis mine so you can't miss it this time. I thought you were knowledgable enough to convert Kraus's independent variable of wavelength to degrees in his graph on page 464 of the 3rd edition of "Antennas For All Applications". Allow me to assist you in that task. The 'X' axis is "Distance from center of antenna in WL" X in X in wavelength degrees 0.00 0 0.05 18 0.10 36 0.15 54 0.20 72 0.25 90 Hope that helps you to understand Kraus's graph better. Using the degree column, the standing wave current, Itot, on that graph equals cos(X). The standing wave current also equals Ifor*cos(-X) + Iref*cos(X) where 'X' is the phase angle of the forward traveling current wave and the rearward traveling current wave. A phasor diagram at 0.02WL = 72 degrees would look something like this: / Iref / / +----- Itot = Ifor*cos(-X) + Iref*cos(X) \ \ \ Ifor Incidentally, from the above phasor diagram, it is easy to see why the phase angle of the standing wave current is always zero (or 180 deg) since Ifor and Iref are rotating in opposite directions at the same phase velocity. -- 73, Cecil http://www.qsl.net/w5dxp |
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On Tue, 16 May 2006 05:54:59 GMT, Cecil Moore
wrote: Roy Lewallen wrote: It looks like Cecil is trying to use "phase" as a function of position, Referenced to the source current, the phase of the forward traveling wave current *IS* directly proportional to position along the dipole. Any competent engineer knows that. So is the phase of the rearward traveling wave current. That is obvious from the equations for those two currents. Those are simply facts of physics that you probably should try to comprehend instead of dismissing them. Inet = Io*cos(X)*cos(wt) = Ifor*cos(-X+wt) + Iref*cos(X-wt) Inet is the standing wave current. X is the distance in degrees from the feedpoint. If the source current is 1.0 amps at 0 degrees, e.g. from EZNEC, at t=0 Inet = Io*cos(X) = Ifor*cos(-X) + Iref*cos(X) As I pointed out some time ago, the envelope of a standing wave isn't in general sinusoidally shaped. Balanis says: "If the diameter of each wire is very small (d lamda) the ideal standing wave pattern of the current along the arms of the dipole is sinusoidal with a null at the end." Kraus says: "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal,..." d lamda for an 80m dipole made out of #18 wire. I'm sorry to hear that you disagree with both Balanis and Kraus. Could you explain how to build one of those antennas that has infinite impedance at its ends? 73 Gary K4FMX |
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Cecil Moore wrote:
Tom Donaly wrote: The key words are "infinitesimally thin," and "generally assumed." With you, Cecil those words become just "thin," and "dead certain." Kraus is using author-speak as most technical authors do to avoid nit-picking from people like you. Balanis uses the words, "very small" for the wire diameter. I'm glad you clarified that for us. I was beginning to wonder about Kraus. Now I know it's just Kraus' message suffering from Cecil distortion. It is true for infinitesimally thin wire *AND* anything close to that condition, i.e. also true for d lamda, according to Balanis who says: "If the diameter of each wire is very small (d lamda), the ideal standing wave pattern of the current along the arms of the dipole is sinusoidal with a null at the end." The diameter of #18 wire is certainly very small compared to a wavelength at 80m (0.003' 246') ensuring that the standing wave current distribution on the real world dipole is sinusoidal within a certain degree of real world accuracy. If you want to see the sinusoidal current waveform for yourself, observe the current distribution reported by EZNEC for a G5RV used on 20m. Anyone with EZNEC, presumably including W7EL, can observe that sinusoidal standing wave current pattern. Give it up, Cecil. You don't even have a coherent notion of the meaning of the term "phase." Selectively quoting, and re-interpreting Bibles in order to make it seem as if the Gods agree with you won't cut it, either. All the simple-minded rural sophistry in the world won't make you right, or the rest of us wrong. 73, Tom Donaly, KA6RUH |
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Gary Schafer wrote:
Could you explain how to build one of those antennas that has infinite impedance at its ends? An open circuit is close enough to infinite to satisfy almost anyone. In virtually every technical textbook, ideal conditions are assumed until one understands the concepts involved. Then the real world conditions are introduced. That's all I am doing - presenting the concepts involved in an ideal dipole as described by Kraus and Balanis. Do secondary real world conditions exist in reality. Of course they do and nobody is saying that they don't. The difference between infinity and ten megohms is often negligible for analysis purposes. -- 73, Cecil http://www.qsl.net/w5dxp |
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Tom Donaly wrote:
Give it up, Cecil. You don't even have a coherent notion of the meaning of the term "phase." Selectively quoting, and re-interpreting Bibles in order to make it seem as if the Gods agree with you won't cut it, either. All the simple-minded rural sophistry in the world won't make you right, or the rest of us wrong. When you lose the technical argument, Tom, you always respond with ad hominem attacks devoid of any technical content. Fact is, the phase of the forward traveling current referenced to the source current is equal to the distance from the source expressed in degrees. The laws of physics will not stand for anything else. That same number of degrees *IS* the phase angle of the traveling wave(s). Every competent engineer knows that as it is obvious from the equations in any good textbook. -- 73, Cecil http://www.qsl.net/w5dxp |
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