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Tom Donaly wrote:
This is just another way of writing 2Acos(kx+d/2)(e^i(wt+d/2). Notice that the part cos(kx+d/2) still contains the phase information? If Cecil were any kind of experimentalist he could easily tease the phase information out of any standing wave on his antenna system. I have previously teased that information from that equation. Perhaps you forgot. It's how to determine the exact phase shift along a thin-wire 1/2WL dipole. I showed how to do that days/weeks/years ago. It's the *phase* of the standing wave current that does not yield any phase information. I have been very careful with that caveat in my statements. cos(kx+d/2) indeed does still contain the phase information. If you will re-read my postings, you will see that I said the *PHASE* term of the reflected current doesn't contain any phase information. FYI, that's the e^i(wt+d/2) term and that part is what Roy used to make his phase measurements which has been my objection for years. It's all archived on Google. It is I, not Roy or Tom, who used the phase information in cos(kx+d/2) to determine phase. When the term containing the phase information is actually used, the delay through the coil is shown to be in the tens of degrees. In the 1/2WL thin-wire dipole, the phase shift between two points is arc-cos(amplitude1) - arc-cos(amplitude2). The only phase information is, as you and Gene Fuller rightly assert, in the amplitude of the standing wave current, NOT in the phase of the standing wave current that Roy measured. If the e^i(wt+d/2) term is used, as Roy and Tom have done, it suffers from the absence of any phase information at all. Gene Fuller said it all days ago: Gene Fuller, W4SZ wrote: In a standing wave antenna problem, such as the one you describe, there is no remaining phase information. Any specific phase characteristics of the traveling waves died out when the startup transients died out. Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again. i.e. there's no remaining phase information in e^i(wt+d/2) term. The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. i.e. there is phase information in the cos(k+d/2) term, but that's not the part of the wave that Roy and Tom were using to determine delay through the coil. I have been hoping someone would jump in who understood the math. To summarize: cos(kx+d/2) is proportional to the *amplitude* of the standing wave current. When I used the amplitude of the standing wave current to estimate the phase, the gurus objected. e^i(wt+d/2) is proportional to the phase of the standing wave current and, ironically contains no phase information, just as Gene asserted. Yet, this is what Roy chose to measure in trying to determine the phase shift through a coil and that's the entire problem with his measurements. He was expecting to measure zero phase shift and he did because there was no phase shift information available from his measurement of the e^i(wt+d/2) term. I told Roy a long time ago, in general, how to calculate the phase shift from the cos(kx+d/2 amplitude term but he replied with "gobbledygook" or some such. -- 73, Cecil http://www.qsl.net/w5dxp |
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