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Cecil Moore wrote:
Jim Kelley wrote: In what way are any of the questions relevant to, or deterministic of the assumption? Answering a question with a question is a well known diversion. Please answer my questions and you will automatically answer yours. One could claim that the questions exemplify your point about diversion. :-) Here's some mo How can a current that changes phase by 3 degrees in 90 degrees of wire be used to measure the EM wave delay through the wire? How can that current be used to measure the delay through a coil positioned in the middle of that wire? Assuming the antenna is 90 degrees in length, the relevant currents can be measured, the maximum is known and the minimum is zero, then: According to the plots that I've seen, the standing wave pattern will show a discontinuous change in amplitude at positions where there is an abrupt change in phase of the traveling waves. Since it's fair to assume propagation velocity is the same in both directions, waves would be phase delayed by the same amount in both directions at a discontinuity, and the combined sum of the two delays would account for the total delay and for the resulting change in amplitude. Since a standing wave can be considered an amplitude vs phase plot (where both phase and amplitude vary with position) and the amplitude is known on both sides of the discontinuity, the amplitude on each side of the discontinuity relates functionally to a corresponding phase on the abscissa of the standing wave curve. The total change in phase is equal to the difference in phase on the two sides of the discontinuity. The phase delay for each traveling wave is then half the total phase change. Whether all of the assumptions are true for the cited case, I don't know. The assumptions that you've made are not always clearly or completely communicated, but would obviously weight heavily in the results. This is also true for EZNEC results. Why not take some actual phase shift measurements for yourself? 73, ac6xg |
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