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#2
August 31st 04, 08:48 PM
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Good grief!
"I Care" wrote in message t... In article , says... "Mark" wrote in message om... OK, Well the fundamental difference is that a radio Tx antenna does not have to move to create a wave. A speaker cone on the other hand is moving to create a sound wave. Relative motion between the Rx and Tx creates Doppler. Not exactly true, at the very least, the EMF on the antenna will cause it to vibrate in the earth's magnetic field, and while this has no connection to it's radiation, Tx is still moving relative to Rx, and while this motion is extremely small, considering the relative wavelengths and propagation speeds, an exact analysis may find that it is similar to the speaker's cone motion when reproducing music. There is no relative motion for an RF radiator. There is relative motion (in general) for a sound radiator. Bob has come up with some very specific cases where there can be no relative motion between acoustical Rx and Tx so those are exception cases. It still has not been established beyond a doubt that there is relative motion concerning Tx and Rx with speaker audio reproduction. There remains an element doubt that the surface of the cone is really the literal sound source. The center of motion of the cone may actually be the literal sound source, and this point doesn't move relative to the listener under normal circumstances. Thus, it might even be postulated that the Tx/Rx relative position with respect to a speaker reproducing music might be more stable that that of an antenna radiating RF in the earth's magnetic field. I'm not presenting this as an actuality, I'm adding yet another real possibility that shows how much we are assuming and how little of what we assuming on a basic level is really firmly grounded in fact. The speaker Doppler distortion debate has popped up here and there over the last forty years are so, with various "proofs" that actually proved very little either way, and I suspect that we may be carrying the debate into new territory this time. It would behoove us to go all the way back and start from the very beginning in examining what we all "know" about the phenomonen. The pay off is that if we really are into new territory, we can all take pride in our parts in the breaking of new ground. Even if it turns out that the old school view is correct, we can still be proud in finally proving it once and for all. It's going to take time, but I look at as a win/win situation, no matter which side we started out on. :-) Why not invite some of the rec.radio.amateur.antenna experts to comment? |
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