About Us

August 31st 04, 06:56 PM

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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