"William Sommerwerck"

I think there are two simple refutations, one theoretical, the other
practical.

Theoretical -- If the output of a driver accurately follows its input
waveform,
how can there be Doppler distortion?


** No driver ever does that - the excursion quadruples every octave
lower you go for the same voltage input.


Practical -- It should be trivial to compute the sidebands produced by
combining
(say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
sidebands, it should be possible to determine what part of them is IM
distortion
(AM components) and what part is Doppler (FM components).


** Bob Cain never mentioned drivers at all.

He may well be referring to Doppler in the air itself.



.............. Phil