[sdiy] Yet another try at explaining beat tones, etc.

[Ian Fritz]

At 08:01 AM 6/5/2009, Needham, Alan wrote:

>Beat frequencies do NOT involve amplitude modulation, just mixing.
>I feel terminology is responsible for some confusion here.

Good point.  There is some semantic difficulty here.  Certainly when you 
have ordinary beats the amplitude is varying.  But this is simply because 
the linear superposition of the two waves creates a varying envelope.  It's 
not like the AM in a radio xmitter, where a nonlinearity is involved.

OTOH, an AM detector in a radio receiver is refered to as a "mixer".  So in 
this context "mixing" is nonlinear, in contradistinction to your statement 
above.  :-)

   Ian