[BC] True wideband

[Tom]

Someone on some list used to have a sig line quoting Mr. Kahn to the 
effect that AM is inherently a better broadband medium, or similar.
Which is partly correct - the 10kHz, 7kHz, or whatever limitation 
placed on the audio is entirely artificial, although was 
state-of-the-art, pretty much, when implemented.  However, the same 
is true of FM - the 15 kHz upper limit is entirely artificial - 
implemented to accommodate additional signals within the 
"envelope".  As an experiment, some 3 AM, run an audio proof on your 
FM - or your AM.  The OLD way - switch everything out, or to bypass, 
test, etc. - Better still, go directly to the transmitter's mono 
audio input.  BUT!!!  Don't stop at 15 kHz.  Take it on out until you 
hit your -3dB point.  Note the frequency - on an FM, you might be 
beyond the range of your audio oscillator! Certainly will be the case 
if you use the composite input; using the mono audio input, the 
limiting factor will be the response curve of the audio stages.
Even on AM, you could be well above 30 kHz... which was Mr. Kahn's 
point.  However, as a practical matter, we're stuck with 7 kHz on AM, 
at best, and 15 kHz on FM - unless you FM guys want to drop ALL your 
subcarriers... Especially the stereo ones...

Tom S.