That is exactly how the Drake SP75 speech processor works - Hank K7HP
You connect your microphone audio to a little AM or DSB generator,
working at some frequency such as 455 kHz. Then you compress or even
clip that signal to increase the average power output. Probably goes
though some bandwidth limiting filters. After that it gets demodulated
back to audio, and feeds the microphone input of the SSB rig. Since the
compression/clipping/whatever is done at some "intermediate frequency"
and then demodulated back down to audio, the IMD "splatter" and
harmonics that are generated, don't get transmitted. Only bandwidth
limited audio goes to the microphone input of the SSB transmitter, and
the SSB transmitter audio stages and RF stages are never driven into
non-linearity. The transmitted signal bandwidth is limited by the usual
crystal or mechanical filters. You get a really dense high average power
signal.
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