[TenTec] RF speech processors

pfizenmayer pfizenmayer at qwest.net
Tue Feb 3 12:09:19 EST 2009

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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