[AMRadio] COMDEL CSP 11


Brian Carling bcarling at cfl.rr.com
Tue Jul 6 08:20:58 EDT 2004


I have a really nice Japanese speech compressor for sale if anyone would like it.

Regards - Brian, AF4K

On 18 Jun 2004 at 17:39, Donald Chester wrote:

> 
> 
> >Any one out there got comments on the Comdel speech processor
> 
> They work on AM as well as SSB.  I built a homebrew version back it
> the late 70's using a set of 64 kHz mechanical filters removed from
> telephone multiplexing equipment.  Mine had better audio quality than
> the original Comdel and was quite effective, but it was nothing to
> write home about.  The design eliminates the harmonic distortion of
> speech clipping, but does nothing to reduce intermodulation
> distortion.  Intermod is much more objectionable than harmonic
> distortion.
> 
> The purpose of the Comdel was to allow for speech clipping on SSB,
> since due to fundamental modulation theory, simply clipping the audio
> to flat peaks before applying it to a SSB generator generates high
> amplitude rf peaks, just exactly the opposite of what you are trying
> to accomplish with clipping.  The extreme case of applying squarewave
> audio to a SSB generator produces peaks of theoritically INFINITE
> amplitude.
> 
> The processor works by generating a low-frequency SSB signal (below
> 100 kHz), clipping and filtering the SSB signal, and demodulating the
> clipped SSB and applying the resulting audio to the transmitter.  The
> result is a near 1:1 peak-to-average ratio with heavy clipping, but
> the intermod makes the audio sound mushy.
> 
> -k4kyv
> 
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