[AMRadio] COMDEL CSP 11


John King jbkking at mtaonline.net
Tue Jul 6 10:08:59 EDT 2004


What is it and what price?
----- Original Message ----- 
From: "Brian Carling" <bcarling at cfl.rr.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Tuesday, July 06, 2004 8:20 AM
Subject: RE: [AMRadio] COMDEL CSP 11


> 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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