[Boatanchors] FS: Comdel CSP 11 Speech Processor

Pete Ferrand petef at sprynet.com
Tue Mar 6 10:13:55 EST 2012

Here's a very nice Comdel CSP 11 RF speech processor that significantly improves the talk power of an ssb transmitter, by 10db says Comdel.

In contrast to all the rigs that use audio processing or DSP based rf compression, the Comdel uses a method of rf clipping that is, according to Comdel, "distortion free". That's not really the case but there is less objectionable distortion than with other analog systems, I believe. Comdel was arguably the first to use an RF processing accessory for ham applications that did not require modifications to the internal circuits of the transmitter.  

The basic idea is that a microphone is plugged into it, and the Comdel is plugged into the microphone input of the transmitter. Inside there is an SSB generator, filter, limiter and demodulator which effectively clips the signal but filters out the harmonics which are generated by clipping. It is effective and was revolutionary in 1968 when this came out and the same technique is used in the current Ten-Tec 715 processor. Clipping has traditionally been the way to achieve the highest modulation density.

The Comdel is all solid state and runs on 9 or 12 volts which may be supplied from the rear panel or provided by 6 D cells inside the unit. With 18ma draw they lasted 300 to 500 hours back then, longer I'm sure with today's cells. There's a clever arrangement such that it only draws power when the PTT is actuated, if you wish.

Here are photos...they're not building them like this anymore:


And here's a two minute mp3 voice demo:


The manual and schematic is available on BAMA:


Price is $100 plus shipping if needed; you may pick it up in the Milwaukee-Chicago area. As is, not returnable. PayPal preferred, otherwise USPS Money Order. Email to petef at sprynet.com

Somers, WI

More information about the Boatanchors mailing list