[Boatanchors] Radio Signal scrambling

[Brian Harris]

My former employer, Philips Semiconductors, used to make a scrambler/unscrambler chip designed for cordless phones to give users some privacy. There were maybe ten programmable inversion choices (frequencies). I have a set of demo boards and some of the chips around here.  The resultant scrambled audio almost seems intelligible but really isn’t. 

WA5UEK 

Sent from my iPhone

> On Jan 10, 2022, at 5:47 PM, KA2PTE <ka2pte at 3950.net> wrote:
> 
> 
> Curious if anyone is familiar about the types of scrambling used in
> military or private type radios, as I have a vintage tape recording
> where 2 stations are transmitting in a scrambled type of audio.
> 
> At first I thought it was SSB, then was advised that since its on a very old 70's cassette
> tape, the tape material has degraded, lost its properties and is the reason why there
> is this kind of distortion present.
> 
> Since then I have had a few audio professionals try to clean it up to no avail.
> Then I noticed the cass tape housing was missing the felt pad inside that presses on the play head
> when in play mode. I thought that was the entire issue, but after an entire transplant of the tape
> into a new housing with the felt pad, the noise and distortion is still there. A segment of the audio
> can be heard in a wave and ogg file here: https://www.mediafire.com/file/xo8nw1vbyigpbvo/Airstrike.zip/file
> 
> Today I played more of the tape and about half way through, the 2 stations get in touch with another 2 stations
> and they are heard perfectly, but anytime the other 2 stations transmit, they sre still distorted and not very readable
> which is why I think this is a secure channel between them I believe.
> 
> Thought maybe some of the older vets around that did radio back then may be able to know for sure if its a scrambler
> or maybe a way to clean it up.
> 
> --
> Steve Hearns [ KA2PTE ]
> 
> 
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