[Boatanchors] Radio Signal scrambling

[Richard Knoppow]

    I don't know all the methods but one was used by RCA on their 
transoceanic point to point telephone service. That was inverted 
independent sideband. I found it easy to get it in the clear with 
any reasonably selective radio that was stable. Could hear both 
sides of conversations using my old Super-Pro.
    The other method was much more sophisticated. This was used 
by AT&T on their point to point telephone service. Called a 
"shuffler", it broke the audio band into about four or five 
sections. These were juggled in relative position with and 
without inversion. You could tell it was speech from the rhythm 
but could get it in the clear without the right decoder. There is 
some detail of the device in the "Bell System Technical Journal" 
somewhere. Subscribers could ask for their calls to be in the 
clear because the quality of the call was better without the 
shuffler operating. This was called "condition A" or something of 
the sort.
    I don't know if the military used this method. It was quite 
effective.

On 1/10/2022 3:47 PM, KA2PTE 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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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL