[Boatanchors] Radio Signal scrambling

[Dave ZL3FJ]

Marconi had a similar system -  five band privacy. It was used on HF links
back in the 60s and 70s. Quite some years ago I had the 'privilege' of
decommissioning and disposal of a full system (both terminals) that had been
used on an HF link between NZ and Antarctica. I may still have the handbooks
here somewhere.
 Dave
ZL3FJ

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Richard Knoppow
Sent: Tuesday, January 11, 2022 14:14
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Radio Signal scrambling

    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
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