[Boatanchors] Radio Signal scrambling

[KA2PTE]

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 ]