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Suppressor-grid modulation

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January 22nd 11, 02:14 PM posted to rec.radio.amateur.boatanchors

Gaius

Gaius is offline

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Posts: 18

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Echoplex, was: Suppressor-grid modulation

In article ,
says...

I remember seeing ads in QST in the 1960's for a device I think was
called "Echoplex." It was supposedly used on commercial and military
voice communications circuits. I never heard one of these in use by a
ham, probably because their cost could buy several Collins S-Line
stations. Doing a Google search brings up lots of echo-effects
processors for guitars and such, but I found nothing for communication
usage. Do any readers here remember the device and its manufacturer
and how it worked?

I have a feeling it's another name for Lincompex, developed by the
British Post Office in 1966. Bell labs in the US apparently then came up
with something very similar - which I seem to remember was named
"Echoplex". Could be wrong - it was all a long time ago.....

Lincompex stands for LINKED COMPRESSOR and EXPANDER. The audio is
heavily compressed, and the pre-compression amplitude variations are
used to frequency modulate a 2900Hz control tone. This is combined with
the compressed audio (300-2700Hz) and fed to the TX. At the other end of
the circuit, the control tone is used by an expander to restore the
original amplitude variations.

Lincompex was used widely on international point to point SSB and ISB
voice circuits - and may still be in use (?)

The equipment was made by Marconi, and possibly ST&C (as was, before
Nortel bought them up).

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