[GreenKeys] Mystery FSK/DFSK demodulator CV-2310/G

[David I. Emery]

On Sat, Nov 24, 2012 at 05:09:13PM -0500, Nick England wrote:
> Howdy men. I received a mystery item photo today - CV-2310/G FSK/DFSK
> demodulator
> photos at http://www.navy-radio.com/puzzlers.htm#cv2310
> I suspect it may be an NSA signals intercept gadget given the ID tag,
> odd shift freqs, and DFSK (did the US military ever use DFSK?)

	This looks like a significantly more recent version of
a NSA/NSG intercept demod I played with in the mid 1960s - obtained
via surplus channels from the NSA Winter Harbor Maine HF intercept
site when I was a student in HS (prep school) in Maine.

	My relic was 3 huge and very heavy 12 U rack mounting boxes...
but appears to have been designed to do basically the same thing as
this thing.

	It also had a CRT, but was all vacuum tube.   Looks like
this thing could very easily have replaced it in that service.

	In any case in that era (50s and 60s) there was lots of
Soviet DFSK (4 tone FSK) in use - especially with synchronous
ARQ type time division multiplex circuits carrying telegram traffic.

	This technology provided two independent tty circuits over one
FSK radio signal (typically 4 equal spaced tones or 4FSK) and seems
to have been often used with two more or less independent streams of
bits.

	I remember copying RTTY on one channel of the such signals
with the other channel carrying synchronous TDM... or repeating
patterns of bits.

	Such signals were very common as HF links between Soviet
empire countries, I suspect a lot I saw were headed to and from Cuba.

	Later on in the 60s a good many such SCPC 4FSK signals were
replaced with VFT signals with multiple 4FSK complexes mixed with
some regular VFT 2FSK tones on one ISB SSB mux transmission.

	I think quite a few of the signals had one channel for the
reverse ARQ link and the other for forward traffic...


-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."