[GreenKeys] FSK on WABC

[David I. Emery]

On Tue, Dec 01, 2009 at 12:44:23PM -0500, Richard Dillman wrote:

> One assumes it was for submarine communications but I wonder if anyone
> has any further details.

	I have read some comments - I believe including some
declassified official document references - to a program involving
PSKing of clear channel AM broadcast transmitters in the SE that put
good signals into Cuba having been used by the CIA to communicate with
operatives inside Cuba around the time of the Bay of Pigs fiasco.  I did
not see any particular technical details of the actual modulation
parameters - either analog or digital (eg baud rate and codes used).

	Apparently some US clear channel AM stations put walloping huge
signal into parts of Cuba and someone came up with the idea of taking
advantage of it... what they used for receivers in the field was not
discussed either, however...

	I have also seen documents about the RTTY FSK being discussed
here - I believe it was intended as a kind of short term quasi
developmental precursor to the GWEN LF ground wave network that was
implemented widely across the US by sometime in the late 70 - or 80s and
kept around until it was mothballed after the  end of the cold war (and
then some sites converted into DGPS stations rather than torn down).

	It was realized that ground wave propagation at LF and BC
frequencies was pretty effective in a disturbed propagation environment
such as might exist peri and post nuclear attack and might provide a
useful backup comms channel.   That certainly was the notion with the
GWEN system (which used a higher data rate in a packet type format on LF
frequencies around 170-190 KHz).

	I also remember actually noticing the FSKing of a couple of
powerful local AM stations back in the late 60s and attempting to copy
it - I have no recollection of being able to recover anything much in
the clear - it is possible I recovered a RYRY / FOX test once, not sure
I remember any other details - but I definitely was not able to get good
enough copy to find any regular actual traffic there and I know the
first few times I heard it I though I was hearing problems with the
receiver stability rather than something real.


-- 
  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."