[CW] 10mhz signals?

[Hans Brakob]

What you were listening to was 16 channels of frequency division multiplexed RTTY.  The equipment most commonly used was the AN/FGC-60-series which accepted up to 16 channels of 100WPM baudot RTTY.  The output was a nominal 3kc wide audio signal transmitted over SSB.  The individual channels were typically individually encrypted in Jason or Orestes.  The system could run dual- or quad-diversity to combat selective fading.  Then, of course, the capacity was reduced to eight or four channels.


73, de Hans, K0HB

On Thu, Jul 25, 2013 at 10:58 AM, Donald Chester <k4kyv at charter.net>
wrote:

>>Covered (encrypted) 100wpm RTTY.
>>Probably military.
> I recall back about 1960 the short wave bands were filled with signals that
> sounded kind of like the old Soviet jammers, but were outside the SWBC
> bands. They were about 3 kHz wide, as I recall. Once, I was playing around
> with the  old phasing type crystal filter and got the bandwidth down to
> about 100 Hz. When I tuned through one of those signals, I could pick out
> about two dozen individual signals that sounded like regular narrow-shift
> RTTY. It was some kind of multiplexing that allowed a large number of
> signals to be transmitted simultaneously. I never operated RTTY, so never
> tried to decode it. Don't know if each individual carrier was regular
> Baudot, or some  non-standard method of encoding.
> Also about that same time, one winter evening I was listening to WSM in
> Nashville, 650 kHz. They used to run a wide variety of programming, not just
> country music. I could hear a clicking sound beneath their modulation, which
> was right at the threshold of being annoying.  I turned on the BFO. Their
> carrier was being frequency-shift keyed just like a RTTY signal. I called
> the station, told them what I was  hearing and asked  what it was. At first,
> the guy who answered the phone denied knowing what I was talking about, so I
> told him to listen, and I put the phone up to the speaker of the receiver
> and let him hear the FSK tone. His response was "Oh you must be listening on
> a short wave receiver. It's an experiment we are  running for the Air
> Force."
> Both diamond shaped Blaw-Knox towers at WSM and WLW each have a brick wall
> built round the base of the tower, whereas most AMBC stations merely use a
> white picket fence. They said the reason was that the stations  were
> transmitting strategic information embedded in their regular programming
> during WWII, and the brick walls were built to prevent possible Nazi or
> Japanese agents from taking pot shots at the tower base insulator.
> Don k4kyv
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