Identify unknown signal or modulation mode commonly heard inthe 1960s
LORAN?
Northe wrote:
Michael,
msg wrote:
Seeking opinions on an old, commonly heard signal (AM) on HF, of some
considerable power, with a very memorable sound.
The sound on the air was much like hearing several P51 fighters
approaching at high airspeed and props not in phase; the spectral
power is mostly in the range of about 200 Hz to 500 Hz with a
varying heterodyne of several Hz. It had a bandwidth of at least
25 kHz (can't say more precisely due to the cheap receivers I had at
the time).
I know exactly what you are talking about. One of the first things I
remember hearing on shortwave radio was that type of signal -- my first
thought was that I was hearing airplanes.
So far I can't find a reference, but as I recall it was a type of
multiplexed teleprinter transmission (maybe also incorporating voice
circuits) -- "something-plex?."
Northe
N6KO
Green Valley AZ
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