"Ron Baker, Pluralitas!" wrote in message
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"msg" wrote in message
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Greetings:

Seeking opinions on an old, commonly heard signal (AM) on HF, of some
considerable power, with a very memorable sound.

This will be a bit difficult to describe and I wonder if some folks

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The sound on the air was much like hearing several P51 fighters
approaching at high airspeed and props not in phase; the spectral

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Regards,

Michael

I remember what you are talking about.
Back in the late 60's using a cheap shortwave
receiver we heard things such that we naturally said,
"That sounds like an airplane." Sounded like someone

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Most likely they were, as others have said, VFT or
something like it. They were almost certainly a

Propagation doesn't seem to have been that good
recently. (Height of summer I guess.)
But I managed to catch a VFT signal tonight at
11103 kHz. Switched to AM mode. It didn't sound
like what I remember from way back when.

Also found a signal at 8488 kHz that I think is
a mil-std-188-110 signal. Switch to AM mode. That
sounded more like what I remember from the
60's.

But mil-std-188-110 didn't exist in the 60's. Maybe there
were similar signals at that time.