I remember back in tech school, (1966) in the air force at Biloxi, MS, we
had classified "sets" so we would go in the classroom and first pull the bulb
out of a couple of signal generators so they looked like they were off. then
we would hook them up to speakers, and set one at 25,000 cps and the other
at 28,000 cps or so, you could not hear either of the signal generators ( too
high of a pitch, but you could hear the 3000 cps squeal from their
hetrodyning.. But you could only pull it once per instructor.. .. same idea,
result..:) tom N6AJR
In a message dated 6/28/2005 7:31:19 P.M. Pacific Standard Time,
The other was an audio frequency generator set to 750 Hz. You would
audibly beat that against a received tone. If the tones matched, you
had only one tone to listen to. If they did not match, you would get
both sum and diff and an audible warbling.
I know I used them with my HW-101. Don't remember if I used them with
my Corsair or '745.
Any of you remember something like this? (I no longer have my
They were probably OP-Amp circuits.
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