Way back about 1978 or so....I built a couple of different circuits
from either QST or 73.
One was a simple audio filter tuned to 750 Hz. A LED would indicated
a received tone equal to 750 hz.
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.
Ex, soon again, N0AOZ
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