Dale:
You could use an LM567 (NE567) tone decoder chip tuned to 750 Hz to
drive the LED. 567's were very popular in touch tone decoders.
Isn't the receive offset in the HW-101 1 kHz, not 750 Hz?
73,
Bob WB2VUF
Dale Saukerson wrote:
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
archived magazines).
They were probably OP-Amp circuits.
Thanks,
Dale Saukerson
Ex, soon again, N0AOZ
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