I had done pretty extensive testing of the latest rendition of the VXO,
Buffer and keying circuit for tube rigs on 40, finding that there were no
instability problems or keying problems on that band with the oscillator and
buffer circuit switched on and off by the keying circuit.
However, when I got around to checking again on 80, I found that there was
some chirp. Since everything is fine on 40, this indicates to me that the
values of the feedback capacitors in the oscillator need to be increased, so
that the oscillator starts and stabilizes quickly enough, as it apparently
does on 40.
With the spot switch ON, supplying 9 volts regulated to the oscillator/buffer
circuit all the time, there was no chirp at all on 80, which confirims that
the keying is not the problem, that the problem lies in the oscillator not
starting and stabilizing quickly enough.
I'll report on my findings as work progresses. It may well be that the
oscillator will still work perfectly well on 40 with the feedback caps
increased enough to ensure good starting on 80. In the meantime, enjoy it as
is on 40, and if you want to put it on another band, scale the values of the
feedback capacitors accordingly.
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