[AMRadio] RE: Yet another receiver update!

[Bob Bruhns]

Hi Brett,

Does the oscillator drift up, or down, as it warms up?  You should
use positive or negative coefficient temperature compensating
capacitors to reduce the drift.  Some of the comp caps can be next
to the coil, other comp caps can be closer to the 6J5.  Nothing is
perfect, but optimum compensation should help a great deal.

Also, you could build a frequency lock loop, using your frequency
counter reading and a small amount of "set" memory.  When you have
the oscillator on a desired frequency, you save the frequency
reading in the "set" memory.  The FLL would then compare your "set"
frequency with the readout, and apply a slow correction to the
oscillator to keep it on frequency.  The FLL must be disabled when
you tune; when you get where you want to be, you enter the reading
in the "set" memory, activate the FLL, and there it stays.  That's
how some old and very useful signal generators work.

  Bacon