[time-nuts] Man with too many clocks.
wes at triconet.org
Fri Nov 4 16:35:08 EDT 2016
On 11/4/2016 12:34 PM, Hal Murray wrote:
> kb8tq at n1k.org said:
>> The only practical way to set the 10811 or 10544 is with a >= 10 turn pot on
>> the EFC. I never have worked out just why there are so many instruments that
>> donâ€™t have a pot on the EFC.
> How would temperature effect that? For that matter, how does temperature
> effect the typical mechanical capacitor? Does anybody play fancy tricks to
> cancel out the mechanical motions? (like the mercury pendulum - as the
> pendulum rod expands the mercury expands in the other direction to keep the
> CG the same)
The variable tuning capacitor in one of the military "frequency meters" (I
forget which one, BC221 leaps to mind) had a small disk on an adjustment screw
that worked against a bi-metallic strip "diving board" to make a temperature
sensitive trimmer capacitor. I suspect, however, that it functioned more to
compensate the inductor than the variable capacitor that was very robust.
Before synthesizers, I built a VFO for a homemade receiver using one of these
cannibalized from a freq meter.
Wes Stewart, N7WS
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