[time-nuts] Vintage Frequency Measurement

Scott Stobbe scott.j.stobbe at gmail.com
Mon Feb 13 20:15:07 EST 2017

On Mon, Feb 13, 2017 at 6:41 PM, Bob Camp <kb8tq at n1k.org> wrote:

> I think what you would find is that it *is* a fairly normal AT cut and the
> data book
> that came with the instrument plotted out the data for the specific
> crystal in
> the device. The usable temperature range was fairly small, so the plot will
> be pretty linear.

Attached is a plot of crystal calibrators temperature stability. Span is
roughly 65 degC.

One of the other aspects I think is intriguing is the DC PSRR of a vacuum
tube crystal oscillator. In the case of a bjt based oscillator you have the
C-V relation for depletion capacitance and the base-emitter dynamic
capacitance as a function of collector current. I would suspect that for a
one active device oscillator, tube vs bjt, a tube crystal oscillator would
be less sensitive to small power supply variations (+- 10% ). Which is a
convenient attribute for a poorly/unregulated battery supply in the vacuum
tube case. Unless filament current has an appreciable impact on frequency,
I wouldn't think so...
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