On Mon, Feb 13, 2017 at 6:41 PM, Bob Camp <kb...@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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