[time-nuts] Vintage Frequency Measurement
scott.j.stobbe at gmail.com
Tue Feb 14 11:20:27 EST 2017
Taking a second look in the manual, they specifically call out that its not
an AT or BT, so I'm not sure what it would be.
Interestingly they describe the thermometer as space-saving and trouble
free alternative to a heater and thermostat apparatus (I guess they weren't
called ovens yet?)
On Mon, Feb 13, 2017 at 10:11 PM, Bob Camp <kb8tq at n1k.org> wrote:
> > On Feb 13, 2017, at 8:15 PM, Scott Stobbe <scott.j.stobbe at gmail.com>
> > 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
> >> 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
> >> be pretty linear.
> > Attached is a plot of crystal calibrators temperature stability. Span is
> > roughly 65 degC.
> Which eyeballs out to be pretty close to an AT. Without knowing the PPM
> scale there isn’t much way to be sure.
> > 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
> > C-V relation for depletion capacitance and the base-emitter dynamic
> > capacitance as a function of collector current. I would suspect that for
> > one active device oscillator, tube vs bjt, a tube crystal oscillator
> > be less sensitive to small power supply variations (+- 10% ).
> Except you *do* have miller effect which pretty much messes things up
> for a triode. A pentode is a bit less sensitive, but you still have issues.
> > Which is a
> > convenient attribute for a poorly/unregulated battery supply in the
> > tube case. Unless filament current has an appreciable impact on
> > I wouldn't think so…
> Umm… errrr …. check it out :)
> Oddly enough, I remember a high school physics lab where they had us plot
> the effect of filament voltage on plate current and gain. Seemed like a
> thing to do to me at the time. Turns out the teacher grew up with
> microwave tubes
> that were tuned by varying the filament. Who knew ??? Pretty strange
> stuff if
> you ask me.
> The bigger issue is the tubes get hot. The heat varies with supply voltage.
> Temperature change is the result. That temperature change messes up
> oscillator stability. You pretty much have to wait for things to hit
> before you do useful stuff ( = let it warm up for an hour or four).
> > <Lampkin105_CrystalTempCo.png>______________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> > and follow the instructions there.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> and follow the instructions there.
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 178402 bytes
Desc: not available
More information about the time-nuts