[time-nuts] Gravity & Crystal Oscillator Calibration

Richard (Rick) Karlquist (N6RK) richard at karlquist.com
Sat Sep 4 23:59:27 EDT 2004

> A friend that does calibration and repair of electronic equipment
> recently gave a paper showing that when a certain model number of
> HP equipment has it's oscillator calibrated in the normal way by
> turning the equipment over on it's side, a noticeable error due
> to gravity is introduced.
> Have Fun,
> Brooke Clarke, N6GCE

A standard spec for high precision oscillators is the so called
"2g turnover" referring to the fact that simply flipping over
an oscillator changes the acceleration by 2g for obvious reasons.
The cause is nonlinearities and stress in the crystal mounting.
This effect is not all that large compared to the accuracy
to which you can set a 10811 with the screwdriver adjustment
and is also not large compared to daily aging.  There is probably
more effect in an instrument due to thermal convection effects
which are also position dependent.  It probably also matters if the
cover is removed to do the adjustment.

The 5071A cesium standard is so accurate that you can see
relativistic effects (in frequency) between HP in Santa Clara, CA near sea
and NIST in Boulder, CO at 5000(?) ft.  We actually flew a couple
of early protos out to Boulder.  NIST's most advanced clocks
can detect the relativistic change just going from downstairs to

Rick Karlquist N6RK

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