[time-nuts] Measuring frequency rather than tuning crystal

[Paul Alfille]

I have a couple of HP 5370s with the beaglebone brain transplant. They come
with a nice 10811 that has a little adjustment screw.

Testing against a Thunderbolt or KS-24361 the 5370 is off by less than 1Hz.

I know the traditional method would be to adjust the crystal slowly and
make careful measurements, but since I have a fancy computer in there, I
wonder if I could just adjust the frequency in software. 64-bit floating
point numbers should have sufficient accuracy. All reported measurments
would be corrected for the actual reference frequency.

Basically, I'd have a 10000000.226 Hz internal reference.

In fact, could I connect the beaglebone to a a GPS 1 pps source and make
this a GPS-disciplined-software-corrected oscillator.

So my question is is this a known technique? The discipline feedback
circuit seems a little different, I'd adjusting for drift and offset, but
not the gain of control-oscillator linkage.