[time-nuts] Measuring frequency rather than tuning crystal

jpbridge at aol.com jpbridge at aol.com
Thu Feb 26 15:36:34 EST 2015


I presume that this is what my TTi TF930 does. Calibration is closed box so I guess the TCXO is free running and the micro inside just uses calibration constants.

James


 

 

 

-----Original Message-----
From: Paul Alfille <paul.alfille at gmail.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Thu, 26 Feb 2015 19:02
Subject: [time-nuts] Measuring frequency rather than tuning crystal


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.
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