[time-nuts] Thunderbolt disciplining process

Mark Sims holrum at hotmail.com
Mon Feb 9 00:18:05 UTC 2009

Hello Tom,

Yes,  the unit could be disciplining based upon the oscillator output.   The DAC changes are much more correlated with the PPS signal than the OSC signal.

The plots are GPS locked.  Time scale is one minute per major horizontal division.

If the DAC envelope changes were due to outside temperature getting into the OCXO,  the same envelope would show up on the units with the "flat line" temperature sensor.  This does not appear to happen.  The DAC envelope offset clearly tracks the temperature sensor changes.  Old units show lots of fine scale temperature changes that are reflected in the DAC curve.  New units show a very flat temperature curve without the corresponding changes to the DAC envelope.

My feeling is the temperature sensor reading supplements the OCXO oven and helps compensate for system level dependencies on temperature.  These would be be more important during periods of holdover.
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