[time-nuts] Rb vs.Crystal OCXO

Tom Van Baak tvb at LeapSecond.com
Sun Apr 27 02:15:19 UTC 2014

> The thunderbolt is one of the best timing devices but not for frequency, if 
> you want high resolution. Over time it is ok but high resolution short 
> gate  times and you see the frequency changes. They use the OCXO to correct for 
> timing  error and if you have a Tracor 527E you can see it. Also how else 
> do you think  they control the 1 pps.
> Bert Kehren

Hi Bert,

Put your TBolt (or any other GPSDO) in holdover (freeze the DAC) and then take a close look again. Tell me what you see. The difference (if any) is due to steering. What's common (if any) is due to the OCXO itself.

Have a look at http://leapsecond.com/pages/gpsdo/ to see the results for 4 common GPSDO. Focus on the left edge of the plots only. Note also that tuning parameters can make a big difference in the results (I used only defaults for those plots).


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