[time-nuts] Segal law: freq difference for GPSDO

Tom Van Baak tvb at LeapSecond.com
Tue Mar 29 23:53:41 EDT 2016


> May be somebody could recognize, what 10.0000014 Mhz could be used for ?

It sort of looks more like an unlocked OCXO than a magic frequency.
Measure phase instead of frequency; see how the phase drifts over time.
Also check if the magic frequency varies or drifts over time.
See if the offset is constant in spite of a one hour power cycle of either GPSDO.

> Its classical case of Segal's law: "A man with a watch knows what time 
> it is. A man with two watches is never sure". This is exact situation. 
> Now I am not sure which GPSDO (if any) is more accurate.

Yes, and www.leapsecond.com for where this madness ends up.

> I have a theory, that may be StarLoc II was customized somehow to 
> produce the freq. slightly different from 10Mhz. But its just a theory.
> Is it worth to compare 1PPS outputs using something like AD8302 + DAC + MCU ?

The TBolt/LH screen seems ok. Send some RS232 commands to the StarLoc. Verify they are both receiving a good number of SV, and maybe even a lot of the same set of SVN.

You can also remove the antenna on one or both units. See if the unusual frequency offset and the ADEV curve looks the same with or without antenna.

/tvb


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