[time-nuts] FE5680 GPS Disciplined Controller Update

Tom Van Baak tvb at LeapSecond.com
Tue Jun 24 20:34:25 UTC 2014


> However it is disappointing that no one has stepped up to tackle the  
> temperature problem. how many have looked at the temperature attachment and  
> clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but 
> there will be one or two orders of magnitude degradation without active 
> fan  temperature control unless the internal temperature compensation is  
> disabled.

Can you clarify the "two orders of magnitude" claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report.

I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 10000 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover.

Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference?

/tvb





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