[time-nuts] RFTG GPSDO and other GPSDO questions...

[Hal Murray]

alank2 at earthlink.net said:
> This got me to wondering - how do other GPSDO units work?  Do they take days
> and weeks to build up enough data to discipline themselves or are there
> faster methods? 

Hours to weeks is a reasonable ballpark.

You want to look at the ADEV graph.  At short Tau, the measurement error 
dominates.  At long Tau, the drift of the O in the GPSDO dominates.  What's 
short?  What's long?  That depends on the O and the environment.

How stable is your temperature?   Do you turn the heat down at night?  That 
probably adds a significant 24 hour term.  Does your air-conditioning cycle 
on/off every hour or so?  ...

How stable is your O?  Junk crystal?  Selected unit in a double oven?  
Rubidium?  ...

If you had good data, you would probably adjust the time-constant of your 
GPSDO to be at the bottom of the ADEV graph.  (which may be broad rather than 
a sharp point)



-- 
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