[time-nuts] need recomendation for a portable 10mhz reference oscilator

John Ackermann N8UR jra at febo.com
Tue Dec 11 23:38:55 UTC 2007


Hal Murray said the following on 12/11/2007 05:57 PM:
>> As great as GPSDO are, the problem with using them in a portable
>> environment is the time it takes to do a survey and then get to final
>> lock; mountain-toppers may not be in one place long enough. 
> 
> What if you use a navigation GPS unit rather than a timing unit?

To get decent (for some definition of "decent") timing, you need to
operate the receiver in "0-D" mode, telling it where it is and letting
it solve just for time.  I haven't done the experiments myself but I
believe that the time accuracy is pretty dramatically degraded when
operating in 2-D or 3-D mode.

> How long does a survey take (in good conditions) and what sort of time 
> constant would you want to use with a navigation box?

It depends on the receiver, but usually it's a few hours to a full day.
 Of course, if you use external software you can use whatever time
period you want.

John

> Does anybody have graphs of the PPS wander from a navigation unit?
> 
> 
> I like the lock-to-rubidium suggestion.
> 
> 





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