[time-nuts] 10811 foam enclosure

Mike S mikes at flatsurface.com
Mon Jan 10 01:43:30 UTC 2011


At 06:36 PM 1/9/2011, Tom Van Baak wrote...
>The outer oven was a hack so Z3801A could meet telecom cell tower cold 
>weather warm-up specs. In other words, the better performance they 
>were looking for in that case was warm-up time; not a tempco or 
>frequency stability spec.

The Nortel GPSR (Z3801A) had a very loose warm up spec, which wouldn't 
have required a double oven by itself: "The GPSR will be permitted a 24 
hour warm-up/training period in the event of a power loss and the 24 
hour holdover requirement shall be met following this training period."

The other basic requirement was "+/-1 us traceable to and synchronous 
with Universal Coordinated Time (UTC) with at least one satellite in 
view." Again, a double oven wouldn't be required for that - the GPS 
receive itself should do better.

OTOH, it had a spec of +/- 7 us for a 24 hour holdover, which required 
a double oven. 




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