[time-nuts] Z3805A high value PU

[Charles P. Steinmetz]

Mark wrote:

>I recently purchased a pair of Z3805A
>
>The problem I am seeing on both is the predicted uncertainty is high 
>compared to other receivers I have seen.
>
>I am experiencing a PU of ~8us for the first and ~24us for the second.
>
>My questions are,
>What could be causing such bad figures?
>Is it an oven problem?
>Can I tweak it out?

The predicted uncertainty is calculated from the character of the 
OCXO drift over some period in the past.  If you just hooked these up 
after they were off for who knows how long and were then shipped, the 
OCXO will not even have begun to settle in.  I never really begin to 
think seriously about how stable an OCXO might be until it has been 
running continuously and undisturbed for several months.

There is every reason to think your units will settle in after being 
run continuously and undisturbed, but there is always the chance that 
they won't.  IMO, you won't be in a position to judge for several 
weeks, at the very least, more likely several months.

Best regards,

Charles