[time-nuts] Z3805A high value PU

[Mark C. Stephens]

Actually, before I plugged the GPS antenna into the second unit, I checked out where it last called home:
LAT N  36:01:05.225
LON E 128:41:48.761
HGT        +1214.14 m  (MSL)

So it was pretty high up somewhere in south Korea.

Regarding the second unit:
After I collected this information, I plugged the antenna in.
I then performed a
:SYSTEM:PRESET
:PTIM:TCOD:FORM F2
:GPS:REF:ADEL 59ns (~40ft lmr200)
:DIAG:GPS:UTC 1

It then went off and did its survey.
For the first 6 hours PU stayed at 432us, then it dropped sharply to 5.6us and then slowly climbed to 18us.
Doesn't seem right to me.

A further question, is there anything else I should reset, via the CLI to give it a new home?


Many thanks,
mark

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Charles P. Steinmetz
Sent: Wednesday, 17 April 2013 12:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3805A high value PU

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








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