[time-nuts] Z3801A EFC Error

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jul 10 14:57:15 UTC 2011


Dear John,

On 07/10/2011 04:38 PM, John Ackermann N8UR wrote:
> I'm getting my two trusty Z3801As up and running after 18 months of
> downtime and a 500 mile move. Unit #1 came up just fine.
>
> Unit #2 has been running for about 18 hours and is working OK except
> that the health status is showing an EFC error. The EFC value is above
> 1e6 (currently 1014166) and is trending downward, though the trend has
> leveled off in the last several hours. I suspect that the health monitor
> error comes on to indicate that EFC is near the end of its range; if I
> query for relative EFC, it comes up at about 93% so perhaps the trigger
> is 90%.
>
> Other than the EFC error in the health monitor, the unit seems to be
> working fine. LEDs show normal activity, the Oven PWR and OCXO health
> status are both OK, and after initial alignment the PPS seems to be
> holding within a handful of nanoseconds. (I'm using GPSCON for tracking.)
>
> It's possible that the EFC could keep trending downward as the unit
> stabilizes, and if that continues to be the direction there should be no
> problem. But if it starts to go up, I'll run out of tuning room soon.
> Assuming there's no other hardware problem, I'd think the normal way to
> address this would be to twiddle the oscillator's coarse frequency
> trimmer to get it centered in the tuning range.

If there is no other systematic source, I would have expected that the 
change of direction in frequency would have already occurred if it is 
there. There is a gentle bump in the 10811s as they heat up, but after 
that there is a stable slope as far as I recall.

> Before I tear into the box, is there a coarse frequency adjustment
> accessible on the dual-oven 10811? If that's not an option, any other
> suggestions on what might be going wrong and how to cure it?

I don't recall that the coarse frequency being accessible, but it could 
be worth checking. What does rings a bell is the oven settings might 
need some care. Maybe time to do some read-up on the oven assembly 
again, for both of us.

I would let it sit for some longer time before really being worried.

Cheers,
Magnus



More information about the time-nuts mailing list