[time-nuts] GPSDO - EFC and fear

[ordnit]

Dear list,
I own a couple of UCCM GPSDO which have been running flawlessy for a 
couple of years. On January the 4th I decided to switch them off for 
scheduled maintenance and noticed that one unit was not locking 
properly. Thanks to the log, I realized that the EFC was near its 
maximum and, an hour later, had exceeded its maximum.

I think that OCXO (Samsung STP2945LF Datecode 1245) has reached a drift 
level which is no longer recoverable by the internal DAC. I still have 
to desolder the OCXO and test it with counter + power supply, in order 
to see the amount of voltage required by the unit in order to reach (or 
approx 10MHz).

Is there a way to fix it? I think that using a bunch a opamps it should 
be possible to fix it, maybe degrading the performances.

In the junk kox I found an old trimble 10MHz OCXO which was removed by a 
dead GPSDO. So I powered it up ( 30+ hours) and mesured its output 
frequency with a HP50131A reading 9.999991 Hz (time gate 1s). By varying 
the Vref voltage (N6075A power supply), I managed to bring the OCXO back 
to 10MHz but... applying 5V. So I think that thix OCXO (dated back to 
2015) has aged out too.

My questions:
- Are my assumption reasonable?
- Is there an OCXO which can replace the STP2495LF having the same Hz 
per Volt sensibility?

Thank you in advance for your help.

Have a nice 2024.


adelmo