Ulf wrote:
the oscillators exhibit a monotonus EFC voltage drift towards 0 volts. About + 1 mV in 3 minutes. * * * Test time has been 3 Days, and I beleive thata 10811 should have been able to reach thermal equilibrium during this time.
There is much more than thermal equilibrium goijng on. Any oscillator that has been disturbed in any manner [meaning, disturbed from a normal state of being powered up and running 24/7/365 in a nice, quiet location] will need more time to settle in.
A disturbance can be most anything -- mechanical shock, humidity change, temperature change, adjusting the frequency, being powered off and back on, etc., etc.
Each oscillator is unique about dealing with disturbances. Some go crazy, wandering around in both directions for weeks or months until they settle and changing the direction of their aging drift. Some settle to a different frequency than they were on before, and need to be adjusted (which is its own disturbance, so it may need to be done a few times over the course of a month or more).
Where being powered down is the disturbance, how badly an oscillator behaves when it is powered back on often depends on how long it has been off. If it has been off for a week or more, you could well be starting all over again, just like with a new oscillator. Also, oscillators that have been off for a long time have often been disturbed in other ways while they were off -- jostling, removal from equipment, being tossed across the room (you'd be horrified at how salvage folks treat oscillators and other delicate instruments, if you knew), being shipped across the country (or around the world), exposed to temperature extremes, etc., etc., etc.
Bottom line -- if a quartz oscillator has been powered off for weeks or more, expect it to take at the very least a week, and in my experience usually considerably longer -- a month, or even a year -- to settle to a drift rate that a time-nut would consider acceptable.
My best 10811-class oscillator is a Symmetricom that looks and works just like a double-oven 10811, which came as original equipment in an HP GPSDO. I thought it would never settle, and it took more than six months to reach a "time-nuts-acceptable" drift rate. It continued to improve for another six months, until it finally settled in as my best 10811-class oscillator. It has been powered up continuously for over twelve years now, and it still is.
Be patient. Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
