[time-nuts] Quartz oscillator slow drift/aging

[AC0XU (Jim)]

Time Gurus-

I have a FPS 1150A quartz oscillator with the 1 PPS disciplining option. With the frequency control set to "manual" I can use the digital thumbwheel control to set 10 MHz correctly. However, for two weeks there has been a steady drift upwards of about 2E-10 per day. I have not seen this behavior in other similar oscillators - the magnitude of the drift seems greater than expected. Any ideas what could be happening?  I have no idea how long the unit was unpowered before I got it - it needed repairs - it may have been years. Is this normal? Should I  expect the drift to decrease over time? Etc?

Thanks!

Jim