[time-nuts] getting a grip on 10811 drift (beginner-ish question)

Chris Howard chris at elfpen.com
Mon Nov 5 14:49:27 UTC 2012


I built a GPSDO using my own power supply,
a VE2ZAZ board, a Trimble Resolution T GPS
and a surplus  HP 10811 oscillator.


I'm having a bit of trouble with it.   I have it set up and
it locks ok and stays in lock so far.  But the recommended
long-term integration setting is not working for me.
I think it is about 3 hours.  At the end of every cycle
it does a control voltage adjustment, always in one direction.
If I understand it right, the oscillator is slowing and needs
an incremental bump downward of control voltage every time.

That seems like it is more than just long term drift.  But
I don't have my head around the quantities I'm looking at.

I can measure the control voltage change over time.  Can I convert that
into a frequency drift?  Or do I need to stop the voltage
adjustments and allow the drift to occur then do a measurement
of that directly somehow?

Is this type of behavior an indication of dire problems
with my 10811 oscillator?

Chris Howard
w0ep



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