Hi,
For better oscillators I let them sit for at least a week, but
preferably a month, before making any judgements on them. The readings
taken is really just their warm-up behavior. Wider phase-noise can be
measured earlier, but very close-in and ADEV/MDEV stabillty, not so much.
Hadamard Deviation can be used to look somewhat below the drift, but in
practice it doesn't fully compensate it out, but it allows to peak below
the drift limit. A drift post-compensation in Stable32 for instance may
work, but loose the first heat-up part as it will confuse the estimator.
Anyway, for this reason I have a couple of oscillator heated on the
labbench so that they are ready when I need to play with them.
Cheers,
Magnus
On 11/08/2017 06:46 PM, Bob Camp wrote:
Hi
One of the weak points of a normal 10811 is that it is not hermetically sealed.
Left
in storage for years, they “soak up” humidity. In some cases it can take a
fairly long
time (weeks, months) for them to fully dry out. Until they have been run for at
least a
week, don’t get excited about the drift.
Bob
On Nov 8, 2017, at 12:24 PM, Ulf Kylenfall via time-nuts <[email protected]>
wrote:
Gentlemen.
I am about to try to repair a second 5065Aand have now tested a number of 10811
Quartzoscillators that was in the junk box.
In order to test the 10811, I put them it in a chassisthat is used for
GPS-locking. Adjust for lockand then monitor the EFC-voltage over time.
Starting out with a lock condition and the EFCvoltage adjusted to -2.500V I can
see that theoscillators exhibit a monotonus EFC voltagedrift towards 0 volts.
About + 1 mV in 3 minutes.
By comparison, I have a 10811-60109that was tested in the same GPS-application
andthis unit is rock-steadyand that does not show any sign of EFC drift.
Test time has been 3 Days, and I beleive thata 10811 should have been able to
reachthermal equilibrium during this time.
I can and will (of course) take them apart.Anything special to look for other
thanthe usual signs of long-term over-heated discretes?
Ulf Kylenfall - SM6GXV
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