[time-nuts] Continously drifting HP 10811...

[Magnus Danielson]

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 <time-nuts at febo.com> 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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