[time-nuts] Counter OCXO behaviour
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Jan 14 21:15:02 UTC 2013
Ed wrote:
>Is it manually adjusted right at the oscillator? If so, just opening
>it up and sticking a screwdriver in there gives it a thermal shock,
>and the adjusted element will have mechanical stress that has to
>settle out too - the value can change for a while.
The 04E standard used in the military surplus 1992s (which are by far
the most common 1992s in the US) is typically labeled "9462 454879,
Rev. A". There has been a fair bit of discussion on the list about
these -- a search of the archive will turn up a number of threads.
Yes, they do tend to take a long while to settle after
adjustment. So long, in fact -- and with oscillatory gyrations above
and below the starting frequency -- that I have speculated on-list
that the adjustment may not be a direct adjustment of the tuned
circuit (e.g., with the usual capacitor on the crystal), but rather
an adjustment to the oven controller setting the crystal temperature.
Because the oscillators are sealed assemblies, I'm not aware of
anyone who has taken one apart for analysis -- so the reason for this
behavior must be considered unknown until we know what is going on inside.
Best regards,
Charles
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