[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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