[time-nuts] HP10811 problem - wrong frequency

Bernd T-Online BNeubig at t-online.de
Sun Jan 13 13:55:56 EST 2008

philipp80 at gmx.de wrote:
> i have a problem with my HP10811 ocxo. I connected it properly to 24V, 12V 
> and to my counter to measure its frequency. The measured frequency is 10.887 
> MHz, but it should be 10MHz (also noted on the 10811).

The oscillator has obviously jumped to the so-called B-mode of the 
SC-cut crystal. The C-Mode operation (3rd overtone) is enforced by a 
circuit consisting of two inductors and two capacitors which is 
connected between base and emitter of the oscillator transistor.
Unfortunately I do not have the shematic in hands here, so I cannot tell 
you the element IDs. Maybe one of the elements suffered of excessive aging.
I can give you more specific help tomorrow, when I am in my office.

Best regards

Facility MOS
Wasemweg 5
D-74821 Mosbach / Germany
fon: +49 (6261) 939834
fax: +49 (6261) 939836

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