[time-nuts] Z3801 misbehaving
Charles Steinmetz
csteinmetz at yandex.com
Tue Feb 2 19:06:38 UTC 2016
John wrote:
>I am now thinking it may be an OCXO outer oven failure. It normally
>runs quite warm. But now, it seems it may be body temperature or maybe a
>little less. The 10811 is different to a stock one but, is the outer oven
>voltage the same? I would think the inner oven should keep it warm enough
>to achieve lock and hold it. The outer oven is mostly to make the inner
>oven's job easier.
Typically, the outer oven of a DO 10811 is on a thermostat. It
receives power only when the OCXO is warming up from cold, and is
switched off when the inner oven gets close to its operating
temperature. So, the outside of the OCXO package is warm during
warmup from cold, then less warm during normal operation. If the
outer oven does not heat, for any reason, the inner oven will
eventually (~30 min.) get the crystal to operating temperature and it
will work normally after that.
The symptoms you have described all suggest very strongly that
something is wrong with the antenna feed to the 3801:
-- bad antenna location (needs to be outdoors with a clear view of
at least the southern half of the sky, assuming you are in the
Northern hemisphere)
-- bad antenna
-- no DC power reaching antenna
-- bad antenna cable
-- bad antenna cable connector(s)
It's possible something is wrong with the 3801, but if it worked
properly when it was taken out of service, it is *much* more likely
that the problem is one of the items listed above.
Best regards,
Charles
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