[time-nuts] CS reservoir depletion

Tom Van Baak tvb at LeapSecond.com
Fri Jan 14 06:01:50 UTC 2011

> Hi Tom been quite a while hope you are well.
> The never run out comments, not from me. Look at the
> previous thread I tagged onto. My humor is that most of
> the CS tubes we get are very long in the tooth usually
> way past whatever anyone would say they are good for.

That is so true. It always amazes to pick up a 30 year old
5061A and find that it still works. Sometimes the reason is
that it is already on its 2nd or 3rd replacement tube before
it went to surplus. In which case you're happy for years.
Other times it may be that the 5061A was used only very
intermittently and the tube is the low S/N original.

A real gem would be one that was kept in cs-off mode except
for a few hours once a month to keep the OCXO within some
loose cal lab spec. Even after decades it would be as good
as new.

For many frequency applications there is no reason to run
in full cs-locked mode. This is also true if you need good
short-term stability. The free-running OCXO in most Cs (and
GPSDO for that matter) are more stable short-term when the
loop is open.


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