[time-nuts] HP 1938 revisited

Richard (Rick) Karlquist richard at karlquist.com
Mon Apr 13 13:16:27 UTC 2009



J. L. Trantham wrote:
> Thanks for the info.
> 
> My plan is to develop a stable GPS disciplined reference suitable for use as
> a reference for Microwave work in the 10 GHz range that can be used in
> portable locations with relatively quick start up. 
> 
> Perhaps the 1938 would be better in the shop where it could be left on for
> weeks/months at a time and an LPRO 101 or a 10811 could be used for the
> portable application.  Reasonably high drift rates could be accommodated if
> the GPS signal is reliable and the time constants (disciplining rate, drift
> rate, etc.) are appropriate.
> 
> Thanks,
> 
> Joe

The advantage of the E1938A over the 10811 is that it has very low 
tempco, which comes into play in the holdover mode (no GPS).  If
you always have GPS, you might as well just use a 10811.  The 5071A
cesium clock uses a 10811 that is disciplined all the time.  There would
be no advantage in replacing it with an E1938A.  The loop in the 5071A
is fairly slow, but would be considered fast by GPS standards.

If the portable location involves severe temperature fluctuations,
then possibly the E1938A could make sense.

Rick Karlquist N6RK
E1938A designer



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