[time-nuts] Is my GPSDO healthy?

Rex rexa at sonic.net
Sat Feb 25 18:51:58 EST 2006

I thought I'd ask opinions here about the quality of my GPSDO.

I have an HP Z3816A. I had it off for a few months (moving things
around) but started it up again several weeks ago. I've noticed it has a
24 hr fluctuation on its EFC control. I think it is related to ambient
temperature and pretty sure it is not a new thing (saw it before too).

Here's an image of the graph from GPSCon...

The periodic fluctuation is on a 24 hr cycle. I haven't made accurate
measurements, but I would estimate the room temp is changing about 4 deg
C over the period. Maximum inflections on the efc graph seem to be
around 4 AM and mins at around 5-6 PM. This makes sense for min/max
ambient temperatures. EFC values seem to be changing about 20 steps over
this cycle.

So my question: does this amount of fluctuation seem normal or is the
OCXO overly sensitive?

(The oscillator in the unit is an MTI 260-0558.)


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