To further underscore Charles point and to add another dimension to the
discussion.,The Z3801A that I have been working to bring back from
intensive care in the last two weeks is sensitive to a very slight
mechanical shock.
The unit was laying open on the bench with all kinds of test clips
hanging out of it (power IN and monitor of the various DC supply
busses). At one point I slightly repositioned the Z3801 and in doing so
"dropped" (front edge only ) about 1/4". Nothing scary but a noticeable
THUMP. Less than a minute later I noticed that the PPS error began
drifting lower and over the next 30 minutes stabilized almost 200ns low.
At that point I powered it down for 5 minutes and then ran a survey
again and it was fine . I repeated the little experiment a couple off
times and each time it received a "thump" it started drifting low.
Simply left alone over a period of several hours it would return to
center around 0 pps on its own. The moral I took away from the little
experiment was to make sure the Z3801A's final resting place on the
bench when it gets out of the hospital and returns to work was in a low
traffic - "quiet" location where it would not get bumped.
Dave
NR1DX
On 2/11/2016 12:16 AM, Charles Steinmetz wrote:
Bob wrote:
I'll see if I can figure out which of these is retracing the "wrong"
way and put it in a unit. I'll let it cook for a couple of days and
then post a plot. Like I said, these are all Trimble 34310-T, though
I know that there were at least two manufacturers for that part
number. They were all positive EFC devices with more or less the same
frequency range.
I would expect all OCXOs with the same part number to have the same type
of crystal (though maybe not from the same manufacturer), so they should
all be the same (within some distribution around nominal) WRT the
*warmup* drift. As to the actual (post-warmup) *retrace* drift, there
is no right or wrong direction. If you let an OCXO go cold 100 times,
wait a day or more (each time), and then power it up, it will likely
retrace up sometimes and down other times. One of my 10811s pretty much
alternates from one cold start to the next (but I very rarely power it
down).
Once again, crystals are very individual devices with very individual
personalities, and they are often unpredictable. They are made to be
powered up and left undisturbed for months/years/decades. Use them that
way, evaluate them that way, and don't waste time puzzling about what
they do for the first month after you power them up. It does not make
any sense to power them on and off "rapidly" (off for less than a week,
on for less than a week) and try to draw conclusions about anything that
matters with respect to their performance.
Best regards,
Charles
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Dave
manu...@artekmanuals.com
www.ArtekManuals.com
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