On 5/2/2016 8:58 AM, Joseph Gray wrote:
After replacing the GPS module in Z3801A #2, I fired it up and let it
run. For over an hour, things looked OK, then the PPS TI/s rose
dramatically. Later, it started back down, Other than a high HUP,
everything else looked good. What would cause this to happen?
https://dl.dropboxusercontent.com/u/19599147/Crazy%20PPS.png
Joe Gray
W5JG
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Joe
I have two Z3801A's and one behaves in a very similar pattern upon
warming up from being unpowered for long stretches.Mine is a little more
extreme even went from "near zero) to about -5e-7 then back up to +1e-6,
before settling down. My theory is that it is a function of the
particular xtal in the TCXO . My unit even has that same little sawtooth
bump in in the EFC value ( just after 0200 in your graph) as well
Compared to my other unit it also takes it several days longer to reach
a long term holdover stability of less than 3ms
Both of my units have been through the VP-Oncore change out...swapping
the receivers between the units did not change the curve particularly
the one with the wide swing stayed that way regardless of which receiver
I had in it
Dave
--
Dave
[email protected]
www.ArtekManuals.com
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