[time-nuts] OCXO Question

[Bob Quenelle]

In testing a new OCXO, I found it had more drift than a previous one.  I'm 
happy with the better one, not so much for the poorer one. I'd like get some 
opinions on whether the performance of both seems reasonable.

I bought both from a US seller. They’re UCT 108663-01, a double oven OCXO. I 
didn't specifically want DOCXO, just had mixed experience with China-based 
sellers and decided to try a US seller. Both have over 100 hours of run 
time.

To compare the 2 OCXO's I let both OCXO's and an LPRO-101 run for about 12 
hours to stabilize. Then I turned off DAC updates so the control voltage was 
constant and collected phase of each OCXO relative to the LPRO-101 every 10 
seconds. I subtracted successive samples and scaled to get mHz. Next I 
subtracted the linear regression line so I could see deviations from 
nominal. I also used exponential averaging with factor 0.1 to clean up the 
noise. I'll attach the graph and see if it makes it through. In summary, 
over the 6 hour run the better OCXO shows a peak to peak deviation of 0.2 
mHz and the poorer one showed 0.9 mHz. This is deviation/wander from 
nominal, not overall drift. The graph also shows room temperature.

I've run a test with both OCXO's in the same box on different days and seen 
similar results so it's not the voltage reference or DAC. I show this test 
because both OCXO's ran at the same time.

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