Mark wrote:
Although the Trimble oscillator has superb phase noise performance, it has TERRIBLE temperature sensitivity.
It appears that most do but some don't. Between the results I have seen posted on the list (Lady Heather screen shots) and my own data, they seem to fall into two groups. I have two with excellent oscillator tempcos, but a third unit I have is about 100x worse and the sign of its tempco is reversed compared to the first two. That one appears to consume approximately the same oven power as the other two, and heats the housing approximately equally, so the oven does not appear to have a gross failure. All three have Trimble 37265 OCXOs.
I initially thought the third unit's oven controller was broken (low gain). Then I noticed that the great majority of posted Lady Heather plots appear to be from units similar to that one, with the much higher tempco and reversed tempco sign compared to my two low-tempco units. But I have seen a few other plots that appear to be from units similar to my first two. The two with the low tempcos do not appear to be inferior to other Tbolts with respect to stability, PN, or aging.
I'm inclined to think that all 37265 OCXOs are supposed to work like my first two, and that the ones with large tempcos are the result of a supply or manufacturing error (most likely, a mismatch between the oven set point and the crystal). But who knows? There do seem to be many more of the ones with large tempcos around. It would be interesting to take a few 37265s apart to see if there are any obvious differences between the high- and low-tempco units, and if tweaking the oven set points would reduce the tempcos of the high-tempco units.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
