Dana wrote:
My experiences with the T'Bolt have not been entirely satisfactory. If I set the loop lime constant long enough to get a satisfying smoothing of the GPS noise (a few hundred seconds), then the thermal sensitivity
> of the VCXO on the T'Bolt rears its ugly head and I see a lot of my > HVAC system cycling instead.
Sounds like you have a not very good Tbolt. First, understand that the original Tbolt was supplied by Trimble with several different VCXOs. ONLY the ones with Trimble 37265 oscillators have low tempcos. Tbolts with other factory-installed oscillators are 100x or more worse.
However, *NOT ALL* 37265 VCXOs give proper tempco performance. In the few samples I've tested, and by reviewing posted data for other 37265 Tbolts, I identified two groups. One group had what I expect for 37265 Tbolt tempcos, while the others (maybe 50%+ of units?) all had tempcos grouped around 100x worse. Generally, these also had tempcos of the opposite sign from the "properly working" units.
I reported this finding on the list in 2012. There is a thread in the archive -- begin here: <https://www.febo.com/pipermail/time-nuts/2012-December/072823.html>
According to Bodnar, his units do have some choices in the time constant setting.
Yeah, but that still doesn't fix the fact that their short-term stability is greatly inferior to any GPSDO with an OCXO, even one that has not been optimized. Exactly what one doesn't want for most time-nut purposes.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
