Hi With a "normal" TBolt running on the bench, it's very obvious that temperature and EFC are directly related to each other. With a little scaling (and possibly an inversion) the plot of one lays down on top of the other. As long as you can eyeball that kind of relation, there's an issue.
Why watch EFC? My assumption is that the OCXO has been on for a good long while and that it's settled down. In a Time Nut environment that's likely a good assumption. I'm also assuming that the supply voltages are stable as is the internal DAC. One is a pretty good bet for list members, the other is a complete guess. Final assumption is that the short term on the OCXO is significantly better than GPS over modest time ranges (very likely true). If all that's true, what you are watching on the EFC is the TBolt correct out the OCXO TC. You could go crazy with auto correlation stuff, but I'm not sure your measure of the outside temperature is going to be good enough to make more than an eyeball approach useful. By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Ultimately what you would like is a setup that never needs to change the EFC (much), so you could run a nice long loop and still have the PPS stay lined up. That *should* give you a significant improvement in short term out of the TBolt. Since it's done with the EFC plot and verified with a cheap thermometer (rather than a bunch of crazy to find gear) it's a reasonable basement Time Nut thing to do. Certainly should add that without all the work done on Lady Heather, you wouldn't have a chance of doing any of this. Can't eyeball a plot you don't have... Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mark Sims Sent: Thursday, January 27, 2011 7:05 AM To: [email protected] Subject: [time-nuts] Temperature stability for Thunderbolt: results With the temperature stabilized, compared to just 1 degree swings in temperature I see a 10 times improvement in the 1PPS standard deviation, and a 3 times improvement in the oscillator and dac control voltage. ------------------------- Between that data and LH's EFC plot you should have some pretty good information on just how much the temperature control is helping. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
