Keep in mind that the 7 min "warmup time" of the PRS-10 is jut the time for the unit to get the physics package close enough to final temperature for the dithering loop to lock to the atomic transition. But based on measurements of current drawn by the oven(s), it takes more like an hour for the ovens to settle down very well.
My own experiments with a well-used "telecom mod" PRS-10 suggest that it takes my unit more like 3 or 4 days to really settle down to its background frequency drift rate. This rate is specified as something like "< 5E-11 per month", which is frankly pretty awful. Mine seems to be better than spec, more like 2E-11 per month (frequency increasing over time). The point here is that there are apparently a number of warm up drift mechanisms operating, some of which take days to sensibly settle down. I've been wondering about the issue of whether it's best to operate a PRS-10 only at times of need, or continuously, with respect to life. I posed the question direct;y to SRS, and they claim that it is better to leave it running all the time. My own "algorithm" has become "leave it on all the time" when I'm around and even remotely active with time-nuttery, but shut it down when I'm away on vacation. This is mostly out of concern for something going wrong with the power supply and burning the house down. Lightning storms are one such risk, for example. Dana K8YUM On Fri, Mar 8, 2019 at 3:00 AM Forrest Christian (List Account) < li...@packetflux.com> wrote: > Hopefully you'll all grace me with a few answers to a beginner > time-nut question or two. > > I have a PRS-10 I've never used other than to power it on with a > recently-acquired heatsink and verify that it seems to operate > correctly and that the operational parameters don't seem out of > tolerance. I would like to use this in the near future as a 10Mhz > reference for a TAPR TICC which I'd like to use to measure the jitter > performance of the PPS output of various consumer GPS receivers, the > goal being to end up with a jitter histogram. > > So three interrelated questions: > > 1) Assuming the PRS-10 has been off for a long time, how long should I > plan on leaving this on for the 10Mhz to stabilize? I see the > longest warmup time on the spec-sheet is 7 minutes - although this > seems a lot shorter than I'd likely use in real life, I'm also not > sure if there's much benefit to an excessively longer warmup time > (like days), would like opinions on this. > > 2) Longer-term I'd like to use the 1PPS output from a Trimble > Thunderbolt to calibrate the PRS10 and adjust if necessary just to > trim out any aging drift on the PRS10. Initially I thought I was > going to discipline the PRS10 on a continual basis with the > Thunderbolt using the PPS input on the PRS10, but I've recently > realized that leaving the PRS10 on permanently might not be the best > option (see Question 3). So I'm looking for opinions on how to keep > the PRS10 calibrated/adjusted. I.E. trim with the trimmer, adjust > using digital commands, etc. > > 3) As implied in #2, I was originally planning on leaving the PRS10 on > a continuous basis. I've read a couple of things which imply that > there is little benefit to doing so, and that every hour it's on > consumes the lamp life. Assuming I only need the highly stable PRS10 > source every few months for things like jitter measurements on 1PPS > sources, is there any benefit to leaving the PRS10 on? > > -- > - Forrest > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
