Hi > On Sep 10, 2016, at 6:40 AM, Charles Steinmetz <[email protected]> wrote: > > Bert wrote: > >> would you please share your settings, this is exactly what we are looking >> for. We are doing it by trial and error but your expertise will help greatly. > > Well, I spent the holiday weekend looking for the "safe place" where I > recorded my final Tbolt tuning parameters -- without success. After I tuned > them and qualified them as fit for long-term duty, I disconnected the com > ports and stashed them away in a very quiet and hard to access location with > just the 10MHz coax connected, so I can't use the comms to extract the > parameters without disturbing the Tbolts (which have now settled nicely, > undisturbed for ~10 years). > > But what I did wasn't rocket science -- I just read up on the tuning > parameters, determined which ones would likely affect the stability of the > 10MHz output, made some educated guesses about the likely best settings, and > started playing. It took me several weeks of experimentation (on and off), > and the parameters I settled on were somewhat different between the two units > I kept (primarily, the loop time constant and damping, which ideally should > be set to complement the particular OCXO in each unit). > > I recommend extreme caution when you hear suggestions to use low loop > damping, or to monkey very much with the oscillator scale factor. I found > that high damping (far above the 1.2 default value) worked best for my units. > (Like you, I care most about the stability and accuracy of the 10MHz output. > I don't even have the PPS turned on.) > > Before you do anything else, I strongly suggest a full factory reset to put > everything into a known state, and work from there. > > You have received some advice to use the "autotune" routine in Lady Heather. > I seem to recall several people reporting that it worked well for them, and > there is nothing to lose by trying it. However, in my case it screwed up the > tuning of both units so badly that I had to do factory resets and then > re-enter my custom parameters. I might have been using a version of LH that > didn't have the latest autotune code, or perhaps the autotune function needs > to start from factory default settings, or maybe the phase of the moon was > wrong -- but I was sure glad I had recorded the tuning parameters I worked > out by experiment, so I didn't have to start over again! Just be prepared to > do another factory reset and start experimenting if autotune doesn't work to > your liking.
The one thing that autotune seems to do well is to come up with the actual sensitivity of the OCXO you have. It depends on a few things to do this so it might go wrong. I’ve never seen it come up with the wrong number. It then appears to drop in a gain and damping that make more sense than the original numbers. Since it is a pre-defined pair of numbers, it is indeed a “one size fits all” solution. Bob > > So, I would suggest: (1) do a full factory reset, let it run for a few weeks, > and take data; (2) use the autotune routine, let it run for a few weeks, and > take data. If you are not satisfied with the results at this point, (3) do > another full factory reset and begin experimenting manually. > > Best regards, > > Charles > > > _______________________________________________ > 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.
