Hi Warren, > Starting from a factory reset, it has something it will use in under 1/2 day.
And that would explain my and Charles' null results. Nice. > If the temperature has not been thru a few cycles and /or the Ageing is still > at a high initial cold start rate and still changing, > the Kalman filter can give very poor results and actually make things worse. > It gets better as time goes on, and after a few days with a predicable Osc, > the Klaman filter will improve enough to help. Were you able to test how quickly, or how well, the filter learned the tempco of the OCXO? > It is a shame the Kalman filter is not also used during normal non holdover > run time. > With a more advanced PID control loop it could be made to work much better. Yes (although please define "much"; are you talking 1% better or 10% better or 2x better). Would it be possible to implement this advanced PID in LH? Or as a first step, and to veryify your conclusions, would it be possible for LH to control the DAC during TBolt hold-over mode? > As it is, because the known systematic error information is not used as a > feed-forward > term to help the PID loop, any temperature change or ageing that does take > place during > control has to be totally corrected by an error signal. In short this means > there will be > unnecessary errors caused by both changing temperature or time if the > Oscillator is not perfect. I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during hold-over mode (where there is no GPS noise) but not for normal operation. > So what does this mean for the average Nut's Tbolt? Mostly nothing. > The only time the temperature sensor has any effect is during holdover. Thanks for stating both these facts so clearly. I cringe every time I hear someone replacing a 1C DS1620 sensor in their TBolt. The TAPR TBolts I tested years ago worked equally well regardless if they were 1C TBolts or ten milli-C TBolts. /tvb _______________________________________________ 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.
