Poul-Henning Kamp skrev: > In message <b6f04190894a41eeaae0305a898a5...@pc52>, "Tom Van Baak" writes: >> Here are ADEV plots and interesting results from a recent >> experiment on varying the time-constant of a GPSDO: >> >> http://www.leapsecond.com/pages/tbolt-tc/ > > Tom, part of the reason for the sub-optimally short default time > constant is to be able to cope with worst-case specs of the > oscillator. > > Even though they are pretty good, shifts in voltage, temperature > and orientation does affect them. > > A very good example of this effect is the NTPD PLL, which > uncritically belives otherwise unplausible good news, and > lengthens the poll-period to 20 minutes and then refuses > to accept that it did it wrong, until i thas seen three > or four (= one hour) samples saying so, after which it > breaks lock and starts over.
Isn't this more due to surrounding (obviously flawed) heuristics rather than the PLL? Interesting never the less. > In a lab setting, it makes sense to increase over the default > time-constant, just remember that it impacts your loops ability > to cope with for instance a 2g turnover. > Most labs would have issues with a 2g turnover. :) Flipping oscillators that runs is evil and should be avoided at all times. Should be in the rulebook for time-nuts. Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.