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. 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. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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.
