On Sep 10, 2015, at 3:46 AM, Gabs Ricalde <gsrica...@gmail.com> wrote: > TL-WR703N, polling GPIO driver, ntpd maxpoll 2 > https://imgur.com/a/ILF9Y <https://imgur.com/a/ILF9Y> > > The offset depends on these things: the stability of the local clock, > PPS jitter, and loop time constant (controlled by the poll interval). > A low PPS jitter means you can use a faster time constant, which can > control the local clock faster when it drifts, which means lower > offsets. > https://www.eecis.udel.edu/~mills/ntp/html/discipline.html > <https://www.eecis.udel.edu/~mills/ntp/html/discipline.html> > https://www.eecis.udel.edu/~mills/database/brief/algor/algor.pdf > <https://www.eecis.udel.edu/~mills/database/brief/algor/algor.pdf> > > You can also improve the stability of the local clock by avoiding rapid > temperature changes. This is the loopstats of a TL-WR841N placed inside > a box where the temperature doesn't change that fast. > https://imgur.com/a/eNT0k <https://imgur.com/a/eNT0k>
Ah, excellent. You can clearly see the frequency offset change vs time over time in that last image due to daily temperature changes rather than load; the first link shows freq vs t graphs with clear steps, suggesting those systems have enough load-- and changing load-- to dominate the frequency changes due to temperature. Looks like your crystal sees ~1.5 pps drift from a 10C change in temp, but I'm just guesstimating. :-) Do you have measurements of the ambient temperature? Regards, -- -Chuck _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
