-------- In message <1409158879.13035.yahoomail...@web142706.mail.bf1.yahoo.com>, Bob St ewart writes:
So here is a pretty interesting way to optimize a GPSDO that I've been playing with for some years. I don't have a formal mathematical formulation of it. It is somewhat related to what Dave Mills calls "the Allan intercept" except this you can actually measure and not just estimate. You run several (long!) test-series with different timeconstants in your PLL, and you record the resultant EFC and phase offset as a function of time. If your timeconstant is too short, you will have a lot of high-frequency signal in the EFC, too long and you get too much high-frequency signal in the phase offset. The optimal timeconstant is where you have the least sum of spectral power where the two curves cross each other. My experience so far is that the curve around the optimum is very flat, getting the timeconstant wrong by a factor of two hardly changes the resultant performance. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
