-------- In message <5583e434-4c72-4a4f-a60b-75a4204ef...@n1k.org>, Bob kb8tq writes:
> Backing up a bit …. the objective is not to minimize overshoot or > keep the loop from oscillating. The issue here is optimizing the noise > output of the combination of GPS + OCXO when combined via > the control loop. It’s a very different objective …. Yes, but a PI loop is still the best mathematical tool for it, you just need the PI loop to have adjustable parameters. Adjusting those parameters after the initial capture is the hard part, because the signal you are looking for is in the "wander" domain. The best I have come up with, is to average the measured phase error to get rid of the GPS jitter/sawtooth, and adjust the PI loop parameters based on the time between sign-changes of that averaged signal. If you plot the histogram of the time between sign-changes, you want the peak below the supposed "allan-intercept" and if you get time intervals more than double the "allan-intercept" you have probably tightend too much. With good modern dual-band GPS receivers, you can probably also steer after the magnitude of the averaged signal, in a sense putting a PI loop around the PI loop. -- 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@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.