Thanks Paul!
I had played around with gain a lot before adding that last bit to the differential algorithm. A word about that: I developed my code without a lot of reference to the PID work by Wescott. I had learned how to do the integral part a different way and hadn't realized it. So, it makes sense that things would go badly wrong without an "iTerm". So, I cut the dTerm in half and divided the pTerm by about 3.5. I left my integral factor the same. This is only a 30 minute run, but the difference is remarkable. I'll play with the gains a bit more to see what happens. http://evoria.net/AE6RV/TIC/GSPDOe.2.png http://evoria.net/AE6RV/TIC/ADEV2.png I'd still like to know whether the tools I have at hand can measure the phase noise on my OCXO. Bob (And yes, I accidentally responded directly to you again so this is a repost to the list.) ________________________________ From: Poul-Henning Kamp <[email protected]> To: Bob Stewart <[email protected]> Sent: Wednesday, August 27, 2014 2:02 PM Subject: Re: [time-nuts] OCXO Phase Noise Measurement in Primitive Conditions -------- In message <[email protected]>, Bob Ste wart writes: Your PLL (PID) has (far) to high gain: You are yanking the EFC around to every single little wiggle in the GPS signal. The curve relative to the Rb should be very, very straight, any wavyness should be on timescales of at least 20-30 minutes, not within single minutes as your first plot shows it. This is a very common beginners fault: I made it myself too :-) Lower the PID gain, until the DAC/EFC line only wiggles the minimum amount necessary to keep the OCXO from drifting away from the Rb... -- 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.
