My daughter and I were discussing what she does for a living with time and phase as a geophysicist and relating that to what I'm trying to do with my GPSDOengine. I explained that I was trying to keep the frequency accurate and stable, while also keeping the phase near a target of 180 degrees. And suddenly, I realized that that's not what I was actually doing. For the "I" term of PID, I was integrating on phase position, which was never going to work.
So, I made a change to start integrating on the phase change from second to second (i.e. frequency error), and I think this is finally performing correctly. The DAC is now very flat, and the phase is moving around as would be expected from Bob's and Tom's comments on the LEA-6T. Here's an ADEV of the GPSDO's OCXO vs the 10811 in my 5335A. It covers a timeframe from about 11:00PM last night to about 11:00AM this morning. This is with the PID running as a PI controller with very small P and I gain values. http://evoria.net/AE6RV/TIC/GPSDO.vs.HP10811.png Bob - AE6RV _______________________________________________ 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.
