Hi Your ADEV is (mostly) a plot of 1-2 ns resolution out over your sample range. It’s not a “typical” three segment ADEV. It’s more likely that any departure from a straight line is random rather than systematic. Yes I’ve spent a lot of time looking at random plots that I was *sure* had significant information in them…..
Bob On Sep 1, 2014, at 9:31 PM, Bob Stewart <[email protected]> wrote: > Hi Poul, > > I've made a few hardware changes and some software changes, and I was > wondering if you (and/or others) would take a look at this plot. The green > is phase over 70,000+ seconds with ~100ps resolution, while the blue is the > ADEV. (The sharp departures in phase are from large temperature changes and > not quite perfect temperature compensation software.) I don't see your > horizontal line down at the bottom, but there are some worrying horizontal > lines between about 3tau and 150tau. Should I take that to mean that I have > some noise/oscillations from about 1/3Hz to 1/150Hz? Those up at about > 150tau I think I can see by eye on another plot of different data. I've got > a lot of data collected from this run (still running) including pTerm, iTerm, > dTerm, and tTerm (temperature) updates to the DAC. I hope to try to tease > something out of that later, though the pTerm and iTerm are mostly +1,0,-1 > stuff. FWIW, in real terms, the dGain is at about 4.2. The phase > starts to get ugly if I bring it much below that. iGain is .01 and pGain is > .05. There are misc damping and limiting factors applied, as well. > > > Just about ready to do a second board with updates from what I've learned, so > any help is appreciated. The plan is to release the source code at some (not > too) future date and make boards available, if there's interest. But I've > still got a lot to do before that. > > > http://evoria.net/AE6RV/TIC/ADEV3.png > > > Bob > > > > > ________________________________ > From: Poul-Henning Kamp <[email protected]> > To: Bob Stewart <[email protected]>; Discussion of precise time and frequency > measurement <[email protected]> > Sent: Thursday, August 28, 2014 1:04 AM > Subject: Re: [time-nuts] OCXO Phase Noise Measurement in Primitive Conditions > > > -------- > In message <[email protected]>, Bob > Ste > wart writes: > > This looks like a step in the right direction. > > The "correct" allan plot will have a clearly visible horizontal > segment somewhere in the 100-10000 second range (depending on OCXO quality). > > This is where the GPS long-term stability "takes over" from the OCXO's > better short-term stability. > _______________________________________________ > 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. _______________________________________________ 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.
