Hi > On Feb 6, 2018, at 3:48 PM, Deirdre O'Byrne <deirdre....@gmail.com> wrote: > > Tom, > > Thanks for the feedback! > > On 6 February 2018 at 20:29, Tom Van Baak <t...@leapsecond.com> wrote: > >> >> 2) Not all decoding errors are equal. Since this is a time code instead of >> arbitrary binary data you can use the internal structure of the data to >> your benefit. >> > > As I said to Poul-Henning, that is the next level of error detection, which > also has application in error correcting some of the "almost-right" signals. > > >> 3) A side-effect of your data set is that you can track performance of the >> oscillator inside the logic analyzer: convert the 700k GPS timestamps into >> interval, find and replace the 4 glitch lines with 2 lines of 1.000150, and >> then use Stable32 or TimeLab to plot. I used a 10 minute running average to >> reduce the 50 us quantization noise. Note the mean frequency of your >> timebase is 152 ppm low. > > > I made it out to be 152.2ppm, which is kinda disappointing. But the signal > analyser cost very little, and you get what you pay for. > > I have not yet wrapped my head around how to create ADEV plots, so thanks > for your work on that - it's interesting to see that (presumed) initial > thermal effect. > > >> Over 8 days this results in a cumulative sampling error of 105 seconds. If >> your decoding algorithms are relative instead of absolute this won't be a >> problem. OTOH, you may be able to use your decoding process to detect this >> drift and then compensate for it in software. You have the beginnings of a >> MSF-Disciplined-Oscillator project. >> > > MSF disciplined oscillator?! I don't trust these receivers to any better > than about the 20ms mark, so such a disciplined oscillator would have quite > a long integration time!
Once upon a time, that *was* how people did disciplined oscillators. Part of the answer to “how?” is that their target accuracies were not as tight as what we now think of as normal. Bob > > Thanks again. > _______________________________________________ > 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. _______________________________________________ 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.