I'm now wading through the GPS data I logged to see if anything happened at the time of the jumps. Will post once I find something.
On 29 November 2013 15:35, Stephan Sandenbergh <ssandenbe...@gmail.com>wrote: > Hi All, > > I have now redone the original experiment (same settings), and this time > round no jumps at all. Strange. This means I cannot reproduce what I > originally measured, making it all the more difficult to hunt down the > issue with certainty. > > Thank you for the good advice thus far. For future measurements I'll stick > to microsecond offsets and stay away from multiples of the various clocking > frequencies. > > I'll post again should I find something that might explain the original > result, or if I perhaps manage to reproduce it. > > Regards, > > Stephan. > > > > > > > On 22 November 2013 14:06, Bob Camp <li...@rtty.us> wrote: > >> Hi >> >> Something is going wrong somewhere. The question is where. Three ideas / >> targets here: >> >> The counter is a 100 ns (10 MHz input) beast, so it *might* be the issue. >> >> The offset source or the GPS might also be the issue (thus avoiding >> 1/10.24 MHz). >> >> The idea with the larger offset is that there is no significant accuracy >> degradation with a modest increase in the offset. The exact value isn’t the >> issue there, just making it larger. That way you will still properly >> capture stuff in the 100 (or more) ns range. >> >> Bob >> >> On Nov 22, 2013, at 4:38 AM, Stephan Sandenbergh <ssandenbe...@gmail.com> >> wrote: >> >> > Hi, >> > >> > Ok, the 53131A trigger settings: I've turned auto trigger off and set >> it to >> > trigger at 2V (I think this is right, but I'll have to go and double >> check >> > the exact threshold setting) threshold. Sensitivity is set to high. >> > >> > Location is GPS surveyed and all M12+'s are set to position hold mode. >> > >> > I did record the time stamped GPS data as well so will go have a look at >> > what happened to the constellation at the time of the jumps. Will post >> when >> > I have results. >> > >> > Sorry if I'm a little slow here, but why is it better to use larger >> > offsets? Also I get that 100ns is exactly one cycle of 10MHz, but why >> would >> > the 53131A have trouble with this? Surely it uses linear interpolators >> > along with digital counters to calculate the result. Also, I assume the >> > counting doesn't happen at 10MHz, but at a much higher multiple. Had it >> > been done at 10MHz I'd understand that skipping a beat would result in >> > 100ns offset. Granted I don't know much about the innards of the 53131A. >> > >> > >> > >> > >> > On 22 November 2013 02:25, Bob Camp <li...@rtty.us> wrote: >> > >> >> Hi >> >> >> >> To be clear - the idea of going to a non-100 ns multiple is a good one. >> >> You probably should avoid multiples of 1/10.24 MHz as well. >> >> >> >> Bob >> >> >> >> On Nov 21, 2013, at 8:00 AM, Azelio Boriani <azelio.bori...@screen.it> >> >> wrote: >> >> >> >>> Yes, do not use tiny offsets, go to 1us: I use microseconds offsets to >> >>> take PPSes measurements . >> >>> >> >>> On Thu, Nov 21, 2013 at 1:34 PM, Bob Camp <li...@rtty.us> wrote: >> >>>> Hi >> >>>> >> >>>> The counter and offset generator both should be quite accurate at a 1 >> >> us offset. That’s large enough that you are outside the range of most >> GPS >> >> jumps. If you are going to move things around, you might as well move >> out >> >> to that vicinity. >> >>>> >> >>>> Bob >> >>>> >> >>>> On Nov 21, 2013, at 6:20 AM, Tom Van Baak <t...@leapsecond.com> >> wrote: >> >>>> >> >>>>>> Below is a plot so you could see exactly what I measured. What is >> >> peculiar >> >>>>>> is that the time jumps by exactly 100ns to 200ns. Almost as if the >> GPS >> >>>>>> receiver decides to offset the time by twice the amount I set it >> to. >> >> Which >> >>>>>> is why I initially thought it might be a firmware thing. I suppose >> >>>>>> multipath is a good explanation, it is just odd that the time >> error is >> >>>>>> exactly 100ns. >> >>>>> >> >>>>> Hi Stephan, >> >>>>> >> >>>>> A quick test you could perform is set the offset to 125 ns instead >> of >> >> 100 ns and see if the jumps still occur, still occur at 100 ns, or now >> >> occur at 125 ns. >> >>>>> >> >>>>> Since you have three M12's offset the third one by 150 ns and see if >> >> it experiences jumps too. >> >>>>> >> >>>>> Question -- are you using the external 10 MHz reference input or >> >> output for any of your 53131A counters? >> >>>>> >> >>>>> /tvb >> >>>>> >> >>>>> _______________________________________________ >> >>>>> 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. >> >>> _______________________________________________ >> >>> 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. >> >> >> > _______________________________________________ >> > 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. >> > > _______________________________________________ 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.