In message <02c801c956c9$4aa089a0$6401a8c0 at WSOffice>, "WarrenS" writes:
>The short of it is that every once in a while the 100 Hz syncs up >for a short time to the 1 Hz As far as I have ever been able to tell, that is not how it works. The 100Hz and 1Hz are generated with the same hardware and same behaviour relative to software. Back when I got my first 100Hz capable Oncore, I measured the 100Hz output against 100Hz generated by the TVB PPSDIV driven by my Cs using my HP5370B and GPIB to collect all samples. The conclusion was that the 100Hz was kicked not once per second but much more often. If the 100Hz had been synched once per second, both FFT and ADEV/MDEV would flag the 1Hz signal resulting from that, and they didn't, and neither does Toms data. I also found, as Tom did, that using the 100Hz was as good as doing the saw-tooth correction, and without getting into a long-winded treaties about the finer points of modulus arithmetic, this also indicates that the 100Hz tickled more often than 1/s and quite likely at every period. I tried to determine if the 100Hz indeed was tickled every period, I expected it to show up in a histogram of the 100Hz signals absolute or relative periods, but there were too much noise to confirm that. Maybe Tom can try to repeat that experiment ? Simply measure a sequence of zero-deadtime period widths of the 100Hz and make a histogram of the absolute widths and relative widths, (the difference in width between period N and N-1.) If we can confirm that the 100Hz signal is updated every cycle, then that explains why Toms and my measurement found the averaged 100Hz to be as good as the negative sawtooth: sqrt(100 - ) ~= 10 Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. Poul BTW >"The The short of it is that every once in a while the 100 Hz syncs up >for a short time to the 1 Hz BTW the 3 times a day or so sync up the above is referring to is the reason that every once in a while the 100 Hz is only as good as the 1 Hz signal for a short while. The 100 Hz is defiantly update or at least different on every cycle, and has about the same peak to peak noise, which is why if nothing but just average the 100 Hz before using it for the 1Hz update, things would get a better. WarrenS _______________________________________________ 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.
