In message <[email protected]>, Steve Rooke writes:
>So why am I saying this, well from what I have read on this group and >on the web, I have been left with a feeling that it was vital to >capture every event over a samplig period to ensure an accurate >measurement. It is vital only to simplify the calculation of the uncertainties on the result more than the result itself. If you skip every other time interval, you have no information about noise of the obvious 1/p frequency, just like Nyquist says. Dividing a 10MHz signal to 1PPS, and measuring the adev on that, therefore gives us no right to talk about what happens on the fast side of tau=1sec. Aperiodic sampling can be an incredible powerfull tool to use instead: Comparing the two 10MHz signals by measuring the difference i duration between ramdomly chosen sequences of thousand samples, gives very detailed information, as long as you know the exact relative placement of your 1k sample runs relative to each other. The mathmatical handling is nasty though. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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.
