It's mathematical in both frequency, and in phase (clock and channel input timing). Depending on relative cable lengths I suspect you can get lucky and see it always wander 1 count above 5 MHz instead of 1 count below 5 MHz. But you should not expect it to do both; that would be 2 counts; your counter is better than that.
/tvb (iPhone4) On Jul 15, 2013, at 8:09 AM, Bob Stewart <[email protected]> wrote: > In this case, I was using the 10MHz output from the GPSDO as the reference > and measuring the 5MHz output from the GPSDO. So, even if the GPSDO is off > in frequency, the relationship between the 10MHz reference and the 5MHz > signal are mathematically fixed. It just seemed strange to me that under > such a circumstance the final count would wander only in the minus direction. > I expected either to see a solid 5.0000000, or to see it wandering between > 4.9999999 and 5.0000001. > > Bob > > > > > >> ________________________________ >> From: Azelio Boriani <[email protected]> >> To: Discussion of precise time and frequency measurement >> <[email protected]> >> Sent: Monday, July 15, 2013 4:47 AM >> Subject: Re: [time-nuts] GPSDO - Does it work? >> >> >> It is normal for a counter to have a +/- 1 count of wander. Then you >> have to consider the reference for that counter. When you connect a >> GPSDO on the input of a counter with its internal reference used as a >> timing source, you are measuring that internal reference accuracy and >> stability, not the GPSDO's one. To verify a new GPSDO it is necessary >> to have another (know good) GPSDO or a Cs reference. Missing that, you >> can use the PPS output of the GPS receiver but then an average process >> is needed: say, a digital 'scope with the display persistence function >> and... wait a lot of time (or use a high resolution TI counter and the >> TimeLab software). >> >> >> > _______________________________________________ > 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.
