Hi 1) Because it's way more fun to do it this way 2) Because some / most PRS-10's don't have the 1 pps input enabled in the firmware they have loaded into them 3) Because you have more control over when you do / don't bump the frequency (you can see what's going on).
Bob On Sep 2, 2013, at 12:21 PM, Robert Darby <bobda...@triad.rr.com> wrote: > This is a dumb question but why not let the PRS-10 set itself using the 1PPS > input and an appropriate time constant? > > Thanks, > Bob Darby > > On 9/2/2013 12:09 PM, Bob Camp wrote: >> Hi >> >> Ok, you are fine with the 10 MHz reading on the 5335 to get things "sort of >> close". Once you get past about 1.0x10^-10 you may want to switch over to a >> pps based approach. More or less: >> >> Fire up 5335 with pps from gps / gpsdo and from the PRS-10. (I'm assuming >> it's a GPSDO) >> Watch the reading for a few seconds, record the average and the time. >> Go have lunch / nap / beer / what ever. >> Check the time and the reading. >> Do the math >> Bump the PRS-10 >> Step / repeat at the couple hour time interval for a day or so. >> Drop back to a couple days, check and (maybe) adjust. >> Drop back to once a week, check and (maybe) adjust. >> >> Note that the 5335 only has to be on while you are actually observing the >> pps. No need for the heat / wear and tear the rest of the time. Your pps >> needs to run all the time, but that's only a problem if there is a power >> outage. >> >> The advantage of doing it this way is you get both high resolution and >> averaging at the same time. Since there's pretty much nothing to set up (no >> computers / no GPIB) it's reasonably foolproof. Assuming that the 5335 is >> doing it's thing and that the GPSDO is good to roughly the same level: >> >> 3 hours is 10800 seconds >> your reading is good to 3 ns (2 on the GPSDO and 1 on the counter) >> you get +/- 3.0x10^-9 at 1 second >> you get about +/- 3x10^-13 at 3 hours. >> >> Since the ADEV of the Rb is much better at the longer Tau's, the data you >> are using is probably a better bet than anything you can do in less time. >> >> Bob >> >> On Sep 2, 2013, at 9:20 AM, Paul <tic-...@bodosom.net> wrote: >> >>>> If you are trying to measure frequency with the 5335 rather than pps >>>> signals >>> Ah, I was unclear. I'm adjusting the 10MHz output. It was pretty far >>> out when I got it. >>> >>> -- >>> Paul >>> _______________________________________________ >>> 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.
