Didier Juges wrote: > Ulrich Bangert wrote: > >> Hi Didier, >> >> you may use the DRIFT section of the graphic editor of PLOTTER to remove >> a phase drift due to a constant frequency offset as seen in this data, >> with the result that you get more "visual resolution" out of it, as in >> the attached PDF. >> >> 73 de Ulrich, DF6JB >> >> >> > Ulrich, > > I ran the OCXO with the new antenna location overnight, except that the > laptop went to sleep some time in the night, so I have lost several > hours of data, which may explain the sudden slope change in the plot > below (I need to save timestamps I guess). However, the remaining data > is good I think. There was no sudden noise, and about 5 phase jumps due > to the OCXO drifting during the observation period. > > I downloaded the latest version of Plotter (10-27) and it's all there. I > was able to quickly remove the phase jumps when the OCXO drifted past > the divided down period, and then remove the remaining slow drift. > > What a nice piece of software! > (even the menu now has a *normal* File->Open :-) > > The latest plots are at the usual place: > http://www.ko4bb.com/Test_Equipment/HP10811-GPS_10-29-2.png > http://www.ko4bb.com/Test_Equipment/HP10811-GPS_10-29-2_Allan.png > > Now that the data collection method seems to be getting close, I wonder > how I should use the data, and what it means. > > The Allan deviation seems to taper around e-10 at 1000 seconds, then it > looks like it wants to keep getting lower. > > As a reminder, this is the HP10811 against the GPS receiver. I am not > sure what I should expect? > > Didier > > PS: I am still planning to measure ambient temperature at the same time > as I collect TI, via the GPIB, using a HP 3478A voltmeter and a > thermistor. This way, I should be able to correlate frequency changes > and temperature changes. I assume I can tell Plotter to ignore the > temperature field or display it with its own scaling. Should I use a > specific character as field delimiter? (such as a comma, or just spaces?) > > (In the short term, temperature data will be thermistor values, until I > write the code to convert in degrees. ) > > Also, if I use time stamps, should I use field delimiter between the > time stamp and the data? > > What is the time stamps are discontinuous (as if the laptop falls asleep > again), will that mess up Plotter? > > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Didier
Unless you have a particularly poor 10811 it is likely that the measured Allan deviation is limited by your the instability of your GPS receiver PPS output. With a good GPS timing receiver setup you should expect an Allan variance perhaps 5x lower than this as illustrated in Ulrich's article for the AMSAT journal. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
