http://www.leapsecond.com/pages/m12/sawtooth.htm
/tvb (i5s) > On Feb 16, 2014, at 4:46 PM, Bob Stewart <b...@evoria.net> wrote: > > The smart guys have already contributed to this thread. What I have is an > example taken when I was doing some testing. The plot at the top is the DAC > on my GDPSO. It is moving the oscillator back and forth about 4.6E-4 Hz. > Not a lot. > > The bottom plot is the interesting one, as it is the 1PPS from my Adafruit > Nav Receiver plotted with respect to the OCXO. The labeling is unfortunate > for this discussion. Just think of "-10" as being +180 degrees of phase, and > -30 as being -180 degrees, for a total phase of 360 degrees between them.. > Notice the plot at about 10:40. It points out that the 1PPS error isn't > nicely spread out. Rather, it moves around as the difference between the > time signal being received from the satellite and the free-running oscillator > in the GPS receiver > > http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/PPS%20Anomaly%202.png > > > Bob > > > > >> ________________________________ >> From: Jimmy D. Burrell <jimmydb...@gmail.com> >> To: Discussion of precise time and frequency measurement >> <time-nuts@febo.com> >> Sent: Sunday, February 16, 2014 1:55 PM >> Subject: [time-nuts] GPS accuracy specs >> >> >> I've looked at several different manufacturer GPS datasheets now regarding >> the 1 PPS output in an attempt to compare apples to apples. Some of them >> rate their 1 PPS output as something on the order of "PPS signals have an >> accuracy ranging 10ns" which seems ambiguous. Does that mean the leading >> edge of their 1PPS is within 10ns of the GPS clock? Or simply that the >> stability of their 1 PPS is within 10ns? Or both? >> >> Perhaps there's an industry standard for these specs of which I'm unaware? >> >> The datasheet for my (presumably much older) Globalsat ER-102 seems, to me >> at least, to be much more clear stating "time reference at the pulse leading >> edge aligned to GPS sec., +/- 1 us". Which I interpret as the leading edge >> of my receiver's 1PPS is aligned with the GPS's clock to within +/- 1 us. >> >> Jim... >> N5SPE >> _______________________________________________ >> 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.
