Mike Monett wrote: > Hello Bruce, > > This is my first attempt to post so I'm not sure if it will work. > > I have been researching the forum archive and find it is by far the > best resource on time and frequency available anywhere. Also, your > posts are extremely helpful to a newcomer. Thanks! > > I am curious about the NIST GPS timing receiver that has a > resolution of a few ps. It doesn't seem possible to get that kind of > precision with conventional GPS methods that produce a 1pps signal. > > Can you describe more how this is done, and do you have any web > links that give more information? > > Thanks, > > Mike Monett > > Mike
They actually use an augmented form of GPS common view for which the GPS PPS signal and its timing variations are largely common to both locations and thus largely cancel when comparing the frequencies at the customer site with the standards at NIST. With a good timing receiver (and antenna location) the sawtooth corrected PPS signal timing noise can be as low as a few nanosec. The "all in view" technique will reduce the noise contribution to the comparison somewhat. The timestamp resolution of better than 30ps or so ensures that time stamp quantisation noise is negligible. It also allows, in principle at least, standalone 3 cornered hat comparisons of the frequency instabilities of the 3 sources connected to the customer instrument. For more detail see: http://tf.nist.gov/timefreq/service/fms.htm Only carrier phase GPS techniques are potentially capable of picosecond noise levels. However there are a large number of effects that have to be taken into account and data reduction and correction is very complex. Bruce _______________________________________________ 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.
