Timing GPS receivers usually have the sawtooth correction message and I saw an application of a delay line to correct the PPS before using it. Of course if you time the PPSes difference with a time-to-digital you don't need to correct the incoming hardware PPS by a delay line, but to implement an all-analog PPS PLL then it can be done. For those of you who use a 10KHz reference signal there is not even the need for a long time constant in the low pass filter: to average 1000 PPSes you need 1000 seconds but to average 1000 10KHz cycles you need only 0.1 seconds.
On Mon, Jan 30, 2012 at 6:15 AM, David <davidwh...@gmail.com> wrote: > The sawtooth error in the PPS output and how they were able to correct > it externally was interesting. I have seen that kind of problem > before in DDS and other applications. > > I wonder what other GPS receivers provide either PPS outputs without > sawtooth noise or a correction message. > > On Sun, 29 Jan 2012 20:40:52 -0800, Hal Murray > <hmur...@megapathdsl.net> wrote: > > > > >> What do you mean by "average"? Do you mean that the GPS and PLL must be > >> kept on for "20 minutes to hours", or did you mean that the PLL loop > filter > >> must have a time constant of 20 minutes to several hours? > > > >You have to compare the characteristics of the oscillator with the > >characteristics of your GPS receiver. > > > >If your local oscillator is very stable, then you want to average over > long > >times (hours, days). If your local oscillator is a good thermometer and > you > >have a very good GPS receiver, then you want a shorter time constant > >(minutes) so you can track temperature changes. > > > >Do you know about hanging bridges? If not, please read Timing for VLBI by > >Tom Clark and Rick Hambly. It's got some wonderful graphs. Once you > >understand those, this discussion will get much more interesting. > > http://gpstime.com/files/tow-time2009.pdf > > _______________________________________________ > 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.