Ron, as I said in my response, there are many other factors with a great influence on the precision. The rubidium oscillator stabilizing the PPS signal has near zero effect if you do not change the motherboard crystal. The temperature has a great influence on the stability, I observed variations of more that 20 to 50 microseconds in the interval from 10 to 35 degrees.
On Jan 30, 10:55 am, "Rob Kimberley" <[EMAIL PROTECTED]> wrote: > Hi Richard > > 500nS is very achievable with GPS. In fact, once installed and running for > 24 hours, you will see better than a factor of 10 than that. > > Factors to bear in mind though for this type of application.... > > 1) Use exactly the same hardware at each site. > > 2) Antenna cable - important to ensure that you enter the correct antenna > delay figure when setting up the receiver to allow for cable delays > (remember you GPS position and hence your time is at the antenna and not the > receiver). 1nS per foot is a good estimate, so a long cable run (with > amplifiers etc) would quiclky put your system time off without the correct > compensation figure. > > 3) Oscillator - a good quality OCXO or most likely a Rubidium are needed, to > allow decent holdover in the unlikely event of loss of GPS. For your 500nS > mission statement, my personal recommendation would be Rubidium, as an OCXO > would quickly pass the 500nS figure if the unit had to flywheel. > > Good luck. > > Rob Kimberley > > "Richard Eich" <[EMAIL PROTECTED]> wrote in message > > news:[EMAIL PROTECTED] > > > [EMAIL PROTECTED] wrote... > >> Richard, > > >> Try clicking on this link: > >>http://tf.nist.gov/timefreq/time/gps.htm > > >> You can achieve precision anywhere between a few milliseconds and a few > >> nanoseconds, > >> depending on how much you are willing to invest. Have you asked > >> yourself how much > >> precision the application needs? You can almost certainly achieve it! > > > Great link, thank you. > > > The app needs 500ns precision. We can set up GPS at each locality, > > but there was a concern about the relative accuracy of GPS receiver > > timestamps if they're sync'ing to different physical sats. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
