Please read the following documents: http://tf.nist.gov/timefreq/time/gps.htm
We may find some diagrams with GPS to NIST time transfer error at: http://tf.nist.gov/timefreq/service/gpstrace.htm We are very happy to see error in the order on magnitude of tens of nanoseconds. I'm sure, on the road to the Internet, there are many other errors: the RS232 port, PC motherboard and it's *bad* 14, 318182 MHz clock, the NTP daemon, the network card, the switches, the routers, etc. What I obtained with my servers are errors around 1 to 10 microseconds from the GPS receiver to the motherboard but no sub microsecond error. https://ecoca.eed.usv.ro/mrtg/ntp1usvro_offset_10.html - the best possible results with the best possible PC I found (P2/333MHz - Fujitsu/Siemens / FreeBSD 5.4 / Garmin GPS 18) - (no, P4, P4 Duo, P4 dual core are not good for timekeeping - I made tens of tests with different machines and different brands and configurations) and a more common result: https://ecoca.eed.usv.ro/mrtg/ntp2usvro_offset.html (any other PC brand and the same hardware / software configuration). I have now two http://www.thinksrs.com/products/PRS10.htm and I plan to use them and I also plan to hack the motherboards 14MHz clocks and replace them with http://www.febo.com/time-freq/hardware/ICS525 boards (driven by the rubidium 10MHz outputs). I'll post here the results and I am sure there wiil be the best we may obtain in a non-professional environment. On Jan 28, 5:59 pm, "Richard B. Gilbert" <[EMAIL PROTECTED]> wrote: > John Allen wrote: > > Richard B. Gilbert wrote: > > >> It should not matter which satellites your site is using, they all > >> keep the same time to within nanoseconds! > > > To satisfy my curiosity without effort on my part, can someone tell me > > where the GPS satellites actually get their time from? > > > John > > > -- > > > John Allen > > Bofferdange, Luxembourg > > allen{at}vo{dot}lu > >http://www.homepages.lu/allenThe Navstar (GPS) satellites have atomic clocks > >(cesium) on board. > These clocks are monitored and controlled by a ground station. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
