According to the wiki-pedia http://www.wikipedia.org/wiki/Atomic_clock "GPS , Galileo and GLONASS : These satellite navigation systems , have a Caesium atomic clock on each satellite, rated from clocks on the ground. The time available is exact, and some instrument-quality navigation units can serve as local time standards." The clocks are maintained according to another atomic clock on the ground at the master control station in the case of GPS. According to http://www.laruscorp.com/tchap05.htm "A GPS receiver can also be used directly as a source of Stratum 1 quality." For those (like me) who didn't know what a stratum clock source is, there's a good overview of the different levels here: Stratum Levels Defined http://www.laruscorp.com/tchap04.htm -Adam Marc Nicholas wrote: >On 11/6/03 14:42, "Robert Rolf" wrote: > > > >>Steve Ruse wrote: >>GSM, CDMA and TDMA networks require extreme precision in their timing so they >>all use GPS disciplined clock references. In fact, old digital cell phones >>are great sources of extremely accurate SMT TCXO's (ppm level) if you don't >>mind the odd ball base frequency. >> >> > >Hmmmm....GPS is considered a Stratum 1 clock source? Seeing as most telecoms >carriers want a Stratum 2 clock reference, you'd have to slave to a Stratum >1 and AFAIK that requires an atomic decay reference source. Hold on...is >there an atomic reference in the GPS satellites? (Going to go Google!) > >-marc > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics