What specifically are you worried about? The entire GPS system being turned off or maybe just a few hours of outage. Do you think maybe they will turn SA back on and degrade GPS' performance? FOr each of these posabilities there is something different you might do so it helps to know what exactly you are worried about.
Most (or all?) cell towers have a backup clock in case GPS stops. What they are mostly worried about is some local transmitter jamming the GPS signal because that actually might happen on a radio tower. What they all do is keep something like a Rubidium oscillator running or an ovenized crystal oscillator (OCXO) either of these will "cary" the system through a 24 hour GPS outage. the Rb unit might take care of your needs (1 millisecond) for weeks of GPS outage Glassnos is going to hve the same problem. The Russian government can change their policy overnight with no warning, just like the US government might and both might be jammed by the same close by transmitter. This applies to Galileo too. Another good backup system is to simply use Internet pool servers for absolute time and then also keep a local Rubidium oscillator running. But then how to know if the Rb is still running at the "correct" rate. Better buy three of them and a spare. But first you have to ask what happens if you clocks are "off". How much money will it cost you if that happens? On Sun, Aug 5, 2012 at 2:36 PM, Miguel Gonçalves <[email protected]> wrote: > Hi there! > > I currently have 2 embedded machines connected to a Garmin 18 LVC and a > Sure GPS board. > > They are NTP servers for my company's LAN and I, at the moment, I get > sub-ms accuracy over the LAN. > > Everything is fine but I am a bit worried about the GPS reliability > because GPS is ruled by the USA. Would a GPS disciplined oscillator solve > any potential problems? A receiver for GLONASS, even though I did not find > any at a reasonable price, would be better? > > An iridium oscillator calibrated, regularly by GPS? > > Too many questions... but in the end I would like to know what is the best > path that I could follow after these GPS receivers. > > Many thanks! > > Regards, > Miguel > > > _______________________________________________ > 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. > -- Chris Albertson Redondo Beach, California _______________________________________________ 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.
