I have a question about if there is a case where the GPS satellite is not available to the GPSDO board. I understand that with the GPSDO board I would be able to put two receivers in two separate locations and they would both get the same timing signal. If the GPSDO modules were to lose the satellite signal for some reason would they still be able to provide a 10 MHz reference? Or is that if you don't have a satellite signal the receivers just fallback to the onboard internal clock. I guess what I'm asking is what exactly happens with the timing if you have a GPSDO module connected and it loses or is not receiving a signal from the satellites? Mike

> I have a question about if there is a case where the GPS satellite is > not available to the GPSDO board. > > I understand that with the GPSDO board I would be able to put two > receivers in two separate locations and they would both get the same > timing signal. If the GPSDO modules were to lose the satellite signal > for some reason would they still be able to provide a 10 MHz > reference? Or is that if you don't have a satellite signal the > receivers just fallback to the onboard internal clock. > > I guess what I'm asking is what exactly happens with the timing if you > have a GPSDO module connected and it loses or is not receiving a > signal from the satellites? > > Mike > > The way GPSDOs work is that there's an internal clock, usually of quite high quality. The GPS satellite signals are used to provide estimates of timing slip between the on-board clock and the satellites. Assuming that the on-board clock on the GPSDO has recently been "in synch", it will slowly drift out-of-synch according to it's "natural" proclivities as a piezoelectric crystal oscillator of reasonably high quality. Once the satellites come back, it will be caused to drift back into synchronization with the satellites. > > -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org