... > Also if you would, I'd like to have a better understand of > what seems like an over obsessions with Low Noise GPSDO. > I do understand the need (or at least the desire) > to have low noise oscillators when using them directly for high > frequency and/or short time scale data taking applications, > and the need for a good stable oscillator where it must maintain > frequency if the GPS signal is lost, > BUT it sounds like this is not what a large percentage of the > second hand GPS trackers discussed here are used for. > It does not seem like it would matter what the noise of the internal > OSC is, if the unit is only being used for averaging things over longer > periods such as looking at phase drift over time when doing freq checks. > Any data taken at a period of say 1000 second to several days is > pretty much limited by the noise of the GPS and not the Oscillator, > so why is there the desire for the low noise oscillators in these cases? > > Warren > ***************** > Often the use of a low noise OCXO is mandated by unstated applications such as:
1) The OCXO output is used to drive the external frequency standard input of a counter. 2) The OCXO output is used calibrate other oscillators to 1E-9 or perhaps a little better and averaging over 1000 seconds or so during adjustments isnt a sensible option. 3) The OCXO output may be used to control the frequency of a microwave transmitter and/or the LO of a receiver which requires low drift and phase noise. 4) Obsession Bruce **************** Bruce Thanks, I'd forgotten about really good counters with resolution better than a1 ns, because I don't have one, Wish I did. and I understand the microwave and Obsession needs, But as far as #2, calibrating to 1E-9 or better, am I forgetting something else? I think even the poorest Osc's, that would ever be put in a GPSDO, have phase noise and drift of under 1 ns, so in 1 sec it could do 1E-9 or in 10 sec 1E-10. Are you saying that 1 to 10 seconds may be too long of time to average over? Warren _______________________________________________ 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.
