WarrenS wrote: > ... > > >> 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 > No, but one likes to have a local standard at least 10 x better than the device being calibrated.
Bruce _______________________________________________ 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.
