Hi
> On Nov 22, 2017, at 5:16 PM, Jerry Hancock <je...@hanler.com> wrote: > > Three questions: > > 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with both > supplying 10Mhz and 1PPS, is there a way to combine the outputs or some other > technique to improve the short and/or long term performance? You can monitor one against the other. Ideally you would want three GPSDO’s and a monitoring setup. That way you can figure out which of the three has gone bad. > > 2) I’ve become interested in Rubidium Disciplined Oscillators recently and > was now thinking of purchasing one of the PRS-10 that I see on Ebay. If I did > that and replaced one of the DOCXOs from one of the Lucent boxes, what impact > would this have on the overall performance both with and without (when in > hold-over)? If you go into holdover, you are the exception. Most setups rarely go into holdover. When they do, it’s because a hurricane just went over the house. Generally that’s not when the focus is going to be on timing experiments. > Basically, is it worth the money to upgrade one of the boxes to a Rubidium > disciplined oscillator assuming the GPS signal is rarely lost? Not worth the money if you are only looking at holdover and have a typical setup. > > 3) Figuring the PRS-10 will cost around $250 when all is said and done, is > there a better option to improve my GPSDO system? Disciplining implies continuously correcting. Rb standards age much less than a typical OCXO. Oddly enough their temperature stability may not be as good as a high end DOCXO. It is fairly common to try to stabilize the environment your standards operate in. To the extent you are successful this reduces the need to deal with temperature. The net effect is that disciplining an Rb at a rate (filter / control loop / manual tweak) of less than a few days actually makes the Rb worse. Coming up with software to “back off” on the tuning is not as simple as it might seem. This comes back to the fact that the GPS signal (or any of the sat signals) are quite noisy. You need to average them over a *long* time to get good performance. Rb’s are enough better than a GPSDO OCXO that the time ranges really stretch out …. > > I basically use the GPSDO as a reference for any equipment that takes an > input. I have no monetary need for a reference, just an interest. For most normal test equipment, a GPSDO output is “plenty good enough”. As a source for fancy timing experiments … maybe not so much. As a phase noise reference or a spur free source for microwave games … also not the best way to go. Bob > > Thanks. > > Jerry > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.