When I first powered them on together, they seemed to drift all over the place with regards to relative phase. For the past hour now, they are keeping around 7 degrees and sometimes dropping to around 4. I think that is pretty amazing given all the stuff between the source and final display. I have the cursors on them now and they are sitting at 2ns difference. I am going to figure out how to plot this possibly using Timelab and my HP 5371a.
> On Nov 17, 2017, at 2:29 PM, Bob kb8tq <[email protected]> wrote: > > Hi > > As the “filter” (or control loop) in some GPSDO’s scales, it impacts the > degree > of “agreement” between the GPSDO’s. Not all GPSDO’s scale filters so not all > exhibit the behavior. The HP / Symmetricom Z38xx units are one family that > do this kind of scaling. > > As the scale moves longer (time) or narrower (frequency) the ADEV improves. > This also depends a bit on the quality of the OCXO you have and the > environment > the GPSDO is in. Somewhat counter intuitively, the level of agreement gets > worse > as the ADEV improves. As the time agreement gets worse and ADEV gets better, > the frequency accuracy (in the frequency nut sense) gets better. > > Again - not all GPSDO’s do this sort of thing. > > Bob > >> On Nov 17, 2017, at 5:15 PM, Arthur Dent <[email protected]> wrote: >> >> I have 2 antennas mounted on opposite ends of a roof and both of them feed >> commercial GPS DA/splitters and I can have as many as 10 receivers running >> at one time for testing. I have also used one of the high frequency type F >> TV passive splitters with one D.C. feed through and added 200-300 ohm >> resistors from the other outputs to ground. All this has seemed to work >> just fine but one of the older receivers apparently radiated its L.O. out >> the antenna coax and would interfere with a couple of other receivers I >> connected to the same DA. >> >> >> >> Connecting one 10 Mhz references to the external trigger on my scope and >> feeding 2 other GPS receivers to the input channels (all from the same >> antenna DA), I can watch the slow drift at 2 ns/div with respect to the >> trigger and sometimes one receiver drift one way as the other receiver >> drifts in the opposite direction and sometimes they drift the same way. The >> drift is generally less than 2 ns but it is there and I assume it depends >> on what the internal ‘housekeeping’ of the receiver is doing and what birds >> they are using. So bottom line, they aren’t ‘locked’ to each other but are >> generally close. >> >> >> -Arthur >> _______________________________________________ >> 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. > > _______________________________________________ > 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. _______________________________________________ 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.
