I would like a treatise on ti reported by gpsdo's. Sent from my iPad
On Oct 21, 2012, at 7:39 PM, "Tom Van Baak" <t...@leapsecond.com> wrote: > David, > > This is problematic, since the Z38xx software is not really measuring the > output of the GPSDO. Instead it's taking the internally reported PLL time > error measurements from the disciplining loop and pretending they are a > measure of real performance as measured against a real frequency standard. > > However, this PLL data can be used to see how well the loop is working; that > in itself can be interesting. For example, differences in an ADEV plot of the > PLL error term can be used to reveal the time constant used by the PLL. So > one can still use the ADEV-style calculation on the phase error of a closed > PLL; but don't confuse this with the actual performance of the GPSDO as a > time/frequency standard. Does this make sense, or shall I explain more? > > Or, if you have some raw data you can send me off-line I'll take a look at it. > > Thanks, > /tvb > > ----- Original Message ----- > From: "David Hooke" <dho...@gmail.com> > To: <time-nuts@febo.com> > Sent: Sunday, October 21, 2012 4:44 PM > Subject: Re: [time-nuts] GPSDO three cornered comparisons > > >> Tom, >> >> The ADEVs I quoted are from the Z83xx software, so I assume it's >> comparing time from the GPS system to it's own oscillator's output, in >> the same way that LH does. I've been monitoring the basic stuff you >> suggested. >> >> It's because I don't have a known reference to compare the units with >> that I want to use the 3-corner method to start sorting the wheat from >> the chaff. >> >> david >> >>>> I have an HP 58503A and a Symmetricom 58503B which are behaving quite >>>> differently to one another using a common antenna. Using Z38xx, there's >>>> almost an order of magnitude difference between the reported ADEVs at >>>> 40k seconds (HP:7e-13, Sym:5e-12). Both have 10811 oscillators and are >>> Where are you getting the "reported ADEVs"? What counter, what reference, >>> what software? >>> >>> Did you happen to periodically log any SCPI data during the runs, so that >>> you can compare SV counts, signal strengths, TI averages, and so on? In >>> general it might be good to have a quick look at this mundane data first. >>> >>> /tvb >>> >>> > > > > _______________________________________________ > 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.
