From: "Tom Van Baak" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Z3801 lockin behaviour Date: Sun, 23 Jul 2006 17:22:25 -0700 Message-ID: <[EMAIL PROTECTED]>
> > Hi! > > > > I have powered up my Z3801A and monitored the 10 MHz on a counter (with > fancy > > histogram and statistics) with the Cs as reference. The Z3801 is moving > around > > quite a bit and the SatStat shows that it hasn't really converged towards > > precission (the 24h time error prediction). Infact, it drops out of lock > into > > holdover every now and then. When it jumps in or out of hold over, a > "large" > > (50 mHz) frequency jump is clearly vissible. I have about 1 mHz of Allan > > Deviation and about 4 in Standard Deviation. > > > > I have made comperative measurements of my counter setup by hooking it up > to my > > Rb, and that is noticeably lower in noise. > > > > Is this to be expected or not? > > > > Any thoughts & recommendations? > > > > Cheers, > > Magnus > > While watching the syst:stat screen did your Z3801A > already complete its multi-hour site survey and the > coarse/fine frequency adjustments? Yes. I explicity had it redo the survey to make sure it was running of the current antenna position. > If it's still in a > start-up acquisition mode ignore the 10 MHz output. It was ramping like hell until the oven stabilized. > If it doesn't lock after a few hours, I'd suggest a full > reset. Also check your signal levels, and elevation > mask. Did it get your lat/lon/alt correct? Seems alright. Get SS values which seems good, occassionally above 200 but rarely below 100. Usually track 5-6 satelites but if it had been a 12 channel receiver I would have had 12 satellites tracked over the 10 degree elevation mask. > The predicted time error won't settle down for a few > days (it's a long time constant), so don't worry about > that quite yet. OK. I'll let it simmer for a few days then. > Not sure what you mean by "The Z3801 is moving > around quite a bit". You should get 10 solid digits > of accuracy out of a Z3801A at short sample times. > That grows to 11 or 12 over several hours; 12 to 13 > over several days (at which point you won't quite be > sure if the errors are your counter, your Z3801A, or > your cesium). The end goal is to compare the Cs, Rb and GPS at various time constants, in which case I will be able to resolve the phase-noise of each of them. Right now I'd say I only have a solid 9 digits. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
