What other patterns, if any, are uncovered if one removes a smoothed sidereal variation?
— Eric > Begin forwarded message: > > From: Jim Harman <j99har...@gmail.com> > Subject: Re: [time-nuts] Three-cornered hat on timelab? > Date: 2017 Apr 29 Sat at 10:14:58 EDT > To: Bob Stewart <b...@evoria.net>, Discussion of precise time and frequency > measurement <time-nuts@febo.com> > Reply-To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > > On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart <b...@evoria.net> wrote: > >> So, back to my question: Where are the large ionospheric phase moves? >> This question has been causing me doubt since I started on this project. >> Or don't I still have enough data collected for this to happen? >> >> Bob >> > > Bob, my test setup is a good deal simpler than yours, but attached is a > plot that I think shows the variations you are looking for quite clearly. > This is data from my homebrew GPSDO, which uses an Adafruit non-timing GPS > module and a run-of-the-mill surplus OCXO. The plot records the phase > comparator output over a period of about 1 week. The time constant of the > PLL is 1024 seconds and it is plotting the 5-minute average TIC values. > > The full horizontal scale is 24 hours. > > The vertical scale shows the data from several days with the traces for > successive days offset upwards by the equivalent of 40 nsec. > > As you can see there is pretty good correlation of the phase error from day > to day and the wiggles migrate to the left a little, corresponding to the > 23:56:04 siderial repeat time of the GPS constellation.This is with a > pretty good antenna location, under a shingle roof in the attic. I > calculate the day-to-day correlation at about 0.8. > > Making the time constant larger increases the variations somewhat, because > the loop does not adjust as much, and they definitely get worse if I use a > less optimal antenna location. > > > > > -- > > --Jim Harman > _______________________________________________ > 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.
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