Hi,
Upload rate could be one. There is some systematics due to jumps from
the old to new estimation. I think I recall a 2 h upload rate, but no
guarantee for that number.
Cheers,
Magnus
On 04/30/2017 06:32 PM, Eric Scace wrote:
What other patterns, if any, are uncovered if one removes a smoothed
sidereal variation?
— Eric
Begin forwarded message:
From: Jim Harman <[email protected]>
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Date: 2017 Apr 29 Sat at 10:14:58 EDT
To: Bob Stewart <[email protected]>, Discussion of precise time and frequency
measurement <[email protected]>
Reply-To: Discussion of precise time and frequency measurement
<[email protected]>
On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart <[email protected]> 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
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