Three-cornered hat on timelab?
Hi Bob,
On 04/27/2017 06:48 PM, Bob Stewart wrote:
Hi Magnus,
Try as I might, the weather and the local power company had other ideas
about my long term capture. I'm running everything but the 5370 from a
UPS. I guess I'm going to have to get batteries for my other UPS and
run the 5370 from that. A one second power loss was all it took to stop
the test.
Annoying, but you got some good values never the less.
Anyway, I did manage to get 376,238 points of data. The data is
captured on a 5370A. The external clock input and the STOP channel are
fed by the 10MHz from my PRS-45A. The START channel is fed by the 10MHz
from one of my GPSDOs. The EXT channel is fed by the 1PPS from another
of my GPSDO units. "EXT ARM" is enabled. So, essentially, at every
1PPS pulse, the phase difference between the two 10MHz feeds is captured.
OK, this seems like a good setup.
I've attached a screenshot of the phase plot which can also be found here:
http://evoria.net/AE6RV/Timelab/Screenshot.png
I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z
Thank you for providing the data, I downloaded it so I can play around
with it, which I naturally did. :)
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?
Your data seems to be more affected by constellation shifts, as the
period of about 43080 s seems to be a period of the constellation.
You either have averaged out to a somewhat incorrect position of your
antenna or you have sub-optimal position of your antenna.
It gives you a peak-to-peak amplitude of about 10 ns or so.
The ionospheric errors has a period of 86400s, so to get a clear
separation of these would take more data. However, playing around with
the data in TimeLab allowed me to filter out some of the other systematics.
The day-to-day variations is noticeable. I wonder how much of that is
thermal though. The building variations was filtered out in the process.
One has to identify a number of these potential disturbances, estimate
their size in order to more clearly see other things. TimeLab has a
notch filter to notch out a particular frequency. It would be nice if an
alternative approach would be to give the notch a period.
One has to recall that even and odd harmonics to a disturbance frequency
can be there, as it is not always a pure sine disturbance.
Cheers,
Magnus
On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart bob@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
Hi Magnus,
OK, a couple of things about my location. I'm in West Houston, and it's not summer yet, so there's a lot of variation in temperature from day to day. Some nights it's in the 40sF and some nights it's in the high 70s or low 80sF. Lots of variation in the days, as well. My antenna is not optimal, at all. The best I could do was to remove the dish from an unused DishTV antenna and install my GPS antenna on top of the little mast they use. It's about the best I can do. In fact, it's better than I expected.
The receiver is a LEA-6T that was put through a 24 hour survey and the position was saved in flash memory. However, there have been lots of power cycles since that survey. Whether or not that affects the result, I don't know.
Still, the point of the test was to understand why I'm not getting these large phase swings. And I think Bob Camp's explanation was good. Maybe in another 5 years the sunspots will be back up and I can see the comparison to now. Bob
From: Magnus Danielson <magnus@rubidium.se>
To: Bob Stewart bob@evoria.net; Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Cc: magnus@rubidium.se
Sent: Saturday, April 29, 2017 6:45 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Hi Bob,
On 04/27/2017 06:48 PM, Bob Stewart wrote:
Hi Magnus,
Try as I might, the weather and the local power company had other ideas
about my long term capture. I'm running everything but the 5370 from a
UPS. I guess I'm going to have to get batteries for my other UPS and
run the 5370 from that. A one second power loss was all it took to stop
the test.
Annoying, but you got some good values never the less.
Anyway, I did manage to get 376,238 points of data. The data is
captured on a 5370A. The external clock input and the STOP channel are
fed by the 10MHz from my PRS-45A. The START channel is fed by the 10MHz
from one of my GPSDOs. The EXT channel is fed by the 1PPS from another
of my GPSDO units. "EXT ARM" is enabled. So, essentially, at every
1PPS pulse, the phase difference between the two 10MHz feeds is captured.
OK, this seems like a good setup.
I've attached a screenshot of the phase plot which can also be found here:
http://evoria.net/AE6RV/Timelab/Screenshot.png
I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z
Thank you for providing the data, I downloaded it so I can play around
with it, which I naturally did. :)
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?
Your data seems to be more affected by constellation shifts, as the
period of about 43080 s seems to be a period of the constellation.
You either have averaged out to a somewhat incorrect position of your
antenna or you have sub-optimal position of your antenna.
It gives you a peak-to-peak amplitude of about 10 ns or so.
The ionospheric errors has a period of 86400s, so to get a clear
separation of these would take more data. However, playing around with
the data in TimeLab allowed me to filter out some of the other systematics.
The day-to-day variations is noticeable. I wonder how much of that is
thermal though. The building variations was filtered out in the process.
One has to identify a number of these potential disturbances, estimate
their size in order to more clearly see other things. TimeLab has a
notch filter to notch out a particular frequency. It would be nice if an
alternative approach would be to give the notch a period.
One has to recall that even and odd harmonics to a disturbance frequency
can be there, as it is not always a pure sine disturbance.
Cheers,
Magnus
Hi Bob,
This is a phase plot of a rubidium to an M12 from a test that I did
back in 2008. The offset and ageing have been removed, but there is
still a bit of wander.
As with your plot, constellation related issues appear the most
obvious. Peak to peak is fairly similar too.
Angus.
On Thu, 27 Apr 2017 16:48:37 +0000 (UTC), you wrote:
Hi Magnus,
Try as I might, the weather and the local power company had other ideas about my long term capture. I'm running everything but the 5370 from a UPS. I guess I'm going to have to get batteries for my other UPS and run the 5370 from that. A one second power loss was all it took to stop the test.
Anyway, I did manage to get 376,238 points of data. The data is captured on a 5370A. The external clock input and the STOP channel are fed by the 10MHz from my PRS-45A. The START channel is fed by the 10MHz from one of my GPSDOs. The EXT channel is fed by the 1PPS from another of my GPSDO units. "EXT ARM" is enabled. So, essentially, at every 1PPS pulse, the phase difference between the two 10MHz feeds is captured.
I've attached a screenshot of the phase plot which can also be found here:http://evoria.net/AE6RV/Timelab/Screenshot.png
I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z
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
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Magnus Danielson <magnus@rubidium.dyndns.org>
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Cc: magnus@rubidium.se
Sent: Tuesday, April 18, 2017 1:09 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Hi Bob,
That is a good solution indeed. Good luck with that measurement run!
One of the fun stuff with Timelab is that you can walk by and check the
developments. I've found that very useful for long measurements (as in
hours and days).
I prepared a cesium for one vendor, and initially they did not care so
much, but then they saw more deviations between the receivers, so they
wanted to sort it out, but discovered that they could not cancel out the
common mode of GPS signals (and its shifts), so then firing up that
cesium was the right thing. I remember writing support emails while
waiting for the airplane in Madrid airport, happy that they was doing a
first run for the right measurement reason. :)
Cheers,
Magnus
On 04/18/2017 04:25 AM, Bob Stewart wrote:
Hi Magnus,
Today I started a long run against my PRS-45A. Maybe this time I won't have a power outage. I'll see what it tells me in a few days.
Bob
Hi Jim,
I'm not sure you're plotting what you think you are, but perhaps I misunderstood. The phase error data contains both the position uncertainty of the Adafruit (constellation, ionosphere, etc) and an error caused by correcting the OCXO using that phase error. IOW, the fact that the phase error puts the OCXO back in phase is problematic.
You might think about disconnecting the EFC from the OCXO and feeding the OCXO directly with a fixed voltage derived from the VRef output of the OCXO, assuming it has one. Then, carefully adjust the VRef voltage so that the phase error changes very slowly. Let it cook for a few days and restabilize, then start logging your phase error. Feed that to Timelab and see what the plot looks like. Timelab should be able to remove the aging, so that you wind up with a plot that's mostly the Adafruit. Of course, that depends on which OCXO you're using. I've had good luck with the Trimble 34310-Ts that are about $20 each depending on the vendor.
Bob
From: Jim Harman <j99harman@gmail.com>
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, April 29, 2017 9:15 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?
On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart bob@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
Jim,
Errors aligning up due to sidreal time is most likely due to the
multipath errors and repeated upload shifts.
Solar shifts would align up on 24 h basis.
The filtering of the time-constant is expected.
Cheers,
Magnus
On 04/29/2017 04:14 PM, Jim Harman wrote:
On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart bob@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.
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.
What other patterns, if any, are uncovered if one removes a smoothed sidereal variation?
— Eric
Begin forwarded message:
From: Jim Harman j99harman@gmail.com
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Date: 2017 Apr 29 Sat at 10:14:58 EDT
To: Bob Stewart bob@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 bob@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.
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 j99harman@gmail.com
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Date: 2017 Apr 29 Sat at 10:14:58 EDT
To: Bob Stewart bob@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 bob@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.
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.
Hi
A lot of the upload and estimate processes have changed over the years. What was true
at "maybe every 2 hours" four years ago might be wrong today. Oddly enough it could be
wrong in either direction. What they can’t change is the coarse resolution of the estimate.
That’s embedded in the rather limited bit stream they have coming down from the sat’s.
Bob
On Apr 30, 2017, at 2:08 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote:
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 j99harman@gmail.com
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Date: 2017 Apr 29 Sat at 10:14:58 EDT
To: Bob Stewart bob@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 bob@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.
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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and follow the instructions there.
Hi,
Upload rates have been important for GALILEO to distinguish itself from GPS.
As GPS has been looking into the future, they have asked about the
bitstream rates and asked increased speed vs. improved redundancy. I
think I recall going towards the later.
Cheers,
Magnus
On 04/30/2017 10:23 PM, Bob kb8tq wrote:
Hi
A lot of the upload and estimate processes have changed over the years. What was true
at "maybe every 2 hours" four years ago might be wrong today. Oddly enough it could be
wrong in either direction. What they can’t change is the coarse resolution of the estimate.
That’s embedded in the rather limited bit stream they have coming down from the sat’s.
Bob
On Apr 30, 2017, at 2:08 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote:
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 j99harman@gmail.com
Subject: Re: [time-nuts] Three-cornered hat on timelab?
Date: 2017 Apr 29 Sat at 10:14:58 EDT
To: Bob Stewart bob@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 bob@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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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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