Re: [time-nuts] Three-cornered hat on timelab?

[Jim Harman]

On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart  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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Re: [time-nuts] Three-cornered hat on timelab?

[Angus]

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 + (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 
> To: Bob Stewart ; Discussion of precise time and frequency 
> measurement  
>Cc: mag...@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
>
>   
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Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

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 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 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  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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Re: [time-nuts] TAPR Oncore M12+ kit

[Chris Albertson]

On this product people are going to want holes drilled and I think a "D"
shape hole for the DB type connector.   The holes would allow easy clamping
but in a two step operation.If I were making these I'd first clamp the
stock over a pair of 123 blocks, mill the holes, then after I hade a batch
of these made,  hole the holes to hold the part a fixture and then mill the
edges.

But that said, I could make a pair of these by hand with hack saw, file and
drill press in about 15 minutes.



On Fri, Apr 28, 2017 at 1:41 PM, Jerry Hancock  wrote:

>
> Generally, the way I mill plates such as these is I surface a piece of
> scrap and then glue (using superglue) the stock down onto the scrap.  I can
> then machine around the edges without worrying about clamping.  With
> pockets though, the torque even when ramping down might break the part
> loose.
>

-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

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 
 To: Bob Stewart ; Discussion of Precise Time and Frequency 
Measurement  
Cc: mag...@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


   
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Re: [time-nuts] Three-cornered hat on timelab?

[Magnus Danielson]

Hi Bob,

For that receiver, you have a pretty good result.
If you haven't moved your antenna, the average result should be fine.
However, with a cesium around you can experiment with minor adjustments 
of position. Best would be to build carrier phase pseudo-range 
measurements and compare with the time-difference to see if there is a 
correlation and then fine-tune that way. I don't recall what you get out 
of the LEA-6T.


You sure has some outdoor temperature variations right now.

It would be interesting to do an outdoor and indoor temperature log and 
try to see the correlation there.


Cheers,
Magnus

On 04/29/2017 04:35 PM, Bob Stewart wrote:

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 
*To:* Bob Stewart ; Discussion of Precise Time and
Frequency Measurement 
*Cc:* mag...@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



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[time-nuts] TAPR Oncore M12+ kit

[Mark Sims]

I'd say screw the gasket / inset crud and go with flat stock or pcb material 
(my Star-4 GPSDO came in a very similar housing and uses PCB endplates.   It's 
much easier and cheaper.  I doubt that very many people will be installing 
these outdoors, etc and need the fancy pants end plates and gaskets..

Two useful things to add to the stock hole pattern is a hole for a 2.1 mm DC 
barrel connector jack and a 1PPS output (but I don't think there is room, so 
get the 1PPS off of the D-sub, maybe with an SMA for the 1PPS, both would fit 
OK?  Perhaps replace the antenna BNC with an SMA?...  my units is elsewhere at 
the moment so I can't do any measurinh).  

On my GPS, I disconnected the power wires from the D-sub and hooked them to a 
2.1 mm jack.  It's much easier than building the adapter "Y" cable.  You use a 
null modem cable or adapter to connect to a PC.
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[time-nuts] TAPR Oncore M12+ kit

[Mark Sims]

OSHPARK has made several boards for me with cutouts.   You put the cutout on 
the milling layer and they recommend putting the word "CUTOUT" within the 
cutout area.   It's been a few years since I had any made that way... best to 
ask them.  Also inquire about the milling bit radius... you can't mill a square 
corner.

---

> The fab house for OSHPark won't make oval holes.
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Re: [time-nuts] Three-cornered hat on timelab?

[Magnus Danielson]

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
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