daily cyclic signal change


nigel
 

Hi Folks,
for a long time now, I have been seeing a daily variation in my received signal. I have been told that it was probably due to a slight misalignment of my ground mounted 1.5 Metre prime focus dish.
The stations location is North Cyprus ( 35.36 N, 33.03 E ) at an elevation of about 100 Metre.
MRTG graphs, showing these variations can be seen here :- http://www.nigelheasman.com/mrtg/SR1/inwin_mrtg_sr1.html
I have tried several times to improve the alignment, following various folks methods and now feel it is the best I can achieve. But, the cyclic variations continue !
The link margins are good enough to enable me to receive the Basic Service as well as High Volume Service 1, so I am happy with the result ( until my dogs crash into it and upset the alignment ! ) BUT I am intrigued by this variation and wondering if the magnitude and/or timing of the peaks and troughs can give a clue as to which part of the alignment could be improved?
Does anyone have any ideas or suggestions, please?
Looking forward to reading any comments!
Thanks
Nigel


Hartmut Schulla
 

Hi!

Geostationary satellites are not really fixed in the orbit. They moves like an 8 around a definite point to save fuel.

The larger your reception dish with a smaller beam, the greater the difference to the actual orbit position.

With an motorized dish you are able to follow the movements oft he satellite.

Regards

Hartmut Schulla

 

Von: MSG-1@groups.io <MSG-1@groups.io> Im Auftrag von nigel
Gesendet: Mittwoch, 5. Mai 2021 15:01
An: MSG-1@groups.io
Betreff: [MSG-1] daily cyclic signal change

 

Hi Folks,
for a long time now, I have been seeing a daily variation in my received signal. I have been told that it was probably due to a slight misalignment of my ground mounted 1.5 Metre prime focus dish.
The stations location is North Cyprus ( 35.36 N, 33.03 E ) at an elevation of about 100 Metre.
MRTG graphs, showing these variations can be seen here :- http://www.nigelheasman.com/mrtg/SR1/inwin_mrtg_sr1.html
I have tried several times to improve the alignment, following various folks methods and now feel it is the best I can achieve. But, the cyclic variations continue !
The link margins are good enough to enable me to receive the Basic Service as well as High Volume Service 1, so I am happy with the result ( until my dogs crash into it and upset the alignment ! ) BUT I am intrigued by this variation and wondering if the magnitude and/or timing of the peaks and troughs can give a clue as to which part of the alignment could be improved?
Does anyone have any ideas or suggestions, please?
Looking forward to reading any comments!
Thanks
Nigel


Ernst Lobsiger
 

Nigel

Could this be a temperature effect with lowest SNR when the LNB gets hot in full
sunshine. Or do you see the same SNR variations if the sky is completly overcast?

Meteosat 11 inclination is 0.13°. As Hartmut said this produces an 8 in the sky.

https://www.eumetsat.int/meteosat-orbital-parameters

Your antenna beam almost scratches the horizon. So this may leed to another
explanation. You can find the effect of antenna pointing errors in this guide:

https://www-cdn.eumetsat.int/files/2020-04/pdf_eumetcast_anten_point_guide.pdf

Let's hope that the lower half of the (app. +/- 0.13°) 8 is not below your horizon.

Regards,
Ernst


nigel
 

Thanks Hartmut. I hadn't fully appreciated that.

Regards

Nigel

On 05/05/2021 16:18, Hartmut Schulla via groups.io wrote:

Hi!

Geostationary satellites are not really fixed in the orbit. They moves like an 8 around a definite point to save fuel.

The larger your reception dish with a smaller beam, the greater the difference to the actual orbit position.

With an motorized dish you are able to follow the movements oft he satellite.

Regards

Hartmut Schulla

 

Von: MSG-1@groups.io <MSG-1@groups.io> Im Auftrag von nigel
Gesendet: Mittwoch, 5. Mai 2021 15:01
An: MSG-1@groups.io
Betreff: [MSG-1] daily cyclic signal change

 

Hi Folks,
for a long time now, I have been seeing a daily variation in my received signal. I have been told that it was probably due to a slight misalignment of my ground mounted 1.5 Metre prime focus dish.
The stations location is North Cyprus ( 35.36 N, 33.03 E ) at an elevation of about 100 Metre.
MRTG graphs, showing these variations can be seen here :- http://www.nigelheasman.com/mrtg/SR1/inwin_mrtg_sr1.html
I have tried several times to improve the alignment, following various folks methods and now feel it is the best I can achieve. But, the cyclic variations continue !
The link margins are good enough to enable me to receive the Basic Service as well as High Volume Service 1, so I am happy with the result ( until my dogs crash into it and upset the alignment ! ) BUT I am intrigued by this variation and wondering if the magnitude and/or timing of the peaks and troughs can give a clue as to which part of the alignment could be improved?
Does anyone have any ideas or suggestions, please?
Looking forward to reading any comments!
Thanks
Nigel


nigel
 

Thanks Ernst.

I see it even on cold cloudy days so don't think it's temperature related.

I have a hill behind the house, in the direction of the satellite so, yes, the dish is looking quite close to my "horizon".

I'm happy to understand that what I am seeing is, most likely, due to the satellite describing a figure of 8 !!

Regards

Nigel


On 05/05/2021 16:44, Ernst Lobsiger via groups.io wrote:
Nigel

Could this be a temperature effect with lowest SNR when the LNB gets hot in full
sunshine. Or do you see the same SNR variations if the sky is completly overcast?

Meteosat 11 inclination is 0.13°. As Hartmut said this produces an 8 in the sky.

https://www.eumetsat.int/meteosat-orbital-parameters

Your antenna beam almost scratches the horizon. So this may leed to another
explanation. You can find the effect of antenna pointing errors in this guide:

https://www-cdn.eumetsat.int/files/2020-04/pdf_eumetcast_anten_point_guide.pdf

Let's hope that the lower half of the (app. +/- 0.13°) 8 is not below your horizon.

Regards,
Ernst


geojohnt@...
 

Hello Nigel,

Good to hear from you again.

Firstly TP 1 has been 'doing something' in the last few days.
You will have seen that Ian and I reported a few days ago that our SNR has increased considerably - but it wasn't to last.
Back to normal a day or so later.
Though I did see another brief increase again yesterday afternoon.

By daily variation, do you mean at 'set' times/periods - your graphs appear to show this.
I too have a variation in SNR during the day - diurnal variation - due to that state of the atmosphere/troposphere.
I wrote an article about this for the GEO Quarterly a few years ago.

I always wondered about whether 'we' would see signal variations due to a satellite's figure of 8 movements but dismissed this as the movements were 'very small.'
However looking at EUMETSAT's dish off pointing graphs as posted by Ernst, you can lose 1 dB 'very easily' with an 0.5 degree dish error when using larger dishes.

Goodness, is it possibly to align a dish to 0.5 degree accuracy or less? 

Best wishes,
John.

 

 




-----Original Message-----
From: nigel <nigel@...>
To: MSG-1@groups.io
Sent: Wed, 5 May 2021 14:00
Subject: [MSG-1] daily cyclic signal change

Hi Folks,
for a long time now, I have been seeing a daily variation in my received signal. I have been told that it was probably due to a slight misalignment of my ground mounted 1.5 Metre prime focus dish.
The stations location is North Cyprus ( 35.36 N, 33.03 E ) at an elevation of about 100 Metre.
MRTG graphs, showing these variations can be seen here :- http://www.nigelheasman.com/mrtg/SR1/inwin_mrtg_sr1.html
I have tried several times to improve the alignment, following various folks methods and now feel it is the best I can achieve. But, the cyclic variations continue !
The link margins are good enough to enable me to receive the Basic Service as well as High Volume Service 1, so I am happy with the result ( until my dogs crash into it and upset the alignment ! ) BUT I am intrigued by this variation and wondering if the magnitude and/or timing of the peaks and troughs can give a clue as to which part of the alignment could be improved?
Does anyone have any ideas or suggestions, please?
Looking forward to reading any comments!
Thanks
Nigel


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

On 05/05/2021 14:44, Ernst Lobsiger via groups.io wrote:
Nigel
[]
Meteosat 11 inclination is 0.13°. As Hartmut said this produces an 8 in the sky.
https://www.eumetsat.int/meteosat-orbital-parameters <https://www.eumetsat.int/meteosat-orbital-parameters>
[]
Regards,
Ernst
Except it's EUTELSAT 10A we are receiving, not Met-11.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


Ian Deans
 

On 05/05/2021 15:35, geojohnt via groups.io wrote:
Hello Nigel,
Good to hear from you again.
Firstly TP 1 has been 'doing something' in the last few days.
You will have seen that Ian and I reported a few days ago that our SNR has increased considerably - but it wasn't to last.
Back to normal a day or so later.
Though I did see another brief increase again yesterday afternoon.
====================================================================

John I too saw a brief increase yesterday, but I suspect it was a switch to their back up station, which I suspect was the explanation for the increase a few days ago as we know that station increases our signal level.

Keep in mind that at the moment Eumetsat are about half way through the 4 day Hotbird 13 test so that is likely to account for your "doing something in the last few days."

Regards
Ian.


geojohnt@...
 

Ian,

Yes that may well be the case.

>Keep in mind that at the moment Eumetsat are about half way through the
>4 day Hotbird 13 test so that is likely to account for your "doing
>something in the last few days."

Oh no!
I thought it was next week!

Further posting to MSG-! coming up now!

John



John I too saw a brief increase yesterday, but I suspect it was a switch

to their back up station, which I suspect was the explanation for the
increase a few days ago as we know that station increases our signal level.

Keep in mind that at the moment Eumetsat are about half way through the
4 day Hotbird 13 test so that is likely to account for your "doing
something in the last few days."

Regards
Ian.


-----Original Message-----
From: Ian Deans via groups.io <iandeans142@...>
To: MSG-1@groups.io
Sent: Wed, 5 May 2021 15:56
Subject: Re: [MSG-1] daily cyclic signal change



On 05/05/2021 15:35, geojohnt via groups.io wrote:
> Hello Nigel,
>
> Good to hear from you again.
>
> Firstly TP 1 has been 'doing something' in the last few days.
> You will have seen that Ian and I reported a few days ago that our SNR
> has increased considerably - but it wasn't to last.
> Back to normal a day or so later.
> Though I did see another brief increase again yesterday afternoon.

====================================================================






Ernst Lobsiger
 

On Wed, May 5, 2021 at 07:51 AM, David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺 wrote:
Except it's EUTELSAT 10A we are receiving, not Met-11.
Puuhh,

of course you are right David. Futher down on this list we have done a lot of investigation
in a thread "Figure 8". I must even have some animated gif data somewhere. Apart from
the 8 there was a drift and periodic reset of EUTELSAT 10A in longitude. Tempi passati ...

Best regards,
Ernst


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

On 05/05/2021 16:04, Ernst Lobsiger via groups.io wrote:
On Wed, May 5, 2021 at 07:51 AM, David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺 wrote:
Except it's EUTELSAT 10A we are receiving, not Met-11.
Puuhh,
of course you are right David. Futher down on this list we have done a lot of investigation
in a thread "Figure 8". I must even have some animated gif data somewhere. Apart from
the 8 there was a drift and periodic reset of EUTELSAT 10A in longitude. Tempi passati ...
Best regards,
Ernst
Yes, I mentioned that to Nigel when he first asked. My impression is that the orbital figure of 8 isn't enough to affect the size of dish we typically use, but Nigel's is 140 cm.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


Ernst Lobsiger
 

On Wed, May 5, 2021 at 08:36 AM, David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺 wrote:
Yes, I mentioned that to Nigel when he first asked.
All

after my "Old Farts" blackout moment I went for a walk and some fresh air. Here is what we did in 2017.
Figure 8 of EUTELSAT E10A actually turned out to be a Figure 0!! I found and copied all the files and
calculations including animated gifs for Edinburg, Kaylar and the E10A sub satellite point SSP on Luna:

http://5.153.116.236:86

You will still find some of our discussions in threads "Figure 8" and/or "Figure 8 revisited" on this list.

Cheers,
Ernst


nigel
 

Hi John,

Good to hear from you, also.

Thanks for your thoughts and yes, I am seeing a "diurnal variation" - i.e. the same pattern repeating each day, but I do not know if it is due to the earths rotation or the satellite describing a figure of 8 ( or 0 - thanks for the reminder of your animations, Ernst! ) about its nominal position.

I  hadn't really thought about what is required to keep a geostationary satellite fixed in position, in relation to a location on earth, when we are both spinning in space. My mind boggles at the maths involved, let alone the technology required. Harmut's comment about the saving in fuel really started me thinking !!

As for getting the alignment within 0.5 degree - I would think that must involve a very precise mounting arrangement - not possible with the bog standard commercial setup. I did plan to try and improve my dish's mounting and adjustment system, but that is still at "the design stage".

More googling and research is needed, I'm sure.

Regards

Nigel



On 05/05/2021 17:35, geojohnt via groups.io wrote:
Hello Nigel,

Good to hear from you again.

Firstly TP 1 has been 'doing something' in the last few days.
You will have seen that Ian and I reported a few days ago that our SNR has increased considerably - but it wasn't to last.
Back to normal a day or so later.
Though I did see another brief increase again yesterday afternoon.

By daily variation, do you mean at 'set' times/periods - your graphs appear to show this.
I too have a variation in SNR during the day - diurnal variation - due to that state of the atmosphere/troposphere.
I wrote an article about this for the GEO Quarterly a few years ago.

I always wondered about whether 'we' would see signal variations due to a satellite's figure of 8 movements but dismissed this as the movements were 'very small.'
However looking at EUMETSAT's dish off pointing graphs as posted by Ernst, you can lose 1 dB 'very easily' with an 0.5 degree dish error when using larger dishes.

Goodness, is it possibly to align a dish to 0.5 degree accuracy or less? 

Best wishes,
John.

 

 




-----Original Message-----
From: nigel <nigel@...>
To: MSG-1@groups.io
Sent: Wed, 5 May 2021 14:00
Subject: [MSG-1] daily cyclic signal change

Hi Folks,
for a long time now, I have been seeing a daily variation in my received signal. I have been told that it was probably due to a slight misalignment of my ground mounted 1.5 Metre prime focus dish.
The stations location is North Cyprus ( 35.36 N, 33.03 E ) at an elevation of about 100 Metre.
MRTG graphs, showing these variations can be seen here :- http://www.nigelheasman.com/mrtg/SR1/inwin_mrtg_sr1.html
I have tried several times to improve the alignment, following various folks methods and now feel it is the best I can achieve. But, the cyclic variations continue !
The link margins are good enough to enable me to receive the Basic Service as well as High Volume Service 1, so I am happy with the result ( until my dogs crash into it and upset the alignment ! ) BUT I am intrigued by this variation and wondering if the magnitude and/or timing of the peaks and troughs can give a clue as to which part of the alignment could be improved?
Does anyone have any ideas or suggestions, please?
Looking forward to reading any comments!
Thanks
Nigel


geojohnt@...
 

Hello Nigel,

I would say that that the diurnal variation we see is more to do with the state of the troposphere and space weather than the figure of 8 movement of our satellites.
When the Sun is on 'our side of the planet' our polarised signals can become slightly twisted as they pass through the various 'excited layers.'

Commercial TV satellites are quite tightly controlled by the satellite operators - but of course their 'movement' is not that important for domestic satellite TV reception with 45 cm receiving dishes - more  important for the service uplinks to the satellite.

Just look at the inclination of MSG-1 and MSG-2 - though they are spin stabilised, not three axis.
They will take some tracking from the ground station control dishs.

On our GEO visits to EUMETSAT we went to the satellite ground station at Ursingen and standing under the giant Meteosat receive/control dishes, they would make a loud clunk every now and again as they tracked the slight movement of the satellite.

You are absolutely right, it's amazing how the geostationary satellite 'stay in the same place.'
One forgets(?) they are actually moving - as the Earth is. 

Regarding our 'dish alignment,' most of us use domestic satellite TV dishes which I would say in their original construction are impossible to align to 100% accuracy.
And as for the Triax 1 m dish - the less said about that, the better.

Several members have designed a sort of Vernier lever system to adjust both elevation and azimuth to very good accuracy.


Regards,
John




-----Original Message-----
From: nigel <nigel@...>
To: MSG-1@groups.io
Sent: Thu, 6 May 2021 8:48
Subject: Re: [MSG-1] daily cyclic signal change

Hi John,
Good to hear from you, also.
Thanks for your thoughts and yes, I am seeing a "diurnal variation" - i.e. the same pattern repeating each day, but I do not know if it is due to the earths rotation or the satellite describing a figure of 8 ( or 0 - thanks for the reminder of your animations, Ernst! ) about its nominal position.
I  hadn't really thought about what is required to keep a geostationary satellite fixed in position, in relation to a location on earth, when we are both spinning in space. My mind boggles at the maths involved, let alone the technology required. Harmut's comment about the saving in fuel really started me thinking !!
As for getting the alignment within 0.5 degree - I would think that must involve a very precise mounting arrangement - not possible with the bog standard commercial setup. I did plan to try and improve my dish's mounting and adjustment system, but that is still at "the design stage".
More googling and research is needed, I'm sure.
Regards
Nigel


On 05/05/2021 17:35, geojohnt via groups.io wrote:
Hello Nigel,

Good to hear from you again.

Firstly TP 1 has been 'doing something' in the last few days.
You will have seen that Ian and I reported a few days ago that our SNR has increased considerably - but it wasn't to last.
Back to normal a day or so later.
Though I did see another brief increase again yesterday afternoon.

By daily variation, do you mean at 'set' times/periods - your graphs appear to show this.
I too have a variation in SNR during the day - diurnal variation - due to that state of the atmosphere/troposphere.
I wrote an article about this for the GEO Quarterly a few years ago.

I always wondered about whether 'we' would see signal variations due to a satellite's figure of 8 movements but dismissed this as the movements were 'very small.'
However looking at EUMETSAT's dish off pointing graphs as posted by Ernst, you can lose 1 dB 'very easily' with an 0.5 degree dish error when using larger dishes.

Goodness, is it possibly to align a dish to 0.5 degree accuracy or less? 

Best wishes,
John.

 

_._,_._,_


Hendrik Fleming
 

After using Eumetcast for a year, I only now got David’s statistics running on my site.... I am very slow... I also watched the daily variation in SNR, also started wondering how to get it stable. Dish is an old motorized dish with a controller stemming from 1997, but was wondering if modifying the whole mount system so that elevation and skew can be changed and controlled with something more modern,  but that is a long-term project for me. 

here is my daily variation of HVS-2 over here in Norway. (Only monitoring it for the past few days, and the major dropout on day 2 was because of a heavy cloud-cover)


 


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

On 01/06/2021 17:22, Hendrik Fleming wrote:
After using Eumetcast for a year, I only now got David’s statistics running on my site.... I am very slow... I also watched the daily variation in SNR, also started wondering how to get it stable. Dish is an old motorized dish with a controller stemming from 1997, but was wondering if modifying the whole mount system so that elevation and skew can be changed and controlled with something more modern,  but that is a long-term project for me.
here is my daily variation of HVS-2 over here in Norway. (Only monitoring it for the past few days, and the major dropout on day 2 was because of a heavy cloud-cover)
Hendrick,

Delighted to see that the software is of some use. If you have a Web site where you could upload that data I'd like to add it to the Europe-wide charts here:


https://www.satsignal.eu/mrtg/performance_eumetcast-europe_link_margin.php

The daily variation has been discussed quite a lot, and I suspect there is no single cause.

- The satellite output may vary - we do see changes from time to time and they are usually obvious when comparing the results from several stations. I don't believe this is a contributing factor.

- The satellite pointing may vary. For those in the centre of the beam sent from the satellite there is little variation, but towards the edge of the coverage the effect will be greater.

- If the receiver dish is not directly pointed at the satellite, the signal will be towards the edge of the beam polar diagram, i.e. not at the flat part of the response but where the response is less a degree or more from the centre. In this part of the response any movement in the apparent satellite position will result in a change of signal level which is much greater than at the top part - the flat part of the response curve.

- The receiver dish may change alignment through temperature changes during the day and night. Perhaps this effect is greater in the summer?

From your system description, I do wonder how accurately you can point your dish with that motor and controller? Satellite TV often has a greater signal level so that small pointing errors go unnoticed. If possible, I suggest trying a very small manual adjustment of the dish pointing to see whether there is any improvement. You should also check the skew (twist) on the LNB as good rejection of the cross-polarised signal is important.

Having said all that (phew!) 4 dB is /just/ adequate. Oslo looks to be a little further off the main beam than Edinburgh, but past experience suggests that the coverage may not be exactly as the prediction shown here (and attached):


https://www-cdn.eumetsat.int/files/2020-04/img_eutelsat_10a_ku_band_cover.jpg

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


Hendrik Fleming
 

David, as soon as I get fiber up here, will put my graphs on-line. Out here in the middle of nowhere, have to rely on LTE-internet that varies even more than the satellite signal. Would be interesting to also plot the variation in the LTE-signal with MRTG, but the router is locked by the ISP, so have no idea how to do it, except maybe pointing a yagi-antenna to the tower and monitor the signal strength that way. Quite possible the temperature variations also have some effect on the signal from Eutelsat, will have to see when winter comes. I was quite pleased that the system worked during winter at -30C and the ice were thick on the dish. Now that I finally have the monitor program running, it will be nice to see. I must just figure out a way to annotate the graphs, to show what happened where, not sure it is possible, though.

Hendrik