Topics

Signal Drop


Ian Deans
 

I am seeing another drop in the signal over the last 48 hours or so, in the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.

Regards
Ian.


Herman Vijlbrief
 

Ian,

Same here in Hoofddorp The Netherlands.

Regards

Herman

Op 26-5-2020 om 12:12 schreef Ian Deans via groups.io:

I am seeing another drop in the signal over the last 48 hours or so, in the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.

Regards
Ian.


geojohnt@...
 

Ian,

I finally got around to putting my 1 m dish into its new - slightly more away from the fir tree - location from the temporary one its been in for a couple of months, late afternoon yesterday.
I don't think it is 'fully aligned' but I was pleased with the results on TP 1 - 12.8 - 12.9 dB SNR with an SR1 at that time and in the evening.

However, this morning 07:30 UTC my SNR was 12.3 - 12.4 dB later dropping to 12.2 - 12.3 dB.

Currently at 11:15 UTC my SNR is 12.5 - 12.6 dB - but it is stepping a bit by 0.3 dB at times.

I'll be monitoring during the day to see if it has gone up again to yesterday's levels at 17:00.

Also at the same time I'm monitoring Eutelsat 10-A on my SatPal spectrum analyser but it does not indicate SNR for EUMETCast owing to the VCM format.
But I do get get full parameters for 10A's TV channels as a guide to any of their changing levels.

I'm also monitoring Eutelsat 9's TV channel parameters/level over time - which I receive on the same dish, with the SatPal meter.

Given the large SNR vertical scale on EUMETCast Europe logging on David's website - 0.0 to 18.0 dB, even that shows 'small variations' of SNR given the large 3 dB scale step between segment SNR levels.
Dare I say that it would be interesting to have a scale a 'very' expanded scale to see these ~ 0.5 db variation in clear sky SNR.

The diurnal SNR variation - that I've always experienced, appears not to be seen by some users???

Regards,
John 





 


-----Original Message-----
From: Ian Deans via groups.io <iandeans142@...>
To: MSG-1@groups.io
Sent: Tue, 26 May 2020 11:12
Subject: [MSG-1] Signal Drop

I am seeing another drop in the signal over the last 48 hours or so, in
the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.

Regards
Ian.






David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

I am seeing another drop in the signal over the last 48 hours or so, in
the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.

Regards
Ian.
==============================

Ian, Herman,

I see no evidence for such a drop over the last 2 days:

https://www.satsignal.eu/mrtg/performance_eumetcast-europe_link_margin.php?period=month

I find it difficult to accept reports with little documented backing.

However, what I have seen recently is a drop in link margin when the sun illuminates the LNB early in the morning (as it happens in my particular configuration). I'm unsure what the cause is - perhaps the cover is becoming warm and that's heating some dust or bird deposit on the cover. I've looked from ground level with binoculars but there's nothing obvious. Perhaps the LNB (or at least its cover) is due for replacement. £10 for the part and £100 labour!

You can see this on yesterday's plot at ~06:30 UTC until ~09:45, and something on today's plot with a rise around 13:20.

https://www.satsignal.eu/mrtg/sr1-dual-link-margin.html

Monitoring is relatively easy to set up with either Ayecka SR1 or TBS/BDADataEx receivers.

https://www.satsignal.eu/wxsat/dvb-s2/sr1-mrtg.html

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


Thorsten Miglus
 

David,

heating up the LNB adds thermal noise to the signal. This causes a drop of the link margin.

Cheeers
Thorsten


On Tue, May 26, 2020 at 04:03 PM, David J Taylor wrote:
Ian, Herman,

I see no evidence for such a drop over the last 2 days:

https://www.satsignal.eu/mrtg/performance_eumetcast-europe_link_margin.php?period=month

I find it difficult to accept reports with little documented backing.

However, what I have seen recently is a drop in link margin when the sun illuminates the LNB early in the morning (as it happens in my particular configuration). I'm unsure what the cause is - perhaps the cover is becoming warm and that's heating some dust or bird deposit on the cover. I've looked from ground level with binoculars but there's nothing obvious. Perhaps the LNB (or at least its cover) is due for replacement. £10 for the part and £100 labour!

You can see this on yesterday's plot at ~06:30 UTC until ~09:45, and something on today's plot with a rise around 13:20.

https://www.satsignal.eu/mrtg/sr1-dual-link-margin.html

Monitoring is relatively easy to set up with either Ayecka SR1 or TBS/BDADataEx receivers.

https://www.satsignal.eu/wxsat/dvb-s2/sr1-mrtg.html

Cheers,
David


Ian Deans
 

On 26/05/2020 15:01, David J Taylor via groups.io wrote:
I am seeing another drop in the signal over the last 48 hours or so, in
the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.
Regards
Ian.
==============================
Ian, Herman,
I see no evidence for such a drop over the last 2 days:
 https://www.satsignal.eu/mrtg/performance_eumetcast-europe_link_margin.php?period=month
I find it difficult to accept reports with little documented backing.
===============================================================================

I am still seeing a drop in signal which I am checking regularily. Dish allignment checked and is OK.

I take your point re no documented evidence, so will avoid any further reports in the future re signal levels.

Ian.


Herman Vijlbrief
 

David,

To give some more documentation, my SNR over the day is comparable with the signal of the station in Huizen-NL
I have a slight smaller dish 125 cm so my SNR is on average over the day 0,2 dB lower than the station in Huizen.
I see that the Huizen signal level is also lower than that it was before.
So for me there is enough link margin left and I have very few packet losses and that is what counts.

Greetings Herman


Ian, Herman,

I see no evidence for such a drop over the last 2 days:

 https://www.satsignal.eu/mrtg/performance_eumetcast-europe_link_margin.php?period=month

I find it difficult to accept reports with little documented backing.

However, what I have seen recently is a drop in link margin when the sun illuminates the LNB early in the morning (as it happens in my particular configuration).  I'm unsure what the cause is - perhaps the cover is becoming warm and that's heating some dust or bird deposit on the cover. I've looked from ground level with binoculars but there's nothing obvious. Perhaps the LNB (or at least its cover) is due for replacement. £10 for the part and £100 labour!

You can see this on yesterday's plot at ~06:30 UTC until ~09:45, and something on today's plot with a rise around 13:20.

 https://www.satsignal.eu/mrtg/sr1-dual-link-margin.html

Monitoring is relatively easy to set up with either Ayecka SR1 or TBS/BDADataEx receivers.

 https://www.satsignal.eu/wxsat/dvb-s2/sr1-mrtg.html

Cheers,
David


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

David,

heating up the LNB adds thermal noise to the signal. This causes a drop of the link margin.

Cheeers
Thorsten
=================================

Yes, it could be just that.

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


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

From: Ian Deans via groups.io
[]
I am still seeing a drop in signal which I am checking regularily. Dish
allignment checked and is OK.

I take your point re no documented evidence, so will avoid any further
reports in the future re signal levels.

Ian.
================================

Ian,

The intention was to encourage you to add the programs allowing you to plot the data automatically, saving you time an effort and providing a long-term record for a year or more. It makes it easier to compare your data with others. All the software is free.

Please do continue to provide reports as the level (well, SNR) is a very critical system parameter for EUMETCast especially in our part of the world!

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


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

David,

To give some more documentation, my SNR over the day is comparable with
the signal of the station in Huizen-NL
I have a slight smaller dish 125 cm so my SNR is on average over the day
0,2 dB lower than the station in Huizen.
I see that the Huizen signal level is also lower than that it was before.
So for me there is enough link margin left and I have very few packet
losses and that is what counts.

Greetings Herman
==========================================

Thanks, Herman. Yes, the drop at Huizen is clear, and yet not at all stations. Why? Atmospheric conditions? A small change at the satellite? I think not at the uplink station, though.

Adding MRTG to record the link margin and whatever other data you might find useful is something you might like to look at.

Oh, that there was another 2 or 3 dB from the satellite! Yes, I know that's double the power.....

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


geojohnt@...
 

Ian and All,

As I thought (hoped) my TP 1 SNR was back up to 12.9 - 13.0 db by 17:00 UTC today.
It is currently 13.0 - 12.9 dB at 20:30 UTC.

Yes, the LNB does get baked in the sun at this time of year so I'm going to try to fashion an umbrella before dawn.

One thing I found was that the TV channels on Eurelsat 10 A and Eutelsat 9 did not show such a drastic change in SNR level.
In fact it was perhaps 0.3 dB at the most - same dish same LNB.

My EUMETCast TP 1 SNR has an overall change in level of 0.8 dB.

I suspect comparing TP 1 with a TV channel on 10-A is irrelevant anyway?

Regards,
John.
 


-----Original Message-----
From: geojohnt via groups.io <geojohnt@...>
To: MSG-1@groups.io <MSG-1@groups.io>
Sent: Tue, 26 May 2020 12:58
Subject: Re: [MSG-1] Signal Drop

Ian,

I finally got around to putting my 1 m dish into its new - slightly more away from the fir tree - location from the temporary one its been in for a couple of months, late afternoon yesterday.
I don't think it is 'fully aligned' but I was pleased with the results on TP 1 - 12.8 - 12.9 dB SNR with an SR1 at that time and in the evening.

However, this morning 07:30 UTC my SNR was 12.3 - 12.4 dB later dropping to 12.2 - 12.3 dB.

Currently at 11:15 UTC my SNR is 12.5 - 12.6 dB - but it is stepping a bit by 0.3 dB at times.

I'll be monitoring during the day to see if it has gone up again to yesterday's levels at 17:00.

Also at the same time I'm monitoring Eutelsat 10-A on my SatPal spectrum analyser but it does not indicate SNR for EUMETCast owing to the VCM format.
But I do get get full parameters for 10A's TV channels as a guide to any of their changing levels.

I'm also monitoring Eutelsat 9's TV channel parameters/level over time - which I receive on the same dish, with the SatPal meter.

Given the large SNR vertical scale on EUMETCast Europe logging on David's website - 0.0 to 18.0 dB, even that shows 'small variations' of SNR given the large 3 dB scale step between segment SNR levels.
Dare I say that it would be interesting to have a scale a 'very' expanded scale to see these ~ 0.5 db variation in clear sky SNR.

The diurnal SNR variation - that I've always experienced, appears not to be seen by some users???

Regards,
John 





 


-----Original Message-----
From: Ian Deans via groups.io <iandeans142@...>
To: MSG-1@groups.io
Sent: Tue, 26 May 2020 11:12
Subject: [MSG-1] Signal Drop

I am seeing another drop in the signal over the last 48 hours or so, in
the region of 0.2 to 0.3 SNR. Hopefully just a temporary drop.

Regards
Ian.






David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

I've mentioned this to EUMETSAT and pointed them towards the group topic. I'm sure that direct reports would be valued.

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


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

Ian and All,

As I thought (hoped) my TP 1 SNR was back up to 12.9 - 13.0 db by 17:00 UTC today.
It is currently 13.0 - 12.9 dB at 20:30 UTC.

Yes, the LNB does get baked in the sun at this time of year so I'm going to try to fashion an umbrella before dawn.

One thing I found was that the TV channels on Eurelsat 10 A and Eutelsat 9 did not show such a drastic change in SNR level.
In fact it was perhaps 0.3 dB at the most - same dish same LNB.

My EUMETCast TP 1 SNR has an overall change in level of 0.8 dB.

I suspect comparing TP 1 with a TV channel on 10-A is irrelevant anyway?

Regards,
John.
=====================================

Most interesting comparisons, John. At lower signal levels I suspect there is a degree of confusion in that we talk of:

signal / noise

but what we are actually measuring is most likely

(signal + noise) / noise

so a change of signal at higher signal levels will result in a greater change in the measurement than at lower levels, where the value will tend to zero 0dB (and not go negative!). Noise isn't measured separately. So was the apparent level of the TV signal higher?

The graphs now clearly show that there was a dip seen by many stations between~14:30 and 15:10 UTC.

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

which may also have confused spot time level comparisons.

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


geojohnt@...
 

David,

Interesting comments.

A problem is, I'm not an RF engineer and I'm just reporting what my SR1 and SatPal meter are showing.
What it all means, is another matter :-)

Last year(?) Klaus Peter suggested I looked into 'atmospherics' effecting satellite signals which I did and I think I wrote a GEO article on my findings.
Of course the sun is very high in the northern hemisphere at the moment so I guess we should expect some 'turbulence?'

LNB umbrella is in place and the LNB is shaded from the sun and keeping cool at 09:00 UTC.
However, my dark grey 1 m dish gets hot enough to fry an egg - so that will be radiating 'thermal energy.'
I wonder if that is a factor?

I have a plan to temporarily deal with the dish warming - watch this space.

SR1 TP 1 SNR down from 13.0 dB last night to 12.6/5 dB at the moment with cool LNB.

Regards,
John

+++++++++++++++++++++


Most interesting comparisons, John.  At lower signal levels I suspect there 
is a degree of confusion in that we talk of:

  signal / noise

but what we are actually measuring is most likely

  (signal + noise) / noise

so a change of signal at higher signal levels will result in a greater 
change in the measurement than at lower levels, where the value will tend to 
zero 0dB (and not go negative!).  Noise isn't measured separately.  So was 
the apparent level of the TV signal higher?

The graphs now clearly show that there was a dip seen by many stations 
between~14:30 and 15:10 UTC.

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

which may also have confused spot time level comparisons.

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

++++++++++++++++++++++++++

-----Original Message-----
From: David J Taylor via groups.io <david-taylor@...>
To: MSG-1@groups.io
Sent: Wed, 27 May 2020 7:01
Subject: Re: [MSG-1] Signal Drop

Ian and All,

As I thought (hoped) my TP 1 SNR was back up to 12.9 - 13.0 db by 17:00 UTC
today.
It is currently 13.0 - 12.9 dB at 20:30 UTC.

Yes, the LNB does get baked in the sun at this time of year so I'm going to
try to fashion an umbrella before dawn.

One thing I found was that the TV channels on Eurelsat 10 A and Eutelsat 9
did not show such a drastic change in SNR level.
In fact it was perhaps 0.3 dB at the most - same dish same LNB.

My EUMETCast TP 1 SNR has an overall change in level of 0.8 dB.

I suspect comparing TP 1 with a TV channel on 10-A is irrelevant anyway?

Regards,
John.
=====================================






David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

David,

Interesting comments.

A problem is, I'm not an RF engineer and I'm just reporting what my SR1 and SatPal meter are showing.
What it all means, is another matter :-)

Last year(?) Klaus Peter suggested I looked into 'atmospherics' effecting satellite signals which I did and I think I wrote a GEO article on my findings.
Of course the sun is very high in the northern hemisphere at the moment so I guess we should expect some 'turbulence?'

LNB umbrella is in place and the LNB is shaded from the sun and keeping cool at 09:00 UTC.
However, my dark grey 1 m dish gets hot enough to fry an egg - so that will be radiating 'thermal energy.'
I wonder if that is a factor?

I have a plan to temporarily deal with the dish warming - watch this space.

SR1 TP 1 SNR down from 13.0 dB last night to 12.6/5 dB at the moment with cool LNB.

Regards,
John
===================================

John,

First thoughts are that a hot dish means the LNB is looking at a warm source rather than the cold sky! Warm means more noise, poorer SNR, lower link margin. However, it depends on what the dish "looks" like at 11 GHz.

Perhaps that grey surface is fully reflective at that frequency, so the LNB is looking at a cold sky. I don't think it will be a perfect reflector, so some dish temperature rise will result in SNR loss.

The other effect is that the LNB will have at least /some/ "seeing" outside the disk of the dish, so a warm background is not desirable. Moving the LNB nearer the dish will result in "seeing" less outside the dish, but having a smaller capture area and hence get a smaller amount of signal.

Keep monitoring!

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


Prem
 

A hot dish can expand or shrink when cooling. It can also distort it's shape very slightly which can affect your signal. There is also your coax cable, mainly copper which will expand and/or shrink to a greater extent than your dish. This can also affect the length of cable which again will slightly affect your signal strength. All coax cables should be cut to the correct length for the frequency that they are being used for. As has already been said, atmospherics plus numerous other spanners in the works without me adding further.

Prem Holdaway (G0DCP)
Phold29@...

-----Original Message-----
From: MSG-1@groups.io [mailto:MSG-1@groups.io] On Behalf Of David J
Taylor via groups.io
Sent: 27 May 2020 10:31
To: MSG-1@groups.io
Subject: Re: [MSG-1] Signal Drop

David,

Interesting comments.

A problem is, I'm not an RF engineer and I'm just reporting what my SR1 and
SatPal meter are showing.
What it all means, is another matter :-)

Last year(?) Klaus Peter suggested I looked into 'atmospherics' effecting
satellite signals which I did and I think I wrote a GEO article on my
findings.
Of course the sun is very high in the northern hemisphere at the moment so
I
guess we should expect some 'turbulence?'

LNB umbrella is in place and the LNB is shaded from the sun and keeping cool
at 09:00 UTC.
However, my dark grey 1 m dish gets hot enough to fry an egg - so that will
be radiating 'thermal energy.'
I wonder if that is a factor?

I have a plan to temporarily deal with the dish warming - watch this space.

SR1 TP 1 SNR down from 13.0 dB last night to 12.6/5 dB at the moment with
cool LNB.

Regards,
John
===================================

John,

First thoughts are that a hot dish means the LNB is looking at a warm source
rather than the cold sky! Warm means more noise, poorer SNR, lower link
margin. However, it depends on what the dish "looks" like at 11 GHz.

Perhaps that grey surface is fully reflective at that frequency, so the LNB
is looking at a cold sky. I don't think it will be a perfect reflector, so
some dish temperature rise will result in SNR loss.

The other effect is that the LNB will have at least /some/ "seeing" outside
the disk of the dish, so a warm background is not desirable. Moving the LNB
nearer the dish will result in "seeing" less outside the dish, but having a
smaller capture area and hence get a smaller amount of signal.

Keep monitoring!

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