not much more progress


Robert Moore
 

A lot of effort by two engineers this morning resulted in raising the SNR to 8.2

I’m getting perfect HRIT imagery and broken RSS. Metop-B seems to be in a loop repeating the same GAC pass over and again. Nothing at all for Metop-C. So, looking a bit bleak.

Second engineer said he thought treetops might be just clipping the signal. He sent the attached photo of his monitor but I don’t know if this adds much to the sum total of our understanding without being able to see the scale on the instrument. They misunderstood the request for a photo and when I received them an hour or so later, they were no good for our purposes – wish they’d given them to me straight away while they had the ladder up.

Just wanted to check, I think there may be a new MDM: I’m currently on v3/1/14.1311

 

Robert

 


Ernst Lobsiger
 

On Sun, Jul 17, 2022 at 02:55 PM, Robert Moore wrote:
A lot of effort by two engineers this morning resulted in raising the SNR to 8.2
Robert,

TBH I don't understand another request for a photo. Your photos from the garden, if properly taken, should exclude the tree blocking theory.
Where do you read the SNR 8.2dB from? The image of the sat meter you just posted shows Carrier/Noise C/N 13dB LinkMargin LM=1.2 dB.

You should also post your TelliCast channels file if you have not followed the renaming of the Basic Service channels that took place this year.

Ernst




geojohnt@...
 

Robert,

Mmmmm.

Was the meter resting on the 'back' of the dish when the photo was taken?
Hence the view of the tree?

The adjacent channels (????) are quite low as well, so it looks(?) like trees are the problem?

Regards,
John


-----Original Message-----
From: Robert Moore <rsmoore@...>
To: MSG-1@groups.io <MSG-1@groups.io>
Sent: Sun, 17 Jul 2022 22:55
Subject: [MSG-1] not much more progress

A lot of effort by two engineers this morning resulted in raising the SNR to 8.2
I’m getting perfect HRIT imagery and broken RSS. Metop-B seems to be in a loop repeating the same GAC pass over and again. Nothing at all for Metop-C. So, looking a bit bleak.
Second engineer said he thought treetops might be just clipping the signal. He sent the attached photo of his monitor but I don’t know if this adds much to the sum total of our understanding without being able to see the scale on the instrument. They misunderstood the request for a photo and when I received them an hour or so later, they were no good for our purposes – wish they’d given them to me straight away while they had the ladder up.
Just wanted to check, I think there may be a new MDM: I’m currently on v3/1/14.1311
 
Robert
 


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

On 17/07/2022 22:55, Robert Moore wrote:
Just wanted to check, I think there may be a new MDM: I’m currently on v3/1/14.1311

Robert

Attachments:

* 20220717_110318.jpg <https://groups.io/g/MSG-1/attachment/33196/0>
Robert,

Sorry to hear about the lack of progress!

You can download the current MSG Data Manager here, where the release notes are
summarised:

https://www.satsignal.eu/software/msg_dm.htm#bundle

As you are getting some data I would not change the MSG Data Manager at the moment.

There were channel changes back in February/March where the channel name for
Metop B and C data changed from EPS-10 to E1B-EPS-10. If you didn't make that
change, it would likely explain why no Metop!

https://www.eumetsat.int/eumetcast-basic-service-channels-reorganisation

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


geojohnt@...
 

Ernst,

Now that is strange?

I hadn't noticed that - the meter does show 13 dB SNR so how can the LM be 1.2 dB???

My current SNR with a 1 m dish, Inverto Black Ultra quad LNB and an SR1 is 13.5 dB and LM of 4.2 dB on HVS-1 and 7.6 dB on BS.

I can't see what polarisation the channel is on.
And it is showing MER - which I thought was a 'product' of a TV signal - which EUMETCast is not.

????

Regards,
John




-----Original Message-----
From: Ernst Lobsiger via groups.io <ernst.lobsiger@...>
To: MSG-1@groups.io
Sent: Mon, 18 Jul 2022 9:20
Subject: Re: [MSG-1] not much more progress

On Sun, Jul 17, 2022 at 02:55 PM, Robert Moore wrote:
A lot of effort by two engineers this morning resulted in raising the SNR to 8.2
Robert,

TBH I don't understand another request for a photo. Your photos from the garden, if properly taken, should exclude the tree blocking theory.
Where do you read the SNR 8.2dB from? The image of the sat meter you just posted shows Carrier/Noise C/N 13dB LinkMargin LM=1.2 dB.

You should also post your TelliCast channels file if you have not followed the renaming of the Basic Service channels that took place this year.

Ernst




Ernst Lobsiger
 

On Mon, Jul 18, 2022 at 04:13 AM, <geojohnt@...> wrote:
I hadn't noticed that - the meter does show 13 dB SNR so how can the LM be 1.2 dB???
John,

yes this never ending story is good for some more mysteries.
As has been pointed out many times on this list the SR1 shows:

LM 8PSK 5/3   (Basic Service) = SNR - 5.9
LM 16APSK 2/3  (HVS-1, HVS-2) = SNR - 9.3

That's about what a LM calculation site showed on the Internet
(I don't find the link anymore), and that's what I have used on my
GNU/Linux TC receivers from the very beginning of DVB-S2 VCM.

That said a LM=1.2dB with C/N=13.0dB is at least rather strange.

Maybe someone takes the image of the sat meter screen to photoshop
to make the rest of the parameters readable. Maybe someone has a recent
spectrum that can be compared to make sure we are at the right place.

Regards,
Ernst


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

On 18/07/2022 12:13, geojohnt via groups.io wrote:
Ernst,

Now that is strange?

I hadn't noticed that - the meter does show 13 dB SNR so how can the LM be 1.2
dB???

My current SNR with a 1 m dish, Inverto Black Ultra quad LNB and an SR1 is 13.5
dB and LM of 4.2 dB on HVS-1 and 7.6 dB on BS.

I can't see what polarisation the channel is on.
And it is showing MER - which I thought was a 'product' of a TV signal - which
EUMETCast is not.

????

Regards,
John
SNR can depend on the bandwidth in which the signal is measured, not sure what
the white dotted lines are supposed to represent - perhaps the nominal channel.
I've attached a 200 MHz scan taken very early this morning showing both
polarisations and both TP1 and TP2 frequencies. This does seem to be broadly
in agreement with the meter shown. Ignore the dB numeric figures.

Of course, one key adjustment is skew on the LNB. A good installer should have
done that, though. You'll see that - at least on my system - the unwanted
vertically polarised signal is stronger than the horizontally polarised wanted one.

Of course, the beam from the dish (thinking about it as a transmitter) will
not be just a constant size cylinder all the way to the satellite. It will
have spreading and side-lobes and hence will see some of the ambient
temperature tree and leaves which generate much more noise than the cold of
space. Optimum LNB focus adjustment may help to minimise this.

I played with Paint Shop Pro 10 a little, but I don't think it improves the
image legibility.

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


Ernst Lobsiger
 

On Mon, Jul 18, 2022 at 06:30 AM, David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺 wrote:
Of course, the beam from the dish (thinking about it as a transmitter) will
not be just a constant size cylinder all the way to the satellite. It will
have spreading and side-lobes and hence will see some of the ambient
temperature tree and leaves which generate much more noise than the cold of
space. Optimum LNB focus adjustment may help to minimise this.
David,

of course sidelobes might take up some noise. But let's come back to
the two photos Robert made from his garden looking up in the direction
of the antenna beam. Assuming these shots were taken as described

https://groups.io/g/MSG-1/message/33173

and even assuming Robert was 20 meters behind the dish, it seems to
me that 2 meters below the antenna center we still don't see these
often cited trees. But this means we have 2/20/Pi*180 = 5.7° free
space below the main axis of the antenna beam. So at least the first
antenna sidelobe shouldn't see these trees either. I remember that
Robert has also indicated a much lower gap to these trees. That's
another contradiction in this never ending story. I hope that Robert
marked this special place in the garden. Then he can give us the
distance from there to the antenna and maybe on a new image we can
check again azimuth and skew (both seemed wrong on first two shots).


Regards,
Ernst