Astra 2G at 28.2E: General Discussion

If V and H are on the same frequency the "unwanted" signal should be at least 20 dB below the wanted one. The SNR will be degraded by approx 0.04 dB. If it's only 10 dB below, it will degrade (SNR) by 0.5 dB which is not so good if you have very low margins to the receiver threshold. So if the unwanted signal is 10 dB stronger than the wanted one, the isolation should be at least 10 dB+"SNR wanted signal, dB"+20 dB. E.g. 10+8+20=38 dB. If there is some frequency offset (half BW) between V and H, maybe we can reduce the requirement slightly but probably not so much....
 
bema said:
If V and H are on the same frequency the "unwanted" signal should be at least 20 dB below the wanted one. The SNR will be degraded by approx 0.04 dB. If it's only 10 dB below, it will degrade (SNR) by 0.5 dB which is not so good if you have very low margins to the receiver threshold. So if the unwanted signal is 10 dB stronger than the wanted one, the isolation should be at least 10 dB+"SNR wanted signal, dB"+20 dB. E.g. 10+8+20=38 dB. If there is some frequency offset (half BW) between V and H, maybe we can reduce the requirement slightly but probably not so much....
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In my case isolation shuold be then 50db, due to 11009V.
Have you compared the Invacom Quad/Quattro with that Inverto, and seen clear better cross polar isolation in that Inverto BU quad/quattro? Shuold we have separate topic, or is there already about these cross polar isolations?
 
After using an Inverto Quad BU for a couple of years on my own 180cm, I recently returned to an Invacom QDF-031, which rejects the interference from the data transponder on 11008V more effectively. Until recently, most people agreed that the Inverto BU (Black Ultra) had the edge, but this appears to be no longer the case. With interleaving of strong Europe and UK beams, many large dishes are struggling to receive the adjacent BBC frequency of 11023. In my case, I was getting zero with the Inverto but now a good signal with the Invacom.
No two installations are the same. The balance of weak/strong transponders varies on location, type and model of LNB, how old it is, and the receiver used.
This issue is also akin to hitting a moving target, as a new transponder can throw out careful adjustments.
Invacom's QDF spec is greater than 30 dB cross-polar rejection. If my maths is correct, this is around seven times higher than Inverto's, for which the manufacturer claims is 22 dB.
Invacom LNBs also have a better balance between H and V polarities and should receive these in more equal proportions to other LNBs, which typically are down on one or the other.
 
popolon said:
In my case isolation shuold be then 50db, due to 11009V.
Have you compared the Invacom Quad/Quattro with that Inverto, and seen clear better cross polar isolation in that Inverto BU quad/quattro? Shuold we have separate topic, or is there already about these cross polar isolations?
Click to expand...
QTF-031 quatro have separate H & V out?
can I use it without switch?
 
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dxsat said:
After using an Inverto Quad BU for a couple of years on my own 180cm, I recently returned to an Invacom QDF-031, which rejects the interference from the data transponder on 11008V more effectively. Until recently, most people agreed that the Inverto BU (Black Ultra) had the edge, but this appears to be no longer the case. With interleaving of strong Europe and UK beams, many large dishes are struggling to receive the adjacent BBC frequency of 11023. In my case, I was getting zero with the Inverto but now a good signal with the Invacom.
No two installations are the same. The balance of weak/strong transponders varies on location, type and model of LNB, how old it is, and the receiver used.
This issue is also akin to hitting a moving target, as a new transponder can throw out careful adjustments.
Invacom's QDF spec is greater than 30 dB cross-polar rejection. If my maths is correct, this is around seven times higher than Inverto's, for which the manufacturer claims is 22 dB.
Invacom LNBs also have a better balance between H and V polarities and should receive these in more equal proportions to other LNBs, which typically are down on one or the other.
Click to expand...

Just to have no doubt, have there been different spec Inverto Quad BU LNBs manufactured? That patent was filed on
Date of filing: 30.03.2012
, so from what year was your LNB manufactured/bought?
 
peeter3000 said:
QTF-031 quatro have separate H & V out?
can I use it without switch?
Click to expand...
That can be used without multiswitch, but then you get only that one fixed polarity/band into which you connect the cable.
 
popolon said:
Just to have no doubt, have there been different spec Inverto Quad BU LNBs manufactured? That patent was filed on
Date of filing: 30.03.2012
, so from what year was your LNB manufactured/bought?
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It was 2012 or 13 I think. Cross polar performance was poor but I am not sure if this recent or from new.
In Madrid, the heat (and UV in the Sierra) is so intense few LNBs can last more than 5 years, and will start to decline after 2 or so.
 
Can't help that Inverto B U's are black, especially in that Spanish sun !
 
popolon said:
In my case isolation shuold be then 50db, due to 11009V.
Have you compared the Invacom Quad/Quattro with that Inverto, and seen clear better cross polar isolation in that Inverto BU quad/quattro? Shuold we have separate topic, or is there already about these cross polar isolations?
Click to expand...

I bought two Invacom QTH-031 last year but both didn't catch any UK beam transponder so I couldn't compare the isolation. The NF was "crap" compared to BU or maybe it was my dish that was not compatible with Invacom LNB. At the same time bought five BU all better than QTH-031 at least from the sensitivity point of view. I selected the best one and modified the vertical low noise amplifier and got it slightly better, approx 0.5 dB. The horizontal amplifier is still better so I turned it 90 degrees and use it for the vertical transponders (HD channels).

Even if the isolation is good from the beginning, leakage can occur later i the chain since the gain is very high etc...
 
bema said:
I bought two Invacom QTH-031 last year but both didn't catch any UK beam transponder so I couldn't compare the isolation. The NF was "crap" compared to BU or maybe it was my dish that was not compatible with Invacom LNB. At the same time bought five BU all better than QTH-031 at least from the sensitivity point of view. I selected the best one and modified the vertical low noise amplifier and got it slightly better, approx 0.5 dB. The horizontal amplifier is still better so I turned it 90 degrees and use it for the vertical transponders (HD channels).

Even if the isolation is good from the beginning, leakage can occur later i the chain since the gain is very high etc...
Click to expand...
But that is different from the QDF-031 (C120 LNB ) with suitable feedhorn. It has to be the quad version as the twin and singles do not work as well and it has been reported it only really works well on larger dishes (1.5m+) but I've not tried it on a smaller dish myself. It's been a very good LNB for me on a 1.8m prime focus Aerial Oy dish in Finland and got me some Astra 2D back in the good old days when things like the MTI LNBs didn't.
 
timo_w2s said:
But that is different from the QDF-031 (C120 LNB ) with suitable feedhorn. It has to be the quad version as the twin and singles do not work as well and it has been reported it only really works well on larger dishes (1.5m+) but I've not tried it on a smaller dish myself. It's been a very good LNB for me on a 1.8m prime focus Aerial Oy dish in Finland and got me some Astra 2D back in the good old days when things like the MTI LNBs didn't.
Click to expand...

It's the "Quatro" version with feedhorn...
 
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popolon said:
That can be used without multiswitch, but then you get only that one fixed polarity/band into which you connect the cable.
Click to expand...
..and if I need only bbc (11023H), then I connect 1 cabel directly to H-low out .. and others empty..
 
I have just changed my LNB and bought an Ultra Black again, maybe next time I'll try Invacom, Fracarro, or MTI if they're better for cross-polarisation.
I personally have lost ITV HD, BBC4 HD, BBCnewsHD, and 4Seven, all the rest seems fine.
 
I find the Opticum LQP-04H quad works well if you have an offset dish but I don't know how good it is at cross polar isolation, it might be worth a try though.
 
bema said:
I bought two Invacom QTH-031 last year ...
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All Invacom xxH all-in-one LNBs are poor. Only the xxF flange C120 versions are acceptably good and of these the Quad is notably better than the twin or single, if fitted with the right feedhorn.
 
I am receiving 28.2 with a 1,5m Gibertini and Invacom TWF-031 with the Gibertini feed. I can not compare BU and Invacom with the signal problems we have now, but what I do know is:

My BU which was replaced by the Invacom had extreme trouble with either horizontal or vertical transponders (don't remember which it was any more). The Invacom solved that problem for me without noticably loosing sensitivity.

When I replaced the BU and looked at the little antennas I saw that they were not even mounted exactly in a right angle to each other - which I would expect to be the correct setup.

As for my last post: I can still receive all HDs at daytime. But when 2G goes into "night mode" the rf level difference between PE and spot increases. At that point I start loosing the signals closest to the PE first, Channe 5 works 24/7 most days, BBC4 sometimes but the rest is almost surely lost as those signals degrade much faster.
 
A simple schematic to demonstrate my experience testing (several) BU quads, vs my current LNB choice for 28E. The BU is excellent for any normal signal. But that Maximum x0-11 just keeps on giving a picture at levels where other lnbs gave up. Maybe just a chance result due to combination of particular dish\sat\receiver.

ql.webp
 
Astra 2D is due to arrive at 5.2E in a couple of days time. Perhaps after that SES will finally update their site with new 2G data as right now it's still listing 2D at 28.2 but with no data. If they don't start updating their satellite fleet page soon it's going to be quite outdated.
 
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