monoblock LNB.

[Tom W H]

I live in Spain and I suspect I could receive channels from Eutelsat @ 25.5e. I am getting 28.2e at the Mo'
I have a 1.0m dish or it could be 1.3m I haven't measured it.
What I want to know is, can I get a monoblock LNB to use on these two satellites so I might be able to watch Bein sport on 25.5?

 

[sonnetpete]

Yes, you can get a monoblock with a 3 degree separation, however these are intended for use on an 80cm size dish. You'd be better off with two LNB's, a small bracket and a diseqc switch.

 

[Tom W H]

80cm dish which I have but it's not large enough to get 28.2e here in Spain we need the 1m plus size dish. I would have thought that the larger the dish the better reception with a 3 degree monobloc lnb?
I use the larger dish for 28.2 and the smaller one for 27.5. I was hoping I could use my lrger dish with a 3 dgree monobloc fo 28.2 and 25.5e?

 

[PaulR]

You won't get a 3 degree monoblock for such a large dish. The feedhorns of a monoblock are obviously fixed and they are AFAIK made for 80cm dishes*. They can be used on a 60cm dish but at reduced efficiency which normally wouldn't matter as 60cm dishes are made for strong signal satellites.

*Imagine an old style cart wheel with spokes. As you move away from the centre the distance between the spokes increases. A monoblock is fixed and can't cope with this. In addition, if you think about a monoblock moving further away from the centre only one of the feedhorns can point directly at the centre, the other will be effectively squinting.

 

[Tom W H]

You won't get a 3 degree monoblock for such a large dish. The feedhorns of a monoblock are obviously fixed and they are AFAIK made for 80cm dishes*. They can be used on a 60cm dish but at reduced efficiency which normally wouldn't matter as 60cm dishes are made for strong signal satellites.

*Imagine an old style cart wheel with spokes. As you move away from the centre the distance between the spokes increases. A monoblock is fixed and can't cope with this. In addition, if you think about a monoblock moving further away from the centre only one of the feedhorns can point directly at the centre, the other will be effectively squinting.

Thanks for your reply. So is there another way I could use my larger dish for two satellites? I'm very new to this stuff so if someone suggested multiple lnb's I would strugle with that as I wouild not know how to set it up???

 

[PaulR]

Unfortunately the only way is a multi-LNB setup. And you're not going to like it when I tell you that the larger the dish, the more difficult it is to accurately align it.

A larger dish may pull in more signal but the trade-off is that the aperture in which you "see" the signal becomes narrower. It's very easy to just miss a satellite as you nudge, nudge, nudge a dish right over the sweet spot!

 

[Tom W H]

Unfortunately the only way is a multi-LNB setup. And you're not going to like it when I tell you that the larger the dish, the more difficult it is to accurately align it.

A larger dish may pull in more signal but the trade-off is that the aperture in which you "see" the signal becomes narrower. It's very easy to just miss a satellite as you nudge, nudge, nudge a dish right over the sweet spot!

Sounds easier to get another dish with it's own lnb. I'm sure it would be fairly easy if I had a meter though?
Never set a dish up so I don't know what it's like to do this. The guys with meters make it look easy I know someone who only just started doing this and he can now set a dish up in no time with his meter.

 

[sonnetpete]

You have two dishes listed in your set up, an 80cm and a 1.3M. Could you use the smaller one for 25.5E? You could then use the two dishes on one receiver with a simple diseqc switch.

 

[Tom W H]

You have two dishes listed in your set up, an 80cm and a 1.3M. Could you use the smaller one for 25.5E? You could then use the two dishes on one receiver with a simple diseqc switch.

No I couldn't use the smaller dish for 28.2 Astra 2 as it needs a larger dish for it so I'm assuming the Eutelasat one would be the same for use here in Spain.
Here we use the larger dish for Astra 2 and the smaller dish for Intelsat 907, although I have since learned that if I was to use a larger dish on the intelsat I would get a stronger reception (I get around 60% atm) and if we get heavy rain or low cloud this goes off altogether.

 

[a33]

What I want to know is, can I get a monoblock LNB to use on these two satellites so I might be able to watch Bein sport on 25.5?

Maybe for your dish size you could try a 4.3 degree monoblock or a 6 degree monoblock for a 80cm dish.
Though they are designed for a different dish size, the distance between the two LNBs inside might be approximately what you need on your 1-1.3 meter dish.
But it really is 'might'. Separate LNBs give much more fine-adjustment possibility .

greetz,
A33

 

[Lazarus]

And, of course, adjustable Monoblocks are now available.

 

[PaulR]

Are they adjustable for angle as well as separation?

 

[PaulR]

Maybe for your dish size you could try a 4.3 degree monoblock or a 6 degree monoblock for a 80cm dish.
Though they are designed for a different dish size, the distance between the two LNBs inside might be approximately what you need on your 1-1.3 meter dish.
But it really is 'might'. Separate LNBs give much more fine-adjustment possibility .

greetz,
A33

They certainly won't work properly as they will be expecting a satellite dish at a certain distance in front of the feedhorn. They will be squinting at any larger dish which will, by necessity, be further away.

 

[a33]

They certainly won't work properly as they will be expecting a satellite dish at a certain distance in front of the feedhorn.

Huh?
As far as I know an LNBf doesn't expect a distance, but just has an opening angle fitting (for universal KU-LNBs) a f/D=0,6 dish.
The same applies to the internal LNBs of a monoblock, I would say.

As most offset dishes have an f/D from about 0,6 to 0,65, I don't see a big problem there.

Or am I missing something here?

greetz,
A33

 

[davemurgtroyd]

Probably the best solution for the larger dish would be a 4 to 15 degree adjustable monobloc such as this - Octagon 0.1dB Flex Feed 4-15 Degree LNB

Simpler to fit than two lnbs but would require a DiSEqC switch as well.

 

[PaulR]

Huh?
As far as I know an LNBf doesn't expect a distance, but just has an opening angle fitting (for universal KU-LNBs) a f/D=0,6 dish.
The same applies to the internal LNBs of a monoblock, I would say.

As most offset dishes have an f/D from about 0,6 to 0,65, I don't see a big problem there.

Or am I missing something here?

greetz,
A33

A single LNB doesn't expect a distance as such as long as the f/D ratio is correct. A monoblock with fixed feedhorns will be pointing towards the focal point of an 80cm dish. On a larger dish the LNB arm is longer and so the monoblock is looking at a focal point somewhere in front of the dish. At the dish's face the two feedhorns will be looking at different places on the surface of the dish.

 

[PaulR]

Probably the best solution for the larger dish would be a 4 to 15 degree adjustable monobloc such as this - Octagon 0.1dB Flex Feed 4-15 Degree LNB

Simpler to fit than two lnbs but would require a DiSEqC switch as well.

That looks as though it's adjustable for angle but not separation so would also be looking at a focal point in front of the dish. The accompanying description doesn't what size dish it's optimised for so I could be mistaken. But, equally, it doesn't specifically say it fits all sizes of dish.

 

[sonnetpete]

No I couldn't use the smaller dish for 28.2 Astra 2 as it needs a larger dish for it so I'm assuming the Eutelasat one would be the same for use here in Spain.

Taking into account your location, 25.5E Eutelsat should be a stronger signal than Astra, and more suited to the smaller dish...

 

[Lazarus]

Taking into account your location, 25.5E Eutelsat should be a stronger signal than Astra, and more suited to the smaller dish...

As I understand it, the smaller dish is already in use for 27.5W, so we could be looking at a third dish.

No precedents for that. No Sirree ;)

 

[a33]

A monoblock with fixed feedhorns will be pointing towards the focal point of an 80cm dish. On a larger dish the LNB arm is longer and so the monoblock is looking at a focal point somewhere in front of the dish.

From what I have seen on forums, and from my own experience with for instance a Visiosat BiSat with G3D multifeed bracket (have you seen pictures of that? They are squinting massively, but nevertheless give good performance),
aiming point isn't that important, and FAR less important than the placing of the phase center of a feedhorn in the signal concentration of a satellite: the (effective) focal point.
I've seen various examples on forums of monoblocks used on various dish sizes, not always the sizes that they were 'intended' for.
I 'm not sure, also, if the two LNB feedhorns in a monoblock really usually make an angle, or if they are pointed along parallel lines?
An LNB's feedhorn must by the way not be 'looking at' a focal point, it must 'be in' the (effective) focal point.

So what matters most for a monoblock is the distance between the two feedhorns, not the aiming angle, as far as my experience goes.
(Though the best aiming angles would of course be to the G-spot; thanks to @RimaNTSS . )

greetz,
A33