Appropriate dish for 28.2E satellites

Dublin Deluge

Hello,

I've been reading up posts here and other websites and I've been learning quite a bit about satellite technology, but I'm still a bit confused. Anyway, I have one question, am I correct in assuming that a 60 cm dish pointing to 28.2E will get all of these FTA channels.

I.e. will it be able to receive signals from these satellites without the need of additional equipiment/several LNBs or a bigger dish?

Eutelsat 28B
Eutelsat 28A
Astra 1N
Astra 2A
Astra 2B
Astra 2F
Astra 2D

There also seem to be two types of 60 cm dish, one with a circular shape and the other one with an elliptical shape. What's the difference between the two? It seems that Sky uses the elliptical shape.

homer911

Can you confirm your location - it depends

watty

There are about 5 shapes of dish.

If you are in Ireland or most of UK, then 60cm is minimum (SE England can use 45cm, extreme Highlands and Isles may need more). More than 110cm might create problems. Larger dishes are harder to point than smaller. At Extreme North West or South West, you might be better with next size dish.

The separation of the satellites may be less than 2km. They are over 45,000km away so for reasonable size dishes they appear as a single radio source. Certainly a 3.7m dish will see some of them separately.

A slightly vertical ellipse on an offset dish gives more east west tolerance and is closer to a circular aspect for LNBF, than the Sky dish which requires a different LNBF as the aspect seen by LNBF is even more oval.

A truly circular edge dish is only optimal when not an offset cut. Note the LNBF is NOT an offset feed, it's prime focus. The DISH is shaped as an offset cut as if part of a larger dish.

A Cassegrain dish uses a central small reflector and has a truly circular edge with LNBF mounted in a hole in the middle.

Avoid perforated dishes as they are made that way for cheapness and lower shipping costs (lower weight). They have same windloading, or even slightly more at some angles and can rust more easily.

zg3409

Dublin Deluge wrote: »

I.e. will it be able to receive signals from these satellites without the need of additional equipiment/several LNBs or a bigger dish?

You can receive all satellites around 28.2/28.5 with the one dish and one LNB. Over time the names change as older satellites are replaced by never ones.

There also seem to be two types of 60 cm dish, one with a circular shape and the other one with an elliptical shape. What's the difference between the two? It seems that Sky uses the elliptical shape.

There is very little difference. The Sky type dish is designed to be a cheap as humanly possible. The LNB it uses matches the shape of the dish, so the holder will not hold other LNBs. It is specifically designed for the UK and Ireland market. It is available in different sizes depending on where you live.

More info on dishes here:
http://www.satcure.co.uk/tech/dishes.htm

The smaller the dish the less directional it is, so the easier it is to align. The larger the dish the more directional it is, so harder to align. However either way correct alignment is extremely critical and most home installed dishes are not aligned properly. For 28.2 /28.5 it is more critical as there is not just one satellite but multiple in nearly the same location and a compromise between each of them is needed.

As said state you location

Dublin Deluge

Thanks for all your replies so far guys! I'm in the Dundrum area in Dublin.

Another related question: I've noticed that some dishes are "mesh" while others are "solid". Is this just to save on costs or does it have an impact in things like wind resistance? Winds can be quite strong here, so I would imagine a mesh dish would be able to tolerate wind better?

snaps

solid is the best way forward. They usually perform better and last a lot longer too.

zg3409

Mesh makes no difference on wind resistance. That is a myth. As said solid dishes are normally much stronger and last much longer.

Dublin Deluge

watty wrote: »

Avoid perforated dishes as they are made that way for cheapness and lower shipping costs (lower weight). They have same windloading, or even slightly more at some angles and can rust more easily.

By "perforated dish" do you mean a "mesh" dish?

watty

No, I mean Perforated. Mesh is only used in Fibreglass dishes just below the surface.

Perforation = metal with holes, like spaghetti drainer. Sky dishes.

Mesh = Woven wires, like flour sieve. Large fibre glass dishes and also transparent plastic dishes.

Holes or gaps in mesh ought to be about 1/10th the shortest wavelength or less. So 3mm is a bit big for Freesat / Sky and 1.5mm a bit big for Saorsat.

Dublin Deluge

thanks for the clarification!

PogMoThoin

If you want something that lasts get an aluminium dish