Is there an affordable satellite system that is in size to a Sky dish available for raw feed?
I assume you mean similar in size to the Sky dishes, i.e. not a large dish? Unfortunately, the small 18-inch dishes are really only suitable for direct-broadcast satellites within the intended service area.
The size of dish you need for reliable reception depends upon the signal strength at the receive site. The strength at any given location is dependent upon the output power of the transmitter on the satellite, the directional pattern of the antenna it uses, and the quality of the receiver/converter on your dish (there are other factors, but those are the main ones).
Again, it's very similar to a flashlight. For a given size bulb, you could have a wide dispersal pattern to give a spread of light across a large area, but no point will be brightly illuminated. If you focus the beam down, you can light up one particular spot much more intensely, but only at the expense of having
less light in the surrounding areas. Satellite beams work in pretty much the same way, and the power and beam patterns are selected for the intended use.
For example, the Astra 2D satellite is intended to carry direct-broadcast programming to homes in the U.K. and Ireland which can be received on small household dishes, so it uses a relatively high-power output and very narrowly focused beam centered on the British Isles in order to give suitably high signal strengths.
Click on the "View footprint" link at the bottom of this page to see the beam effect:
http://www.ses-astra.com/corpSite/siteSections/ASTRAFleet/astra2d/As you can see from that, although the typical 18" dishes are fine within the U.K., to receive Astra 2D when you're on the edges of the beam in, say, the south of France, you would need a dish of at least 3 feet diameter.
As you mentioned Nilesat as being of interest, let's take a look at Nilesat 101 at 7 deg. west:
http://www.nilesat.com.eg/nilesat_eirp_Enlarg.htmThe beam pattern is adjusted to give the strongest signal around the intended primary area of reception, the part outlined by the 50.1dBW contour, with weaker coverage across much of the rest of northern Africa, signal levels down to 47.1dBW (by the way, the decibel scale is logarithmic, so the signal on the 47.1 contour is only
half the power of that on the 50.1 line).
Given an average modern receiver setup, a dish of around 30" would be sufficient within the 50.1 contour area, but by the time you get out to the 47.1 line in western Africa or the far southern part of Spain, you'd need to go to at least 4 ft. The further out from the beam you go, the weaker the signal and the bigger the dish needed. The strength would be so low in the U.K. as to require a rather large dish.
If you look at the various satellites listed on the Lyngsat website, you'll see links in the "Beam" column which take you to the maps for most of the satellites.
Here's one more to give you an idea:
http://www.hispasat.com/FlotaSat/pop_up_cobH1C-2.htmI have a little chart somewhere which gives a guide as to the required dish size for a a particular signal strength. I'll try and post it later.
In general terms though, don't expect the Sky-type 18" dishes to be any good for anything except the direct-to-home broadcasts within the intended service area. For the more exotic fare, there's no getting away from installing a much larger dish.