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Freesat reception - all about dishes

Satellite reception has both advantages and disadvantages compared with terrestrial (aerial) reception.

Satellite reception has both advantages and disadvantages compa
published on UK Free TV

Satellite reception has both advantages and disadvantages compare with terrestrial (aerial) reception.

By using much higher frequencies (gigahertz, compared to terrestrial televisions megahertz) more transmission channels called transponders (the satellite equivalent of multiplexes) can be provided. For example, there are only six Freeview multiplexes, but Sky or Freesat users can access two hundred satellite transponders.

Aside from exceptional weather conditions (very heavy rain for example) digital satellite provides stable pictures and audio. Where Freeview transmitters are no more than 732 metres above sea level, the geostationary satellites used for television are 35,800,000 metres above the equator so reception is possible even where buildings, trees and hills make terrestrial reception impossible.

The downside of the transmitters being 22,300 miles up in the air is that the signals are very, very weak - so standard TV aerial is of little use. When the signals are sent to the satellites, huge dish transmitters are used to uplink the signal to the satellite. These are tens of metres from side to side, and feature an emitter that generates the signal, which is first bounced of a mirror (called a reflector) and then off the surface of the parabolic dish.

There are many satellites in the sky over the equator. Often these are in clusters over a particular position, for example there are four used for UK television are at 28.2 degrees east. There is another cluster over the 19.2 degrees east positions that are used for German television.

To receive these very weak signals from the satellite, it is necessary to use a dish for reception too. By using a reflective dish, this concentrates the signals onto a small device called a LNB. This is held in front of the dish by a metal arm.

The size of dish for reception is typically much smaller; often 60cm to 100cm in diameter, but the exact size depends upon the transmitting satellite transponder. To keep the transmission power levels down to levels that can be powered by the satellite's solar panels, each beam is focused on a particular area of the Earth's surface. If you are trying to receive the signal at the centre of this zone, a small dish is required. At the outer edges, you may need a 5 metre dish. Maps of these zones are provided by the satellite companies, and are called satellite footprints.

When the dish is installed it must be aligned carefully as the signal is very weak. The installer needs to know the inclination and the azimuth from the ground location to the satellite. If you install yourself you will find that there are markings on the dish that are used to point the dish in the correct position. It is important that the view of the satellite will not be blocked, so must take into account leaves growing on trees and potential building works.

For many people the LNB will have a single cable connected to it, however if you have Sky+ or a multi-room installation the LNB package will actually contain four receivers a quad-LNB. Unlike terrestrial television where you can split the aerial cable to feed more than one Freeview box or television set, with satelite reception you cannot. So, a Sky+ box with two receivers (so you can watch one thing and record another) has two cables connecting the box to the dish.

The cable that connects the dish to the receiver must be satellite grade cable. Whilst this looks superficially like the cable used to connect and aerial to a television, a higher grade cable is required for satellite reception.

Here is an image of a co-axial cable. This sort of cable is used to connect any type of receiving aerial to the reception equipment.

RG6, PF100 and PH100 are all types of coax cable that are suitable for the very weak signals that are received by a satellite dish. (The power is the same as you would receive from a one-bar electric heater on the moon).

The conductor in the centre passes the signals received from the dish to the set-top box. This is made from steel in RG6 cable, and from copper in the RF100 and PH100 types. This makes RG6 less suitable in the UK where rain can damage the cable.

The shielding is responsible for keeping unwanted external interference from damaging the signal. In the cheaper cable this will be a foil wrap, in better specified cables this is a braid (or mesh) of copper wires. The sheild in the RF100 covers 58% of the cable.

The non-conducting layer between the shield and the conductor is called the dielectric. This can be either a solid (RG6), foam (RF100) or air-spaced (PH100) dielectric. This makes the cables progressively more flexible (ie bendy without damage).

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Saturday, 2 April 2011
John P
8:07 PM

My Post Code is LE17 4RX and I receive from Sutton Coalfield
and hence receive only West Midlands News etc.
I would like to receive East Midlands News from Waltham but the village church (tower etc) is plumb in line with the 46 degree bearing for the Waltham transmitter.
Is the logical way forward via a dish & Freesat, please?

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John P's 2 posts GB flag
John's: mapJ's Freeview map terrainJ's terrain plot wavesJ's frequency data J's Freeview Detailed Coverage
Monday, 4 April 2011
Lost without TV
12:58 PM

i have bought a satellite finder kit, contains compass and box thing to be connected to the dish and the cable that runs to the box!! The box makes a noise as though it's picking up something but still the signal strength and quality are a 0%...According to the compass i'm pointing in the right direction, i tried another cable in the box and dish, still gets power but nothing else....Please can you advise why there would be 0% in both strength and quality if the dish is pointing to the correct location. Am i missing something? Thanks very much.

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Lost without TV's 2 posts FR flag
Mike Dimmick

1:32 PM

Lost without TV: Check for a broken, loose or disconnected cable. Also, if you've tried to split the cable, disconnect the splitter - each tuner in each Freesat box (you may have two if it's a recorder) has to be able to send a signal back up the cable to the LNB to select the correct mode for the channel.

If you've added a diplexer, to combine aerial signals onto the same cable, check that it's wired correctly and isn't blocking the voltage sent from the Freesat box to power the LNB, or the mode selection signals.

If you've replaced a cable, it may not be the right sort. Regular TV 'low-loss' coax drops a lot of signal over its length, compared to 'satellite-grade' cable.

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Mike Dimmick's 2,486 posts GB flag
Mike's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
1:32 PM

Hi, I have recently moved. I have been given an old Sky box and Scart lead. The previous owner left the Sky dish and there are two cables coming into the lounge. One of them is two thin cables which are stuck together. Which cable goes where? Sorry this is a silly question but I am not technical :)

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AnnieSalsa's 2 posts EU flag
Mike Dimmick

1:42 PM

John P: There are some hills blocking line-of-sight to Waltham as well as the church. The prediction, which includes terrain but not buildings, is variable to poor. Very careful siting of a fringe reception antenna might work, but it's also likely to be expensive.
All BBC services are free-to-air on satellite, but some ITV1 regions are only available encrypted, requiring a Sky box and viewing card. ITV1 Central East is one of them - weirdly, it's the only separate news region that is, while there are some news areas that have more than one advertising micro-region free-to-air.
You can get a dish, box and viewing card from Sky without a subscription for £175, including installation. See FREESAT from Sky - Call now to order .
You may find it simpler to just watch your preferred local news bulletin online. See BBC - BBC One Programmes - East Midlands Today for the BBC, and
Central Regional News (ITV Central Tonight) - ITV Local
for ITV. (RG47SH)

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Mike Dimmick's 2,486 posts GB flag
Mike Dimmick

1:50 PM

AnnieSalsa: It's most likely that the twin cable goes back to the satellite dish. If this is a plain Sky box, not a recorder, it probably has a single input marked LNB IN. Connect one half of the twin cable to this.

If it's a Sky+ box, connect one half to LNB 1 IN and the other to LNB 2 IN.

The other cable, if it also has a screw thread, is probably for multi-room installations. If there's a socket or cable in another room, perhaps the main bedroom, it's possible that the single cable in the lounge runs from there to the bedroom. If you want to watch Sky or Freesat in the bedroom, you could connect that cable to the LNB OUT on the lounge box, and another box to the socket or cable in the bedroom.

However, you will find that the box in the bedroom will only be able to show some of the channels when the box in the lounge is on. To be able to select any channel, you'd need a completely separate cable all the way back to the dish.

If it's just a push-in type it's either a downlead from an aerial, for analogue TV and Freeview, or it could be intended to distribute the RF modulated output of the Sky box to other rooms (there's an aerial loop-through socket on the Sky box for this). To watch this in another room, you'd have to tune the TV's analogue tuner into the frequency that the Sky box is putting its output on.

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Mike Dimmick's 2,486 posts GB flag
Mike's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Wednesday, 13 April 2011
2:39 PM

hi J've just moved into a new flat and it has a dish on the outside wall, but it seems to have a normal co-ax cable coming of it, is this freesat or sky? if it is freesat can i buy a receiver and just plug it in ?
whats the difference in the dishes do they point the same way? how can i tell. no one in the buiklding knows what the last tennant had.

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Michael's 1 post GB flag

3:59 PM

Michael: Freesat and Sky use the same satellites, you can just buy a Freesat box from a store and plug it in. You can get a basic Freesat box from Argos, for example, for £30.

This is probably the best way to test the connection.

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Briantist's 38,915 posts GB flag
Monday, 18 April 2011
4:09 PM

Help - Ive had a freesat box for ages which worked fine. Then it suddenly started struggling to find signal until it gave up all together. I purchased a new box, which on the first installatio had a good strength signal and brought up all the channels. Switched it on the morning after and no signal on any channel = no channels! How can I have lost signal overnight, nothing was unplugged or moved. Has the problem got to be with my dish? Thanks Georgie

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Georgie's 1 post GB flag

7:04 PM

Georgie: I would guess from this that your LNB has failed, and will require replacement. You can get new ones for about £30.

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Briantist's 38,915 posts GB flag
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