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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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Wednesday, 20 April 2011
10:54 PM

I have just purchased a Panasonic Viera television with built in freeview HD and now I need to put up a dish which will be a DIY job.
My question is do I need a specific dish to recieve HD tv from the satelite or are all dishes able to recieve HD.

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Maurice's 1 post GB flag
Thursday, 21 April 2011

4:26 AM

Maurice: You can't use a dish with Freeview HD, only Freesat HD.

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Briantist's 38,915 posts GB flag

4:12 PM

Maurice - I've just bought a Panasonic Viera TV which, like yours, has both Freeview HD and Freesat HD tuners built in. Briantist is right, it is Freesat HD that needs a dish whereas Freeview HD will be avaialble through your aerial (if you are in an area that has switched over to digital only).
If you want to do a DIY job I would suggest the Screwfix Freesat installation kit which is just over £40 and includes dish,LNB,brackets, cable etc. If you do not want to DIY then look in yellow pages for satellite installers and get a couple of quotes.

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SteveW's 59 posts GB flag
Sunday, 24 April 2011
11:04 AM

i have panasonic freesat t.v which was working fine of old sky sat dish then came up no signal. think sat dish might of ad its day i installed a new one but unfortunately that didnt help. so i found my old sky box plugged it in and it picks up 99% of freesat channels of my new dish. so is freesat broke on my t.v or do i get sat man to come look at sat dish.

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k.hammond's 1 post GB flag

1:09 PM

k.hammond: It does rather sound like a problem with the set.

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Briantist's 38,915 posts GB flag
Friday, 6 May 2011
8:44 PM

have a sky dish which works fine for free sky channels on old sky box. Considering Freesat+ HD recorder. Will this work with existing dish

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Mark's 1 post GB flag

10:43 PM

Mark: Yes, but you will have to fit a quad-LNB to provide you with more than one output, and another cable.

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Briantist's 38,915 posts GB flag
Saturday, 7 May 2011
john large
2:34 PM

hi have just got freesatkit with hd for home
i would like to get aportable dish for the caravan and take the hd box with me do i need a hd dish also the size of a dish for uk use

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john large's 1 post GB flag

8:09 PM

john large: No special dish is required for HD channels.

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Briantist's 38,915 posts GB flag
Mark Aberfan Aerials

8:16 PM

Hi John Large,

This is the sort of thing you need,

Sky/Freesat mini satellite dish kit for caravan camping | eBay

Mark Aberfan Aerials

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Mark Aberfan Aerials's 1,059 posts GB flag
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