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).
I know this is like saying how long is a piece of string but what I was thinking was this. I have a standardsky mini dish somtimes in bad weather or for no reason at all the picture freezes for a few seconds or starts to pixulate. more prone on some stations than others, so would a biger dish make any diferance? Im in the midlands LE100NS
The larger the surface area of the dish, the more signal it can reflect into the LNB, so the more stable the TV picture and sound. A bigger dish would certainly make a difference, but situations such as torrential rain will degrade the signal beyound what a domestic sized dish can compensate for.
Ian: they work as a network of 1000s of tiny receivers, rather than one receiver with a concentrating reflective dish. Channel 4 and five are supposed to be part of the BBC/ITV Freesat project which has been put on hold for another year.
I wish to cancel my Sky + package and have instead bought a new DVD player with a built in hard drive and built in freeview. The only problem now is that I do not have any connections to an external aerial and I cannot not get any decent digital connection with an internal aerial. Can I plug in my original sky lead and use my sky dish as an external TV digital ariel? I just thought this would save me alot of hassle and money.
Hi,your Freeview will not work with an indoor ariel, you need a top quality outdoor one usually an upgrade of normal ones. I have an ON Digitalbox and recieve channel 4 & 5 + sky news and sky3 and all terrestrialchannels. You can obtain most sky channels if you contact TOPUP TV who will sell youvarious sky pakages from £9.99/month quite a saving compared to sky.
Ian Grice Sunday 24 December 2006 12:39AM Hinckley
do a google search on Cubsat, cubesat, digicube and DigiGlobe. for satellite dishes that are in Disguise. Great if you are not alowed one.
Graham Ireland Saturday 30 December 2006 4:43PM Wirral
I had been with sky for a number of years.
I cancelled my subscription on 21/11/6. Now all I get through the digibox is an on screen message detailing " No SatelliteSignal Being Received". Is it just coincidence that on 20/11/6 (when the subscription was still extant) the satellite signal was just fine but a day later (when the subscription was determined) there is mysteriously no signal being received and Sky maintain it is the equipment that is faulty?
Graham Ireland: try removing your card and powering the box off. Wait 30 seconds and re-apply the power, but do not insert the card. If the 998 Welcome channel is seen, only then insert the card. When you cancel your subscription you keep the free channels.
i can getfreeview in my living room but not in my bedroom they are both conected to the same aerial
Chris Joyce Thursday 29 March 2007 9:06AM Ballindalloch
I have a old Hotbird satellite system with an 80cm dish. I want to use it to recieve freeview.
It picks up Hotbird fine, but when I try to pick up other satellites I get nothing. Do I need to change the LNB, the reciever, or is the elivation different? what is the correct bearing for Freeview? (I have a seperate Sky set up and that works OK). I live in the north of Scotland (AB37 9JN)
Chris Joyce: As there are lots of Hotbird satellites, it's hard to say. You would, to be honest, probably have better results fitting a quad-LNB to your existing Sky dish and using the other outputs for that for Freesat. (Note also, Freesat is not Freeview).
Chris Joyce Friday 30 March 2007 11:20AM Ballindalloch
Hi Thanks for your quick response, but it realy is of no help.
The Sky setup is on my house, and the Old Hotbird system is about 300m away on my workshop. I notice that you have Mentioned Astra 2 N,S & D are thoes the stellites carrying the FreeSat chanells? if so could you tell me their orbital position or positions? Also what Band do they use, I seem to recall that my LNB is "K" band.
I am in a block of flats where the lease does not allow me to have an external aerial but want to get a FTA satellitesignal. I am on the South coast and do have a balcony with line of site to Astra This would mean the dish being behind glass. Is there a realistic chance that I would get a usable signal?
Freeview is not an alternative as there no Freeview signal in this area (I can't even get Channel 5!).
Been living abroad for some time, my self all my expats friends would like to have BBC 1,2. Is there any chance of us getting BBC without having to go to the expense of buying a 3 m dish. The majority would gladly pay a licence fee to the BBC, could you give me any information, how we could receive a wonderful BBC abroad
Great site! I however am still at a loss as to which digital service to choose. I live in BT370ZN and currently have analogue which also receives RTE which I don't want to lose. I am buying a new TV with freeview and HD. Should I go for digital aerial, Freesat or Sky? I really would prefer to have no subscription charges but will put up with this if necessary!
Barbara: If you can get a digitalsignal from Divis then this will work fine, and it's always worth getting a TV with a digital tuner, because it will work at some stage (even if it's 2012). If you want to watch HD, satellite is the only option, but you may wish to wait until BBC Freesat launches, as this may have HDTV, which FreesatfromSky does not.
Hi Brian, my parents want to get freesat for their caravan in Welshpool , problem is there is a tree right where the dish would have to point, so a very weak signal, there is another dish that can be used, but the landowner will not let them cut a trench to lay wires, is there a inexpensive wireless option?
Dave Tuesday 17 April 2007 9:50PM
I have been given an old Pace Prima analoguereceiver and a dish to go with it. Is it possible to use any of this equipment to receive freesat? What might I need to upgrade? or should I just dump the lot and start again? In which case can you offer any advice on best/cheapest options? I am not in a Freeview or cable area and therefore only have satellite as an option.
Many thanks in advance.
i have a pace box,skydigibox.model no.bskyb2200.and original dish ,willi be able to connect up to my tele at my caravan and recieve freeview chanels..do i need the sky card or will any other type of card do i no longer subscribe to sky.
I already have sky digital (not multiroom) which is wired so I can receive sky on all TV's in the house. I would also like to have freesat available on all TV's in the house so that, for instance, the children can watch CBeebies while I watch Sky Sports. Do I need a new dish and receiver or can the old dish and receiver be modified and used? Also, will the existing remote eye work with freesat?
Dev Singh: If you want select different channels in different rooms you need to have a digibox with each TV, then a satellite-grade cable to the dish from each digibox AND change the LNB on the end of the dish's arm to a four-output Quad-LNB. This will drive four set-top boxes. The remote eye would be redundant.
Richard Alderson: The satellite and terrestrial set top boxes cannot be interchanged. Your TV needs to me marked "HD Ready" and have a DVI or HDMI input to work with satellite HD. You can plug a FreesatfromSky box into any TV. BBC Freesat service, yes, launches next Spring.
Can i receive Freesat in Spain in particular in the city of Leon, in the region of Castilla y Leon.
Since the BBC are no longer broadcasting
short wave radio to western Europe, I have no way of keeping in touch with
english news and as Freesat also provides radio as well as BBC TV this seems a practicle to receive english tv and radio in Spain