uncletony created this page to give a basic introduction on how Satellite Television works.

• The first section of this page will tell you how to get up and running so you can view the five major UK terrestrial channels from Satellite (called the Sky 'FreeSat' service).
• The remainder of the page is a semi-technical introduction to satellite TV, how it works and some stuff about scrambling.

*** Just read the bits that interest you! ***

If you wish to make suggestions. correct problems and/or errors, offer advice or simply want to have a chat then please e-mail me here.

Many parts of the UK are poorly served by terrestrial Digital Television (DVB-T).

If you live outside a Freeview coverage area (click here to check using your postcode) and cannot see the extra programming available, an alternative is to get a satellite TV system. It really doesn't cost too much for a basic system (GBP150 or less).

Read on to learn what you need to do ....

Firstly, a short introduction:
TV and radio programming aimed primarily at the UK comes from a group of satellites located at 28° east of South. They are called 'Astra-2A, Astra-2B, ..., etc, and EuroSat'. The main provider of satellite television for the UK is Sky and virtually all their channels are scrambled. To unlock Sky channels a dedicated receiver-box and a special viewing card are needed. The viewing card contains special electronic codes which unlock the channels you pay for each month. Getting these Sky programmes can be expensive (average GBP30+ a month).

What can you get for free from Satellite?
The BBC broadcasts all its TV and radio channels from the Astra-2D satellite without any form of scrambling. ITV-1, ITV-2 and ITV-3 are also broadcast without scrambling, but at the moment due to contractural obligations Channel 4 and FIVE remain encrypted. The signal beam is very narrow to discourage viewing outside the UK. Anyone within the coverage area of the 2D signal (see footprint image) will be able to get these channels with the most basic equipment set-up. The bonus is that there are a lot of other encryption-free English language channels broadcasting from the other satellites which are co-located at the same position in space as Astra-2D.
For much more information on Astra-2D go here.

What about the scrambled channels (Ch-4 , FIVE, etc)?
At the end of October 2004 Sky introduced a special viewing card which allows access to these scrambled commercial channels. The condition is that you must have a dedicated Sky receiver (a 'Digibox'), and the special viewing card (which has a one-off cost of GBP20). After the Digibox and viewing card combination are connected up to the dish and authorised (this is done over the phone) the system will be enabled allowing you to see ITV-1, ITV-2 Channel Four and Five for at least 2 years.

Remember: Having a Sky Digibox is a must.

A FTA (Free-to-Air) satellite receiver will NOT allow you to watch any of the scrambled commercial channels whether you have the viewing card or not (because the viewing card only works inside a dedicated Sky Digibox). It is worth mentioning that the Sky Digibox will pick up all the unscrambled channels and let you view them.

Where do I start?
There is a choice between buying a secondhand Digibox (about GBP50) plus dish/LNB (about GBP20) plus viewing card (GBP20) and go for the fun(?) of a D-I-Y installation, or to pay GBP150 to Sky and they'll arrange for the basic installation of dish/LNB and Digibox, including the viewing card.

For more info on programme choice, visit www.freesatfromsky.com and read the Q&A section.

IMPORTANT - If you have your own digibox, dish and LNB and can install it yourself (or have a mate to do it) you DO NOT need to pay any additional money except £20 for the card to get all the free-to-air satellite channels.

uncletony created this part of the page to give a general introduction on how Satellite Television works.

TV broadcast satellites are placed in orbit directly above the equator at a height of about 36000km. They travel through space at the same speed the earth's rotation - so to us on the ground the satellite appears to be stationary. This is known as a geo-synchronous (or geo-stationary) orbit.

Ground controllers fire on-board jet thrusters occassionally to keep the satellite in the specified position in space. This is the major factor in determining the 'life' of a satellite.

In Europe the orbital location of a satellite on the Clark Belt is given by the number of degrees to the East or West of due South (for example: Astra 1 = 19.2°E, Hispasat = 30°W). This is the Azimuth.

Getting signals to and from the Satellite

Television and radio programme signals are sent from the various originating studios to an Earth up-link station. From there the gathered 'bouquet' of programmes is transmitted into space using a dish aimed at the orbiting spacecraft. This is known as the 'up-link'. The frequency is about 14GHz (in Europe)

The satellite receives these signals, amplifies them and transmits them back towards earth on a different frequency. This work is done by a transponder. This 'down-link' operates at about 11GHz (in Europe), in the so-called Ku microwave band).

A group of satellites in the same orbital position (such as Eutelsat's 'Hotbird') may have a combined total of more than 70 transponders. A transponder rebroadcasts 1 analogue TV channel or as many as 14 digital TV channels (this depends on the digital compression techniques used:- lower compression = less channels = better pictures).

This kind of broadcasting is known as DTH (Direct-to-Home broadcasting).

Each satellite has a massive array of solar cells. Some satellites are cube-shaped and have huge wing-like solar cell arrays extending from the main body, while others are cylindrical and have their entire surface coated with solar cells. The cells convert sunlight into electricity to operate the satellite, providing power for the transponders and to maintain the charge on the standby batteries for the times when the satellite is in the shadow of the Earth.

Up-link station at Leuk, operated by Swiss PTT

The satellites used for radio and television broadcasting are not usually owned by the broadcasting companies.
Broadcasters lease the technical facilities from the satellite owner. In Europe the two major satellite providers are Eutelsat and SES-Astra.
The earth stations required to send the programmes up to the satellite (called the 'up-link') are provided by a variety of organisations in many many different countries. Some of these are commercial organisations (eg BT in UK) and some are government agencies (eg national PTT authorities).

This is the actual signal strength map (or Footprint) of the Astra 1G and 1H satellites (as published by the owners of the satellites, SES-Astra). Both 'birds' are located in the same orbital position in space at 19.2°E.

The antenna on the satellite directs the signal down to a specific land area. Just as the beam from a flashlight gets wider and weaker over distance so does the satellite radio signal.

Contour lines on the map show the required dish size for satisfactory all-weather reception.

Note that these satellites have a signal beam dedicated to covering the Canary Islands. This arrangement is known as a 'spot-beam'.

Tuning into Satellite TV and Radio ...

To tune in to satellite TV some specific receiving equipment is needed.

The most obvious item is the dish. The dish is the antenna (aerial). It works like a curved mirror to collect, reflect and concentrate the radio energy from the satellite and focusses it into the throat of the LNB (Low Noise Block).

The LNB amplifies these very weak signals and converts them to a lower frequency (from about 11GHz down to about 2GHz), the so-called intermediate frequency. This signal travels along the coaxial cable to the Receiver unit in the home. It is very important to use the correct type of coax cable - ask your supplier for CT-100, or better.

The Receiver (often called the set-top box, STB) performs all the electronic signal processing that is required to recover the TV signal. In addition it sends power and control signals up the cable to the LNB. The Receiver is connected to the TV set either by an antenna (aerial / RF) lead or SCART cable. Operation of the receiver and channel selection is normally done with an infra-red remote control unit.

This basic principle of getting the satellite TV signal is the same whether an analogue or digital system is being used. However, the electronic processing of digital and analogue signals is very different indeed.
Digital signals comply with the DVB-S (Digital Video Broadcasting - Satellite) protocol. Look for the DVB logo. For an analogue signal, the signal strength is very important, but for digital reception as much care must be paid to maximizing signal quality (the higher the quality number the less bit-rate errors the receiver will have to cope with).

More Dishes, More Satellites

For a greater choice of programming it is possible to 'look' at several satellites. This can be done by using a motorized dish or a combination of several fixed dishes and LNB's.

To use multiple dishes a simple switching system called DiSEqC (Digital Satellite Equipment Control™ - developed by Eutelsat) is all that is needed, but the receiver must be DiSEqC compatable. The DiSEqC switch is usually fitted near the dishes and a single cable feeds to the Receiver. The Receiver box sends control signals along the cable to the DiSEqC switch to automatically select the correct combination of dish/LNB and satellite.

Upgraded versions of the DiSEqC protocol allow for control of motorised dishes (DiSEqC 1.2 and 2.0).

For detailed spec of DiSEqC™ protocol go here

A different type of motorized system is the horizon-to-horizon (H-H) method. Here an electrically operated screw-jack pushes and pulls the dish which pivots on a special mounting bracket. This makes the dish accurately follow the position of the satellites along the Clark Belt. Receivers incorporating this type of motor drive will usually have 'Positioner' included in the name/description.

For even greater flexibility LNB's are available with single, dual, quad or octo (8) outputs. Each output is totally independent from the others. This allows multiple receivers (living room, bedroom, kitchen, etc) to connect to a single dish/LNB.

Pointing the Dish

To receive a strong and reliable signal in all weathers the dish must be pointed directly at the satellite.
Select a position where the path to the satellite is clear and unobstructed (for example a tree without leaves in winter will cause no problem - but in summer virtually no signals will get through to the dish).

"Pointing the dish" means setting the Azimuth and Elevation correctly.

• Elevation is the angle between horizontal and the satellite in orbit on the Clarke Belt.
  (In the UK this ranges from about 21° in the far north of Scotland to about 27° in the south of England [for Astra 1]).
  
  
• Azimuth is the position (east or west of south) where the satellite is located (19°E, 1°W, etc).
  
  
• Skew (or polarization offset) is the final little tweak required to get the strongest possible signal from the satellite. Instead of having the LNB fixed vertically in it's holder, a few degrees of clockwise (right) or anticlockwise (left) twist from the vertical is applied to compensate for the position of the satellite being either east or west of due south (in the northern hemisphere). The skew applied in northern UK for Astra-1, 19°E, is 10° clockwise. This increases to 16.5° for viewing Astra-2 at 28°E

When setting up your dish it is important to take into account the difference between true North and magnetic North. This is called the Magnetic Declination (or Variation)
Download this useful FREE program from Pangolin Comms to easily calculate the Magnetic Variation at your location anywhere in the world.
If you've got a dish you've gotta have this .... download SWMLink from Swedish Microwave. Among the many things it can do, this useful application is probably the best there is for calculating dish Az, El and Skew from any location on the globe for any satellite on the Clarke Belt. And best of all it's for FREE....
To find your Latitude and Longitude go to www.streetmap.co.uk and enter your UK postcode. Once the map is displayed then click on 'Click here to Convert/Measure coordinates...'. Your location details will be shown in a new table.     Dead Useful!
For worldwide locations go to www.heavens-above.com to find your Latitude and Longitude

Introduction to satellite Transponders

Transponders are interleaved using opposite polarity

Adjacent transponders are transmitted with alternate polarity. This allows more transponders to be used within the frequency band(s) allocated to satellite DTH broadcasting. The LNB is capable of switching between signal polarity.

Each transponder on a satellite has a typical bandwidth of 27MHz.
A single analogue channel will occupy this whole space. Up to 14 compressed digital TV channels can be fitted into the same space.

Video signal is 6 MHz wide. Main Audio carrier is at 6.60 Mhz
Additional audio sub-carriers at 180kHz spacing are used for stereo TV sound, alternate languages and/or radio stations

Symbol Rate represents the data rate (typically 27500Kbps) - see below.
FEC is the Forward Error Correction factor inserted by the broadcaster. The data stream can include TV, Radio and/or computer data.

Modulation

The analogue system uses FM (Frequency Modulation).

The digital system uses QPSK (Quadrature Phase Shift Keying) modulation.
This works by changing the phase of the In-phase (I) carrier from 0° to 180° and the Quadrature-phase (Q) carrier between 90° and 270°. This is used to indicate the four states of a 2-bit binary code. Each state of these carriers is referred to as a Symbol.

Introduction to Encryption (Scrambling)

The television and radio programmes which can be watched by anyone with a basic receiver are known as Free-to-Air (FTA).

Many broadcasters charge a subscription for their programmes, and to prevent unauthorized viewing the signals are scrambled (encrypted). There are several digital encryption systems - for example Cryptoworks, Conax, Irdeto, Mediaguard, Viaccess, etc. In Europe the majority of the few remaining analogue encrypted channels are beamed towards Scandinavia. These services use the MAC TV standard, and the scrambling system is Eurocrypt.

To unlock a channel the viewer needs a Receiver with a Conditional Access Module (CAM) that matches the encryption system being used. On payment of a fee the programme provider will supply the viewer with a viewing card containing special codes (called keys) to unlock only the subscribed channels. Copyright and other legislation normally does not allow the purchase and viewing of programmes in one country which are intended for another country (for example: it is not permitted for viewers in Spain to watch encrypted programmes 'aimed' at the UK by SkyTV).

Some Receivers are dedicated to one television network and one encryption system (for instance in the UK, SkyTV can only be picked-up on a receiver with an embedded (built-in) Videoguard CAM). In this case the subscriber's viewing card is linked electronically to one specific receiver.

Many Receivers are available with a common interface (CI). This is a single or double 'slot' into which one or more CAM's can be inserted. Once the CAM is in the receiver the necessary viewing card is inserted into the CAM.

The CAM has been designed to have the same physical format as a PCMCIA Card (which are extensively used in lap-top computers (Modems, etc)).

For the satellite enthusiast a wide range of experimental CAM's are available (Magic Module, Axas-II, Matrix Reloaded, Dragon, etc). Many reportedly operate on several of the encryption systems. Various models of these CAM's are advertised in hobby-related magazines.

There are a few Receivers on the market which have an embedded experimental CAM (so-called UCAS - Universal Conditional Access System). These Receivers usually have at least one additional slot for another CAM.

Conditional Access Module (CAM)
External and Internal views

Receivers with built-in hard disk drives are becoming very popular. When combined with the appropriate CAM and viewing card it is a simple matter to record any TV programme to disk ready to be replayed at a later date. Most have twin tuners which allows the recording of one channel while viewing another.

The Dreambox receiver operates very much like a computer. It uses an IBM 'Power-PC' processor and uses the Linux operating system. Because of the open access of Linux code many Dreambox enthusiasts create and modify software to continually improve the receivers operation. For an introduction

Two or three manufacturers offer PCI-style Satellite Receiver cards that fit inside a computer (regrettably only operating on MS Windows). Not only do these cards receive the programmes and store an unlimited amount of channel data, some versions of these cards can make the computer hard-disk operate as a personal digital video recorder (a 'PVR'). Also available are USB satellite Receivers for PC's and Mac's which connect to the computer with a USB cable .

To support the hobbist there are a few monthly magazines and several Internet Forums/newsgroups. By using appropriate search parameters on 'Google' (or other search engines) you will readily track these areas down.

Useful Links

Two of the most respected sources of up-to-the-minute listings of satellite transponders and programme providers are at:
www.lyngsat.com and www.satcodx.com

For the very best in technical info about digital and analogue satellite TV go to Martin Pickering's very own site:
www.satcure.co.uk

For information specifically on Astra 2D (where the majority of British TV channels are found) visit this site:www.astra2d.com

For up-to-the-minute stuff about all aspects of Satellite TV visit the 'What Satellite' magazine pages at:
www.wotsat.com

For loads of up-to-date stuff about technical and political apects of UK satellite and terrestrial Digital TV visit:
www.dtg.org.uk

For info about installation of dishes (for Sky) and aerials (for Freeview) visit the Confederation of Aerial Industries Ltd:
www.cai.org.uk

For a very technical discussion of terrestrial and satellite DVB go here

For ex-pats who need info about receiving Astra-2D outside the normal footprint go here

For uncletony's page about UK Television go here