1. Satellite Television Introduction
TV broadcast satellites are placed in orbit directly above the equator in a height of around
36000km. They travel through space in the same speed earth's rotation - so to us on the
ground the satellite seems to be stationary. This is known as a geo-synchronous (or geo-
stationary) orbit.
Ground controllers fire on-board jet thrusters occassionally to help keep the satellite in the
specified position in space. This will be the major factor in determining the 'life' of your
satellite, as onboard fuel does eventually come to an end.
In Europe the orbital location of the satellite on the Clark Belt emerges by the quantity of
degrees to the East or West of due South (for instance: Astra 1 = 19.2°E, Hispasat = 30°W).
This will be the Azimuth.
The Clarke Belt
The concept of geo-stationary satellites was first suggested by Arthur C Clarke in an article
written for Wirless World magazine in October 1946.
The region in space occupied by these satellites is commonly referred to as 'The Clarke Belt'
Getting signals both to and from the Satellite
Television and radio programme signals are sent from your various originating studios with
an Earth up-link station. From there the gathered 'bouquet' of programmes is transmitted into
space employing a dish aimed with the orbiting spacecraft. This is called the 'up-link'. The
frequency is around 14GHz (in Europe)
The satellite receives these signals, amplifies them and transmits it well towards earth over a
different frequency. This work is performed by a transponder. This 'down-link' operates at
about 11GHz (in Europe), within the so-called Ku microwave band).
A group of satellites within the same orbital position (for example Eutelsat's 'Hotbird') will
have a combined total greater than 70 transponders. A transponder rebroadcasts 1 analogue
TV channel or possibly 14 digital TV channels (this depends for the digital compression
techniques used:- lower compression = less channels = better pictures).
This form of broadcasting is known as DTH (Direct-to-Home broadcasting).
Each satellite includes a massive variety of solar cells. Some satellites are cube-shaped and
still have huge wing-like solar cell arrays extending through the main body, and some are

2. cylindrical and also have their entire surface coated with solar cells. The cells convert
sunlight into electricity to function the satellite, providing power to the transponders also to
maintain the charge about the standby batteries for the times when the satellite is in the
shadow of the Earth.
The satellites useful for radio and television broadcasting usually are not usually owned from
the broadcasting companies.
Broadcasters lease the technical facilities from your satellite owner. In Europe both major
satellite providers are Eutelsat and SES-Astra.
The earth stations necessary to send the programmes up to the satellite (known as the 'up-
link') are provided by the variety of organisations in lots of many different countries. Some of
these are commercial organisations (eg BT in UK) and some are government departments
(eg national PTT authorities).
The Footprint
This will be the actual signal strength map (or Footprint) with the Astra 1G and 1H satellites
(as published through the owners in the satellites, SES-Astra). Both 'birds' are located within
the same orbital position in space at 19.2°E.
The antenna on the satellite directs the signal as a result of a specific land area. Just as the
beam from your flashlight gets wider and weaker over distance the same is true the satellite
radio signal.
Contour lines for the map show the mandatory dish size for satisfactory all-weather
reception.
Tuning into Satellite TV and Radio
To hear satellite TV some specific receiving products are needed.
The greatest item will be the dish. The dish will be the antenna (aerial). It works just like a
curved mirror to collect, reflect while keeping focused the radio energy from the satellite and
focusses it in to the throat with the LNB (Low Noise Block).
The LNB amplifies these very weak signals and converts them to a lower frequency (from
about 11GHz as a result of less than 2GHz), the so-called intermediate frequency. This
signal travels across the coaxial cable towards the Receiver unit inside home.
The Receiver (often referred to as set-top box, STB, or Digibox etc) performs every one of
the electronic signal processing that is necessary to recover the TV signal. In addition it
sends power and control signals inside the cable for the LNB. The Receiver is connected to
the TV set either by an antenna (aerial / RF) lead or SCART cable. Operation with the

3. receiver and channel selection is normally done with an infra-red remote control unit.
This basic principle of getting the satellite TV signal may be the same whether an analogue
or digital product is being used. However, the electronic processing of digital and analogue
signals is quite 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 extremely important, but also
for digital reception just as much care have to be paid to maximizing signal quality (the higher
the quality number the less bit-rate errors the receiver must cope with).
More Dishes, More Satellites
For a greater choice of programming you'll be able to 'look' at several satellites. This can be
done by utilizing a motorized dish or a combination of several fixed dishes and LNB's.
To use multiple dishes a straightforward switching system called DiSEqC (Digital Satellite
Equipment Control™ - manufactured by Eutelsat) 's all that is needed, though the receiver
have to be DiSEqC compatable. The DiSEqC switch is normally fitted nearby the dishes plus
a single cable feeds to the Receiver. The Receiver box sends control signals across the
cable towards the DiSEqC exchange signal of automatically pick the correct blend of
dish/LNB and satellite.
Upgraded versions with the DiSEqC protocol allow for control of motorised dishes (DiSEqC
1.2 and two.0).
A different kind of motorized satellite system is the horizon-to-horizon (H-H) method. Here an
electrically operated screw-jack pushes and pulls the dish which pivots over a special
mounting bracket. This makes the dish accurately continue with the position of the satellites
over the Clark Belt. Receivers incorporating this sort of motor drive will usually have
'Positioner' included within the name/description.
For sustained flexibility LNB's can be purchased with single, dual, quad or octo (8) outputs.
Each output is very independent in the others. This allows multiple receivers (lounge,
bedroom, kitchen, etc) for connecting to just one dish/LNB.
If 'looking' at two closely spaced satellites (eg Hotbird [13°E] and Astra-1 [19E°]) you are able
to use one dish and a couple LNB's mounted with a special extension arm. The dish then
one LNB is focussed about the weaker of the two satellites. The second LNB is moved over
the extension arm until an adequate signal through the second, stronger satellite is received
(this picture shows a single output LNB 'looking' at Hotbird and a quad output LNB 'looking' at
Astra-1 - remember that one output through the quad LNB isn't in use).

4. Thank you for reading
satellite