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UHF Television Reception In the United Kingdom the broadcasters currently provide a service to over 99% of the population from a network of 51 high power main station transmitters supplemented by a large number of smaller relay stations. Each station radiates four services at equal power: ITV, Channel 4 (S4C in Wales), BBC-1 and BBC-2 (including Teletext) normally through a common aerial, thus providing similar coverage areas. This also avoids a proliferation of transmitting aerials and usually provides the viewer with all four television channels from a single receiving aerial. (Note: The new Channel 5 is limited to 33 transmitters covering about 74% of the UK population using differing power levels and may require a separate aerial).
Four or five transmission frequencies or channels, are required at each transmitting station, one for each programme, out of the 44 channels available by international agreement for UHF broadcasting. This means that the network has been planned in a manner which avoids mutual interference between stations using the same transmission channels. The radiated power of the transmitters must therefore be strictly controlled. In general the powers are chosen so that at the average home good results are achievable by use of a modest aerial mounted externally at roof height and clear of obstructions. Most viewers will be within the service area of a transmitter and in some overlap areas may have the choice of an alternative service. The first step to achieving good reception is to find out which transmitter provides the best signals at your home.
Viewers who are situated less advantageously can still achieve good results by using a larger aerial possibly with a preamplifier. In areas where field strengths are somewhat lower and the construction of a relay station cannot be justified, the use of a high gain receiving aerial and a masthead preamplifier may be required.
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