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Terrestrial television

From Academic Kids

Terrestrial television (also known as over-the-air or OTA) is the traditional method of television broadcast signal delivery, by radio waves transmitted through open space. Terrestrial television broadcasting dates back to the very beginnings of television as a medium itself with the first long-distance public television broadcast from Washington, DC on April 7, 1927. Aside from transmission by high-flying planes moving in a loop using a system developed by Westinghouse called Stratovision, there was virtually no other method of television delivery until the 1950s with the advent of cable television, or community antenna television (CATV). The first non-terrestrial method of delivering television signals that in no way depended on a signal originating from a traditional terrestrial source began with the use of communications satellites during the 1960s and 1970s.

In the United States and most of the rest of North America as well, terrestrial television underwent a revolutionary transformation with the eventual acceptance of the NTSC standard for color television broadcasts in 1953. Later, Europe and the rest of the world either chose between the later PAL and SECAM color television standards, or adopted NTSC.

In addition to the threat from CATV, analog terrestrial television is now also subject to competition from satellite television and distribution of video and film content over the Internet. The technology of digital terrestrial television has been developed as a response to these challenges. The rise of digital terrestrial television, especially HDTV, may mark an end to the decline of broadcast television reception via traditional receiving antennas, which can receive over-the-air HDTV signals.

In North America, terrestrial broadcast television operates on TV channels 2 through 6 (VHF-low band, known as band I in Europe), 7 through 13 (VHF-high band, known as band III elsewhere), and 14 through 69 (UHF television band, elsewhere bands IV and V). Channel numbers represent actual frequencies used to broadcast the television signal. Additionally, television translators and boosters can be used to rebroadcast a terrestrial TV signal using an otherwise unused channel to cover areas with marginal reception. A chart showing the North American television bandplan can be found here.

In the UK, UHF frequencies were first used in 1964 with the introduction of BBC2. Television broadcasting on VHF frequencies was discontinued on January 6, 1985.

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