Terrestrial television

"Air TV" redirects here. For the anime, see Air (visual novel).
Over the Air antenna

Terrestrial television or broadcast television is a type of television broadcasting in which the television signal is transmitted by radio waves to the TV receiver from a terrestrial (Earth based) transmitter, a television station, and received with an antenna. The term is more common in Europe, while in North America it is referred to as broadcast television or sometimes over-the-air television (OTA). The term "terrestrial" is used to distinguish this type from the newer technologies of satellite television (direct broadcast satellite or DBS television), in which the television signal is transmitted to the receiver from an overhead satellite, and cable television, in which the signal is carried to the receiver through a cable.

Terrestrial television was the first technology used for television broadcasting, with the first long-distance public television broadcast from Washington, D.C., on 7 April 1927. The BBC began broadcasting in 1929, and had a regular schedule of television programmes in 1930. However these early experimental systems had insufficient picture quality to attract the public, due to their mechanical scan technology, and television didn't become widespread until after World War 2 with the advent of electronic scan technology. The television broadcasting business followed the model of radio networks, with local television stations in cities and towns affiliated with television networks, either commercial (in USA) or government-controlled (in Europe), which provided content. Television broadcasts were in black and white until the 1960s, when color television broadcasting began.

There was virtually no other method of television delivery until the 1950s with the beginnings of cable television and community antenna television (CATV). CATV was, initially, simply a re-broadcast of over-the-air signals. With the widespread adoption of cable across the United States in the 1970s and 80s, viewing of terrestrial television broadcasts have been in decline; in 2013 it was estimated that about 7% of US households used an antenna.[1][2] A slight increase in use began around 2010 due to swichover to digital terrestrial television broadcasts, which offer pristine image quality over very large areas, and offered an alternate to CATV for cord cutters.

Europe

Following the ST61 conference, UHF frequencies were first used in the UK in 1964 with the introduction of BBC2. In UK, VHF channels were kept on the old 405-line system, while UHF was used solely for 625-line broadcasts (which later used PAL colour). Television broadcasting in the 405-line system continued after the introduction of four analogue programmes in the UHF bands until the last 405-line transmitters were switched off on January 6, 1985. VHF Band III was used in other countries around Europe for PAL broadcasts until planned phase out and switchover to digital television.

The success of analogue terrestrial television across Europe varied from country to country. Although each country had rights to a certain number of frequencies by virtue of the ST61 plan, not all of them were brought into service.

North America

In North America 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. Japan also uses a version of NTSC.

In North America, terrestrial broadcast television operates on television channels 2 through 6 (VHF-low band, 47 to 88 MHz, known as band I in Europe), 7 through 13 (VHF-high band, 174 to 240 MHz, known as band III elsewhere), and 14 through 69 (UHF television band, 470 to 854 MHz, 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 television signal using an otherwise unused channel to cover areas with marginal reception. A chart showing the North American television bandplan can be found at the North American broadcast television frequencies page.

Analog television channels 2 through 6, 7 through 13 and 14 through 51 are only used for LPTV translator stations in the U.S. Channels 52 through 69 are still used in exceptional circumstances for LPTV translators in some remote regions of Canada. The Canadian Broadcasting Corporation received permission to continue analog broadcasting at severely reduced power levels in some mandatory markets until January 8, 2012. It was expected that these transmitters would be shut down rather than converted to digital. Some older cathode ray tube television sets have a built-in transmitter.

The rise of digital terrestrial television, especially high-definition television (HDTV), may mark an end to the decline of broadcast television reception by traditional receiving antennas, which can receive over-the-air HDTV signals.

Asia

Terrestrial television broadcast in Asia started as early as 1939 in Japan through a series of experiments done by NHK Broadcasting Institute of Technology. However, these experiments were interrupted by the beginning of the World War II in the Pacific. On February 1, 1953, NHK (Japan Broadcasting Corporation) began broadcasting. On August 28, 1953, Nippon TV (Nippon Television Network Corporation), the first commercial television broadcaster in Asia was launched. Meanwhile, in the Philippines, Alto Broadcasting System (now ABS-CBN), the first commercial television broadcaster in Southeast Asia, launched its first commercial terrestrial television station DZAQ-TV on October 23, 1953 with the help of Radio Corporation of America (RCA).

Digital terrestrial television

By the mid 1990s, the interest in digital television across Europe was such the CEPT convened the "Chester '97" conference to agree means by which digital television could be inserted into the ST61 frequency plan.

The introduction of digital television in the late 1990s and early years of the 21st century led the ITU to call a Regional Radiocommunication Conference to abrogate the ST61 plan and to put a new plan for digital broadcasting only in its place.

In December 2005 the European Union decided to cease all analog audio and analog video television transmissions by 2012 and switch all terrestrial television broadcasting to digital audio and digital video (all EU countries have agreed on using DVB-T). The Netherlands completed the transition in December 2006, and some EU member states decided to complete their switchover as early as 2008 (Sweden), and (Denmark) in 2009. While the UK began the switch in late 2007, it was not completed until 24 October 2012. Norway ceased all analogue television transmissions on December 1, 2009.[3] Two member states (not specified in the announcement) have expressed concerns that they might not be able to proceed to the switchover by 2012 due to technical limitations; the rest of the EU member states had stopped analog television transmissions by the end 2012.

Many countries are developing and evaluating digital terrestrial television systems.

Australia has adopted the DVB-T standard and the government's industry regulator, the Australian Communications and Media Authority, has mandated that all analogue transmissions will cease by 2012. Mandated digital conversion commenced early in 2009 with a graduated program. The first centre to experience analog switch-off will be the remote Victorian regional town of Mildura, in 2010. The government will supply underprivileged houses across the nation with free digital set-top DTV converter boxes in order to minimise any conversion disruption. Australia's major free-to-air television networks have all been granted digital transmission licences and are each required to broadcast at least one high-definition and one standard-definition channel into all of their markets.

In North America a specification laid out by the ATSC has become the standard for digital terrestrial television. In the United States the Federal Communications Commission (FCC) set the final deadline for the switchoff of analog service for June 12, 2009. All television receivers must now include a digital tuner. In Canada, the Canadian Radio-television and Telecommunications Commission (CRTC), set August 31, 2011 as the date that over-the-air analog transmission service ceased in most parts of the country except in Northern Canada. [4] [5] In Mexico the Federal Telecommunications Institute (IFT) set the final deadline for the end of Analog Television for December 31, 2015.

Competition for radio spectrum

In late 2009, US competition for the limited available radio spectrum led to debate over the possible re-allocation of frequencies currently occupied by television, and the FCC began asking for comments on how to increase the bandwidth available for wireless broadband. Some have proposed mixing the two together, on different channels that are already open (like White Spaces), while others have proposed "repacking" some stations and forcing them off certain channels, just a few years after the same thing was done (without compensation to the broadcasters) in the DTV transition in the United States.

Some US commentators have proposed the closing down of over-the-air TV broadcasting, on the grounds that available spectrum might be better used, and requiring viewers to shift to satellite or cable reception. This would eliminate mobile TV, which has been delayed several years by the FCC's decision to choose ATSC and its proprietary 8VSB modulation, instead of the worldwide COFDM standard used for all other digital terrestrial broadcasting around the world. Compared to Europe and Asia, this has hamstrung mobile TV in the US, because ATSC cannot be received while in motion (or often even while stationary) without ATSC-M/H as terrestrial DVB-T or ISDB-T can even without DVB-H or 1seg.

The National Association of Broadcasters has organized to fight such proposals, and public comments are also being taken by the FCC through mid-December 2009, in preparation for a plan to be released in mid-February 2010.

See also

References

  1. ↑ "CEA Study Says Seven Percent of TV Households Use Antennas", '"TVTechnology, 30 July 2013
  2. ↑ "Nielsen: Broadcast Reliance Grew in 2012", TVTechnology, 14 January 2013
  3. ↑ "DVB - Digital Video Broadcasting - Norway". Digital Video Broadcasting Project.
  4. ↑ "The Commission establishes a new approach for Canadian conventional television" (Press release). Canadian Radio-television and Telecommunications Commission. 2007-05-17. Retrieved 2007-05-17.
  5. ↑ "Broadcasting Public Notice CRTC 2007-53". Sections 50 to 80. Canadian Radio-television and Telecommunications Commission. 2007-05-17. Retrieved 2007-05-17.

External links

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