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Terrestrial television or broadcast television is a type of television broadcasting in which the television signal is transmitted by radio waves from the terrestrial (Earth based) transmitter of a television station to a TV receiver having 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 II 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 transition to color television in the 1950s and 60s.
There was no other method of television delivery until the 1950s with the beginnings of cable television and community antenna television (CATV). CATV was, initially, only a re-broadcast of over-the-air signals. With the widespread adoption of cable across the United States in the 1970s and 1980s, viewing of terrestrial television broadcasts has been in decline; in 2013, it was estimated that about 7% of US households used an antenna. A slight increase in use began after the 2009 final conversion to digital terrestrial television broadcasts, which offer HDTV image quality as an alternative to CATV for cord cutters.
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.
In 1941, the first NTSC standard was introduced by the National Television System Committee. This standard defined a transmission scheme for a black and white picture with 525 lines of vertical resolution at 60 fields per second. In the early 1950s, this standard was superseded by a backwards-compatible standard for color television. The NTSC standard was used in the Americas as well as Japan until the introduction of digital television.
In the late 1990s and early 2000s, the Advanced Television Systems Committee developed the ATSC standard for digital high definition terrestrial transmission. This standard was eventually adopted by many North American countries, including the United States, Canada, Dominican Republic, El Salvador, Guatemala, Honduras, and Mexico.
North American terrestrial broadcast television operates on analog channels 2 through 6 (VHF-low band, 54 to 88 MHz, known as band I in Europe), 7 through 13 (VHF-high band, 174 to 216 MHz, known as band III elsewhere), and 14 through 51 (UHF television band, 470 to 698 MHz, elsewhere bands IV and V). Unlike with analog transmission, ATSC channel numbers do not correspond to radio frequencies. Instead, a virtual channel is defined as part of the ATSC stream metadata so that a station can transmit on any frequency but still show the same channel number. Additionally, broadcast translators and signal boosters can be used to rebroadcast a terrestrial television signal using an otherwise unused channel to cover areas with marginal reception. (see North American broadcast television frequencies for frequency allocation charts)
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 by some existing stations, but these channels must be vacated if telecommunications companies notify the stations to vacate that signal spectrum.
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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
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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. 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 switch-off 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 metropolitan areas and provincial capitals. In Mexico, the Federal Telecommunications Institute (IFT) set the final deadline for the end of Analog Television for December 31, 2015.
The total elimination of analog broadcast television service is a very unfortunate move since reception of a digital broadcast television signal requires a much stronger signal than reception of an analog signal. A weak digital signal or interference results in no reception whereas a weak analog signal even with interference will still give useful, intelligible, although less than ideal reception. In fringe areas, inclement conditions, cable outage, emergency situations due to bad weather, natural disaster, or other unfortunate circumstance such as war, a useful digital broadcast television signal may not be present. Hence it is highly desirable to have good analog broadcast television service available which has now essentially been outlawed by misdirected government agencies. Most current model television sets are capable of receiving analog signals as well as digital signals.
Two of the major network digital television stations, WTOL-TV (CBS) and WTVG-TV (ABC) in Toledo, Ohio, which has a 240 square mile urban area with a population of over 500,000, are only licensed to run low power transmitters, around 15kW. The FCC wants you to subscribe to a cable or satellite service to generate tax dollars. For a 15kW station you need to be within 5 miles or so of the transmitter for reliable reception, especially if you are in an area with many trees and do not have an outdoor antenna on a tower tall enough to reach above nature's canopy under which the signal becomes very weak in wet weather. With digital television there is only perfect picture and sound, unintelligible garbage, or nothing at all. More commonly, major metropolitan stations run transmitters in the 500kW to 1000kW range which gives more reliable reception over a much wider area. The other three major network Toledo area digital broadcast television stations, 49.5kW WGTE (PBS), 118kW WNWO (NBC), and 110kW WUPW (FOX), have more powerful transmitters but still reception is less than reliable with an indoor antenna at 10 to 12 miles out from the station transmitter.
Competition for radio spectrum
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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.