Terrestrial television
Terrestrial television (also known as
over-the-air,
OTA or
broadcast television) was the traditional method of
television broadcast signal delivery prior to the advent of
cable and
satellite television. Although still in wide use, in some countries it is slowly becoming obsolete but in others, digital terrestrial has become popular. It works via
radio waves transmitted through open space, usually unencrypted (commonly known as "free-to-air" television).
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, D.C., 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.
Japan also uses a version of NTSC.
In addition to the threat from Cable Television, 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 Europe, a planning conference ("ST61") held under the auspices of the
International Telecommunications Union in
Stockholm in
1961 allocated frequencies the Bands IV and V for the first time for broadcast television use. It also superseded the 1951 Plan (also made in Stockholm) which had first allocated Band II frequencies for FM radio and Band III frequencies for television.
Following the ST61 conference, UHF frequencies were first used in the
UK in
1964 with the introduction of
BBC2. Television broadcasting in Band III continued after the introduction of four analogue programmes in the UHF bands until the last VHF transmitters were switched off on
January 6,
1985.
The success of terrestrial analogue television across Europe varies from country to country. Although each country has rights to a certain number of frequencies by virtue of the ST61 plan, not all of them have been bought into service.
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 Radiocommunications Conference to
abrogate the ST61 plan and to put a new plan for digital broadcasting only in its place.
In December 2005 the
EU has decided to cease all analogue television transmissions by the year 2012 and switch all terrestrial television broadcasting to digital. Some EU member states have decided to complete this switchover as early as October 2006 (the
Netherlands) and 2008 (
Sweden). 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 are expected to stop analogue television transmissions by 2012.
Many countries are developing and evaluating digital terrestrial television systems.
In North America a specification laid out by the
ATSC has become the standard for digital terrestrial television. In the
United States the
FCC has set a tentative deadline for the closing of analog service in December of 2008. All television receivers with a 25 inch display or larger must now include a
digital tuner. Sets from 13 to 24 inches must include digital tuners by July 1, 2007.
*
Broadcast television systems
*
Lists of television channels for lists by country and language.
*
Television channel frequencies*
ATSC tuner*
TVRadioWorld TV stations directory*
W9WI.com (Terrestrial repeater and TV hobbyist information)
