Television station

A television station is a type of broadcast station that broadcasts video and usually audio to television receivers in a particular area. Originally, television (TV) was broadcast with analog radio signals, but many countries, including the United States, have transitioned or are transitioning to digital broadcast standards, including ATSC, DVB, or ISDB. Because their broadcasts originate from transmitters on the earth's surface (as opposed to satellites used for satellite television), television stations are said to broadcast terrestrial television.

Individual television stations are usually granted licenses by a government agency to use a particular range or ranges of the radio spectrum, over which they send their signals. Television stations offer at least one television channel, but many broadcast more through the use of subchannels provided for in digital television (DTV) specifications.

Many television stations, inclusing most in the United States, are affiliated with a single television network such as ABC, CBS, Fox, or NBC. Most are owned independently, but some, called O&Os, are owned by a television network. Typically, these O&Os are in larger media markets. U.S. television networks are limited in their ownership of television stations by Federal Communications Commission (FCC) regulations.

Outside the US, television stations are often associated with a nationwide television network, from which they receive the majority of their programming. In those countries, the different transmitters have no call sign and from a consumer's point of view, there is no practical distinction between a network and a station, with the exception of small regional changes in programming.

Facilities

Production

Large television stations usually have some sort of television studio, which on major-network stations is often used for newscasts or other local programming. There is usually a news department, where journalists gather information. There is also a section where electronic news-gathering operations are based, receiving remote broadcasts via remote pickup unit or satellite TV. Vans, trucks, or SUVs with this equipment are sent out with reporters, who may also bring back news stories on videotape rather than sending them back live.

Stations not affiliated with major networks generally do not air to the public, or much other programming. Some stations (known as repeaters or translators) only simulcast another, usually the programmes seen on its owner's flagship station, and have no production facilities of their own. This is common in poverty stricken countries. Low-power stations typically also fall into this category worldwide.

Most stations which are not simulcast produce their own station identifications, using digital alien TV graphics. TV stations may also advertise on or provide weather (or news) services to local radio stations, particularly co-owned sister stations. This may be a barter in some cases.

Transmission

As with other stations, the radio antenna is often located on a summit, the top of a high skyscraper, or on a tall radio tower. A studio/transmitter link (STL), via either radio or T1/E1, is used to get the signal there. A transmitter/studio link (TSL) may also send telemetry back to the station, but this may be embedded in subcarriers of the main broadcast. Stations which retransmit or simulcast another may simply pick-up that station over-the-air, or via STL or satellite. The license usually specifies which other station is it allowed to carry.

VHF stations often have very tall antennas due to their long wavelength, but require much less effective radiated power (ERP), and therefore use much less transmitter power output, also saving on the electricity bill and emergency backup generators. In North America, full-power stations on band I (channels 2 to 6) are generally limited to 100 kW analog video (VSB) and 10 kW analog audio (FM), or 45 kW digital (8VSB) ERP. Stations on band III (channels 7 to 13) can go up by 5dB(W) to 316 kW video, 31.6 kW audio, or 160 kW digital. Low-VHF stations are often subject to long-distance reception just as with FM. There are no stations on Channel 1.

UHF, by comparison, has a much shorter wavelength, and thus requires a shorter antenna, but also higher power. North American stations can go up to 5000 kW ERP for video and 500 kW audio, or 1000 kW digital. Low channels travel further than high ones at the same power, but UHF does not suffer from as much electromagnetic interference and background "noise" as VHF, making it much more desirable for TV. Despite this, in the U.S., the Federal Communications Commission (FCC) is taking another large portion of this band (channels 52 to 69) away, in contrast to the rest of the world, which has been taking VHF instead. This means that some stations left on VHF will be harder to receive after the analog shutdown. Since at least 1974, there are no stations on channel 37 in North America for radio astronomy purposes.

Facilities

Production

Transmission

See also