Broadcasting in the United States: Difference between revisions
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The rest of all broadcasting is done by private companies who all but have an ownership of the channel they operate on, even though the fiction of holding a hearing for a license renewal is done by the FCC every few years. Each individual station owns its own transmitter site and facilities (there is no central infrastructure like the UK's "Freeview", where multiple broadcasters share the BBC's antenna sites).
Recent changes have increased the number of broadcast stations one entity may own, thus allowing very large companies like [[Clear Channel]] Communications (iHeart Radio) or Sinclair Broadcasting to own hundreds of radio or TV stations that reach something like 20% of the entire country. Back when the national networks had considerable more reach, they were each limited to no more than seven owned-and-operated broadcast stations (and no more than five VHF stations). These would usually be in the largest urban markets; the rest of the stations would be "affiliates" which carried the network programming but were owned independently. PBS used a slightly different pattern in which the individual local broadcasters were "member stations" who, collectively, owned the network.
[[American Television Stations]] often display a prominent local channel number in their branding, such as the "circle seven" logo on WABC-TV and KABC-TV. This number usually corresponds to whatever frequency the station used before the digital transition; these are virtual channel numbers and that broadcaster with the big red "2" logo may well now be a digital [[Ultra High Frequency|UHF station]] today. If the same station is using digital compression to send multiple program streams simultaneously, the over-the-air subchannels will have numbers like 2.1, 2.2, 2.3... which appear on no other medium.
In the 1920s, the United States switched to its current pattern of station call signs. The original convention was created for [[Morse Code]] shipboard telegraphy; the ships had 'K' callsigns in the Atlantic and 'W' callsigns in the west, while the land stations reversed this pattern. The few remaining three-letter callsigns mostly date to the era of network AM radio broadcasts, although many of the historic calls were carried over to FM and eventually to TV.
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