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Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broadcast television, in which the television signal is transmitted over-the-air by radio waves and received by a television antenna, or satellite television, in which the television signal is transmitted over-the-air by radio waves from a communications satellite and received by a satellite dish on the roof. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation.
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave transmissions, but also on the longwave and shortwave radio bands.
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum, in a one-to-many model. Broadcasting began with AM radio, which came into popular use around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, most implementations of electronic communication were one-to-one, with the message intended for a single recipient. The term broadcasting evolved from its use as the agricultural method of sowing seeds in a field by casting them broadly about. It was later adopted for describing the widespread distribution of information by printed materials or by telegraph. Examples applying it to "one-to-many" radio transmissions of an individual station to multiple listeners appeared as early as 1898.
Radio navigation or radionavigation is the application of radio waves to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination.
Radio broadcasting is the broadcasting of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station, while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver (radio). Stations are often affiliated with a radio network that provides content in a common radio format, either in broadcast syndication or simulcast, or both. The encoding of a radio broadcast depends on whether it uses an analog or digital signal. Analog radio broadcasts use one of two types of radio wave modulation: amplitude modulation for AM radio, or frequency modulation for FM radio. Newer, digital radio stations transmit in several different digital audio standards, such as DAB, HD radio, or DRM.
Terrestrial television, or over-the-air television (OTA) is a type of television broadcasting in which the content is transmitted via radio waves from the terrestrial (Earth-based) transmitter of a TV station to a TV receiver having an antenna. The term terrestrial is more common in Europe and Latin America, while in Canada and the United States it is called over-the-air or simply broadcast. This type of TV broadcast is distinguished from newer technologies, such as satellite television, in which the signal is transmitted to the receiver from an overhead satellite; cable television, in which the signal is carried to the receiver through a cable; and Internet Protocol television, in which the signal is received over an Internet stream or on a network utilizing the Internet Protocol. Terrestrial television stations broadcast on television channels with frequencies between about 52 and 600 MHz in the VHF and UHF bands. Since radio waves in these bands travel by line of sight, reception is generally limited by the visual horizon to distances of 64–97 kilometres, although under better conditions and with tropospheric ducting, signals can sometimes be received hundreds of kilometers distant.
Georgia Public Broadcasting (GPB) is a state network of PBS member television stations and NPR member radio stations serving the U.S. state of Georgia. It is operated by the Georgia Public Telecommunications Commission, an agency of the Georgia state government which holds the licenses for most of the PBS and NPR member stations licensed in the state. The broadcast signals of the nine television stations and 19 radio stations cover almost all of the state, as well as parts of Alabama, Florida, North Carolina, South Carolina and Tennessee.
Very High Frequency Omnidirectional Range Station (VOR) is a type of short-range VHF radio navigation system for aircraft, enabling aircraft with a VOR receiver to determine the azimuth, referenced to magnetic north, between the aircraft to/from fixed VOR ground radio beacons. VOR and the first DME(1950) system to provide the slant range distance, were developed in the United States as part of a U.S. civil/military programm for Aeronautical Navigation Aids in 1945. Deployment of VOR and DME(1950) began in 1949 by the U.S. CAA. ICAO standardized VOR and DME(1950) in 1950 in ICAO Annex ed.1. Frequencies for the use of VOR are standardized in the very high frequency (VHF) band between 108.00 and 117.95 MHz Chapter 3, Table A. To improve azimuth accuracy of VOR even under difficult siting conditions, Doppler VOR (DVOR) was developed in the 1960s. VOR is according to ICAO rules a primary means navigation system for commercial and general aviation, (D)VOR are gradually decommissioned and replaced by DME-DME RNAV 7.2.3 and satellite based navigation systems such as GPS in the early 21st century. In 2000 there were about 3,000 VOR stations operating around the world, including 1,033 in the US, but by 2013 the number in the US had been reduced to 967. The United States is decommissioning approximately half of its VOR stations and other legacy navigation aids as part of a move to performance-based navigation, while still retaining a "Minimum Operational Network" of VOR stations as a backup to GPS. In 2015, the UK planned to reduce the number of stations from 44 to 19 by 2020.
Direction finding (DF), or radio direction finding (RDF), is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an inadvertant source, a naturally-occurring radio source, or an illicit or enemy system. Radio direction finding differs from radar in that only the direction is determined by any one receiver; a radar system usually also gives a distance to the object of interest, as well as direction. By triangulation, the location of a radio source can be determined by measuring its direction from two or more locations. Radio direction finding is used in radio navigation for ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. During the Second World War, radio direction finding was used by both sides to locate and direct aircraft, surface ships, and submarines.
HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. HD radio generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily by AM and FM radio stations in the United States, U.S. Virgin Islands, Canada, Mexico and the Philippines, with a few implementations outside North America.
FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high-fidelity sound over broadcast radio. FM broadcasting offers higher fidelity—more accurate reproduction of the original program sound—than other broadcasting techniques, such as AM broadcasting. It is also less susceptible to common forms of interference, having less static and popping sounds than are often heard on AM. Therefore, FM is used for most broadcasts of music and general audio. FM radio stations use the very high frequency range of radio frequencies.
South Dakota Public Broadcasting (SDPB) is a network of non-commercial educational television and radio stations serving the U.S. state of South Dakota. The stations are operated by the South Dakota Bureau of Information and Telecommunication, an agency of the state government which holds the licenses for all of the PBS and NPR member stations licensed in South Dakota except KRSD in Sioux Falls, which is owned and run by Minnesota Public Radio, and KAUR in Sioux Falls, which is owned by Augustana University and operated by MPR. SDPB has studios and offices in Rapid City and Sioux Falls with headquarters being located in the Al Neuharth Media Center on the campus of the University of South Dakota in Vermillion.
Mississippi Public Broadcasting (MPB) is the public broadcasting network serving the U.S. state of Mississippi. It is owned by the Mississippi Authority for Educational Television (MAET), an agency of the state government that holds the licenses for all of the PBS and NPR member stations in the state. MPB's headquarters is located on Ridgewood Road in northeast Jackson. The public broadcaster was established as Mississippi Educational Television.
In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual program stream, and multiplexing to combine them into a single signal. The practice is sometimes called "multicasting".
WTMO-CD is a low-power, Class A television station in Orlando, Florida, United States, broadcasting the Spanish-language network Telemundo. Owned and operated by NBCUniversal's Telemundo Station Group, the station has studios at the intersection of Sand Lake Road and Orange Blossom Trail in unincorporated Orange County, and its transmitter is located on Lake Sparling Road in Pine Hills.
A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator (U.S.), re-broadcaster (Canada), repeater or complementary station (Mexico), is a broadcast transmitter which repeats the signal of a radio or television station to an area not covered by the originating station.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver; this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
The digital television transition in the United States was the switchover from analog to exclusively digital broadcasting of terrestrial television programming. Under the Digital Transition and Public Safety Act of 2005, full-power broadcasting of analog television in the United States was initially planned to have ceased after February 17, 2009, but this was delayed to June 12, 2009 after the passage of the DTV Delay Act on February 4, 2009. This date was a further delay from the original date of December 31, 2006 as stipulated in the Telecommunications Act of 1996. The delay to June 12 was to assist households on a waiting list for coupons for digital converter boxes, funding for which was provided by the American Recovery and Reinvestment Act of 2009.
References
- ↑ "Trefeinon". Signalling Record Society. Retrieved 8 March 2017.
