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, Sweden , Norway Radio broadcasting is transmission of audio signal, audio (sound), sometimes with related
metadata Metadata is "data" that provides information about other data". In other words, it is "data about data". Many distinct types of metadata exist, including descriptive metadata, structural metadata, administrative metadata, reference metadata, sta ...
, by
radio wave Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). At 300 GHz, th ...
s intended to reach a wide
audience An audience is a group of people who participate in a show or encounter a work of art, literature (in which they are called "readers"), theatre, music (in which they are called "listeners"), video games (in which they are called "players"), or ...
. In terrestrial radio broadcasting the radio waves are broadcast by a land-based
radio station , Sweden , Norway Radio broadcasting is transmission of audio signal, audio (sound), sometimes with related metadata, by radio waves intended to reach a wide audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-base ...
, while in
satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a ''broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than terr ...
the radio waves are broadcast by a
satellite In the context of spaceflight, a satellite is an object that has been intentionally placed into orbit. These objects are called artificial satellites to distinguish them from natural satellites such as Earth's Moon. On 4 October 1957 the Sovi ...
in Earth orbit. To receive the content the listener must have a broadcast radio receiver (''radio''). Stations are often affiliated with a
radio network There are two types of radio network currently in use around the world: the one-to-many (simplex communication) broadcast network commonly used for public information and mass-media entertainment, and the two-way radio (duplex communication) type us ...
which provides content in a common
radio format A radio format or programming format (not to be confused with broadcast programming) describes the overall content broadcast on a radio station. The radio format emerged mainly in the United States in the 1950s, at a time when radio was compelled ...
, either in
broadcast syndication Broadcast syndication is the practice of leasing the right to broadcasting television shows and radio programs to multiple television stations and radio stations, without going through a broadcast network. It is common in the United States where b ...
or
simulcast Simulcast (a portmanteau of simultaneous broadcast) is the broadcasting of programs or events across more than one medium, or more than one service on the same medium, at exactly the same time (that is, simultaneously). For example, Absolute Radio ...
or both. Radio stations broadcast with several different types of
modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains information ...
:
AM radio 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 (also known as "AM band") transmiss ...
stations transmit in AM (
amplitude modulation#REDIRECT Amplitude modulation#REDIRECT Amplitude modulation {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...
),
FM radio in Henderson, Nevada and broadcasts at a frequency of 95.5 MHz. FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide hig ...
stations transmit in FM (
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog frequen ...
), which are older
analog audio Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog s ...
standards, while newer digital radio stations transmit in several
digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samples ...
standards: DAB (
digital audio broadcasting Digital audio broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services in many countries around the world but not in North America where HD Radio is the standard for digital radio. The DAB standard was initiate ...

digital audio broadcasting
),
HD radio#REDIRECT HD Radio#REDIRECT HD Radio {{R from other capitalisation ...
{{R from other capitalisation ...
, DRM (
Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting, partic ...
).
Television broadcasting A television network or broadcaster is a telecommunications network for distribution of television program content, where a central operation provides programming to many television stations or pay television providers. Until the mid-1980s, televi ...
is a separate service which also uses radio frequencies to broadcast television (
video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode ray tube (CRT) systems wh ...
) signals.


History

The earliest
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitte ...
stations were
radiotelegraphy Wireless telegraphy or radiotelegraphy is transmission of telegraph signals by radio waves. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies for transmitting telegraph signals without wires, s ...
systems and did not carry audio. For audio broadcasts to be possible, electronic detection and amplification devices had to be incorporated. The
thermionic valve A vacuum tube, an electron tube, valve (British usage) or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a ...
(a kind of vacuum tube) was invented in 1904 by the English physicist
John Ambrose Fleming Sir John Ambrose Fleming FRS (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube, designed the radio transmitter with which the first transatlantic radio ...
. He developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, or
cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in which ...
, was capable of
thermionic emission in a low pressure mercury gas-discharge lamp showing white thermionic emission mix coating on the central portion of the coil. Typically made of a mixture of barium, strontium and calcium oxides, the coating is sputtered away through normal use, of ...
of electrons that would flow to the '' plate'' (or ''
anode An anode is an electrode through which the conventional current enters into a polarized electrical device. This contrasts with a cathode, an electrode through which conventional current leaves an electrical device. A common mnemonic is ACID, fo ...
'') when it was at a higher voltage. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons. Later known as the
Fleming valve The Fleming valve, also called the Fleming oscillation valve, was a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. I ...
, it could be used as a
rectifier A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation is performed by the inverter. The process is kn ...

rectifier
of alternating current and as a radio wave
detector In the broadest definition, a sensor is a device, module, machine, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is always ...
. This greatly improved the
crystal set crystal radio marketed to children. The earphone is on left. The antenna wire, right, has a clip to attach to metal objects such as a bedspring, which serve as an additional antenna to improve reception. A crystal radio receiver, also called a ...
which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker. However, what was still required was an amplifier. The
triode A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 1906 A ...

triode
(mercury-vapor filled with a control grid) was created on March 4, 1906, by the Austrian
Robert von Lieben The name Robert is an ancient Germanic given name, from Proto-Germanic "fame" and "bright" (Hrōþiberhtaz). Compare Old Dutch ''Robrecht'' and Old High German ''Hrodebert'' (a compound of ''Hruod'' (Old Norse: Hróðr) "fame, glory, honour ...
independent from that, on October 25, 1906,
Lee De Forest Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor and early pioneer in radio and in the development of sound-on-film recording used for motion pictures. He had over 180 patents, but also a tumultuous career—he boasted th ...

Lee De Forest
patented his three-element
Audion The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906.De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers ...
. It wasn't put to practical use until 1912 when its amplifying ability became recognized by researchers. By about 1920, valve technology had matured to the point where radio broadcasting was quickly becoming viable. However, an early audio transmission that could be termed a ''broadcast'' may have occurred on
Christmas Eve Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus. Christmas Day is observed around the world, and Christmas Eve is widely observed as a full or partial holiday in anticipation of ...
in 1906 by
Reginald Fessenden Reginald Aubrey Fessenden (October 6, 1866 – July 22, 1932) was a Canadian-born inventor, who did a majority of his work in the United States and also claimed U.S. citizenship through his American-born father. During his life he received hundreds ...
, although this is disputed. While many early experimenters attempted to create systems similar to
radiotelephone A radiotelephone (or radiophone) is a radio communication system for transmission of speech over radio. Radiotelephony means transmission of sound (audio) by radio, in contrast to ''radiotelegraphy'', which is transmission of telegraph signal ...
devices by which only two parties were meant to communicate, there were others who intended to transmit to larger audiences.
Charles Herrold Charles David "Doc" Herrold (November 16, 1875 – July 1, 1948) was an American inventor and pioneer radio broadcaster, who began experimenting with audio radio transmissions in 1909. Beginning in 1912 he apparently became the first person to make ...
started broadcasting in
California California is a state in the Western United States. With over 39.3million residents across a total area of approximately , it is the most populous and the third-largest U.S. state by area. It is also the most populated subnational entity in N ...
in 1909 and was carrying audio by the next year. (Herrold's station eventually became KCBS). In The Hague, the Netherlands,
PCGG PCGG (also known as the Dutch Concerts station) was a radio station located at The Hague in the Netherlands, which began broadcasting a regular schedule of entertainment programmes on 6 November 1919. The station was established by engineer Hanso I ...
started broadcasting on November 6, 1919, making it, arguably the first commercial broadcasting station. In 1916,
Frank Conrad Frank Conrad (May 4, 1874 – December 10, 1941) was an electrical engineer, best known for radio development, including his work as a pioneer broadcaster. He worked for the Westinghouse Electrical and Manufacturing Company in East Pittsburgh, Penn ...
, an electrical engineer employed at the
Westinghouse Electric Corporation The Westinghouse Electric Corporation was an American manufacturing company founded in 1886 by George Westinghouse. It was originally named Westinghouse Electric & Manufacturing Company, and was renamed Westinghouse Electric Corporation in 1945. T ...
, began broadcasting from his
Wilkinsburg, Pennsylvania Wilkinsburg is a borough in Allegheny County, Pennsylvania, United States, with a population of 15,930 as of the 2010 census. Wilkinsburg is part of the Pittsburgh metropolitan area. The borough of Wilkinsburg was named for John Wilkins, Jr., a Unit ...
garage with the call letters 8XK. Later, the station was moved to the top of the Westinghouse factory building in
East Pittsburgh, Pennsylvania East Pittsburgh is a borough in Allegheny County, Pennsylvania, about southeast of the confluence of the Monongahela and the Allegheny rivers at Pittsburgh. The population in 1900 stood at 2,883, and in 1910, at 5,615. As of the 2010 census, the bo ...
. Westinghouse relaunched the station as KDKA on November 2, 1920, as the first commercially licensed radio station in the United States. The
commercial broadcasting Commercial broadcasting (also called private broadcasting) is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship. It was the United States′ first model of radio (and l ...
designation came from the type of
broadcast license A broadcast license is a type of spectrum license granting the licensee permission to use a portion of the radio frequency spectrum in a given geographical area for broadcasting purposes. The licenses generally include restrictions, which vary fr ...
;
advertisement Advertising is a marketing communication that employs an openly sponsored, non-personal message to promote or sell a product, service or idea.William J. Stanton. ''Fundamentals of Marketing''. McGraw-Hill (1984). Sponsors of advertising are t ...
s did not air until years later. The first licensed broadcast in the United States came from KDKA itself: the results of the Harding/Cox Presidential Election. The
Montreal Montreal ( ; officially Montréal, , Tio'tia:ke in Mohawk) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as ''Ville-Marie'', or "City of Mary", it is named after Mount Royal ...
station that became CFCF began
broadcast programming Broadcast programming is the practice of organizing and/or ordering (scheduling) of broadcast media shows, typically radio and television, in a daily, weekly, monthly, quarterly or season-long schedule. The executive in charge of selecting the p ...
on May 20, 1920, and the
Detroit (strait) , nicknames = The Motor City, Motown, Renaissance City, City of the Straits, The D, D-Town, Hockeytown, The Automotive Capital of the World, Rock City, The 313, The Arsenal of Democracy, The Town That Put The Worl ...
station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time. In 1920, wireless broadcasts for entertainment began in the UK from the
Marconi Research Centre Marconi Research Centre is the former name of the current BAE Systems Applied Intelligence Laboratories facility at Great Baddow in Essex, United Kingdom. Under its earlier name, research at this site spanned military and civilian technology cove ...
2MT at
Writtle The village and civil parish of Writtle lies west of Chelmsford, Essex, England. It has a traditional village green complete with duck pond and a Norman church, and was once described as "one of the loveliest villages in England, with a ravishin ...
near
Chelmsford, England Chelmsford () is a city and the county town of Essex, in the East of England. It is located in the London commuter belt, approximately northeast of the notional centre of London at Charing Cross and approximately from Colchester. The urban ar ...
. A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous
soprano A soprano () is a type of classical female singing voice and has the highest vocal range of all voice types. The soprano's vocal range (using scientific pitch notation) is from approximately middle C (C4) = 261 Hz to "high A" (A5) = 880&nbs ...
Dame
Nellie Melba Dame Nellie Melba GBE (born Helen Porter Mitchell; 19 May 186123 February 1931) was an Australian operatic soprano. She became one of the most famous singers of the late Victorian era and the early 20th century, and was the first Australian to a ...
on June 15, 1920, where she sang two arias and her famous trill. She was the first artist of international renown to participate in direct radio broadcasts. The 2MT station began to broadcast regular entertainment in 1922. The
BBC The British Broadcasting Corporation (BBC) is a public service broadcaster, headquartered at Broadcasting House in Westminster, London. It is the world's oldest national broadcaster, and the largest broadcaster in the world by number of emplo ...

BBC
was amalgamated in 1922 and received a
Royal Charter#REDIRECT Royal charter#REDIRECT Royal charter#REDIRECT Royal charter#REDIRECT Royal charter {{R from other capitalisation ... {{R from other capitalisation ... {{R from other capitalisation ...
{{R from other capitalisation ...
in 1926, making it the first national broadcaster in the world, followed by
Czech Radio Český rozhlas (ČRo) is the public radio broadcaster of the Czech Republic, operating since 1923. The service broadcasts throughout the Czech Republic nationally and locally. Its four national services are Radiožurnál, Dvojka, Vltava and Plu ...
and other European broadcasters in 1923. Radio Argentina began regularly scheduled transmissions from the
Teatro Coliseo 200px, The first theatre The Teatro Coliseo is a theatre in Retiro neighbourhood in Buenos Aires, Argentina which opened on July 8, 1905. History The Coliseum Theatre opened in 1905 as living the American circus clown Frank Brown, of great importa ...
in
Buenos Aires Buenos Aires ( or ; ), officially Autonomous City of Buenos Aires, is the capital and largest city of Argentina. The city is located on the western shore of the Río de la Plata, on South America's southeastern coast. "Buenos Aires" can be trans ...

Buenos Aires
on August 27, 1920, making its own priority claim. The station got its license on November 19, 1923. The delay was due to the lack of official Argentine licensing procedures before that date. This station continued regular broadcasting of entertainment and cultural fare for several decades. Radio in education soon followed and colleges across the U.S. began adding radio broadcasting courses to their curricula. Curry College in Milton, Massachusetts introduced one of the first broadcasting majors in 1932 when the college teamed up with WLOE in Boston to have students broadcast programs.


Stations

A ''radio broadcasting station'' is usually associated with wireless transmission, though in practice broadcasting transmission (sound and television) take place using both wires and
radio wave Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). At 300 GHz, th ...
s. The point of this is that anyone with the appropriate receiving technology can receive the broadcast. In line to
ITU Radio Regulations The ITU Radio Regulations (short: RR) regulates on law of nations scale radiocommunication services and the utilisation of radio frequencies. It is the supplementation to the Constitution and Convention of the International Telecommunication Unio ...
(article1.61) each ''broadcasting station'' shall be classified by the service in which it operates permanently or temporarily.


Types

Broadcasting by radio takes several forms. These include AM and FM stations. There are several subtypes, namely
commercial broadcasting Commercial broadcasting (also called private broadcasting) is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship. It was the United States′ first model of radio (and l ...
,
non-commercial educational A non-commercial educational station (NCE station) is a radio station or TV station that does not accept on-air advertisements (TV ads or radio ads), as defined in the United States by the Federal Communications Commission (FCC) and was originally i ...
(NCE)
public broadcasting Public broadcasting involves radio, television and other electronic media outlets whose primary mission is public service. In many countries of the world, funding comes from governments, especially via annual fees charged on receivers. In the Unite ...
and
non-profit A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in contrast with an entity that oper ...
varieties as well as
community radio#REDIRECT Community radio#REDIRECT Community radio {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...
, student-run
campus radio Campus radio (also known as college radio, university radio or student radio) is a type of radio station that is run by the students of a college, university or other educational institution. Programming may be exclusively by students, or may in ...
stations, and
hospital radio Hospital radio is a form of audio broadcasting produced specifically for the in-patients of hospitals, primarily in the United Kingdom. Hospital radio has been found to be beneficial to patients, lifting their mood and aiding recovery. There are ...
stations can be found throughout the world. Many stations broadcast on
shortwave Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3–30 MHz (100 to 10 metre ...
bands using AM technology that can be received over thousands of miles (especially at night). For example, the
BBC The British Broadcasting Corporation (BBC) is a public service broadcaster, headquartered at Broadcasting House in Westminster, London. It is the world's oldest national broadcaster, and the largest broadcaster in the world by number of emplo ...
, VOA, VOR, and
Deutsche Welle Deutsche Welle (; "German wave" in German) or DW is a German public state-owned international broadcaster funded by the German federal tax budget. The service is available in 30 languages. DW's satellite television service consists of channels i ...

Deutsche Welle
have transmitted via shortwave to Africa and Asia. These broadcasts are very sensitive to atmospheric conditions and solar activity.
Nielsen Audio Nielsen Audio (formerly Arbitron) is a consumer research company in the United States that collects listener data on radio broadcasting audiences. It was founded as the American Research Bureau by Jim Seiler in 1949 and became national by merging ...
, formerly known as Arbitron, the
United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major self-governing territories, 326 India ...
-based company that reports on radio audiences, defines a "radio station" as a government-licensed AM or FM station; an HD Radio (primary or multicast) station; an internet stream of an existing government-licensed station; one of the satellite radio channels from
XM Satellite Radio XM Satellite Radio (XM) was one of the three satellite radio (SDARS) and online radio services in the United States and Canada, operated by Sirius XM Holdings. It provided pay-for-service radio, analogous to subscription cable television. Its servi ...
or
Sirius Satellite Radio Sirius Satellite Radio was a satellite radio (SDARS) and online radio service operating in North America, owned by Sirius XM Holdings. Headquartered in New York City, with smaller studios in Los Angeles and Memphis, Sirius was officially launch ...
; or, potentially, a station that is not government licensed.


AM

AM stations were the earliest broadcasting stations to be developed. AM refers to
amplitude modulation#REDIRECT Amplitude modulation#REDIRECT Amplitude modulation {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...
, a mode of broadcasting radio waves by varying the amplitude of the carrier signal in response to the amplitude of the signal to be transmitted. The medium-wave band is used worldwide for AM broadcasting. Europe also uses the
long wave In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the ea ...
band. In response to the growing popularity of
FM stereo in Henderson, Nevada and broadcasts at a frequency of 95.5 MHz. FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide hig ...
radio stations in the late 1980s and early 1990s, some
North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to ...

North America
n stations began broadcasting in
AM stereo AM stereo is a term given to a series of mutually incompatible techniques for radio broadcasting stereo audio in the AM band in a manner that is compatible with standard AM receivers. There are two main classes of systems: independent sideband (ISB) ...
, though this never gained popularity, and very few receivers were ever sold. The signal is subject to interference from electrical storms (
lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions in the atmosphere or ground temporarily equalize themselves, causing the instantaneous release of as much as one gigajoule of energy. ...
) and other
electromagnetic interference 300px, Electromagnetic interference in analog TV signal Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electri ...
(EMI). One advantage of AM radio signal is that it can be detected (turned into sound) with simple equipment. If a signal is strong enough, not even a power source is needed; building an unpowered
crystal radio receiver crystal radio marketed to children. The earphone is on left. The antenna wire, right, has a clip to attach to metal objects such as a bedspring, which serve as an additional antenna to improve reception. A crystal radio receiver, also called a ...
was a common childhood project in the early decades of AM broadcasting. AM broadcasts occur on
North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to ...

North America
n airwaves in the
medium wave Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with limited sound quality. During daytime, only local stations can be received. Propagation in t ...
frequency range of 525 to 1705 kHz (known as the “standard broadcast band”). The band was expanded in the 1990s by adding nine
channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austr ...
from 1605 to 1705 kHz. Channels are spaced every 10 kHz in the
Americas The Americas (also collectively called America) is a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with their associated i ...
, and generally every 9 kHz everywhere else. AM transmissions cannot be ionospherically propagated during the day due to strong absorption in the D-layer of the ionosphere. In a crowded channel environment, this means that the power of regional channels which share a frequency must be reduced at night or directionally beamed in order to avoid interference, which reduces the potential nighttime audience. Some stations have frequencies unshared with other stations in North America; these are called
clear-channel station A clear-channel station is an AM radio station in North America that has the highest protection from interference from other stations, particularly concerning night-time skywave propagation. The system exists to ensure the viability of cross-countr ...
s. Many of them can be heard across much of the country at night. During the night, absorption largely disappears and permits signals to travel to much more distant locations via ionospheric reflections. However, fading of the signal can be severe at night. AM radio transmitters can transmit audio frequencies up to 15 kHz (now limited to 10 kHz in the US due to FCC rules designed to reduce interference), but most receivers are only capable of reproducing frequencies up to 5 kHz or less. At the time that AM broadcasting began in the 1920s, this provided adequate fidelity for existing microphones, 78 rpm recordings, and loudspeakers. The fidelity of sound equipment subsequently improved considerably, but the receivers did not. Reducing the bandwidth of the receivers reduces the cost of manufacturing and makes them less prone to interference. AM stations are never assigned adjacent channels in the same service area. This prevents the sideband power generated by two stations from interfering with each other.
Bob Carver Robert W. (Bob) Carver is an American designer of audio equipment based in the Pacific Northwest. Educated as a physicist and engineer, he found an interest in audio equipment at a young age. He applied his talent to produce numerous innovative hi ...
created an
AM stereo AM stereo is a term given to a series of mutually incompatible techniques for radio broadcasting stereo audio in the AM band in a manner that is compatible with standard AM receivers. There are two main classes of systems: independent sideband (ISB) ...
tuner employing
notch filter In signal processing, a band-stop filter or band-rejection filter is a filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels. It is the opposite of a band-pass filter. A notch filter is a ba ...
ing that demonstrated that an AM broadcast can meet or exceed the 15 kHz baseband bandwidth allotted to FM stations without objectionable interference. After several years, the tuner was discontinued. Bob Carver had left the company and the Carver Corporation later cut the number of models produced before discontinuing production completely.


Shortwave, medium wave and long wave

See
shortwave Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3–30 MHz (100 to 10 metre ...
for the differences between shortwave,
medium wave Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with limited sound quality. During daytime, only local stations can be received. Propagation in t ...
, and
long wave In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the ea ...
spectra. Shortwave is used largely for national broadcasters, international propaganda, or
religious broadcasting Religious broadcasting is the dissemination of television and/or radio content that intentionally has religious ideas, religious experience, or religious practice as its core focus. In some countries, religious broadcasting developed primarily wit ...
organizations.


FM

Image:2006FM broadcast stations.PNG, 260px,
FM radio in Henderson, Nevada and broadcasts at a frequency of 95.5 MHz. FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide hig ...
broadcast stations in 2006 FM refers to
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog frequen ...
, and occurs on VHF airwaves in the frequency range of 88 to 108 MHz everywhere except
Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , image_coat = Imperial Seal of Japan.svg , alt_coat = Golden circle subdivided ...
and
Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the largest country in the world, covering and encompassing more than one-eighth of the Earth's inhabited l ...
. Russia, like the former Soviet Union, uses 65.9 to 74 MHz frequencies in addition to the world standard. Japan uses the 76 to 90 MHz frequency band.
Edwin Howard Armstrong Edwin Howard Armstrong (December 18, 1890 – February 1, 1954) was an American electrical engineer and inventor, who developed FM (frequency modulation) radio and the superheterodyne receiver system. He held 42 patents and received numerous award ...
invented FM radio to overcome the problem of
radio-frequency interference 300px, Electromagnetic interference in analog TV signal Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electri ...
(RFI), which plagued AM radio reception. At the same time, greater fidelity was made possible by spacing stations further apart in the
radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper ...
spectrum. Instead of 10 kHz apart, as on the AM band in the US, FM channels are 200 kHz (0.2 MHz) apart. In other countries, greater spacing is sometimes mandatory, such as in New Zealand, which uses 700 kHz spacing (previously 800 kHz). The improved fidelity made available was far in advance of the audio equipment of the 1940s, but wide interchannel spacing was chosen to take advantage of the noise-suppressing feature of wideband FM. Bandwidth of 200 kHz is not needed to accommodate an audio signal — 20 kHz to 30 kHz is all that is necessary for a narrowband FM signal. The 200 kHz bandwidth allowed room for ±75 kHz signal deviation from the assigned frequency, plus guard bands to reduce or eliminate adjacent channel interference. The larger bandwidth allows for broadcasting a 15 kHz bandwidth audio signal plus a 38 kHz stereo "subcarrier"—a piggyback signal that rides on the main signal. Additional unused capacity is used by some broadcasters to transmit utility functions such as background
music Music is the art of arranging sounds in time to produce a composition through the elements of melody, harmony, rhythm, and timbre. It is one of the universal cultural aspects of all human societies. General definitions of music include common e ...
for public areas,
GPS The Global Positioning System (GPS), originally Navstar GPS, Announcements from Vice President Al Gore and the Clinton Administration in 1998 initiated these changes, which were authorized by the U.S. Congress in 2000. During the 1990s, GPS ...
auxiliary signals, or financial market data. The AM radio problem of interference at night was addressed in a different way. At the time FM was set up, the available frequencies were far higher in the spectrum than those used for AM radio - by a factor of approximately 100. Using these frequencies meant that even at far higher power, the range of a given FM signal was much shorter; thus its market was more local than for AM radio. The reception range at night is the same as in the daytime. All FM broadcast transmissions are line-of-sight, and ionospheric bounce is not viable. The much larger bandwidths, compared to AM and SSB, are more susceptible to phase dispersion. Propagation speeds (celerities) are fastest in the ionosphere at the lowest sideband frequency. The celerity difference between the highest and lowest sidebands is quite apparent to the listener. Such distortion occurs up to frequencies of approximately 50 MHz. Higher frequencies do not reflect from the ionosphere, nor from storm clouds. Moon reflections have been used in some experiments, but require impractical power levels. The original FM radio service in the U.S. was the
Yankee Network :''For the radio network of the New York Yankees, see New York Yankees Radio Network''. The Yankee Network was an American radio network, based in Boston, Massachusetts, with affiliate radio stations throughout New England. At the height of its inf ...
, located in
New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces of ...

New England
. Regular FM broadcasting began in 1939 but did not pose a significant threat to the AM broadcasting industry. It required purchase of a special receiver. The frequencies used, 42 to 50 MHz, were not those used today. The change to the current frequencies, 88 to 108 MHz, began after the end of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all the great powers—forming two opposing milit ...
and was to some extent imposed by AM broadcasters as an attempt to cripple what was by now realized to be a potentially serious threat. FM radio on the new band had to begin from the ground floor. As a commercial venture, it remained a little-used audio enthusiasts' medium until the 1960s. The more prosperous AM stations, or their owners, acquired FM licenses and often broadcast the same programming on the FM station as on the AM station ("
simulcasting Simulcast (a portmanteau of simultaneous broadcast) is the broadcasting of programs or events across more than one medium, or more than one service on the same medium, at exactly the same time (that is, simultaneously). For example, Absolute Radio ...
"). The FCC limited this practice in the 1960s. By the 1980s, since almost all new radios included both AM and FM tuners, FM became the dominant medium, especially in cities. Because of its greater range, AM remained more common in rural environments.


Pirate radio

Pirate radio is illegal or non-regulated radio transmission. It is most commonly used to describe illegal broadcasting for entertainment or political purposes. Sometimes it is used for illegal two-way radio operation. Its history can be traced back to the unlicensed nature of the transmission, but historically there has been occasional use of sea vessels—fitting the most common perception of a pirate—as broadcasting bases. Rules and regulations vary largely from country to country, but often the term pirate radio generally describes the unlicensed broadcast of FM radio, AM radio, or shortwave signals over a wide range. In some places, radio stations are legal where the signal is transmitted, but illegal where the signals are received—especially when the signals cross a national boundary. In other cases, a broadcast may be considered "pirate" due to the type of content, its transmission format, or the transmitting power (wattage) of the station, even if the transmission is not technically illegal (such as a webcast or an amateur radio transmission). Pirate radio stations are sometimes referred to as bootleg radio or clandestine stations.


Terrestrial digital radio

Digital radio Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services. Types In digital broadcasting systems ...
broadcasting has emerged, first in
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It comprises the westernmost peninsulas of the continental landmass of Eurasia, and is bordered by the Arctic Ocean to the north, the Atlant ...
(the
UK The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for the United Kingdom. Some prefer to use Britain as shortha ...
in 1995 and
Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German , demonym = German , government_type = Federal parliamentary republi ...
in 1999), and later in the United States, France, the Netherlands, South Africa, and many other countries worldwide. The simplest system is named DAB Digital Radio, for
Digital Audio Broadcasting Digital audio broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services in many countries around the world but not in North America where HD Radio is the standard for digital radio. The DAB standard was initiate ...

Digital Audio Broadcasting
, and uses the
public domain The public domain consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. As examples, the works of William Shakespea ...
EUREKA 147 Digital audio broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services in many countries around the world but not in North America where HD Radio is the standard for digital radio. The DAB standard was initiate ...

EUREKA 147
(Band III) system. DAB is used mainly in the UK and South Africa. Germany and the Netherlands use the DAB and DAB+ systems, and France uses the L-Band system of DAB Digital Radio. The broadcasting regulators of the United States and Canada have chosen to use
HD radio#REDIRECT HD Radio#REDIRECT HD Radio {{R from other capitalisation ...
{{R from other capitalisation ...
, an
in-band on-channel In-band on-channel (IBOC) is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency. By utilizing additional digital subcarriers or sidebands, digital information is "multiplexed" on a ...
system that puts digital broadcasts at frequencies adjacent to the analog broadcast. HD Radio is owned by a
consortium A consortium (plural: consortia) is an association of two or more individuals, companies, organizations or governments (or any combination of these entities) with the objective of participating in a common activity or pooling their resources for a ...
of private companies that is called
iBiquity iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio. Based in Columbia, Maryland, with additional offices in Basking Ridge, New Jersey, and Auburn Hills, Michigan, iBiquity is a privately ...
. An international
non-profit A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in contrast with an entity that oper ...
consortium
Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting, partic ...
(DRM), has introduced the
public domain The public domain consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. As examples, the works of William Shakespea ...
DRM system, which is used by a relatively small number of broadcasters worldwide.


International broadcasting

Broadcasters in one country have several reasons to reach out to an audience in other countries. Commercial broadcasters may simply see a business opportunity to sell advertising or subscriptions to a broader audience. This is more efficient than broadcasting to a single country, because domestic entertainment programs and information gathered by domestic news staff can be cheaply repackaged for non-domestic audiences. Governments typically have different motivations for funding international broadcasting. One clear reason is for ideological, or
propaganda Propaganda is communication that is primarily used to influence an audience and further an agenda, which may not be objective and may be selectively presenting facts in order to encourage a particular synthesis or perception, or using loaded la ...

propaganda
reasons. Many government-owned stations portray their nation in a positive, non-threatening way. This could be to encourage business investment in or tourism to the nation. Another reason is to combat a negative image produced by other nations or internal dissidents, or insurgents.
Radio RSARadio RSA: The Voice of South Africa was the international broadcasting service of the Republic of South Africa. It was run by the South African Broadcasting Corporation from its inception on 1 May 1966 until its demise in 1992 following the end of ...
, the broadcasting arm of the apartheid South African government, is an example of this. A third reason is to promote the ideology of the broadcaster. For example, a program on
Radio Moscow of 1969 Image:1979 stamp Radio Moscow.png, 200px, Stamp of 1979 Radio Moscow ( rus, Pадио Москва, r=Radio Moskva), also known as Radio Moscow World Service, was the official international broadcasting station of the Union of Soviet Soci ...
from the 1960s to the 1980s was ''What is Communism?'' A second reason is to advance a nation's foreign policy interests and agenda by disseminating its views on international affairs or on the events in particular parts of the world. During the
Cold War The Cold War was a period of geopolitical tension between the Soviet Union and the United States and their respective allies, the Eastern Bloc and the Western Bloc, after World War II. Historians do not fully agree on the dates, but the per ...
the American
Radio Free Europe Radio Free Europe/Radio Liberty (RFE/RL) is a United States government-funded organization that broadcasts and reports news, information and analysis to countries in Eastern Europe, Central Asia, Caucasus and the Middle East where it says that ...
and
Radio Liberty Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitte ...
and Indian Radio AIR were founded to broadcast news from "behind the
Iron Curtain The Iron Curtain was a political boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1991. The term symbolizes the efforts by the Soviet Union (USSR) to block itself and its sate ...
" that was otherwise being censored and promote dissent and occasionally, to disseminate
disinformation Disinformation is false or misleading information that is spread deliberately to deceive. This is a subset of misinformation. The English word ''disinformation'' is a loan translation of the Russian ''dezinformatsiya'', derived from the title of ...
. Currently, the US operates similar services aimed at
Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is a country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located in the northern Caribbean where the Car ...
(
Radio y Televisión Martí Radio Televisión Martí is an American radio and television international broadcaster based in Miami, Florida, financed by the Federal government of the United States through the U.S. Agency for Global Media (formerly Broadcasting Board of Governo ...
) and the
People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6 million square kilometers (3.7 million m ...
,
Vietnam , image_map = , map_caption = , capital = Hanoi , coordinates = , largest_city = Ho Chi Minh City , languages_type = National language , languages ...
,
Laos , national_anthem = "Pheng Xat Lao") , image_map = , map_caption = , capital = Vientiane , coordinates = , largest_city = capital , official_languages = Lao , recognised_languages = French , languages_type = Spoken languages , languages = ...
and
North Korea North Korea (Korean: /, MR: ''Chosŏn''; literally /, MR: ''Pukchosŏn'', or /, RR: ''Bukhan'' in South Korean usage), officially the Democratic People's Republic of Korea (DPRK or DPR Korea; Korean: /, ''Chosŏn Minjujuŭi Inmin Kong ...
(
Radio Free Asia Radio Free Asia (RFA) is a United States government-funded news service that broadcasts radio programs and publishes online news, information and commentary to readers and listeners in Asia. The service, which provides editorially independent re ...
). Besides ideological reasons, many stations are run by religious broadcasters and are used to provide religious education, religious music, or worship service programs. For example,
Vatican Radio Vatican Radio ( it, Radio Vaticana; la, Statio Radiophonica Vaticana) is the official broadcasting service of Vatican City. Set up in 1931 by Guglielmo Marconi, today its programs are offered in 47 languages, and are sent out on short wave, DRM, ...
, established in 1931, broadcasts such programs. Another station, such as
HCJB HCJB, "The Voice of the Andes", was the first radio station with daily programming in Ecuador and the first Christian missionary radio station in the world. The station was founded in 1931 by Clarence W. Jones, Reuben Larson, and D. Stuart Clark. ...
or
Trans World Radio Trans World Radio (TWR) is a multinational evangelical Christian media distributor. The largest Christian media organization in the world, it uses mediumwave or high-powered AM and shortwave transmitters, local FM radio stations, cable, satellite, ...
will carry brokered programming from evangelists. In the case of the
Broadcasting Services of the Kingdom of Saudi Arabia The Saudi Broadcasting Authority (SBA), formerly Saudi Broadcasting Corporation (SBC) and the Broadcasting Services of the Kingdom of Saudi Arabia (BSKSA), is a governmental entity of Saudi Arabia, organized under the Ministry of Media. BSKSA ope ...
, both governmental and religious programming is provided.


Extensions

Extensions of traditional radio-wave broadcasting for audio broadcasting in general include
cable radio Cable radio or cable FM is a concept similar to that of cable television, bringing radio broadcasting into homes and businesses via coaxial cable. It is generally used for the same reason as cable TV was in its early days when it was "community ante ...
, local wire
television network A television network or broadcaster is a telecommunications network for distribution of television program content, where a central operation provides programming to many television stations or pay television providers. Until the mid-1980s, televi ...
s,
DTV radio Digital-television radio, DTV radio, or DTR describes the audio channels that are provided with a digital television service. These channels are delivered by cable television, direct-broadcast satellite or digital terrestrial television. In terms of ...
,
satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a ''broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than terr ...
, and
internet radio Internet radio (also web radio, net radio, streaming radio, e-radio, IP radio, online radio) is a digital audio service transmitted via the Internet. Broadcasting on the Internet is usually referred to as webcasting since it is not transmitted b ...
via
streaming media Streaming media is multimedia that is constantly received by and presented to an end user while being delivered by a provider over the Internet. The verb ''to stream'' refers to the process of delivering or obtaining media in a continuous mann ...
on the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a ''network of networks'' that consists of private, pub ...

Internet
.


Satellite

The enormous entry costs of space-based satellite transmitters and restrictions on available
radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 30 Hz to 300 GHz. Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunic ...
licenses has restricted growth of
Satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a ''broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than terr ...
broadcasts. In the US and
Canada Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total ...

Canada
, just two services,
XM Satellite Radio XM Satellite Radio (XM) was one of the three satellite radio (SDARS) and online radio services in the United States and Canada, operated by Sirius XM Holdings. It provided pay-for-service radio, analogous to subscription cable television. Its servi ...
and
Sirius Satellite Radio Sirius Satellite Radio was a satellite radio (SDARS) and online radio service operating in North America, owned by Sirius XM Holdings. Headquartered in New York City, with smaller studios in Los Angeles and Memphis, Sirius was officially launch ...
exist. Both XM and Sirius are owned by
Sirius XM Satellite Radio Sirius XM Holdings Inc. is an American broadcasting company headquartered in Midtown Manhattan, New York City that provides satellite radio and online radio services operating in the United States. It was formed by the 2008 merger of Sirius Sate ...
, which was formed by the merger of XM and Sirius on July 29, 2008, whereas in
Canada Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total ...

Canada
,
XM Radio Canada XM Radio Canada was the operating name of Canadian Satellite Radio Holdings Inc. (or "CSR"), a Canadian communications and media company, which was incorporated in 2002 to broadcast satellite radio in Canada. Following the merger of Sirius XM Radio ...
and
Sirius Canada Sirius Canada was a Canadian company, a partnership between Slaight Communications, the Canadian Broadcasting Corporation and Sirius Satellite Radio, which was one of three services licensed by the CRTC on June 16, 2005 to introduce satellite radio ...
remained separate companies until 2010.
Worldspace 1worldspace, known for most of its existence simply as WorldSpace, is a defunct satellite radio network that in its heyday provided service to over 170,000 subscribers in eastern, southern and northern Africa, the Middle East, and much of Asia with ...
in Africa and Asia, and
MobaHO! was a mobile satellite digital audio/video subscription based broadcasting service in Japan, whose services began on October 20, 2004 and ended on March 31, 2009 at 3:00 pm Japan time. MobaHO! used the ISDB digital broadcast specification. The satel ...
in Japan and the ROK were two unsuccessful satellite radio operators which have gone out of business.


Program formats

Radio program formats differ by country, regulation, and markets. For instance, the U.S.
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction over the ...
designates the 88–92 megahertz band in the U.S. for non-profit or educational programming, with advertising prohibited. In addition, formats change in popularity as time passes and technology improves. Early radio equipment only allowed program material to be broadcast in real time, known as ''live'' broadcasting. As technology for
sound recording In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...
improved, an increasing proportion of broadcast programming used pre-recorded material. A current trend is the
automation Automation describes a wide range of technologies that reduce human intervention in processes. Human intervention is reduced by predetermining decision criteria, subprocess relationships, and related actions — and embodying those predetermi ...
of radio stations. Some stations now operate without direct human intervention by using entirely pre-recorded material sequenced by
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as programs. These programs enable computers to perform a wid ...

computer
control.


See also

* Broadcasting construction permit *
Call sign In broadcasting and radio communications, a call sign (also known as a call name or call letters—and historically as a call signal—or abbreviated as a call) is a unique designation for a transmitter station. In the United States of America, th ...
*
Disc jockey A disc jockey, more commonly abbreviated as DJ, is a person who plays recorded music for an audience. Most common types of DJs include radio DJs, club DJs (who work at a nightclub or music festival), mobile DJs (who are hired to work at public ...
(DJ) *
History of broadcasting It is generally recognized that the first radio transmission was made from a temporary station set up by Guglielmo Marconi in 1895 on the Isle of Wight. This followed on from pioneering work in the field by a number of people including Alessand ...
*
International broadcastingInternational broadcasting, in a limited extent, began during World War I, when German and British stations broadcast press communiqués using Morse code. With the severing of Germany's undersea cables, the wireless telegraph station in Nauen was the ...
* List of radio topics * Low power radio station *
Radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitte ...
*
Radio antenna In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an ...
*
Radio network There are two types of radio network currently in use around the world: the one-to-many (simplex communication) broadcast network commonly used for public information and mass-media entertainment, and the two-way radio (duplex communication) type us ...
*
Radio personality A radio personality (American English) or radio presenter (British English) is a person who has an on-air position in radio broadcasting. A radio personality who hosts a radio show is also known as a radio host, and in India and Pakistan as a radio ...
* RF modulation * Sports commentator * Television station


References


Further reading

* Briggs Asa. ''The History of Broadcasting in the United Kingdom'' (Oxford University Press, 1961). * Crisell, Andrew. ''An Introductory History of British Broadcasting'' (2002
excerpt
* Ewbank Henry and Lawton Sherman P. ''Broadcasting: Radio and Television'' (Harper & Brothers, 1952). * Fisher, Marc. ''Something In The Air: Radio, Rock, and the Revolution That Shaped A Generation'' (Random House, 2007). *Carl Hausman, Hausman, Carl, Messere, Fritz, Benoit, Philip, and O'Donnell, Lewis, Modern Radio Production, 9th ed., (Cengage, 2013) * Head, Sydney W., Christopher W. Sterling, and Lemuel B. Schofield. ''Broadcasting in America." (7th ed. 1994). * Lewis, Tom, ''Empire of the Air: The Men Who Made Radio'', 1st ed., New York : E. Burlingame Books, 1991. . "Empire of the Air: The Men Who Made Radio" (1992) by Ken Burns was a PBS documentary based on the book. * Pilon, Robert, Isabelle Lamoureux, and Gilles Turcotte. ''Le Marché de la radio au Québec: document de reference''. [Montréal]: Association québécoise de l'industrie du dique, du spectacle et de la video, 1991. unpaged. ''N.B''.: Comprises: Robert Pilon's and Isabelle Lamoureux' ''Profil du marché de radio au Québec: un analyse de Média-culture''. -- Gilles Turcotte's ''Analyse comparative de l'écoute des principals stations de Montréal: prepare par Info Cible''. * Ray, William B. ''FCC: The Ups and Downs of Radio-TV Regulation'' (Iowa State University Press, 1990). * Russo, Alexan der. ''Points on the Dial: Golden Age Radio Beyond the Networks'' (Duke University Press; 2010) 278 pages; discusses regional and local radio as forms that "complicate" the image of the medium as a national unifier from the 1920s to the 1950s. * Scannell, Paddy, and Cardiff, David. ''A Social History of British Broadcasting, Volume One, 1922-1939'' (Basil Blackwell, 1991). * Schramm, Wilbur, ed. ''The Process and Effects of Mass Communication'' (1955 and later editions) articles by social scientists ** Schramm, Wilbur, ed. ''Mass Communication'' (1950, 2nd ed. 1960); more popular essays * Schwoch James. ''The American Radio Industry and Its Latin American Activities, 1900-1939'' (University of Illinois Press, 1990). * Stewart, Sandy. ''From Coast to Coast: a Personal History of Radio in Canada'' (Entreprises Radio-Canada, 1985). xi, 191 p., ill., chiefly with b&w photos. * Stewart, Sandy. ''A Pictorial History of Radio in Canada'' (Gage Publishing, 1975). v, [1], 154 p., amply ill. in b&w mostly with photos. SBN 7715-9948-X * White Llewellyn. ''The American Radio'' (University of Chicago Press, 1947).


External links

;General
Federal Communications Commission website
- fcc.gov
DXing.info
- Information about radio stations worldwide
Radio-Locator.com
Links to 13,000 radio stations worldwide
BBC reception adviceDXradio.50webs.com
"The SWDXER" - with general SWL information and radio antenna tips
RadioStationZone.com
- 10.000+ radio stations worldwide with ratings, comments and listen live links
Online-Radio-Stations.org
- The Web Radio Tuner has a comprehensive list of over 50.000 radio stations
UnwantedEmissions.com
- A general reference to radio spectrum allocations
Radio stanice
- Search for radio stations throughout the Europe
Radio Emisoras Latinas
- has a directory with thousands of Latin America Radio Stations
MY FM Radio Live
- MY FM Radio Live - Internet radio broadcast {{DEFAULTSORT:Radio Broadcasting Radio broadcasting,