Radio broadcasting is transmission by radio waves intended to reach a
wide audience. Stations can be linked in radio networks to broadcast a
common radio format, either in broadcast syndication or simulcast or
both. Alternatives to terrestrial radio broadcasting include cable
radio, local wire television networks, satellite radio, and internet
radio via streaming media on the Internet. The signal types can be
either analog audio or digital audio.
2.4 Pirate radio
2.5 Terrestrial digital radio
3 Program formats
4 See also
6 Further reading
7 External links
See also: History of radio § Broadcasting, and History of
The earliest radio stations were radiotelegraphy systems and did not
carry audio. For audio broadcasts to be possible, electronic detection
and amplification devices had to be incorporated.
The thermionic valve was invented in 1904 by the English physicist
John Ambrose Fleming. He developed a device he called an "oscillation
valve" (because it passes current in only one direction). The heated
filament, or cathode, was capable of thermionic emission of electrons
that would flow to the plate (or anode) 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, it could be
used as a rectifier of alternating current and as a radio wave
detector. This greatly improved the crystal set 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
The triode (mercury-vapor filled with a control grid) was patented on
March 4, 1906, by the Austrian Robert von Lieben independent
from that, on October 25, 1906,
Lee De Forest
Lee De Forest patented his
three-element Audion. 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
Christmas Eve in 1906 by Reginald Fessenden, although this is
disputed. While many early experimenters attempted to create
systems similar to radiotelephone devices by which only two parties
were meant to communicate, there were others who intended to transmit
to larger audiences.
Charles Herrold started broadcasting in
California in 1909 and was carrying audio by the next year. (Herrold's
station eventually became KCBS).
In The Hague, the Netherlands,
PCGG started broadcasting on November
6, 1919, making it, arguably the first commercial broadcasting
station. In 1916, Frank Conrad, an electrical engineer employed at the
Westinghouse Electric Corporation, began broadcasting from his
Wilkinsburg, Pennsylvania garage with the call letters 8XK. Later, the
station was moved to the top of the Westinghouse factory building in
East Pittsburgh, Pennsylvania. Westinghouse relaunched the station as
KDKA on November 2, 1920, as the first commercially licensed radio
station in America. The commercial broadcasting designation came
from the type of broadcast license; advertisements 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
Montreal station that became CFCF began broadcast
programming on May 20, 1920, and the
Detroit 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
Marconi Research Centre
Marconi Research Centre
Writtle near Chelmsford, England. A
famous broadcast from Marconi's New Street Works factory in Chelmsford
was made by the famous soprano Dame
Nellie Melba on 15 June 1920,
where she sang two arias and her famous trill. She was the first
artist of international renown to participate in direct radio
2MT station began to broadcast regular entertainment
in 1922. The
BBC was amalgamated in 1922 and received a Royal Charter
in 1926, making it the first national broadcaster in the
world, followed by Czech
Radio and other European broadcasters
Radio Argentina began regularly scheduled transmissions from the
Teatro Coliseo in
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.
Transmission diagram of sound broadcasting (AM and FM)
Broadcasting by radio takes several forms. These include AM and FM
stations. There are several subtypes, namely commercial broadcasting,
non-commercial educational (NCE) public broadcasting and non-profit
varieties as well as community radio, student-run campus radio
stations, and hospital radio stations can be found throughout the
world. Many stations broadcast on shortwave bands using AM technology
that can be received over thousands of miles (especially at night).
For example, the BBC, VOA, VOR, and
Deutsche Welle have transmitted
via shortwave to Africa and Asia. These broadcasts are very sensitive
to atmospheric conditions and solar activity.
Nielsen Audio, formerly known as Arbitron, the United States-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
Radio or Sirius Satellite Radio; or, potentially, a
station that is not government licensed.
See shortwave for the differences between shortwave, medium wave, and
long wave spectra.
Shortwave is used largely for national
broadcasters, international propaganda, or religious broadcasting
Main article: AM broadcasting
AM broadcasting stations in 2006
AM stations were the earliest broadcasting stations to be developed.
AM refers to amplitude modulation, 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
band. In response to the growing popularity of FM stereo radio
stations in the late 1980s and early 1990s, some North American
stations began broadcasting in AM stereo, though this never gained
popularity, and very few receivers were ever sold.
The signal is subject to interference from electrical storms
(lightning) and other electromagnetic interference (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
was a common childhood project in the early decades of AM
AM broadcasts occur on North American airwaves in the medium wave
frequency range of 525 to 1705 kHz (known as the “standard broadcast
band”). The band was expanded in the 1990s by adding nine channels
from 1605 to 1705 kHz. Channels are spaced every 10 kHz in
the Americas, 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
stations. 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 created an
AM stereo tuner
employing notch filtering 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.
Main article: FM broadcasting
FM radio broadcast stations in 2006
FM refers to frequency modulation, and occurs on
VHF airwaves in the
frequency range of 88 to 108 MHz everywhere except
Japan and Russia.
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 invented
FM radio to overcome the problem of
radio-frequency interference (RFI), which plagued AM radio reception.
At the same time, greater fidelity was made possible by spacing
stations further apart in the radio frequency 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
for public areas, 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.
FM radio service in the U.S. was the Yankee Network,
located in 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 and was to some extent imposed by AM broadcasters as an attempt
to cripple what was by now realized to be a potentially serious
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"). 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.
Main article: 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
Terrestrial digital radio
Digital radio broadcasting has emerged, first in
Europe (the UK in
Germany in 1999), and later in the United States, France, the
Netherlands, South Africa, and many other countries worldwide. The
most simple system is named DAB Digital Radio, for Digital Audio
Broadcasting, and uses the public domain 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.
In the United States, digital radio isn't used in the same way as
Europe and South Africa. Instead, the
IBOC system is named HD Radio
and owned by a consortium of private companies that is called
iBiquity. An international non-profit consortium Digital Radio
Mondiale (DRM), has introduced the public domain DRM system.
This section needs expansion. You can help by adding to it. (November
Satellite radio broadcasters are slowly emerging, but the enormous
entry costs of space-based satellite transmitters and restrictions on
available radio spectrum licenses has restricted growth of this
market. In the USA and Canada, just two services, XM Satellite Radio
and Sirius Satellite
Radio exist. Both XM and Sirius are owned by
Sirius XM Radio, which was formed by the merger of XM and Sirius on
July 29, 2008, whereas in Canada, XM
Canada and Sirius Canada
remained separate companies until 2010. Worldspace in Africa and Asia,
and MobaHO! in
Japan and the ROK were two unsuccessful satellite radio
operators which have gone out of business.
Radio program formats differ by country, regulation, and markets. For
instance, the U.S.
Federal Communications Commission
Federal Communications Commission 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 improved, an increasing proportion of
broadcast programming used pre-recorded material. A current trend is
the automation of radio stations. Some stations now operate without
direct human intervention by using entirely pre-recorded material
sequenced by computer control.
Broadcasting construction permit
Disc jockey (DJ)
History of broadcasting
List of radio topics
Low power radio station
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^  DRP 179807
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That Shaped A Generation (Random House, 2007).
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"Empire of the Air: The Men Who Made Radio" (1992) by
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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
Schwoch James. The American
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White Llewellyn. The American
Radio (University of Chicago Press,
Look up radio broadcasting in Wiktionary, the free dictionary.
Federal Communications Commission
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 advice
DXradio.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
Radio stanice - Search for radio stations throughout the Europe
Radio Emisoras Latinas - has a directory with thousands of Latin
autocww.colorado.edu - Broadcasting,
Radio and Television
Radio Live - MY FM
Radio Live -
Internet radio broadcast
Internet television and radio (Webcast
BitTorrent television and movies)
Pirate radio / Pirate television
Adult television channels
Children's interest channel / Children's television series
Men's interest channel
Movie television channels
Music radio /
Sports television channels
Women's interest channel
Broadcast television systems
Digital on-screen graphic
Television news screen layout
Links to related articles
List of radio stations in Africa
Cape Verde (Cabo Verde)
Central African Republic
Democratic Republic of the Congo
Republic of the Congo
Ivory Coast (Côte d'Ivoire)
São Tomé and Príncipe
States with limited
Sahrawi Arab Democratic Republic
Canary Islands / Ceuta / Melilla (Spain)
Mayotte / Réunion (France)
Saint Helena / Ascension Island / Tristan da
Cunha (United Kingdom)
List of radio stations in Asia
East Timor (Timor-Leste)
United Arab Emirates
British Indian Ocean Territory
Cocos (Keeling) Islands
List of radio stations in Europe
Bosnia and Herzegovina
States with limited
Isle of Man
List of radio stations in North America
Antigua and Barbuda
Saint Kitts and Nevis
Saint Vincent and the Grenadines
Trinidad and Tobago
British Virgin Islands
Saint Pierre and Miquelon
Turks and Caicos Islands
United States Virgin Islands
List of radio stations in South America
South Georgia and the South Sandwich Islands
Category:Lists of radio stations by city, country, format, language,