Radio broadcasting is transmission of
audio
Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to:
Sound
*Audio signal, an electrical representation of sound
*Audio frequency, a frequency in the audio spectrum
* Digital audio, representation of sou ...
(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 which provides content in a common
radio format, either in
broadcast syndication or
simulcast or both. Radio stations broadcast with several different types of
modulation:
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") transmis ...
stations transmit in AM (
amplitude modulation),
FM radio stations transmit in FM (
frequency modulation), which are older
analog audio
Analog recording is a technique used for the recording of analog signals which, among many possibilities, allows analog audio for later playback.
Analog audio recording began with mechanical systems such as the phonautograph and phonograph. L ...
standards, while newer digital radio stations transmit in several
digital audio standards: DAB (
digital audio broadcasting),
HD radio, DRM (
Digital Radio Mondiale).
Television broadcasting is a separate service which also uses radio frequencies to broadcast television (
video) signals.
History
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 (a kind of vacuum tube) 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
Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature (releasing of energy supplied by heat). This occurs because the thermal energy given to the charge carrier overcomes the work function of the mater ...
of electrons that would flow to the ''
plate
Plate may refer to:
Cooking
* Plate (dishware), a broad, mainly flat vessel commonly used to serve food
* Plates, tableware, dishes or dishware used for setting a table, serving food and dining
* Plate, the content of such a plate (for example: ...
'' (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
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
. This greatly improved the
crystal set
A crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. It uses only the power of the received radio signal to produce sound, needing no external power. It is named for its most impo ...
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 (mercury-vapor filled with a control grid) was created on March 4, 1906, by the Austrian
Robert von Lieben
Robert von Lieben (September 5, 1878, in Vienna – February 20, 1913, in Vienna) was an Austrian entrepreneur, and self-taught physicist and inventor. Lieben and his associates Eugen Reisz and Siegmund Strauss invented and produced a ga ...
independent from that, on October 25, 1906,
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 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 hundre ...
, 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
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 mak ...
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
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 ...
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, P ...
, 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 the United States. The
commercial broadcasting 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 f ...
;
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 Election. The
Montreal station that became
CFCF began
broadcast programming on May 20, 1920, and the
Detroit
Detroit ( , ; , ) is the largest city in the U.S. state of Michigan. It is also the largest U.S. city on the United States–Canada border, and the seat of government of Wayne County. The City of Detroit had a population of 639,111 at t ...
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 2MT
2MT was the first British radio station to make regular entertainment broadcasts, and the "world's first regular wireless broadcast" for entertainment. Transmissions began on 14 February 1922 from an ex-Army hut next to the Marconi laboratories ...
at
Writtle near
Chelmsford, England
Chelmsford () is a city in the City of Chelmsford district in the county of Essex, England. It is the county town of Essex and one of three cities in the county, along with Southend-on-Sea and Colchester. It is located north-east of Londo ...
. A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous
soprano Dame
Nellie Melba
Dame Nellie Melba (born Helen Porter Mitchell; 19 May 186123 February 1931) was an Australian operatic dramatic coloratura soprano (three octaves). She became one of the most famous singers of the late Victorian era and the early 20th centur ...
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
2MT was the first British radio station to make regular entertainment broadcasts, and the "world's first regular wireless broadcast" for entertainment. Transmissions began on 14 February 1922 from an ex-Army hut next to the Marconi laboratories ...
station began to broadcast regular entertainment in 1922. The
BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
and other European broadcasters in 1923.
Radio Argentina began regularly scheduled transmissions from the
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. By 1931, a majority of U.S. households owned at least one
(article1.61) each ''broadcasting station'' shall be classified by the service in which it operates permanently or temporarily.
Broadcasting by radio takes several forms. These include
stations. There are several subtypes, namely
stations can be found throughout the world. Many stations broadcast on
bands using AM technology that can be received over thousands of miles (especially at night). For example, the
...