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
Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including:
* Descriptive metadata – the descriptive ...
, by
radio wave
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...
s to
radio receiver
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. Th ...
s belonging to a public
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, 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 ter ...
the radio waves are broadcast by a
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
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 ...
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 broadcasting, ...
, 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 ...
or
simulcast
Simulcast (a portmanteau of simultaneous broadcast) is the broadcasting of programmes/programs or events across more than one resolution, bitrate or medium, or more than one service on the same medium, at exactly the same time (that is, simultane ...
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 informatio ...
:
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") transm ...
stations transmit in AM (
amplitude modulation
Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to ...
),
FM radio
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 high fidelity sound over broadcast radio. FM broadcasting is cap ...
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 Run-length limited#FM: .280. ...
), 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
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, sa ...
standards: DAB (
digital audio broadcasting
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 syst ...
),
HD radio
HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. It generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used ...
, 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—pa ...
).
Television broadcasting
A television network or television 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-1 ...
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) syste ...
) 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 transmit ...
stations were
radiotelegraphy
Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies for ...
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, 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 rad ...
. 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 whi ...
, 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 mate ...
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
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
'') 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. ...
, 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 (converting DC to AC) is performed by an Power ...
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
A crystal detector is an obsolete electronic component used in some early 20th century radio receivers that consists of a piece of crystalline mineral which rectifies the alternating current radio signal. It was employed as a detector ( de ...
. 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 19 ...
(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
Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor and a fundamentally important early pioneer in electronics. He invented the first electronic device for controlling current flow; the three-element "Audion" triode va ...
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 ...
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
A radiotelephone (or radiophone), abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to '' radiotelegraphy'', which is radio transmission of telegrams (mes ...
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
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
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
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 ...
, began broadcasting from his
Wilkinsburg, Pennsylvania
Wilkinsburg is a borough in Allegheny County, Pennsylvania. The borough has a population of 15,930 as of the 2010 census. Wilkinsburg is part of the Pittsburgh metropolitan area. The borough was named for John Wilkins Jr., a United States Army o ...
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 2020 census, t ...
. 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 (an ...
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 ...
;
advertisement
Advertising is the practice and techniques employed to bring attention to a product or service. Advertising aims to put a product or service in the spotlight in hopes of drawing it attention from consumers. It is typically used to promote a ...
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, ) is the List of the largest municipalities in Canada by population, second-most populous city in Canada and List of towns in Quebec, most populous city in the Provinces and territories of Canada, Canadian ...
station that became
CFCF began
broadcast programming
Broadcast programming is the practice of organizing or ordering (scheduling) of broadcast media shows, typically radio and television, in a daily, weekly, monthly, quarterly or season-long schedule.
Modern broadcasters use broadcast automatio ...
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 th ...
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 co ...
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 ravis ...
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
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&n ...
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 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
...