HOME
        TheInfoList






AM broadcasting is a radio broadcasting technology, which employs 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") transmissions, but also on the longwave and shortwave radio bands.

The earliest experimental AM transmissions began in the early 1900s. However, widespread AM broadcasting was not established until the 1920s, following the development of vacuum tube receivers and transmitters. AM radio remained the dominant method of broadcasting for the next 30 years, a period called the "Golden Age of Radio", until television broadcasting became widespread in the 1950s and received most of the programming previously carried by radio. Subsequently, AM radio's audiences have also greatly shrunk due to competition from FM (frequency modulation) radio, Digital Audio Broadcasting (DAB), satellite radio, HD (digital) radio and Internet streaming.

AM transmissions are much more susceptible than FM or digital signals are to interference, and often have lower audio fidelity. Thus, AM broadcasters tend to specialise in spoken-word formats, such as talk radio, all news and sports, leaving the broadcasting of music mainly to FM and digital stations.

AM and FM modulated signals for radio. AM (Amplitude Modulation) and FM (Frequency Modulation) are types of modulation (coding). The electrical signal from program material, usually coming from a studio, is mixed with a carrier wave of a specific frequency, then broadcast. In the case of AM, this mixing (modulation) is done by altering the amplitude (strength) of the carrier wave, proportional to the original signal. In contrast, in the case of FM, it is the carrier wave's frequency that is varied. A radio receiver contains a demodulator that extracts the original program material from the broadcast wave.

Early broadcasting development

One of the earliest radio broadcasts, French soprano Mariette Mazarin singing into Lee de Forest's arc transmitter in New York City on February 24, 1910.
Lee de Forest used an early vacuum-tube transmitter to broadcast returns for the Hughes-Wilson presidential election returns on November 7, 1916, over 2XG in New York City. Pictured is engineer Charles Logwood

The idea of broadcasting — the unrestricted transmission of signals to a widespread audience — dates back to the founding period of radio development, even though the earliest radio transmissions, originally known as "Hertzian radiation" and "wireless telegraphy", used spark-gap transmitters that could only transmit the dots-and-dashes of Morse code. In October 1898 a London publication, The Electrician, noted that "there are rare cases where, as Dr. [Oliver] Lodge once expressed it, it might be advantageous to 'shout' the message, spreading it broadcast to receivers in all directions".[2] However, it was recognized that this would involve significant financial issues, as that same year The Electrician also commented "did not Prof. Lodge forget that no one wants to pay for shouting to the world on a system by which it would be impossible to prevent non-subscribers from benefiting gratuitously?"[3]

On January 1, 1902, Nathan Stubblefield gave a short-range "wireless telephone" demonstration, that included simultaneously broadcasting speech and music to seven locations throughout Murray, Kentucky. However, this was transmitted using induction rather than radio signals, and although Stubblefield predicted that his system would be perfected so that "it will be possible to communicate with hundreds of homes at the same time", and "a single message can be sent from a central station to all parts of the United States", he was unable to overcome the inherent distance limitations of this technology.[4]

The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U.S. Navy stations.[5] In Europe, signals transmitted from a station located on the Eiffel tower were received throughout much of Europe. In both the United States and France this led to a small market of receiver lines designed geared for jewelers who needed accurate time to set their clocks, including the Ondophone in France,[6] and the De Forest RS-100 Jewelers Time Receiver in the United States[7] The ability to pick up time signal broadcasts, in addition to Morse code weather reports and news summaries, also attracted the interest of amateur radio enthusiasts.

Early amplitude modulation (AM) transmitter technologies

It was immediately recognized that, much like the telegraph had preceded the invention of the telephone, the ability to make audio radio transmissions would be a significant technical advance. Despite this knowledge, it still took two decades to perfect the technology needed to make quality audio transmissions. In addition, the telephone had rarely been used for distributing entertainment, outside of a few "telephone newspaper" systems, most of

The idea of broadcasting — the unrestricted transmission of signals to a widespread audience — dates back to the founding period of radio development, even though the earliest radio transmissions, originally known as "Hertzian radiation" and "wireless telegraphy", used spark-gap transmitters that could only transmit the dots-and-dashes of Morse code. In October 1898 a London publication, The Electrician, noted that "there are rare cases where, as Dr. [Oliver] Lodge once expressed it, it might be advantageous to 'shout' the message, spreading it broadcast to receivers in all directions".[2] However, it was recognized that this would involve significant financial issues, as that same year The Electrician also commented "did not Prof. Lodge forget that no one wants to pay for shouting to the world on a system by which it would be impossible to prevent non-subscribers from benefiting gratuitously?"[3]

On January 1, 1902, Nathan Stubblefield gave a short-range "wireless telephone" demonstration, that included simultaneously broadcasting speech and music to seven locations throughout Murray, Kentucky. However, this was transmitted using induction rather than radio signals, and although Stubblefield predicted that his system would be perfected so that "it will be possible to communicate with hundreds of homes at the same time", and "a single message can be sent from a central station to all parts of the United States", he was unable to overcome the inherent distance limitations of this technology.[4]

The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U.S. Navy stations.[5] In Europe, signals transmitted from a station located on the Eiffel tower were received throughout much of Europe. In both the United States and France this led to a small market of receiver lines designed geared for jewelers who needed accurate time to set their clocks, including the Ondophone in France,[6] and the De Forest RS-100 Jewelers Time Receiver in the United States[7] The ability to pick up time signal broadcasts, in addition to Morse code weather reports and news summaries, also attracted the interest of amateur radio enthusiasts.

Early amplitude modulation (AM) transmitter technologies

It was immediately recognized that, much like the telegraph had preceded the invention of the telephone, the ability to make audio radio transmissions would be a significant technical advance. Despite this knowledge, it still took two decades to perfect the technology needed to make quality audio transmissions. In addition, the telephone had rarely been used for distributing entertainment, outside of a few "Nathan Stubblefield gave a short-range "wireless telephone" demonstration, that included simultaneously broadcasting speech and music to seven locations throughout Murray, Kentucky. However, this was transmitted using induction rather than radio signals, and although Stubblefield predicted that his system would be perfected so that "it will be possible to communicate with hundreds of homes at the same time", and "a single message can be sent from a central station to all parts of the United States", he was unable to overcome the inherent distance limitations of this technology.[4]

The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U.S. Navy stations.[5] In Europe, signals transmitted from a station located on the Eiffel tower were received throughout much of Europe. In both the United States and France this led to a small market of receiver lines designed geared for jewelers who needed accurate time to set their clocks, including the Ondophone in France,[6] and the De Forest RS-100 Jewelers Time Receiver in the United States[7] The ability to pick up time signal broadcasts, in addition to Morse code weather reports and news summaries, also attracted the interest of amateur radio enthusiasts.

It was immediately recognized that, much like the telegraph had preceded the invention of the telephone, the ability to make audio radio transmissions would be a significant technical advance. Despite this knowledge, it still took two decades to perfect the technology needed to make quality audio transmissions. In addition, the telephone had rarely been used for distributing entertainment, outside of a few "telephone newspaper" systems, most of which were established in Europe. With this in mind, most early radiotelephone development envisioned that the device would be more profitably developed as a "wireless telephone" for personal communication, or for providing links where regular telephone lines could not be run, rather than for the uncertain finances of broadcasting.

Reginald Fessenden. The original spark-gap radio transmitters were impractical for transmitting audio, since they produced discontinuous pulses known as "damped waves". Fessenden realized that what was needed was a new type of radio transmitter that produced steady "undamped" (better known as "continuous wave") signals, which could then be "modulated" to reflect the sounds being transmitted.

Fessenden's basic approach was disclosed in U.S. Patent 706,737, which he applied for on May 29, 1901, and was issued the next year. It called for the use of a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology, a continuous-wave (CW) transmitter.[8] Fessenden began his research on audio transmissions while doing developmental work for the United States Weather Service on Cobb Island, Maryland. Because he did not yet have a continuous-wave transmitter, initially he worked with an experimental "high-frequency spark" transmitter, taking advantage of the fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He later reported that, in the fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile),[9] which appears to have been the first successful audio transmission using radio signals. However, at this time the sound was far too distorted to be commercially practical.[10] For a time he continued working with more sophisticated high-frequency spark transmitters, including versions that used compressed air, which began to take on some of the characteristics of arc-transmitters.[11] Fessenden attempted to sell this form of radiotelephone for point-to-point communication, but was unsuccessful.[12]

Alternator transmitter

Fessenden's work with high-frequency spark transmissions was only a temporary measure. His ultimate plan for creating an audio-capable transmitter was to redesign an electrical alternator, which normally produced alternating current of at most a few hundred (Hz), to increase its rotational speed and so generate currents of tens-of-thousands Hz, thus producing a steady continuous-wave transmission when connected to an aerial. The next step, adopted from standard wire-telephone practice, was to insert a simple carbon microphone into the transmission line, to modulate the carrier wave signal to produce AM audio transmissions. However, it would take many years of expensive development before eve

Fessenden's basic approach was disclosed in U.S. Patent 706,737, which he applied for on May 29, 1901, and was issued the next year. It called for the use of a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology, a continuous-wave (CW) transmitter.[8] Fessenden began his research on audio transmissions while doing developmental work for the United States Weather Service on Cobb Island, Maryland. Because he did not yet have a continuous-wave transmitter, initially he worked with an experimental "high-frequency spark" transmitter, taking advantage of the fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He later reported that, in the fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile),[9] which appears to have been the first successful audio transmission using radio signals. However, at this time the sound was far too distorted to be commercially practical.[10] For a time he continued working with more sophisticated high-frequency spark transmitters, including versions that used compressed air, which began to take on some of the characteristics of arc-transmitters.[11] Fessenden attempted to sell this form of radiotelephone for point-to-point communication, but was unsuccessful.[12]

Fessenden's work with high-frequency spark transmissions was only a temporary measure. His ultimate plan for creating an audio-capable transmitter was to redesign an electrical alternator, which normally produced alternating current of at most a few hundred (Hz), to increase its rotational speed and so generate currents of tens-of-thousands Hz, thus producing a steady continuous-wave transmission when connected to an aerial. The next step, adopted from standard wire-telephone practice, was to insert a simple carbon microphone into the transmission line, to modulate the carrier wave signal to produce AM audio transmissions. However, it would take many years of expensive development before even a prototype alternator-transmitter would be ready, and a few years beyond that for high-power versions to become available.[13]

Fessenden worked with General Electric's (GE) Ernst F. W. Alexanderson, who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50 kHz, although at low power. Th

Fessenden worked with General Electric's (GE) Ernst F. W. Alexanderson, who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50 kHz, although at low power. The alternator-transmitter achieved the goal of transmitting quality audio signals, but the lack of any way to amplify the signals meant they were somewhat weak. On December 21, 1906, Fessenden made an extensive demonstration of the new alternator-transmitter at Brant Rock, Massachusetts, showing its utility for point-to-point wireless telephony, including interconnecting his stations to the wire telephone network. As part of the demonstration, speech was transmitted 18 kilometers (11 miles) to a listening site at Plymouth, Massachusetts.[14]

An American Telephone Journal account of the December 21 alternator-transmitter demonstration included the statement that "It is admirably adapted to the transmission of news, music, etc. as, owing to the fact that no wires are needed, simultaneous transmission to many subscribers can be effected as easily as to a few",[14] echoing the words of a handout distributed to the demonstration witnesses, which stated "[Radio] Telephony is admirably adapted for transmitting news, stock quotations, music, race reports, etc. simultaneously over a city, on account of the fact that no wires are needed and a single apparatus can distribute to ten thousand subscribers as easily as to a few. It is proposed to erect stations for this purpose in the large cities here and abroad."[15] However, other than two holiday transmissions reportedly made shortly after these demonstrations, Fessenden does not appear to have conducted any radio broadcasts for the general public, or to have even given additional thought about the potential of a regular broadcast service, and in a 1908 article providing a comprehensive review of the potential uses for his radiotelephone invention, he made no references to broadcasting.[16]

Because there was no way to amplify electrical currents at this time, modulation was usually accomplished by a carbon microphone inserted directly in the antenna wire. This meant that the full transmitter power flowed through the microphone, and even using water cooling, the power handling ability of the microphones severely limited the power of the transmissions. Ultimately only a small number of large and powerful Alexanderson alternators would be developed. However, they would be almost exclusively used for long-range radiotelegraph communication, and occasionally for radiotelephone experimentation, but were never used for general broadcasting.

Almost all of the continuous wave AM transmissions made prior to 1915 were made by versions of the arc converter transmitter, which had been initially developed by Valdemar Poulsen in 1903.[17] Arc transmitters worked by producing a pulsating electrical arc in an enclosed hydrogen atmosphere. They were much more compact than alternator transmitters, and could operate on somewhat higher transmitting frequencies. However, they suffered from some of the same deficiencies. The lack of any means to amplify electrical currents meant that, like the alternator transmitters, modulation was usually accomplished by a microphone inserted directly in the antenna wire, which again resulted in overheating issues, even with the use of water-cooled microphones. Thus, transmitter powers tended to be limited. The arc was also somewhat unstable, which reduced audio quality. Experimenters who used arc transmitters for their radiotelephone research included Ernst Ruhmer, Quirino Majorana, Charles "Doc" Herrold, and Lee de Forest.

Vacuum tube transmitters

electrolytic detector and thermionic diode (Fleming valve) were invented by Reginald Fessenden and John Ambrose Fleming, respectively. Most important, in 1904–1906 the crystal detector, the simplest and cheapest AM detector, was developed by G. W. Pickard. Homemade crystal radios spread rapidly during the next 15 years, providing ready audiences for the first radio broadcasts. One limitation of crystals sets was the lack of amplifying the signals, so listeners had to use earphones, and it required the development of vacuum-tube receivers before loudspeakers could be used. The dynamic cone loudspeaker, invented in 1924, greatly improved audio frequency response over the previous horn speakers, allowing music to be reproduced with good fidelity.[19] AM radio offered the highest sound quality available in a home audio device prior to the introduction of the high-fidelity, long-playing record in the late 1940s.

Listening habits changed in the 1960s due to the introduction of the revolutionary transistor radio, (Regency TR-1, the first transistor radio released December 1954) which was made possible by the invention of the transistor in 1948. (The transistor was invented at Bell labs and released in June 1948). Their compact size — small enough to fit in a shirt pocket — and lower power requirements, compared to vacuum tubes, meant that for the first time radio receivers were readily portable. The transistor radio became the most widely used communication device in history, with billions manufactured by the 1970s. Radio became a ubiquitous "companion medium" which people could take with them anywhere they went.

Early experimental broadcasts

The demarcation between what is considered "experimental" and "organized" broadcasting is largely arbitrary. Listed below are some of the early AM radio broadcasts, which, due to their irregular schedules and limited purposes, can be classified as "experimental":

  • Christmas Eve 1906 Until the early 1930s, it was generally accepted that Lee de Forest's series of demonstration broadcasts begun in 1907 were the first transmissions of music and entertainment by radio. However, in 1932 an article prepared by Samuel M. Kintner, a former associate of Reginald Fessenden, asserted that Fessenden had actually conducted two earlier broadcasts.[20] This claim was based solely on information includ

    Listening habits changed in the 1960s due to the introduction of the revolutionary transistor radio, (Regency TR-1, the first transistor radio released December 1954) which was made possible by the invention of the transistor in 1948. (The transistor was invented at Bell labs and released in June 1948). Their compact size — small enough to fit in a shirt pocket — and lower power requirements, compared to vacuum tubes, meant that for the first time radio receivers were readily portable. The transistor radio became the most widely used communication device in history, with billions manufactured by the 1970s. Radio became a ubiquitous "companion medium" which people could take with them anywhere they went.

    The demarcation between what is considered "experimental" and "organized" broadcasting is largely arbitrary. Listed below are some of the early AM radio broadcasts, which, due to their irregular schedules and limited purposes, can be classified as "experimental":

    • Christmas Eve 1906 Until the early 1930s, it was generally accepted that Lee de Forest's series of demonstration broadcasts begun in 1907 were the first transmissions of music and entertainment by radio. However, in 1932 an article prepared by Samuel M. Kintner, a former associate of Reginald Fes

      People who weren't around in the Twenties when radio exploded can't know what it meant, this milestone for mankind. Suddenly, with radio, there was instant human communication. No longer were our homes isolated and lonely and silent. The world came into our homes for the first time. Music came pouring in. Laughter came in. News came in. The world shrank, with radio.

      — Red Barber, sportscaster, [32]
In July 1912, Charles "Doc" Herrold began weekly broadcasts in San Jose, California, using an arc transmitter.
Broadcasting in Germany began 1922 as a Post Office monopoly on a subscription basis, using sealed receivers which could only receive one station.

Following World War I, the number of stations providing a regular broadcasting service greatly increased, primarily due to advances in vacuum-tube technology. In response to ongoing activities, government regulators eventually codified standards for which stations could make broadcasts intended for the general public, for example, in the United States formal recognition of a "broadcasting service" came with the establishment of regulations effective December 1, 1921,[33] and Canadian authorities created a separate category of "radio-telephone broadcasting stations" in April 1922.[34] However, there were numerous cases of entertainment broadcasts being presented on a regular schedule before their formal recognition by government regulators. Some early examples include:

  • July 21, 1912 The first person to transmit entertainment broadcasts on a regular schedule appears to have been Charles "Doc" Herrold, who inaugurated weekly programs, using an arc transmitter, from his Wireless School station in San Jose, California.[35] The broadcasts continued until the station was shut down due to the entrance of the United States into World War I in April 1917.
  • March 28, 1914 The Laeken station in Belgium, under the oversight of Robert Goldschmidt, inaugurated a weekly series of concerts,[36] transmitted at 5:00 p.m. on Saturdays. These continued for about four months until July, and were ended by the start of World War I.[37] In August 1914 the Laeken facilities were destroyed, to keep them from falling into the hands of invading German troops.
  • November 1916 De Forest perfected "Oscillion" power vacuum tubes, capable of use in radio transmitters, and inaugurated daily broadcasts of entertainment and news from his New York "Highbridge" station, 2XG. This station also suspended operations in April 1917 due to the prohibition of civilian radio transmissions following the United States' entry into World War I.[38] Its most publicized program was the broadcasting of election results for the Hughes-Wilson presidential election on November 7, 1916, with updates provided by wire from the New York American offices. An estimated 7,000 radio listeners as far as 200 miles (320 kilometers) from New York heard election returns interspersed with patriotic music.[39]
  • April 17, 1919 Shortly after the end of World War I, F. S. McCullough at the Glenn L. Martin aviation plant in Cleveland, Ohio, began a weekly series of phonograph concerts.[40] However, the broadcasts were soon suspended, due to interference complaints by the U.S. Navy.[41]
  • November 6, 1919 The first scheduled (pre-announced in the press) Dutch radio broadcast was made by Nederlandsche Radio Industrie station PCGG at The Hague, which began regular concerts broadcasts. It found it had a large audience outside the Netherlands, mostly in the UK. (Rather than true AM signals, at least initially this station used a form of narrowband FM, which required receivers to be slightly detuned to receive the signals using [33] and Canadian authorities created a separate category of "radio-telephone broadcasting stations" in April 1922.[34] However, there were numerous cases of entertainment broadcasts being presented on a regular schedule before their formal recognition by government regulators. Some early examples include:

    • July 21, 1912 The first person to transmit entertainment broadcasts on a regular schedule appears to have been Charles "Doc" Herrold, who inaugurated weekly programs, using an arc transmitter, from his Wireless School station in San Jose, California.[35] The broadcasts continued until the station was shut down due to the entrance of the United States into World War I in April 1917.
    • March 28, 1914 The Laeken station in Belgium, under the oversight of Robert Goldschmidt, inaugurated a weekly series of concerts,[36] transmitted at 5:00 p.m. on Saturdays. These continued for about four months until July, and were ended by the start of World War I.[37] In August 1914 the Laeken facilities were destroyed, to keep them from falling into the hands of invading German troops.
    • November 1916 De Forest perfected "Oscillion" power vacuum tubes, capable of use in radio transmitters, and inaugurated daily broadcasts of entertainment and news from his New York "Highbridge" station, 2XG. This station also suspended operations in April 1917 due to the prohibition of civilian radio transmissions following the United States' entry into World War I.[38] Its most publicized program was the broadcasting of election results for the Hughes-Wilson presidential election on November 7, 1916, with updates provided by wire from the New York American offices. An estimated 7,000 radio listeners as far as 200 miles (320 kilometers) from New York heard election returns interspersed with patriotic music.[39]
    • April 17, 1919 Shortly after the end of World War I, F. S. McCullough at the Glenn L. Martin aviation plant in Cleveland, Ohio, began a weekly series of phonograph concer

      Because most longwave radio frequencies were used for international radiotelegraph communication, a majority of early broadcasting stations operated on mediumwave frequencies, whose limited range generally restricted them to local audiences. One method for overcoming this limitation, as well as a method for sharing program costs, was to create radio networks, linking stations together with telephone lines to provide a nationwide audience.

      United States

      In the U.S., the American Telephone and Telegraph Company (AT&T) was the first organization to create a radio network, and also to promote commercial advertising, which it called "toll" broadcasting. Its flagship station, WEAF (now WFAN) in New York City, sold blocks of airtime to commercial sponsors that developed entertainment shows containing commercial messages. AT&T held a monopoly on quality telephone lines, and by 1924 had linked 12 stations in Eastern cities into a "chain". The Radio Corporation of America (RCA), General Electric and Westinghouse organized a competing network around its own flagship station, RCA's WJZ (now WABC) in New York City, but were hampered by AT&T's refusal to lease connecting lines or allow them to sell airtime. In 1926 AT&T sold its radio operations to RCA, which used them to form the nucleus of the new NBC network.[54] By the 1930s, most of the major radio stations in the country were affiliated with networks owned by two companies, NBC and CBS. In 1934, a third national network, the Mutual Radio Network was formed as a cooperative owned by its stations.

      United Kingdom

      A BBC receiver licence from 1923. The British government required listeners to purchase yearly licences, which financed the stations.

      A second country which quickly adopted network programming was the United Kingdom, and its national network quickly became a prototype for a state-managed monopoly of broadcasting.[55] A rising interest in radio broadcasting by the British public pressured the government to reintroduce the service, following its suspension in 1920. However, the government also wanted to avoid what it termed the "chaotic" U.S. experience of allowing large numbers of stations to operate with few restrictions. There were also concerns about broadcasting becoming dominated by the Marconi company.[56] Arrangements were made for six large radio manufacturers to form a consortium, the British Broadcasting Company (BBC), established on 18 October 1922, which was given a monopoly on broadcasting. This enterprise was supported by a tax on radio sets sales, plus an annual license fee on receivers, collected by the Post Office.[57] Initially the eight stations were allowed regional autonomy. In 1927, the original broadcasting organization was replaced by a government chartered British Broadcasting Corporation.[58] an independent nonprofit supported solely by a 10 shilling receiver license fee.[58] A mixture of populist and high brow programmes were carried by the National and Regional networks.

      "Golden Age of Radio"

      When broadcasting began in 1920, music was played on air without regard to its copyright status. Music publishers challenged this practice as being copyright infringement, which for a time kept many popular tunes off the air, and this 1925 editorial cartoon shows a rich publisher muzzling two radio performers. The radio industry eventually agreed to make royalty payments.

      The period from the early 1920s through the 1940s is often called the "Golden Age of Radio". During this period AM radio was the main source of home entertainment, until it was replaced by television. For the first time entertainment was provided from outside the home, replacing traditional forms of entertainment such as oral storytelling and music from family members. New forms were created, including radio plays, mystery serials, soap operas, quiz shows, variety hours, situation comedies and children's shows. Radio news, including rem

      In the U.S., the American Telephone and Telegraph Company (AT&T) was the first organization to create a radio network, and also to promote commercial advertising, which it called "toll" broadcasting. Its flagship station, WEAF (now WFAN) in New York City, sold blocks of airtime to commercial sponsors that developed entertainment shows containing commercial messages. AT&T held a monopoly on quality telephone lines, and by 1924 had linked 12 stations in Eastern cities into a "chain". The Radio Corporation of America (RCA), General Electric and Westinghouse organized a competing network around its own flagship station, RCA's WJZ (now WABC) in New York City, but were hampered by AT&T's refusal to lease connecting lines or allow them to sell airtime. In 1926 AT&T sold its radio operations to RCA, which used them to form the nucleus of the new NBC network.[54] By the 1930s, most of the major radio stations in the country were affiliated with networks owned by two companies, NBC and CBS. In 1934, a third national network, the Mutual Radio Network was formed as a cooperative owned by its stations.

      United KingdomA second country which quickly adopted network programming was the United Kingdom, and its national network quickly became a prototype for a state-managed monopoly of broadcasting.[55] A rising interest in radio broadcasting by the British public pressured the government to reintroduce the service, following its suspension in 1920. However, the government also wanted to avoid what it termed the "chaotic" U.S. experience of allowing large numbers of stations to operate with few restrictions. There were also concerns about broadcasting becoming dominated by the Marconi company.[56] Arrangements were made for six large radio manufacturers to form a consortium, the British Broadcasting Company (BBC), established on 18 October 1922, which was given a monopoly on broadcasting. This enterprise was supported by a tax on radio sets sales, plus an annual license fee on receivers, collected by the Post Office.[57] Initially the eight stations were allowed regional autonomy. In 1927, the original broadcasting organization was replaced by a government chartered British Broadcasting Corporation.[58] an independent nonprofit supported solely by a 10 shilling receiver license fee.[58] A mixture of populist and high brow programmes were carried by the National and Regional networks.

      "Golden Age of Radio"

      radio plays, mystery serials, soap operas, quiz shows, variety hours, situation comedies and children's shows. Radio news, including remote reporting, allowed listeners to be vicariously present at notable events.

      Radio greatly eased the isolation of rural life. Political officials could now speak directly to millions of citizens. One of the first to take advantage of this was American president Franklin Roosevelt, who became famous for his fireside chats during the Great Depression. However, broadcasting also provided the means to use propaganda as a powerful government tool, and contributed to the rise of fascist and communist ideologies.

      Decline in popularity

      In the 1940s two new broadcast media, FM radio and television, began to provide extensive competition with the established broadcasting services. The AM radio industry suffered a serious loss of audience and advertising revenue, and coped by developing new strategies. Network broadcasting gave way to format broadcasting: instead of broadcasting the same programs all over the country, stations individually adopted specialized formats which appealed to different audiences, such as regional and local news, sports, "talk" programs, and programs targeted at minorities. Instead of live music, most stations began playing less expen

      Radio greatly eased the isolation of rural life. Political officials could now speak directly to millions of citizens. One of the first to take advantage of this was American president Franklin Roosevelt, who became famous for his fireside chats during the Great Depression. However, broadcasting also provided the means to use propaganda as a powerful government tool, and contributed to the rise of fascist and communist ideologies.

      In the 1940s two new broadcast media, FM radio and television, began to provide extensive competition with the established broadcasting services. The AM radio industry suffered a serious loss of audience and advertising revenue, and coped by developing new strategies. Network broadcasting gave way to format broadcasting: instead of broadcasting the same programs all over the country, stations individually adopted specialized formats which appealed to different audiences, such as regional and local news, sports, "talk" programs, and programs targeted at minorities. Instead of live music, most stations began playing less expensive recorded music. However, the ongoing development of alternative transmission systems, including Digital Audio Broadcasting (DAB), satellite radio, and HD (digital) radio, continued the decline of the popularity of the traditional broadcast technologies. These new options, including the introduction of Internet streaming, particularly resulted in the reduction of shortwave transmissions, as international broadcasters found ways to reach their audiences more easily.[59]

      AM stereo