Radio broadcasting


Radio broadcasting is the transmission of signals, especially audio, to receivers using radio waves over a wide area. Listeners require a broadcast radio receiver to receive these signals. "Terrestrial" broadcasts, including AM, FM, and DAB stations, originate from land-based transmitters, whereas satellite radio signals originate from a satellite in Earth orbit.
Radio stations may produce their own programming or be affiliated with a radio network that provides content either through broadcast syndication or by simulcasting, or both. The most common transmission technologies are analog and digital. Analog radio uses one of two modulation methods: amplitude modulation or frequency modulation. Digital radio stations transmit using one of several digital audio standards, such as DAB, HD Radio, or DRM.

History

Pre-radio

Electronic distribution originated, to a limited extent, with the invention of the telegraph. The most common example, "tickers", were primarily used to distribute stock price information. An additional subscription service was time signals. The concept of audio broadcasting was first developed after the invention of telephone. In a few locations, most commonly in Europe, telephone newspapers were established, to provide news and entertainment to subscribers. These systems had the advantage of being able to charge individual customers. However, a lack of a way to amplify signals meant that their ranges were generally limited to a single municipality.
Some early inventors foresaw wireless transmission's potential. In 1902, Nathan Stubblefield, who had developed wireless transmissions using ground conduction, envisioned that: "...any one having a receiving instrument, which would consist merely of a telephone receiver and a few feet of wire, and a signaling gong, could, upon being signaled by a transmitting station in Washington, or nearer, if advisable, be informed of weather news. Eventually it will be used for the general transmission of news of every description."

Radio

Although it was quickly recognized that radio transmissions were capable of being broadcast to a scattered audience without needing connecting wires, there was skepticism about its finances. In an 1898 review of early radio transmissions, then known as "Hertzian telegraphy", a reviewer opined: "As to the practical applications, there were occasions when one wanted to 'shout to the world'—as in distributing political speeches to the Press—and for such a purpose the Hertz-wave and the coherer might be of service. But 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?". Another limitation was that many countries required listeners to be licensed in order to operate a radio receiver.
The earliest radio broadcasting stations transmitted radiotelegraphy dots-and-dashes, for such things as time signals and weather reports, or provided news summaries intended for inclusion in shipboard newspapers. This had limited audiences, because of the need to understand Morse code. Because there was no way to collect fees from listeners, these stations were commonly operated by national governments. Beginning in 1904, the U.S. Navy broadcast daily time signals and weather reports, and a Canadian Marconi station in Camperdown, Nova Scotia began transmitting time signals in 1907. In Europe, a station located at the Eiffel Tower in Paris, France, transmitted time signals that were audible throughout the continent.
Although most radio stations during the first two decades of the 1900s employed radiotelegraphic transmissions, there was also experimental development of audio transmissions, mostly using "amplitude modulation" signals. The first AM technologies included high-frequency spark, alternator, and arc transmitters. However, it was not until the development of vacuum-tube transmitters that widespread audio broadcasting became practical. In addition, most early experimenters worked to create radiotelephone systems for private communication, and few were interested in broadcasting information and entertainment to general audiences.
Early examples of audio broadcasts included:
  • On 1902, Julio Cervera Baviera was able to make audio transmissions from Xàbia and received in Ibiza.
  • On December 21, 1906, Reginald Fessenden successfully demonstrated audio transmissions using an alternator transmitter at Brant Rock, Massachusetts, USA. An article in the December 1932 issue of The Proceedings of the Institute of Radio Engineers by former Fessenden associate Samuel M. Kintner, reviewed information from a January 29, 1932, letter from Fessenden, which reported that shortly after the initial demonstrations, Fessenden had made the first of two radio broadcasts of music and entertainment on the evening of December 24, 1906, using the alternator transmitter. He also stated that a second program was broadcast on December 31. Fessenden claimed that the two programs had been widely publicized in advance, and the Christmas Eve broadcast had been heard "as far down" as Norfolk, Virginia, while the New Year Eve's broadcast had reached listeners in the West Indies. However, despite Fessenden's assertion that these broadcasts were widely heard along the U.S. eastern coast, extensive research has failed to find any contemporary confirmation of these broadcasts.
  • Far better documented are the early broadcasts of Lee de Forest, using an arc transmitter. In February 1907, he transmitted electronic telharmonium music from his laboratory station in New York City. This was followed later that year by a series of demonstrations that included Eugenia Farrar singing "I Love You Truly".
  • Charles Herrold, who opened the Herrold College of Wireless and Engineering in San Jose, California, USA in 1909, reported that in 1910, using a high-frequency spark transmitter, he had broadcast "wireless phone concerts to local amateur wireless men". He later switched to arc transmitters, and in 1912 reported broadcasting weekly concerts.
  • Robert Goldschmidt inaugurated a series of weekly concerts on March 28, 1914, using a high-frequency spark transmitter located at Laeken, Belgium.
  • Lee de Forest established experimental station 2XG in the Highbridge section of New York City, which was one of the first to use a vacuum-tube transmitter. The station featured a nightly "wireless newspaper" broadcast. On November 7, 1916, the station, in conjunction with the New York American, broadcast results for the U.S. presidential election.
The outbreak of World War One largely suspended the development of civilian radio. However, during this period major improvements were made in vacuum-tube technology, which went into service after the end of wartime restrictions. All of the following examples used vacuum-tube transmitters:
  • After the wartime restrictions were lifted, Lee de Forest relicenced 2XG, his New York City station, which resumed nightly broadcasts in November 1919. However, this station was shut down after de Forest relocated it without first getting permission. He subsequently moved its transmitter to the California Theater in San Francisco, where it was relicensed and resumed operations as 6XC. In 1921, de Forest described 6XC as the "first radio-telephone station devoted solely" to broadcasting to the public.
  • In The Hague, the Netherlands, Hans Idzerda's station, PCGG, started broadcasting on November 6, 1919, using narrow-band frequency modulation, making it arguably the first commercial broadcasting station.
  • Radio Argentina began regularly scheduled transmissions in Buenos Aires on August 27, 1920, initially from the Teatro Coliseo, where they broadcast an opera series for 19 days. 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.
  • In early 1919, the Canadian Marconi facility at Montreal, Quebec, Canada received a surplus wartme transmitter, and its test transmissions, over experimental station XWA, evolved into broadcasts, starting with a May 20, 1920 concert. This was followed by weekly broadcasts.
  • Entertainment radio broadcasts in the UK began in 1920, with occasional broadcasts by the Marconi Research Centre station, 2MT at Writtle near Chelmsford, England. On June 15, 1920, a widely publicized broadcast was made by soprano Dame Nellie Melba from Marconi's New Street Works factory in Chelmsford. This was the first artist of international renown to make a radio broadcast. However, later that year, the broadcasts were banned by the Post Office, due to complaints that the broadcasts were interfering with military communication.
  • Beginning on August 20, 1920, the Detroit News in Detroit, Michigan, USA, began daily broadcasts over what it called the Detroit News Radiophone. This station, later licensed as station WWJ, in 1945 ran an advertisement with the claims that it was the "World's First Station" and where "commercial radio broadcasting began".
  • After reviewing multiple post-war experimental efforts in the United States, in the words of Erik Barnouw, "There was a ferment of interest, but without sense of direction—until something happened in Pittsburgh." Frank Conrad was a Westinghouse Electric Corporation electrical engineer. He also held a license for an experimental station, 8XK, located in his garage at his Wilkinsburg, Pennsylvania home. After seeing a local newspaper advertisement for radio receivers capable of picking up the 8XK broadcasts, Westinghouse's Harry P. Davis decided to see if there was a broad consumer market for receivers produced by the company. Westinghouse began regular broadcasts with election returns on the evening of November 2, 1920, over station 8ZZ located at its East Pittsburgh, Pennsylvania, USA headquarters. This has generally been recognized as the first commercially licensed radio station in the United States.
Effective December 1, 1921, the U.S. Department of Commerce issued regulations formally establishing a broadcasting service, and by the end of 1922, there were over 500 licensed stations. Canada soon followed, and began issuing broadcasting station licenses in April 1922. 2MT in Great Britain began regular entertainment broadcasts in 1922, and that year the British Broadcasting Company was formed and given a national broadcasting monopoly. It received a Royal Charter in 1926, making it the first national broadcaster in the world, followed by Czechoslovak Radio and other European broadcasters in 1923.
File:Control room and radio studio in Fabianinkatu headquarters of Yleisradio, ca 1938.jpg|thumb|Control room and radio studio of the Finnish broadcasting company Yleisradio in the 1930s.