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 come from stations on land, and include AM and FM (both analog); and DAB (digital). Audio is also broadcast via satellite in both digital and analog, originating from a satellite in orbit around Earth.
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 (AM) or frequency modulation (FM). Digital radio stations transmit using one of several digital audio standards, such as DAB (Digital Audio Broadcasting), HD Radio, or DRM (Digital Radio Mondiale).
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.""Telephoning Without Wires" by Trumbull White, Our Wonderful Progress: The World's Triumphant Knowledge and Works, Book 2, "The World's Science and Invention", 1902, pages 297–302. 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?"."Hertzian Telegraphy at the Physical Society", Electrician (London), January 28, 1898, pages 452–453. 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. 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."The First Wireless Time Signal" by Captain J. L. Jayne, The American Jeweler, October 1912, page 411. In Europe, a station located at the Eiffel Tower in Paris, France, transmitted time signals that were audible throughout the continent."The Eiffel Tower and its Early Radio" by Lloyd Butler, March 2013. It also transmitted time signals so audiences unfamiliar with Morse code could listen for the "beep" to adjust their clocks and watches. These audiences were international, with evidence of families in London catching the time signal from the Eiffel tower.Rikitianskaia, Maria, Gabriele Balbi, and Katharina Lobinger. 2018. ‘The Mediatization of the Air. Wireless Telegraphy and the Origins of a Transnational Space of Communication, 1900-1910s’. Journal of Communication 68 (4): 758–79.https://doi.org//10.1093/joc/jqy030 The weather reports were also a form of entertainment for the audiences of this time.Rikitianskaia, Maria. 2024. The Global Wireless: Transnational Radiotelegraphy and Its Disruption in World War I. De Gruyter.
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" (AM) signals. The first AM technologies included high-frequency spark, alternator, and arc transmitters. However, it was not until the development of vacuum-tube (also known as "valve") 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."Experiments and Results in Wireless Telephony" by John Grant, The American Telephone Journal. Part I: January 26, 1907, pages 49–51; Part II: February 2, 1907, pages 68–70, 79–80. An article in the December 1932 issue of The Proceedings of the Institute of Radio Engineers by former Fessenden associate Samuel M. Kintner,"Pittsburgh's Contributions to Radio" by S. M. Kintner, Proceedings of the Institute of Radio Engineers, December 1932, pages 1849–1862. 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 (Christmas Eve), using the alternator transmitter. He also stated that a second program was broadcast on December 31 (New Year's Eve). 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.Fessenden, Builder of Tomorrows by Helen Fessenden, 1940, pages 153–154. 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. by James E. O'Neal, Radio World, October 25, 2006. (radioworld.com) by James E. O'Neal, Radio World, December 23, 2008. (radioworld.com) 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.Father of Radio by Lee de Forest, 1950, page 225. This was followed later that year by a series of demonstrations that included Eugenia Farrar singing "I Love You Truly",I Looked and I Listened by Ben Gross, 1954, page 48."I Was First to Sing Over the Radio" by Eugenia H. Farrar, The American Swedish Monthly, January 1955, pages 10, 26. although the claim that the New York Herald reported this broadcast has not been verified.
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".Charles Herrold: Inventor of Radio Broadcasting by Gorden Greb and Mike Adams, 2003, page 6. He later switched to arc transmitters, and in 1912 reported broadcasting weekly concerts."Will Give Concert by Wireless Telephone", San Jose Mercury Herald, July 21, 1912, page 27."Musical Concert by Wireless Telephone", San Diego Union, July 23, 1912, page 19. Robert Goldschmidt inaugurated a series of weekly concerts on March 28, 1914, using a high-frequency spark transmitter located at Laeken, Belgium."Radio Telephony: Article V" by Alfred N. Goldsmith, The Wireless Age, May 1917, page 565. 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."Election Returns Flashed by Radio to 7,000 Amateurs", The Electrical Experimenter, January 1917, page 650. George C. Cannon, of New Rochelle, New York, reported making nightly entertainment broadcasts over his Special Amateur station, 2ZK, from December 1916 until the following February."Who Was the First to Broadcast?" (George C. Cannon correspondence), Radio Broadcast, November 1924, pages 81-82.
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."'Broadcasting' News by Radiotelephone" (letter from Lee de Forest), Electrical World, April 23, 1921, page 936. In The Hague, the Netherlands, Hans Idzerda's station, PCGG, started broadcasting on November 6, 1919, using narrow-band frequency modulation (FM), making it arguably the first commercial broadcasting station.Nieuwe Rotterdamsche (Netherlands) Courant, November 5, 1919, page 4. 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.Atgelt, Carlos A. "Early History of Radio Broadcasting in Argentina." The Broadcast Archive (Oldradio.com). 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."Wireless Concert Given for Ottawa", Montreal Gazette, May 21, 1920, page 4. This was followed by weekly broadcasts.