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AM broadcasting

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") transmissions, but also on the longwave and shortwave radio bands.

"AM radio" redirects here. For the song by Everclear, see AM Radio (song). For the American musical group, see AM Radio (band).

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 much of the programming previously carried by radio. Later, AM radio's audiences declined greatly due to competition from FM (frequency modulation) radio, Digital Audio Broadcasting (DAB), satellite radio, HD (digital) radio, Internet radio, music streaming services, and podcasting.


Compared to FM or digital transmissions, AM transmissions are more expensive to transmit due to the necessity of having to transmit a high power carrier wave to overcome ground losses, and the large antenna radiators required at the low broadcast frequencies, but can be sent over long distances via the ionosphere at night; however, they are much more susceptible to interference, and often have lower audio fidelity.[1][2] Thus, AM broadcasters tend to specialize in spoken-word formats, such as talk radio, all-news radio and sports radio, with music formats primarily for FM and digital stations.

Christmas Eve 1906. Until the early 1930s, it was generally accepted that '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.[22] This claim was based solely on information included in a January 29, 1932, letter that Fessenden had sent to Kintner. (Fessenden subsequently died five months before Kintner's article appeared.) In his letter, Fessenden reported that, on the evening of December 24, 1906 (Christmas Eve), he had made the first of two broadcasts of music and entertainment to a general audience, using the alternator-transmitter at Brant Rock, Massachusetts. Fessenden remembered producing a short program that included playing a phonograph record, followed by his playing the violin and singing, and closing with a Bible reading. He also stated that a second short program was broadcast on December 31 (New Year's Eve). The intended audience for both transmissions was primarily shipboard radio operators along the Atlantic seaboard. Fessenden claimed these two programs had been widely publicized in advance, with the Christmas Eve broadcast heard "as far down" as Norfolk, Virginia, while the New Year’s Eve broadcast had been received in the West Indies.[23] However, extensive efforts to verify Fessenden's claim during both the 50th[24] and 100th[25] anniversaries of the claimed broadcasts, which included reviewing ships' radio log accounts and other contemporary sources, have so far failed to confirm that these reported holiday broadcasts actually took place.

Lee de Forest

1907-1912. Lee de Forest conducted multiple test broadcasts beginning in 1907, and was widely quoted promoting the potential of organized radio broadcasting. Using a series of arc transmitters, he made his first entertainment broadcast in February 1907, transmitting electronic music from his Parker Building laboratory station in New York City.[26] This was followed by tests that included, in the fall, Eugenia Farrar singing "I Love You Truly" and "Just Awearyin' for You".[27] Additional promotional events in New York included live performances by famous Metropolitan Opera stars such as Mariette Mazarin and Enrico Caruso. He also broadcast phonograph music from the Eiffel Tower in Paris. His company equipped the U.S. Navy's Great White Fleet with experimental arc radiotelephones for their 1908 around-the-world cruise, and the operators broadcast phonograph music as the ships entered ports like San Francisco and Honolulu.[28]

telharmonium

June 1910. In a June 23, 1910, notarized letter that was published in a catalog produced by the Electro Importing Company of New York, Charles "Doc" Herrold reported that, using one of that company's spark coils to create a "high frequency spark" transmitter, he had successfully broadcast "wireless phone concerts to local amateur wireless men". Herrold lived in San Jose, California.

[29]

1913. Robert Goldschmidt began experimental radiotelephone transmissions from the , near Brussels, Belgium, and by March 13, 1914, the tests had been heard as far away as the Eiffel Tower in Paris.[30]

Laeken station

1914–1919. "University of Wisconsin electrical engineering Professor Edward Bennett sets up a personal radio transmitter on campus and in June 1915 is issued an Experimental radio station license with the call sign 9XM. Activities included regular Morse Code broadcasts of weather forecasts and sending game reports for a Wisconsin-Ohio State basketball game on February 17, 1917.

[31]

January 15, 1920. Broadcasting in the United Kingdom began with impromptu news and phonograph music over 2MT, the 15 kW experimental tube transmitter at Marconi's factory in , Essex, at a frequency of 120 kHz. On June 15, 1920, the Daily Mail newspaper sponsored the first scheduled British radio concert, by the famed Australian opera diva Nellie Melba.[32] This transmission was heard throughout much of Europe, including in Berlin, Paris, The Hague, Madrid, Spain, and Sweden. Chelmsford continued broadcasting concerts with noted performers. A few months later, in spite of burgeoning popularity, the government ended the broadcasts, due to complaints that the station's longwave signal was interfering with more important communication, in particular military aircraft radio.[33]

Chelmsford

August 27, 1920. Argentina made the first mass radio transmission as a communication medium. Medicine students of the UBA made the first radio program by transmitting Wagner's Parsifal on radio and picked up by about 100 amateurs in the city, emitting from the roof of the Teatro Colón. They kept transmitting over the nights different operas being the first in offering a radio program. There were known as the "Locos de la azotea" (the crazies of the roof).

[34]

(DRM), a digital radio method using the bands LW, MW, SW, and the VHF bands

Digital Radio Mondiale

Amplitude modulation

a digital system for adding low bitrate information to an AM broadcast signal

Amplitude Modulation Signalling System

a hybrid digital radio format for AM broadcasting

CAM-D

(ERP), standardised definition of radio frequency power

Effective radiated power

Extended AM broadcast band

History of radio

List of 50 kW AM radio stations in the United States

Lists of radio stations in North America

Oldest radio stations

the hobby of receiving distant AM radio stations on the mediumwave band.

MW DXing