page_title: Timeline of radio
section_title: Audio broadcasting (1915 to 1950s)
hierarchical_section_title: Timeline of radio / Audio broadcasting (1915 to 1950s)
caption_attribution_description: English: Federal Radio Commission seal
context_page_description: The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history.
context_section_description: 1916: First regular broadcasts on 9XM (now WHA) – Wisconsin state weather, delivered in Morse Code
  1919: First clear transmission of human speech, (on 9XM) after experiments with voice (1918) and music (1917).
  1920: Regular wireless broadcasts for entertainment began in Argentina, pioneered by the group around Enrique Telémaco Susini.
  1920: Spark-gap telegraphy stopped.
  20 August 1920: E.W. Scripps's WWJ in Detroit received its commercial broadcasting license and started broadcasting. It has carried a regular schedule of programming to the present. Broadcasting was not yet supported by advertising. The stations owned by manufacturers and department stores were established to sell radios and those owned by newspapers to sell papers and express the opinions of the owners.
  31 August 1920: The first known radio news program was broadcast by station 8MK, the unlicensed predecessor of WWJ (AM) in Detroit, Michigan.
  October 1920: Westinghouse in Pittsburgh, Pennsylvania became the first US commercial broadcasting station to be licensed when it was granted call letters KDKA. (Their engineer Frank Conrad had been broadcasting from his own station since 1916.)
  1921: In Australia, Charles Maclurcan of 2CM commenced broadcasting Sunday night classical music concerts on the long wave band (214 kHz.), using seven watts. 2CM was issued with the first broadcasting licence in Australia (Licence No.1, signed by Prime Minister William Morris (Billy) Hughes,) in December 1922. However, many current historian recognise 2SB as the first official broadcaster in Australia, in 1923.
  26 February 1922: In California, Joseph Franklin Rutherford transmitted his first radio Bible sermon.
  1922: Regular wireless broadcasts for entertainment began in the UK from the Marconi Research Centre at Writtle near Chelmsford, England. Early radios ran the entire power of the transmitter through a carbon microphone.
  23 November 1923: 2SB was the first Australian station to be officially recognised.
  23 May 1925 : First broadcast in Tbilisi, Georgia.
  Mid 1920s:
  Amplifying vacuum tubes revolutionized radio receivers and transmitters; Westinghouse engineers improved them. (Before that, the most common type of receiver was the crystal set, although some early radios used some type of amplification through electric current or battery.)
  Inventions of the triode amplifier, generator, and detector enabled audio radio.
  Fessenden and Lee de Forest pioneered the invention of amplitude-modulated radio (AM radio), so more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of spectra). Westinghouse bought DeForest's and Armstrong's patent.
  1920s: Radio was first used to transmit pictures visible as television.
  Early 1930s: Single sideband (SSB) and frequency modulation (FM) were invented by amateur radio operators. By 1940, they were established commercial modes.
  Westinghouse was brought into the patent allies group, General Electric, American Telephone and Telegraph, and Radio Corporation of America, and became a part owner of RCA. All radios made by GE and Westinghouse were sold under the RCA label 60% GE and 40% Westinghouse. ATT's Western Electric would build radio transmitters. The patent allies attempted to set up a monopoly, but they failed due to successful competition. Much to the dismay of the patent allies, several of the contracts for inventor's patents held clauses protecting "amateurs" and allowing them to use the patents. Whether the competing manufacturers were really amateurs was ignored by these competitors.
  These features arose:
  Commercial (United States; governmental (Europe) station networks; or a dual system, firstly in Australia in 1924 and in Canada in 1932.
  Federal Radio Commission
  Federal Communications Commission
  Race towards shorter waves and FM
  1933: FM radio was patented; Edwin H. Armstrong invented it. FM uses frequency modulation of the radio wave to minimize static and interference from electrical equipment and the atmosphere, in the audio program.
  1937: W1XOJ, the first experiment
caption: Federal Radio Commission.