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The first commercial AM Audion vacuum tube radio transmitter, built in 1914 by Lee De Forest who invented the Audion in 1906. During the mid-1920s, amplifying vacuum tubes revolutionized radio receivers and transmitters. John Ambrose Fleming developed a vacuum tube diode. Lee de Forest placed a screen, added a "grid" electrode, creating the triode.
Before the discovery of electromagnetic waves and the development of radio communication, there were many wireless telegraph systems proposed and tested. [4] In April 1872 William Henry Ward received U.S. patent 126,356 for a wireless telegraphy system where he theorized that convection currents in the atmosphere could carry signals like a telegraph wire. [5]
1920s: Radio was first used to transmit pictures visible as television. 1926: Official Egyptian decree to regulate radio transmission stations and radio receivers. [40] Early 1930s: Single sideband (SSB) and frequency modulation (FM) were invented by amateur radio operators. By 1940, they were established commercial modes.
The obelisk, a memorial stone and a stele in honor of the implementation in 1900 by inventor A.S. Popov of the first practical radio communication session, Hogland; Memorial stone in honor of the invention of the radio in 1895 by A. S. Popov, Kronshtadt, Toulonskaya Alley, Yachtennaya Square; Sign 100 years of radio (1997), Sevastopol
The next year the company used the same concept to begin establishing the first radio network. [107] The WEAF and WJZ chains. At the same time in early 1922 that it announced the beginning of advertisement-supported broadcasting, AT&T also introduced its plans for the development of the first radio network. [104]
3 October – The first International Radiotelegraph Convention opens in Berlin. 24 December – Reginald Fessenden makes the first radio broadcast: a poetry reading, a violin solo and a speech. Lee de Forest invents the audion .
An early resonant transformer invented by Braun used in the coherer radio receivers in wireless telegraphy radio systems made by the Telefunken company in 1903. Following the invention of his tube, Braun also began researching in the field of wireless telegraphy. A key issue in early radio technology was the development of a reliable receiver.
Milestones in radio: the first half century (1895–1945). The UNESCO courier (February 1997), p. 16–21; Radio Review/Radio Listeners Guide (1925–1929), Broadcasting Yearbook (1935–2010), World Radio TV Handbook (1947–) Berg, Jerome S. The early shortwave stations: a broadcasting history through 1945 (2013) radioheritage.net