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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]
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.
A spark-gap transmitter for generating radio frequency electromagnetic waves. Such devices served as the transmitters for most early wireless systems. 24 December 1906: Reginald Fessenden uses an Alexanderson alternator and rotary spark-gap transmitter to make the first radio audio broadcast, from Brant Rock, Massachusetts.
The first Audion AM radio transmitter, built by Lee de Forest and announced April, 1914 Some of the earliest Audion AM radio transmitters, built by de Forest around 1916. The invention of the Audion oscillator in 1912 made inexpensive sound radio transmission possible, and was responsible for the advent of radio broadcasting around 1920.
Until the early 1930s, it was generally accepted that Lee de Forest, who conducted a series of test broadcasts beginning in 1907, and who was widely quoted promoting the potential of organized radio broadcasting, was the first person to transmit music and entertainment by radio. De Forest's first entertainment broadcast occurred in February ...
Along with the arc converter invented in 1903, the Alexanderson alternator was one of the first radio transmitters that generated continuous waves. In contrast, the earlier spark-gap transmitters generated a string of damped waves. These were electrically "noisy"; the energy of the transmitter was spread over a wide frequency range, so they ...
Guglielmo Marconi, who built the first radio receivers, with his early spark transmitter (right) and coherer receiver (left) from the 1890s. The receiver records the Morse code on paper tape Generic block diagram of an unamplified radio receiver from the wireless telegraphy era [4] Example of transatlantic radiotelegraph message recorded on paper tape by a siphon recorder at RCA's New York ...
Valdemar Poulsen (23 November 1869 – 23 July 1942) was a Danish engineer who developed a magnetic wire recorder called the telegraphone in 1898. He also made significant contributions to early radio technology, including the first continuous wave radio transmitter, the Poulsen arc, [1] which was used for a majority of the earliest audio radio transmissions, before being supplanted by the ...