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| quikcafe.com | History of radio | Discovery and development | Wireless age | 20th century | Uses of radio | Audio | Data | Digital Radio |
Discovery and development
| The theoretical basis of the propagation of electromagnetic waves was first described in 1873 by James Clerk Maxwell in his paper to the Royal Society A dynamical theory of the electromagnetic field, which followed his work between 1861 and 1865. Towards the end of 1875 while experimenting with the telegraph Thomas Edison noted a phenomenon that he termed "etheric force", announcing it the press on November 28. He abandoned research when Elihu Thomson, among others, ridiculed the idea. (In 1885 Edison took out a patent on a system of radio communication between ships which he then sold to Guglielmo Marconi). In 1878 David E. Hughes was the first to transmit and receive radio waves when he noticed that his induction balance caused noise in the receiver of his homemade telephone. He demonstrated his discovery to the Royal Society in 1880 but was told it was merely induction. It was Heinrich Rudolf Hertz who, between 1886 and 1888, first validated Maxwell's theory through experiment, demonstrating that radio radiation had all the properties of waves (now called Hertzian waves), and discovering that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. | |
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Mahlon Loomis was issued U.S. Patent 129971 on July 30, 1872.
Roberto Landell de Moura, a Brazilian priest and scientist,
conducted experiments after 1893 (but at least by 1894). He did not
publicize his achievement until 1900. Claims have been made that
Nathan Stubblefield invented radio before either Tesla or Marconi,
but his device seems to have worked by induction transmission rather
than radio transmission. PICTURE O RADIO Invention The identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. The controversy over who invented the radio, with the benefit of hindsight, can be broken down as follows: Q1: Who invented 'wireless transmission of data' (spark-gap radio)? A1: Nikola Tesla holds the US patent for the invention of the radio. Q2: Who invented amplitude-modulated (AM) radio, so that more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of the spectrum)? A2: Reginald Fessenden] and Lee de Forest. Q3: Who invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics? A3: Edwin H. Armstrong and Lee de Forest. Early radios ran the entire power of the transmitter through a carbon microphone. While some early radios used some type of amplification through electric current or battery, through the mid 1920s the most common type of receiver was the crystal set. In the 1920s, amplifying vacuum tube radio receivers and transmitters. |
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| quikcafe.com | History of radio | Discovery and development | Wireless age | 20th century | Uses of radio | Audio | Data | Digital Radio |