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| quikcafe.com | History of radio | Discovery and development | Wireless age | 20th century | Uses of radio | Audio | Data | Digital Radio |
History of radio
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Originally, radio technology was called 'wireless telegraphy', which
was shortened to 'wireless'. The prefix radio- in the sense of
wireless transmission is first recorded in the word radio conductor,
coined by the French physicist Edouard Branly in 1897 and based on
the verb to radiate. 'Radio' as a noun is said to have been coined
by advertising expert Waldo Warren (White 1944). The word appears in
a 1907 article by Lee de Forest, was adopted by the United States
Navy in 1912 and became common by the time of the first commercial
broadcasts in the United States in the 1920s. (The noun
'broadcasting' itself came from an agricultural term, meaning
'scattering seeds'.) The American term was then adopted by other
languages in Europe and Asia, although Britain retained the term
'wireless' until the mid-20th century. The pre- and early history of radio is the history of its technology. Later, the history is dominated by programming and contents, which is closer to general history. |
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The identity of the original inventor of radio, at the time called
wireless telegraphy, is contentious. The key invention for the
beginning of "wireless transmission of data using the entire
frequency spectrum", known as the spark-gap transmitter, has been
attributed to Nikola Tesla, Guglielmo Marconi, and Alexander Popov. In 1820, Hans Christian Ørsted discovered the relationship between electricity and magnetism in a very simple experiment. He demonstrated that a wire carrying a current was able to deflect a magnetized compass needle. In 1831, Michael Faraday began a series of experiments in which he discovered electromagnetic induction. The relation was mathematically modeled by Faraday's law, which subsequently became one of the four Maxwell equations. Faraday proposed that electromagnetic forces extended into the empty space around the conductor, but did not complete his work involving that proposal. 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. In 1878 David E. Hughes realized the transmission and reception of 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, 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. Claims have been made that Murray, Kentucky farmer Nathan Stubblefield invented radio during the period of 1885–1892, but his devices seem to have worked by induction transmission rather than radio transmission. In 1893 in St. Louis, Missouri, Tesla gave a public demonstration of "wireless" radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described in detail the principles of radio communication. [1] The apparatus that he used contained all the elements that were incorporated into radio systems before the development of the "oscillation valve", the early vacuum tube. Tesla was the first to apply the mechanism of electrical conduction to wireless practices. Also, he initially used sensitive electromagnetic receivers [2], that were unlike the less responsive coherers later used by Marconi and other early experimenters. After the public demonstrations of radio communication that Tesla made in 1893, the principle of radio communication—sending signals through space to receivers—was publicized widely. A public demonstration of transmission and reception of radio waves used for communication was performed by the Russian physicist Alexander Popov at the Russian Physical and Chemical Society on May 7, 1895—which has since been celebrated in the Russian Federation as "Radio Day". In 1896, Marconi was awarded a patent for radio with British Patent 12039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. This was recognized as the world's first patent for radio, though it used various earlier techniques of Tesla, and resembled the instrument demonstrated by Popov. In 1897 Marconi established the radio station on the Isle of Wight, England. The same year in the U.S., Tesla applied for two key radio patents which were issued in early 1900. The U.S. Patent Office reversed its decision in 1904, awarding Marconi a patent for the invention of radio, possibly influenced by Marconi's financial backers in the States, who included Thomas Edison and Andrew Carnegie. This also allowed the U.S. government (among others) to avoid having to pay the royalties that were being claimed by Tesla for use of his patents. |
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