Radio

Radio is the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of light.

History and 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:

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:Q1: Who invented 'wireless transmission of data using the entire frequency spectrum' (spark-gap radio)?

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:A1: Nikola Tesla, Guglielmo Marconi, and Alexander Popov (possibly in that order).

Related Topics:
Nikola Tesla - Guglielmo Marconi - Alexander Popov

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: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)?

Related Topics:
Amplitude-modulated - AM

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:A2: Reginald Fessenden http://www.invent.org/hall_of_fame/59.html and Lee de Forest.

Related Topics:
Reginald Fessenden - Lee de Forest

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:Q3: Who invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics?

Related Topics:
Frequency-modulated - FM

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:A3: Edwin H. Armstrong and Lee de Forest.

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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 tubes revolutionized both radio receivers and transmitters.

Related Topics:
1920s - Crystal set - Vacuum tube - Radio receiver - Transmitter

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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. 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.

Related Topics:
1873 - James Clerk Maxwell - Royal Society - 1861 - 1865 - David E. Hughes - Induction balance - Telephone - Induction - Heinrich Rudolf Hertz - 1886 - 1888 - Hertzian wave - Wave equation

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William Henry Ward was issued {{US patent|126356}} on April 30, 1872. Mahlon Loomis was issued {{US patent|129971}} on July 30, 1872. 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.

Related Topics:
William Henry Ward - April 30 - 1872 - Mahlon Loomis - July 30 - Landell de Moura - Nathan Stubblefield - Induction - Radio transmission

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Wireless age

In 1893 in St. Louis, Missouri, Tesla made the first public demonstration of radio communication.

Related Topics:
1893 - St. Louis - Missouri

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Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of radio communication. http://www.ieee-virtual-museum.org/collection/people.php?taid=&id=1234597&lid=1 The apparatus that he used contained all the elements that were incorporated into radio systems before the development of the vacuum tube. He initially used magnetic receivers, unlike the coherers used by Marconi and other early experimenters. http://www.teslasociety.com/teslarec.pdf

Related Topics:
Franklin Institute - Philadelphia - National Electric Light Association - Vacuum tube

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On 19 August 1894, British physicist Sir Oliver Lodge demonstrated the reception of Morse code signalling using radio waves using a detecting device called a coherer, a tube filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884. Edouard Branly of France and Popov of Russia later produced improved versions of the coherer. Popov, who was the first to develop a practical communication system based on the coherer, is usually considered by his own countrymen to have been the inventor of radio. The Indian physicist, Jagdish Chandra Bose, demonstrated publicly the use of radio waves in November of 1894 in Calcutta, but he was not interested in patenting his work.http://www.ieee-virtual-museum.org/collection/people.php?taid=&id=1234735&lid=1

Related Topics:
19 August - 1894 - Oliver Lodge - Iron - Temistocle Calzecchi-Onesti - 1884 - Edouard Branly - Jagdish Chandra Bose - Calcutta

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In 1896 Marconi was awarded what is sometimes recognised as the world's first patent for radio with British Patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for. In 1897 he established the world's first radio station on the Isle of Wight, England. The same year in the U.S., some key developments in radio's early history were created and patented by Tesla. 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. Some believe this was made for financial reasons, allowing the U.S. government to avoid having to pay the royalties that were being claimed by Tesla for use of his patents.

Related Topics:
1896 - British - Patent - 1897 - Isle of Wight - England - U.S. Patent Office - 1904 - Thomas Edison - Andrew Carnegie

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In 1909, Marconi, with Karl Ferdinand Braun, was also awarded the Nobel Prize in Physics for "contributions to the development of wireless telegraphy". However, Tesla's patent (number 645576) was reinstated in 1943 by the U.S. Supreme Court, shortly after his death. This decision was based on the fact that prior art existed before the establishment of Marconi's patent. Some believe the decision was also made for financial reasons, to allow the U.S. government to avoid having to pay damages that were being claimed by the Marconi Company for use of its patents during World War I.

Related Topics:
1909 - Karl Ferdinand Braun - Nobel Prize in Physics - Tesla's patent - 1943 - U.S. Supreme Court - World War I

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"Wireless" factories and vacuum tubes

Marconi opened the world's first "wireless" factory in Hall Street, Chelmsford, England in 1898, employing around 50 people. Around 1900, Tesla opened the Wardenclyffe Tower facility and advertised services. By 1903, the tower structure neared completion. Various theories exist on how Tesla intended to achieve the goals of this wireless system (reportedly, a 200 kW system). Tesla claimed that Wardenclyffe, as part of a World System of transmitters, would have allowed secure multichannel transceiving of information, universal navigation, time synchronization, and a global location system.

Related Topics:
Chelmsford, England - 1898 - 1900 - Wardenclyffe Tower - 1903

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The next great invention was the vacuum tube detector, invented by a team of Westinghouse engineers. On Christmas Eve, 1906, Reginald Fessenden (using his heterodyne principle) transmitted the first radio audio broadcast in history from Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible. The world's first radio news program was broadcast August 31, 1920 by station 8MK in Detroit, Michigan. The world's first regular wireless broadcasts for entertainment commenced in 1922 from the Marconi Research Centre at Writtle near Chelmsford, England.

Related Topics:
Vacuum tube - Westinghouse - Christmas Eve - 1906 - Reginald Fessenden - Heterodyne principle - Brant Rock, Massachusetts - O Holy Night - Violin - Bible - August 31 - 1920 - Detroit, Michigan - 1922 - Marconi - Writtle - Chelmsford, England

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20th century

Developments in the early 20th century (1900-1959):

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• Aircraft used commercial AM radio stations for navigation. This continued through the early 1960s when VOR systems finally became widespread (though AM stations are still marked on U.S. aviation charts).
• In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes.
• Radio was used to transmit pictures visible as television as early as the 1920s. Standard analog transmissions started in North America and Europe in the 1940s.
• In 1954, Regency introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5V Battery".

Developments in the latter half of the 20th century (1960-1999):

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• In 1960, Sony introduced their first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was durable, because there were no tubes to burn out. Over the next twenty years, transistors displaced tubes almost completely except for very high power, or very high frequency, uses.
• In 1963 color television was commercially transmitted, and the first (radio) communication satellite, TELSTAR, was launched.
• In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links.
• In the 1970s, LORAN became the premier radio navigation system. Soon, the U.S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987.
• In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software radio that could become a different radio on the fly by changing software.
• Digital transmissions began to be applied to broadcasting in the late 1990s.