2008-08-04T05:12:00.000-07:00

Radio is the transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, or phase. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.

The meaning and usage of the word "radio" has developed in parallel with developments within the field and can be seen to have three distinct phases: electromagnetic waves and experimentation; wireless communication and technical development; and radio broadcasting and commercialization. Many, many individuals -- inventors, engineers, developers, businessmen -- contributed to produce the modern idea of radio and thus the origins and 'invention' are multiple and controversial.

James Clerk Maxwell, a Scottish scientist, developed the theoretical basis for explaining electromagnetism. He predicted that electric and magnetic fields can couple together to form electromagnetic waves. Heinrich Hertz, a German scientist, is credited with being the first to produce and detect such waves at radio frequencies, in 1888, using a sparkgap transmitter in the Ultra High Frequency range.

In 1893, Nikola Tesla, in America, first demonstrated the principles of wireless communications. Tesla would later ultimately hold the patent rights in the United States. Ignoring prior art, some have suggested that the U.S. Supreme Court was influenced in its decision by the fact that the Marconi Company was suing the United States Government for use of its patents in World War I at the time. Physicists and inventors such as John Stone Stone and Alexander Stepanovich Popov have cited Tesla as the originator of wireless communications.In August 1894, Oliver Lodge, an English physicist and writer, transmitted radio signals at a meeting of the British Association for the Advancement of Science at the University of Oxford. In 1895, Guglielmo Marconi, an Italian inventor, began experimenting with wireless and went on to develop the world's first commercial system of radio communication. In 1896, Marconi was granted the the world's first wireless telegraphy patent by the British Patent Office. Marconi has been generally credited with the development of radio by most scholars and historians. In 1909, Marconi was jointly awarded the Nobel Prize for Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy." In 1943 the U.S. Supreme Court overturned Marconi's wireless patents and granted patent ownership to Nikola Tesla

Amateur radio station with multiple receivers and transceivers

Originally, radio or radiotelegraphy was called "wireless telegraphy", which was shortened to "wireless". The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, coined by the French physicist Edouard Branly in 1897 and based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray"). "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 term was then adopted by other languages in Europe and Asia, although British Commonwealth countries continued to use the term "wireless" until the mid-20th century.

In recent years the term "wireless" has gained renewed popularity through the rapid growth of short-range computer networking, e.g., Wireless Local Area Network (WLAN), WiFi and Bluetooth, as well as mobile telephony, e.g., GSM and UMTS. Today, the term "radio" often refers to the actual transceiver device or chip, whereas "wireless" refers to the system and/or method used for radio communication, hence one talks about radio transceivers and Radio Frequency Identification (RFID), but about wireless devices and wireless sensor networks.

Although the invention of radio was long attributed to Guglielmo Marconi, the identity of the original inventor of radio (at the time called wireless telegraphy) is contentious. Development from a laboratory demonstration to commercial utility spanned several decades and required the efforts of many practitioners. In 1943 Tesla was granted the patent for the invention of radio when the U.S. Supreme Court overturned many of Marconi's radio patents.

Other significant contributions include:

In 1887, David E. Hughes transmitted signals by radio using a clockwork-keyed Spark Transmitter, achieving a range of approximately 500 metres.
In 1888, Heinrich Hertz produced and measured the Ultra High Frequency range (via a sparkgap transmitter).
In 1891, Nikola Tesla began wireless research. He developed means to reliably produce radio frequencies, publicly demonstrated the principles of radio, and transmitted long-distance signals.
Between 1893 and 1894, Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments. He did not publicise his achievement (publicly broadcasting human voice) until 1900 but later obtained a Brazilian patent.
In 1894 in Kolkata (Calcutta), Sir Jagdish Chandra Bose (J. C. Bose) invented the mercury coherer, together with the telephone receiver.
Alexander Stepanovich Popov, in 1894, built his first radio receiver, which contained a coherer, although in actuality the coherer was first invented by Edouard Branly. Popov demonstrated the coherer, further refined as a lightning detector, to the Russian Physical and Chemical Society on May 7, 1895.
In 1894, Guglielmo Marconi read about Hertz's and Tesla's work on wireless telegraphy, and began his own experiments.
In August 1894, Oliver Lodge, an English physicist and writer, transmitted radio signals at a meeting of the British Association for the Advancement of Science at the University of Oxford.
Late 1896 to early 1897, Tesla received wireless signals transmitted from the Houston Street lab in New York City to West Point, "a distance of about 30 miles."
In March 1897 Marconi transmitted wireless telegraphy signals over a distance of two miles on Salisbury Plains, followed in May 1897 by a test over water between Lavernock and Flat Holm in the Bristol Channel, a distance of just over three miles. He then moved the receiving equipment to Brean Down Fort and extended the range to just under ten miles.
In December of 1901 Guglielmo Marconi received the first transatlantic radio communication over a distance of 2,000 miles (3,200 km) from Poldhu, UK, to St. Johns, Newfoundland. Marconi was celebrated worldwide for this achievement. Soon after the patent was given to Marconi. He later received the Nobel Prize.
In early 1900s Canadian engineer-inventor Reginald Fessenden _[1] and American engineer Lee de Forest invented amplitude-modulated (AM) radio, allowing an audio signal to be sent over the air.
In 1935 Edwin H. Armstrong invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics.
In 1943, the U.S. Supreme Court acknowledged that Marconi's work wasn't original because he had used 17 of Tesla's patents to accomplish his broadcasts, and the patent ownership is given back to Nikola Tesla. However, Tesla died shortly before the decision was announced.