RADIO
Radio is the wireless 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. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency. 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 word 'radio' is used to describe this phenomenon, and television and radio transmissions are classed as radio frequency emissions.
Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency. 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 word 'radio' is used to describe this phenomenon, and television and radio transmissions are classed as radio frequency emissions.
Originally, radio or radioteleography 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 American term was then adopted by other languages in Europe and Asia, although British Commonwealth countries retained the term 'wireless' until the mid-20th century. In Japanese, the term 'wireless' is the basis for the term 'radio wave' although the term for the device that listens to radio waves is literally 'device for receiving sounds'.
In recent years the term 'wireless' has gained renewed popularity through the rapid growth of short range networking, e.g. WLAN ('Wireless Local Area Network'),WiFi, 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.
In recent years the term 'wireless' has gained renewed popularity through the rapid growth of short range networking, e.g. WLAN ('Wireless Local Area Network'),WiFi, 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.
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. The controversy over who invented the radio, with the benefit of hindsight, can be broken down as follows:
In 1878, David E. Hughes transmitted Morse code by radio at and below the super low frequency range (via a clockwork transmitter).
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. He obtained a U.S. patent for the invention of the radio, as defined as "wireless transmission of data."
Between 1893 and 1894, Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments. He did not publicise his achievement until 1900 but later obtained Brazilian and American patents.
Alexander Stepanovich Popov, in 1894, built his first radio receiver, which contained a coherer. Further refined as a lightning detector, he presented it to the Russian Physical and Chemical Society on May 7, 1895.
Guglielmo Marconi was an early radio experimenter. He realised the first long distance transmissions and founded the first commercial organisation devoted to the development and use of radio
Reginald Fessenden and Lee de Forest 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).
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 1878, David E. Hughes transmitted Morse code by radio at and below the super low frequency range (via a clockwork transmitter).
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. He obtained a U.S. patent for the invention of the radio, as defined as "wireless transmission of data."
Between 1893 and 1894, Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments. He did not publicise his achievement until 1900 but later obtained Brazilian and American patents.
Alexander Stepanovich Popov, in 1894, built his first radio receiver, which contained a coherer. Further refined as a lightning detector, he presented it to the Russian Physical and Chemical Society on May 7, 1895.
Guglielmo Marconi was an early radio experimenter. He realised the first long distance transmissions and founded the first commercial organisation devoted to the development and use of radio
Reginald Fessenden and Lee de Forest 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).
Edwin H. Armstrong invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics.
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