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| | Radio (from Latin: — radiate, emit beams, radius — ray) is a technology of wireless transfer of information by means of electromagnetic waves of radio frequency band.
History and invention of radio:
During a lecture, Nicola Tesla demonstrates the principles of radio communication, 1891. Traditionally, Italian engineer Guglielmo Marconi (1896) is considered as the creator of first successful information exchange system with the help of radio waves (radio telegraphy. As in the case of majority of authors of massive inventions, predecessors existed even for Marconi. In Russia, A.S. Popov is considered as the “inventor of radio”, who had built a radio receiver in 1895. In USA, Nicola Tesla is considered as inventor of radio \, who patented his radio transmitter in 1893 and receiver in 1895; Priority of Tesla before Marconi was acknowledged in judicial order in 1943. In France, for a long time, Edouard Branly, who invented coherer (1890), was considered as the inventor of wireless telegraphy. First inventor of methods of transmission and reception of electromagnetic waves (which, for long time, were called “Hertzian Waves”) is their pioneer, German scientist Heinrich Hertz (1888).
Radio communication —form of communication, which uses radio waves, easily propagated in space, as signal carrier.
Working principle:
Transmission takes place in the following manner: The transmitting signal is modulated into more high frequency oscillation (carrier) at the transmitting side. Thus obtained modulated signal is radiated by antenna into space. At the reception side, radio waves catch the modulated signal in antenna and then, the received modulated signal is demodulated. After demodulation, the obtained signal has certain (possibly permissible) differences with the signal, which was transmitted through transmitter.
Propagation of radio waves from source to the receiver can take place in several routes simultaneously. Such propagation is called “Multi path propagation”. Fading may occur due to multi path propagation and changes in parameters of medium. Fading is change in levels of received signal. During multi-path propagation, change in signal level takes place due to interference i.e at reception point, electromagnetic field represents sum of radio-waves of one and the same signal, displaced in time.
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