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