10, February 2017

History of Radio and Communication Systems

A radio communication system sends radio signals. The types of deployed radio systems depend on technology, standards, regulations, allocation of radio spectrum, user needs, positioning service and investment.
The radio equipment involved in the communication systems comprises a transmitter and a receiver each having an antenna and the appropriate terminal equipment, such as a microphone on the transmitter and a loudspeaker in the receiver in the case of a system Voice communication. The power consumed in a transmitting station varies as a function of the communication and transmission distance conditions. The power received at the receiving station is usually only a small fraction of the output of the transmitter, since the communication depends on the reception of information, not on the energy that has been transmitted.
Conventional radio systems using frequency multiplexing (FDM) as a strategy for dividing and sharing the bandwidth of available radio frequencies for simultaneous communications of different parties. Modern radio communication systems include those that divide a Time Division Multiplexing (TDM) and Multiplexing Code Division (MDP) frequency band as an alternative to the conventional FDM strategy. These systems offer different advantages in support of multiple users, beyond the FDM strategy that was ideal for broadcasting, but less for applications such as mobile phones.
A radio communication system can send information one way. For example, broadcasting a single transmitter sends signals to several receivers. Two stations can take turns sending and receiving, using a single radio frequency; This is called “simplex”. Using two radio frequencies, two stations can continuously and simultaneously send and receive signals – this operation is called “duplex”.
In 1864, James Clerk Maxwell mathematically showed that electromagnetic waves can propagate through space. The effects of electromagnetic waves (previously unexplained “remote action”) were observed before and after Maxwell’s work by many inventors and experimenters, including Luigi Galvani (1791), Peter Samuel Munk (1835), Joseph Henry (1842) ), Edwin Houston, Elihu Thomson, Thomas Edison (1875) and David Edward Hughes (1878) Edison gave the effect called “etheric force” and Hughes sparkled a pulse up to 500 yards (460 m) with a portable receiver, but nobody could identify what caused the phenomenon and usually thrown as electromagnetic induction.In 1886, Heinrich Hertz noticed the same phenomenon of sparks and in published experiments (1887- 1888), was able to demonstrate the existence of electromagnetic waves in an experiment confirming Maxwell’s theory of electromagnetism.
The discovery of these “waves” (radio waves) has caused many physicist experiments. A conference of August 1894, the British physicist Oliver Lodge, where he transmitted and received “waves” at distances up to 50 meters, was followed a year later with experiments Indian physicist Jagadish Bose microwave radio Optical and construction of a radio-based detector Russian physicist Alexander Stepanovich Popov. From the end of 1894, Guglielmo Marconi began to pursue the idea of ​​building a wireless telegraph system based on hertzian (radio) waves. Marconi won a patent on the system in 1896 and developed into a commercial communication system in the coming years.
Radio systems early twentieth century transmitted messages only by continuous wave code. The first attempts to develop an amplitude modulation system for voice and music were demonstrated in 1900 and 1906, but had little success. The First World War accelerated the development of radio for military communications, and this was the first vacuum tubes were applied to radio transmitters and receivers. Electronic amplification was an important development in modifying the radius of an experimental experimental apparatus experts. After the war, commercial broadcasting began in the 1920s and became an important medium for entertainment and information media. The Second World War accelerated the development of the new radio for the purpose of warplanes and ground communication, navigation and radar. After the war, the experiences on television that had been interrupted resumed, and also became an important means of home entertainment.

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