HISTORY OF THE RADIO

With the telegraph and telephone, and the man could communicate over long distances, even across the seas through undersea cables, but only between the points where these cables were arriving. But there remained incommunicado ships, vehicles, sparsely populated, and so on. Overcoming these difficulties became possible with a series of discoveries: During the development of electricity, had appeared several theories to explain many kinds of electrical phenomena, is creia the principle that the action happened electrical distance on the various bodies so that we can experience. But the discovery of electric current caused any doubt that mysterious action. Faraday did not believe in this action adistancia, and in 1835, writing on a form perfected battery Voltaic, noted that the current spreading as if there were discrete particles of electricity. The ideas of Faraday did not fall into oblivion and his compatriot Maxwell picked up the thirty years later, to translate them into mathematical language, making them the most momentous consequences. James Clerk Maxwell in 1867 presented his theory electromagnetic (electric and magnetic) to the Royal Society of London. This theory, obtained by pure mathematical calculation, predicted the possibility of creating and spreading electromagnetic waves in space. These waves are propagated in space at a speed of 300 thousand kilometres per second. The first attempts to confirm this theory were made by Professor Fitzgerald, of Dublin, but did not give practical results until the German physicist Hertz, who was unaware of investigations Fitzgerald, undertook the same task. The German Heinrich Hertz in 1887, experimentally confirmed the theory Maxwel, studying radio and electromagnetic waves with its oscillator and a resonator, the first wireless transmission, which since then was named in his honor relay. This experiment served to confirm Maxwell's ideas and left the possibility of producing electric waves from a distance and capture through a suitable apparatus. It was therefore the first attempt radio through electromagnetic waves, and the first practical outcome of which was to germinate whole series of experiments. The discovery of Hertz, but revealed the existence of electromagnetic waves and their properties to PARC of light waves, thus confirming the theory brilliantly Maxwell, had no immediate practical results, because the resonator, which revealed the presence of waves , Could only operate at very short distance from the device that produces. In 1884 Calzecchi Onesti discovered the electrical conductivity taking the iron filings in the presence of electromagnetic waves, or the relay The French Branly, in 1890, built his primitive choesor (cohesor), which allowed verify the presence of radio waves, that is to detect, and that would be used by all researchers then wanted the wireless communication (wirelessly). The cohesor Branly consists of a glass tube within which iron filings are somewhat tight, between two metal poles that communicate with an electric battery. The resistance of the filings is too high for passing the flow of the stack, but in the presence of a wave that terrestrial conductivity and increases the flow passing through the device can be felt by electric sound a buzzer. With the device could Branly captured the relay at distances much more significant than the resonator Hertz, but, anyway, could not be obtained yet practical applications. The Russian Popov believed found in the pipe Branly a device sensitive to reveal the progress of storms, electric shocks because of the clouds cause the formation of tempestuous waves, can be revealed by the cohesor. The Russian Popov (1859-1905) found the best system to radiate (send) and capture the airwaves: the antenna, consisting of wire. After perfecting this device, Popov added to the system receiving a wire spread vertically, so that when elevated in the atmosphere, might better capture the power swings. This thread was joined by one end to one of the poles of cohesor, while the other end communicating with soil and thus any potential difference was established between those poles, caused by the passage of an electromagnetic wave from the clouds tempestuous, had sounded the bell of the apparatus, which more or less frequent repiqueteo gave idea of the progress of the storm. Thus was born the first antenna, so named because, to sustain the wire devised by Popov, had used a support resembling the antennae or masts of ships. On March 24, 1896 performed the first wireless communication signals. These first transmissions were made up of simple impulses, obtained by powerful electric shock power stored in capacitors or bottles of Leyden. A spiral wire driver, located a few metres from the discharge, producing a discharge between their lower open ends. The oscillator Hertz, the detector Branly and antenna Popov were therefore the three elements essential to establish a radio system, but it was also necessary to provide a package that could be operated safely for commercial applications. Nobody had been able to achieve this, until in 1895 Marconi conducted experiments that provided the final title of the inventor of radio. This phenomenon began to show that electrical resonance was studied by Marconi, which in Bologna (Italy) in 1896 and only 20 years old got his first practical reported. Using a wire or vertical "antenna" instead of rings and cut using a "sensor" or equipment which allowed discover very weak signals, soon succeeded in establishing communication distances up to 2400 m. Was gradually increasing the scope of its transmissions, until in 1896 and asked obtubo the first patent for a system of wireless telegraphy. Guillermo Marconi at the time of his first experiments and its primitive emitting sparks. The wavelength used was located over 200 meters, which forced to use antennas colossal dimensions. The receiver based its operation in the so-called cohesor. Brandley and Lodge were two of its major improvement. In essence, the cohesor consisted of a glass tube filled with iron filings, which in the presence of a high frequency signal from the antenna, became conductor and allowed the passage of a stream that shareholders a ringer. When the flow disappeared cohesor continued driving, so it should be given a blow for the disabled. These details give an idea of the difficulties that researchers were then. One of the receptors used by Marconi, we can appreciate the "antenna", "cohesor", "headset" and batteries. In 1897, English O.J. Lodge invented the ratings system, which allows to use the same receiver to receive different broadcasts. In 1897, using a transmitter formed by an induction coil and raising large transmitting and receiving antennas with the help of kites (comets), increased the scope of the team to 14.5 km. It also showed that transmission could be over the sea, establishing communication between two boats of the Italian Navy, at distances of 19 km above the figure gives an idea of your receiver. The first radio contact took place in France in 1898 between the Eiffel Tower and the Pantheon (4 km.) In Paris. In 1899 again the researcher and inventor Guillermo Marconi managed to send a message by radio through the English Channel linking Dover with Wimereux (46 km.). In this year 1899, which occurred the first demonstration of the value of radio communications to give more security to travel at sea when the ship's crew RF Mathews "was saved after boat collision with a lighthouse, thanks to call for help by radio. Transmitting antenna installed by Marconi in Poldhu But in reality it can be said that the Era of wireless telegraphy began a raw day, December 12, 1901, at 12:30 pm and after raising the receiving antenna with balloons and kites up to 120 meters. tall, in some abandoned barracks in St. John's (Canada) where Marconi helped by Srs. Paget and Kemp, managed to capture a series of three points, the letter S Morse code, a signal that just walk the 3,600 miles separating Marconi (Poldhu) Cornwall, Great Britain (England). This signal was the culmination of many years of experimentation. After the incident transatlantic Marconi in 1901, in the United States is experiencing a rapid development in the self-testing equipment and TSF (wireless telegraphy). By the year of 1900 began to use the crystal detectors to detect Galena replacing cohesor Branly, the galena was much more sensible, but still unstable. The detector crystal galena, allows electrical flow into one direction, forerunner of semiconductors. In 1904, English J.A. Fleming contributed to radio the first type of vacuum valve, diode, which apart from allowing other applications to replace the cumbersome advantage galena detector, which continued to use it in small receivers until the fifties. Fleming valve used as a detector With the invention in 1905 of the lamp Triode (also called "audion") by the American-Lee De Forest, and could amplify electrical signals used in radio and generating waves that were not sparks as hitherto. Valve "Audio" invented by De Forest in 1905 With tensions of only a few hundred volts was possible to obtain a sign of continued and sustained transmission, which quickly quashed transmitters sparks. But indeed, the continuous signal was easily modulated by microphones coal, the type that are still commonly used in phones today, and allowed the transmission of voice. It was this same Dr. Lee DeForest which launched the first radio broadcasts of music and voice, using the bulb of his invention to generate electromagnetic waves, rather than sparks. Its transmissions from his home in California were rather experimental until finally, in 1920, the Westinhouse Electric and Manufacturing Co.., Established in Pittsburgh the first commercial station radiofusora: the well-known "KDKA." That the radio gave way to radiotelephony, which would have a huge field of possibilities to the great human adventure in communications.