1.HISTORY
Discovery of electromagnetic waves [edit] The theoretical basis of propagation of electromagnetic waves were first described by James Clerk Maxwell in a document addressed to the Royal Society entitled A dynamic theory of electromagnetic field, which described his work between the years 1861 and 1865. Heinrich Hertz, between 1886 and 1888, was the first to experimentally validate the theory of Maxwell, proving that radiation had all the radio wave properties and discovering that the electromagnetic equations could be reformulated into a partial differential equation called equation wave. Hertz took a giant step in affirming that the waves were propagated at a speed electromagnetic similar to the speed of light, and put together the groundwork for sending the first signal. As a tribute to Hertz by this discovery, electromagnetic waves became known as terrestrial. These scientists had the technical basis for the radio to succeed, since the propagation of electromagnetic waves was essential to develop which subsequently has become a major mass media.
2.First transmission by radio
It is difficult to attribute the invention of radio, in its time called "wireless telegraphy", a single person. In different countries acknowledges paternity in key local Stepanovich Alexander Popov made his first demonstrations in St. Petersburg, Russia; Nikola Tesla in St. Louis, Missouri, United States and Guillermo Marconi who was first implemented and marketed the invention from the Kingdom Unido. In 1896, Marconi won the world's first patent on radio, British Patent 12039, improvements in the transmission of electrical impulses and signals and an apparatus for doing so. Countries like France and Russia refused to recognize its patent for that invention, referring to the publications of Popov, prior in time. On May 7, 1895 the Russian professor and engineer Alexander Stepanovich Popov had submitted a receiver capable of detecting electromagnetic waves. Ten months later, on March 24, 1896, and with a complete system of receipt-issuing telegraph messages, sent the first telegraph message between two buildings at the University of St. Petersburg located at a distance of 250 m. The text of this first telegraph message was: "Heinrich Hertz." In 1897 Marconi mounted the first radio station in the world in the Isle of Wight in southern England and in 1898 opened the first factory in the world of wireless transmission equipment in Hall Street (Chelmsford, UK) using it around 50. In 1899 Marconi managed to establish a character telegraphic communication between Britain and France. Only two years later, in 1901, this would be achieved as a minutiae for the first time to transmit signals across the ocean Atlanta. Nikola Tesla, in St. Louis (Missouri, USA), made his first public demonstration of radio in 1893. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association described and demonstrated in detail the principles of radio. Its appliances already contained all the elements that were used in radio systems to the development of vacuum tubes. In the U.S., some key developments in the early history of radio were created and patented in 1897 by Tesla. However, the Patent Office of the United States reversed its decision in 1904 and awarded to Marconi a patent for the invention of radio, possibly influenced by the financial sponsors of Marconi in the United States, among them Thomas Edison and Andrew Carnegie. On December 12, 1901, Marconi transmitted for the first time Morse signals by electromagnetic waves.
3.developed during the twentieth century
In 1906, Alexander Lee of Forest improved the invention of John Fleming, with its Triode giving greater coverage and quality of transmission, allowing the proliferation of radio broadcasts. In 1907, invented the valve that modulates the radio waves that are received and thus created waves in the high-power transmission. In 1909 Marconi, with Karl Ferdinand Braun, was also awarded the Nobel Prize in Physics for their "contributions to the development of wireless telegraphy." However, Tesla's patent number 645576 was restored in 1943 by the U.S. Supreme Court, shortly after his death because of a coronary thrombosis. The decision was based on the fact that there was a pre-existing work before the establishment of Marconi's patent. There is a belief that this was done apparently for financial reasons, to allow the U.S. government avoid paying damages being claimed by the Marconi company for using its patents during the First World War. He also made claims in the sense that Nathan Stubblefield invented the radio before Tesla and Marconi, but his device, apparently operated by transmitting induction rather than radio transmission. The great new invention was the vacuum tube detector, invented by a team of engineers from Westinghouse. The Christmas Eve of 1906, using the heterodyne principle, Reginald Fessenden from Brant Rock transmitted Station (Massachusetts) the first audio broadcasting history. Thus, ships at sea could hear a broadcast that included Fessenden playing the violin singing O Holy Night and reading a passage from the Bible. A big step in the quality of receivers, occurs in 1918 when Edwin Armstrong invented the Super. The first broadcast transmissions, for entertainment, began in 1920 in Argentina. On August 27 from the roof of the Coliseum Theater, Radio Argentina transmitted Society of Richard Wagner's opera, Parsifal. Starting well with the programming of the first radio station broadcasting in the world.
4.Outstanding dates
1873. The Scottish physicist James Clerk Maxwell gets the general equations of propagation of electromagnetic waves. 1887. The German physicist Heinrich Hertz manages to prove the existence of electromagnetic waves. In addition, he discovered the photoelectric effect through a downloader or resonator. 1890. The French physicist Edouard Branly invents a device that receives signals telegraphy without using wires. 1896. The Russian Alexander Popov engineer invents the first radio antenna. He also built the first recipient of electromagnetic waves. 1908. In California takes place the first radio broadcast of a private nature of the hands of CH.D.Herrold, who farmers of the State. 1914-1918. The use of radio as a communicative beginning to be used between the armies during the First World War. The usefulness of this medium lies in its strategic value of wireless communication and serves to maintain the confidentiality of communications. 1920. first broadcast transmissions for entertainment. This happens on August 27 from the terrace of the Coliseum Theatre de la Ciudad de Buenos Aires.El project was headed by Dr. Enrique Telémaco Susini and its three partners: Cesar Guerrico, Luis Romero Carranza and Miguel Mujica, then known as' The Follies of the roof. " It starts operating in the U.S. city of the KDKA Pittsburgh, known for being the first radio station that broadcasts a continuous and regular programming. 1922. The French Maurice Vinot emits from Paris early newsletters with news and sports. This is possible thanks to the station and Radiola news agency Havas.
