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The invention of radio - The result of work by a number of scientists, engineers, and inventors.
The invention of the radio not only involved a number of inventors, engineers, and even companies, but it also was developed about the same time and was somewhat intertwined with the development of the telegraph and the telephone.
Important developments that preceded radio
Heinrich Rudolf Hertz was the experimental physicist to confirm Maxwell's work in the laboratory. Hertz did not devise a system for actual He showed that radio radiation had all the properties of electromagnetic radiation and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. Hertz's setup was a primitive radio system capable of transmitting and receiving radio waves through free space.
For a radio transmitter Hertz used a dipole antenna, and a high-voltage electrical capacitive spark discharge. His detector in some experiments was another dipole antenna connected to a narrow spark gap. A small spark in this gap signified detection of the radio waves.
When he added cylindrical reflectors behind his dipole antennas, Hertz could detect radio waves about 20 meters from the transmitter. He did not try to transmit further because he wanted to prove Electromagnetism/electromagnetic theory, not to develop the invention of the radio. In fact, Hertz stated that "It's of no use whatsoever... this is just an experiment that proves Maestro Maxwell was right - we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there."
The father of wireless telegraphy, Nikola Tesla, was one of the first to patent a means to reliably produce radio waves. Tesla used his high voltage resonance transformer, the Tesla coil, in radio-wave propagation experiments. The antenna consisted of a top-loaded electrical conductor that was connected to a high-voltage terminal of the transformer. The opposing high-voltage terminal was grounded.
Between 1895 and 1899, Tesla claimed to have received wireless signals transmitted over long distances although there is no independent evidence to support this. After 1896, the transmitter consisted of an RF alternator and produced undamped (or continuous) waves in the neighborhood of 50,000 Hertz. The receiver consisted of a powerful electromagnet, two large condensers, and a taut steel wire. The wire was placed within the magnetic field, and in conjunction with the condensers formed a tuned circuit. Nikola Tesla was issued a number of patents dealing with the transmission of energy through the air and mentioned sending messages the same way.
Alexander Stepanovich Popov
Beginning in the early 1890s, Alexander Stepanovich Popov conducted experiments similar to the work of Hertz's. In 1894 he built his first radio receiver. Further refined as a lightning detector, he presented it to the Russian Physical and Chemical Society on May 7, 1895, and the day has been celebrated in the Russian Federation as "Radio Day". The paper on his findings was published the same year (December 15 1895). Popov had recorded, at the end of 1895, that he was hoping for distant signaling with radio waves.
In 1900 a radio station was established under Popov's instructions on Hogland island (Suursaari) to provide two-way communication by wireless telegraphy between the island and the battleship General-Admiral Apraksin. By February 5 messages were being received reliably.
Guglielmo Marconi, was an Italian-Irish electrical engineer known for the development of a practical wireless telegraphy system. Marconi, who has been called the father of radio, is said to have read about the experiments that Hertz did and about Tesla's work while vacationing in 1894. It was at this time that Marconi began to understand that radio waves could be used for wireless communications.
Initially Marconi used a transmitter to ring a bell in a receiver in his laboratory. He then replaced Hertz's vertical dipole with a vertical wire topped by a metal sheet, with an opposing terminal connected to the ground. For a receiver, Marconi used a spark gap with a metal powder coherer, a detector developed by Edouard Branly and other experimenters. Marconi was successful in transmitting radio signals for about a mile by 1895.
In 1902, Marconi transmitted from his station in Glace Bay, Nova Scotia, Canada, across the Atlantic and on 18 January 1903 a Marconi station built near Wellfleet, Massachusetts in 1901 sent a message of greetings from Theodore Roosevelt, the President of the United States, to King Edward VII of the United Kingdom, marking the first transatlantic radio transmission originating in the United States.
Marconi would later found the Marconi Company and would receive the 1909 Nobel Prize in Physics jointly with Karl Ferdinand Braun.
Marconi's reputation is based on his accomplishments in radio communications and commercializing practical systems. He demonstrated of the use of radio for wireless communications, providing ships wireless communications saving lives, established the first transatlantic radio service, and built the first stations for the British short wave service.
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