Sunday, June 7, 2009

History of Wireless Telegraphy

Gugliemo Marconi

Many scientists have made contributions to the practical aspects of wireless radio broadcasting. In the 1860s the British scientist James Clerk Maxwell predicted the possibility of generating electromagnetic waves that would travel at the speed of light. Twenty years later the German physicist Heinrich Hertz demonstrated this radiation (hence the word radio). He found that when he generated sparks between two metal balls they could be found by a metal loop with a gap in it. Smaller sparks were seen jumping across this gap. Later experimenters managed to increase the distance across which Hertzian waves could be transmitted, and in 1894 a British scientist, Oliver Lodge, sent Morse-code signals over a distance of half a mile.

In 1895 the Russian physicist, Aleksandr Stepanovich Popov, built a receiver to detect electromagnetism in the atmosphere and he predicted that it might be used to pick up generated signals. The next year he arranged a demonstration in the University of St Petersburg where messages were sent and received between different points.

Meanwhile, electromagnetism work was being carried out independently in Italy by a young scientist, Guglielmo Marconi. He was the son of a wealthy Italian landowner and an Irish mother. Marconi was educated at the Technical Institute of Livorno and attended the University of Bologna. In 1890 he began experimenting with wireless telegraphy. The apparatus he used was based on the ideas of the German physicist, Heinrich Hertz. Marconi improved Hertz's design by earthing the transmitter and receiver, and found that an insulated aerial enabled him to increase the distance of transmission.

After patenting his wireless telegraphy system in 1896 he established the Marconi's Wireless Telegraph Company in London. In 1898 Marconi successfully transmitted signals across the English Channel and in 1901 established communication with St. John's, Newfoundland, from Poldhu in Cornwall.

The first wireless transmission was made in 1892 by William Preece. Marconi, disappointed by a lack of support from the Italian government, decided to move to London. During his early work he also found out that the radio waves could be reflected into narrow beams by using sheets of metal sheets around the antenna. Marconi had an Irish cousin who helped him take out his first patent. As a result of the interest of the British Post Office he improved the system and was able to send a signal nine miles across the Bristol Channel. Marconi was now making great progress with his work and was able to communicate with a French wireless station that was some 31 miles across the English Channel. I n 1901 Marconi established communication with St. John's, Newfoundland, from Poldhu in Cornwall.

Marconi's system was adopted by the Royal Navy. During the First World War wireless telepathy was widely employed by wartime ground forces. Large naval vessels were fitted with radios, although when they were used, it did make it easier for enemy submarines to discover where they were. Reconnaissance aircraft that had enough power to carry wireless sets (they weighed 50kg) were able to communicate the position of enemy artillery.

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