|
Guglielmo marconi
Following shortly after Heinrich Hertz's physics lab demonstrations, Marconi developed what is generally recognized as the first practical "generator" of radio waves in Italy in 1895. (There are several conflicting claims of primacy, including one for a Russian named Aleksander Stepanovich Popov in the same year.) Because the Italian government declined to back his efforts, Marconi moved to England.
During the 1895 to 1901 period, Marconi worked on improving his new "wireless telegraph," attempting to sell it to the British Navy. Also attempting to sell his development to the British Post Office, Marconi demonstrated transmission over several miles in 1897.
Marconi transmitted the results of the International Ocean Yacht Races off Sandy Hook, NJ to the New York Herald Tribune in October, 1899. He finally received British patent 12,039 on July 2, 1897 for "Improvements in Transmitting Electrical Impulses and Signals and in Apparatus therefor." Patent 7,777 (issued April 16, 1900) covered a selective tuning device to resonate the antenna circuit of a spark transmitter.
The first transatlantic transmissions were attempted from a two tower circular array at Poldhu, England. The wooden towers were each 200 feet (61 meters). Transmission was approximately 500 meters or 600 kHz with an input power to a spark transmitter of around 18 kilowatts. Originally, 20 towers were built into the array, however, the towers were toppled by storms in November 1901, and the two replacement towers were hastily built for the transatlantic transmission. (Later, they were replaced with four permanent towers.)
Reception of the letter "S," three dots, was reported by Marconi on December 12, 1901, at Signal Hill, St. Johns, Newfoundland. The transmitter was manned by John Ambrose Fleming, professor of University College in London, later to invent the diode vacuum tube.
In 1909 Marconi shared the Nobel Prize awarded for the field of Physics.
|
