Guglielmo Marconi


Guglielmo Marconi
(1874 - 1937)


Italian physicist and inventor of a successful system of radio telegraphy (1896). In 1909 he received the Nobel Prize for Physics, which he shared with German physicist Ferdinand Braun. He later worked on the development of shortwave wireless communication, which constitutes the basis of nearly all modern long-distance radio.

Education and early work.
Marconi's father was Italian and his mother Irish. Educated first in Bologna and later in Florence, Marconi then went to the technical school in Leghorn, where, in studying physics, he had every opportunity for investigating electromagnetic wave technique, following the earlier mathematical work of James Clerk Maxwell and the experiments of Heinrich Hertz, who first produced and transmitted radio waves, and Sir Oliver Lodge, who conducted research on lightning and electricity.
In 1894 Marconi began experimenting at his father's estate near Bologna, using comparatively crude apparatus: an induction coil for increasing voltages, with a spark discharger controlled by a Morse key at the sending end and a simple coherer (a device designed to detect radio waves) at the receiver. After preliminary experiments over a short distance, he first improved the coherer; then, by systematic tests, he showed that the range of signaling was increased by using a vertical aerial with a metal plate or cylinder at the top of a pole connected to a similar plate on the ground. The range of signaling was thus increased to about 2.4 km (1.5 miles), enough to convince Marconi of the potentialities of this new system of communication. During this period, he also conducted simple experiments with reflectors around the aerial to concentrate the radiated electrical energy into a beam instead of spreading it in all directions.

Receiving little encouragement to continue his experiments in Italy, he went, in 1896, to London, where he was soon assisted by Sir William Preece, the chief engineer of the post office. Marconi filed his first patent in England in June 1896 and, during that and the following year, gave a series of successful demonstrations, in some of which he used balloons and kites to obtain greater height for his aerials. He was able to send signals over distances of up to 6.4 km on the Salisbury Plain and to nearly 14.5 km across the Bristol Channel. These tests, together with Preece's lectures on them, attracted considerable publicity both in England and abroad, and in June 1897 Marconi went to La Spezia, where a land station was erected and communication was established with Italian warships at distances of up to 19 km.

There remained much skepticism about the useful application of this means of communication and a lack of interest in its exploitation. But Marconi's cousin Jameson Davis, a practicing engineer, financed his patent and helped in the formation of the Wireless Telegraph and Signal Company, Ltd. (changed in 1900 to Marconi's Wireless Telegraph Company, Ltd.). During the first years, the company's efforts were devoted chiefly to showing the full possibilities of radiotelegraph. A further step was taken in 1899 when a wireless station was established at South Foreland, England, for communicating with Wimereux in France, a distance of 50 km; in the same year British battleships exchanged messages at 121 km.

In September 1899, Marconi equipped two U.S. ships to report to newspapers in New York City the progress of the yacht race for the America's Cup. The success of this demonstration aroused worldwide excitement and led to the formation of the American Marconi Company. The following year the Marconi International Marine Communication Company, Ltd., was established for the purpose of installing and operating services between ships and land stations. In 1900 also, Marconi filed his now-famous patent No. 7777 for Improvements in Apparatus for Wireless Telegraphy. The patent, based in part on earlier work in wireless telegraphy by Sir Oliver Lodge, enabled several stations to operate on different wavelengths without interference. (In 1943 the U.S. Supreme Court overturned patent No. 7777, indicating that Lodge, Nikola Tesla, and John Stone appeared to have priority in the development of radio-tuning apparatus.)


Major discoveries and innovations.
Marconi's great triumph was, however, yet to come. In spite of the opinion expressed by some distinguished mathematicians that the curvature of the Earth would limit practical communication by means of electric waves to a distance of 161-322 km, Marconi succeeded in December 1901 in receiving at St. John's, Nfd., signals transmitted across the Atlantic Ocean from Poldhu in Cornwall, England. This achievement created an immense sensation in every part of the civilized world, and, though much remained to be learned about the laws of propagation of radio waves around the Earth and through the atmosphere, it was the starting point of the vast development of radio communications, broadcasting, and navigation services that took place in the next 50 years, in much of which Marconi himself continued to play an important part.
During a voyage on the U.S. liner Philadelphia in 1902, Marconi received messages from distances of 1,125 km (700 miles) by day and 3,200 km (2,000 miles) by night. He thus was the first to discover that, because some radio waves travel by reflection from the upper regions of the atmosphere, transmission conditions are sometimes more favourable at night than during the day. This circumstance is due to the fact that the upward travel of the waves is limited in the daytime by absorption in the lower atmosphere, which becomes ionized--and so electrically conducting--under the influence of sunlight. In 1902 also, Marconi patented the magnetic detector in which the magnetization in a moving band of iron wires is changed by the arrival of a signal causing a click in the telephone receiver connected to it. During the ensuing three years, he also developed and patented the horizontal directional aerial. Both of these devices improved the efficiency of the communication system. In 1910 he received messages at Buenos Aires from Clifden in Ireland over a distance of approximately 9,650 km (6,000 miles), using a wavelength of about 8,000 m (about 5 miles). Two years later, Marconi introduced further innovations that so improved transmission and reception that important long-distance stations could be established. This increased efficiency allowed Marconi to send the first radio message from England to Australia in September 1918.

In spite of the rapid and widespread developments then taking place in radio and its applications to maritime use, Marconi's intuition and urge to experiment were by no means exhausted. In 1916, during World War I, he saw the possible advantages of shorter wavelengths that would permit the use of reflectors around the aerial, thus minimizing the interception of transmitted signals by the enemy and also effecting an increase in signal strength. After tests in Italy (20 years after his original experiments with reflectors), Marconi continued the work in Great Britain and, on a wavelength of 15 m (49 feet), received signals over a range of 30-160 km (20-100 miles). In 1923 the experiments were continued on board his steam yacht Elettra, which had been specially equipped. From a transmitter of 1 kilowatt at Poldhu, Cornwall, signals were received at a distance of 2,250 km (1,400 miles). These signals were much louder than those from Caernarvon in Wales on a wavelength several hundred times as great and with 100 times the power at the transmitter. Thus began the development of shortwave wireless communication that, with the use of the beam aerial system for concentrating the energy in the desired direction, is the basis of most modern long-distance radio communication. In 1924 the Marconi company obtained a contract from the post office to establish shortwave communication between England and the countries of the British Commonwealth.

A few years later Marconi returned to the study of still shorter waves of about 0.5 m (1.6 feet). At these very short wavelengths a parabolic reflector of moderate size gives a considerable increase in power in the desired direction. Experiments conducted off the coast of Italy on the yacht Elettra soon showed that useful ranges of communication could be achieved with low-powered transmitters. In 1932, using very short wavelengths, Marconi installed a radiotelephone system between Vatican City and the pope's palace at Castel Gandolfo. In later work Marconi once more demonstrated that even radio waves as short as 55 cm (22 inches) are not limited in range to the horizon or to optical distance between transmitter and receiver.

Marconi received many honours and several honorary degrees. He was awarded the Nobel Prize for Physics (1909) for the development of wireless telegraphy; sent as plenipotentiary delegate to the peace conference in Paris (1919), in which capacity he signed the peace treaties with Austria and with Bulgaria; created marchese and nominated to the Italian senate (1929); and chosen president of the Royal Italian Academy (1930).

 

BIBLIOGRAPHY.
Degna Marconi, My Father, Marconi (1962); W.P. Jolly, Marconi (1972); W.J. Baker, A History of the Marconi Company (1970).



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