Marconi's first transmitter,
consisting of a copper sheet capacitive
antenna(top) connected to a
Righi spark gap(left) powered by an
induction coil(center) with a telegraph key
(right) to switch it on and off to
spell out text messages in Morse code.
Thursday, July 21, 2016
Tribute to Guglielmo Marconi on his 79th death anniversary-Part II
Continue from yesterday's article -
Marconi made his first demonstration of his system for the British government in July 1896. A further series of demonstrations for the British followed—by March 1897, Marconi had transmitted Morse code signals over a distance of about 6 kilometres (3.7 mi) across Salisbury Plain. On 13 May 1897, Marconi sent the world's first ever wireless communication over open sea. The experiment, based in Wales, witnessed a message transversed over the Bristol Channel from Flat Holm Island to Lavernock Point in Penarth, a distance of 6 kilometres (3.7 mi). The message read "Are you ready". The transmitting equipment was almost immediately relocated to Brean Down Fort on the Somerset coast, stretching the range to 16 kilometres (9.9 mi).
Impressed by these and other demonstrations, Preece introduced Marconi's ongoing work to the general public at two important London lectures: "Telegraphy without Wires", at the Toynbee Hall on 11 December 1896; and "Signaling through Space without Wires", given to the Royal Institution on 4 June 1897. Numerous additional demonstrations followed, and Marconi began to receive international attention. In July 1897, he carried out a series of tests at La Spezia, in his home country, for the Italian government. A test for Lloyds between Ballycastle and Rathlin Island, Ireland, was conducted on 6 July 1898. The English channel was crossed on 27 March 1899, from Wimereux, France to South Foreland Lighthouse, England, and in the autumn of 1899, the first demonstrations in the United States took place, with the reporting of the America's Cup international yacht races at New York.
At the turn of the 20th century, Marconi began investigating the means to signal completely across the Atlantic in order to compete with the transatlantic telegraph cables. Marconi established a wireless transmitting station at Marconi House, Rosslare Strand, Co. Wexford in 1901 to act as a link between Poldhu in Cornwall, England and Clifden in Co. Galway, Ireland. He soon made the announcement that the message was received at Signal Hill in St John's, Newfoundland (now part of Canada) on 12 December 1901, using a 500-foot (150 m) kite-supported antenna for reception—signals transmitted by the company's new high-power station at Poldhu, Cornwall. The distance between the two points was about 2,200 miles (3,500 km). It was heralded as a great scientific advance, yet there also was—and continues to be—considerable skepticism about this claim. The exact wavelength used is not known, but it is fairly reliably determined to have been in the neighborhood of 350 meters. The tests took place at a time of day during which the entire transatlantic path was in daylight. We now know (although Marconi did not know then) that this was the worst possible choice. At this medium wavelength, long distance transmission in the daytime is not possible because of heavy absorption of the sky wave in the ionosphere. It was not a blind test; Marconi knew in advance to listen for a repetitive signal of three clicks, signifying the Morse code letter S. The clicks were reported to have been heard faintly and sporadically. There was no independent confirmation of the reported reception, and the transmissions were difficult to distinguish from atmospheric noise. (A detailed technical review of Marconi's early transatlantic work appears in John S. Belrose's work of 1995.) The Poldhu transmitter was a two-stage circuit.
On 17 December 1902, a transmission from the Marconi station in Glace Bay, Nova Scotia, Canada became the world's first radio message to cross the Atlantic from North America. In 1901, Marconi built a station near South Wellfleet, Massachusetts that sent a message of greetings on 18 January 1903 from United States President Theodore Roosevelt to King Edward VII of the United Kingdom. However, consistent transatlantic signalling was difficult to establish.Feeling challenged by skeptics, Marconi prepared a better organized and documented test. In February 1902, the SS Philadelphia sailed west from Great Britain with Marconi aboard, carefully recording signals sent daily from the Poldhu station. The test results produced coherer-tape reception up to 1,550 miles (2,490 km), and audio reception up to 2,100 miles (3,400 km). The maximum distances were achieved at night, and these tests were the first to show that radio signals for medium wave and long wave transmissions travel much farther at night than in the day. During the daytime, signals had only been received up to about 700 miles (1,100 km), less than half of the distance claimed earlier at Newfoundland, where the transmissions had also taken place during the day. Because of this, Marconi had not fully confirmed the Newfoundland claims, although he did prove that radio signals could be sent for hundreds of kilometres, despite some scientists' belief that they were essentially limited to line-of-sight distances.
Marconi began to build high-powered stations on both sides of the Atlantic to communicate with ships at sea, in competition with other inventors. In 1904, a commercial service was established to transmit nightly news summaries to subscribing ships, which could incorporate them into their on-board newspapers. A regular transatlantic radio-telegraph service was finally begun on 17 October 1907 between Clifden Ireland and Glace Bay, but even after this the company struggled for many years to provide reliable communication to others.
The role played by Marconi Co. wireless in maritime rescues raised public awareness of the value of radio and brought fame to Marconi, particularly the sinking of the RMS Titanic on 15 April 1912 and the RMS Lusitania on 7 May 1915. RMS Titanic radio operators Jack Phillips and Harold Bride were not employed by the White Star Line but by the Marconi International Marine Communication Company. After the sinking of the ocean liner on 15 April 1912, survivors were rescued by the RMS Carpathia of the Cunard Line. Also employed by the Marconi Company was David Sarnoff, who later headed RCA. Wireless communications were reportedly maintained for 72 hours between Carpathia and Sarnoff, but Sarnoff's involvement has been questioned by some modern historians. When Carpathia docked in New York, Marconi went aboard with a reporter from The New York Times to talk with Bride, the surviving operator.
On 18 June 1912, Marconi gave evidence to the Court of Inquiry into the loss of Titanic regarding the marine telegraphy's functions and the procedures for emergencies at sea. Britain's postmaster-general summed up, referring to the Titanic disaster: "Those who have been saved, have been saved through one man, Mr. Marconi...and his marvelous invention." Marconi was offered free passage on Titanic before she sank, but had taken Lusitania three days earlier. As his daughter Degna later explained, he had paperwork to do and preferred the public stenographer aboard that vessel.
Over the years, the Marconi companies gained a reputation for being technically conservative, in particular by continuing to use inefficient spark-transmitter technology which could only be used for radiotelegraph operations, long after it was apparent that the future of radio communication lay with continuous-wave transmissions which were more efficient and could be used for audio transmissions. Somewhat belatedly, the company did begin significant work with continuous-wave equipment beginning in 1915, after the introduction of the oscillating vacuum tube (valve). The New Street Works factory in Chelmsford was the location for the first entertainment radio broadcasts in the United Kingdom in 1920, employing a vacuum tube transmitter and featuring Dame Nellie Melba. In 1922, regular entertainment broadcasts commenced from the Marconi Research Centre at Great Baddow, forming the prelude to the BBC, and he spoke of the close association of aviation and wireless telephony in that same year at a private gathering with Florence Tyzack Parbury, and even spoke of interplanetary wireless communication.
In 1914, Marconi was made a Senator in the Italian Senate and appointed Honorary Knight Grand Cross of the Royal Victorian Order in the UK. During World War I, Italy joined the Allied side of the conflict, and Marconi was placed in charge of the Italian military's radio service. He attained the rank of lieutenant in the Italian Army and of commander in the Italian Navy. In 1929, he was made a marquess by King Victor Emmanuel III. Marconi joined the Italian Fascist party in 1923. In 1930, Italian dictator Benito Mussolini appointed him President of the Royal Academy of Italy, which made Marconi a member of the Fascist Grand Council.
Marconi died in Rome on 20 July 1937 at age 63, following a series of heart attacks, and Italy held a state funeral for him.
Yesterday was his 79th death anniversary. PB Parivar offers tribute to this great scientist from the core of our heart.
Source of information :- https://en.wikipedia.org/wiki/Guglielmo_Marconi