RADIO CROSSES THE ATLANTIC

On 12 December 1901, Guglielmo Marconi received a radio signal that had been sent by his colleagues across the Atlantic. Although wireless telegraphy was not new - it had started to be used commercially by coastal shipping three years previously - Marconi's demonstration was exceptional.

To begin with, there was no reason to suppose that a radio signal would follow the curvature of the earth. As an eminent scientist said at the time, "there is a mountain of water one hundred miles high to be got over, and electric waves tend to go straight".

Despite this, Marconi - at 27 years of age - persuaded the hard-headed directors of his newly formed Wireless Telegraph Company to invest £50,000 and a lot of time in the experiment. This was a considerable investment - equal to several millions of pounds today - by a small company still existing on its capital.

Marconi's confidence was based on his experience of radio transmissions around England¹, to France and to an experimental station in the south west of Ireland. For the Atlantic attempt, he set up a new station at Poldhu in Cornwall. His aerial comprised twenty-four ships' masts each 200 feet high, and the transmitter was powered by a 32 brake horsepower engine driving a 25 kilowatt alternator whose 2,000 volts were then boosted to 20,000 volts. At the receiving end, in St John's Newfoundland, Marconi waited with kites and balloons to hold an aerial wire aloft. In the event, a kite with 500 feet of wire received the first signals - the three dots of the Morse code letter S   

Public reaction was mixed. The Daily Telegraph reported, "The view generally held is that "electric strays" were responsible for activating the delicate instrument" while The Times and the technical press - despite accepting that the message had been sent - were doubtful that transatlantic wireless communication had any practical application.

Better news, however, came in an unlikely form. The Anglo-American Telegraph Company immediately wrote to Marconi saying that it had a monopoly on communications in Canada's Newfoundland and Marconi was to stop transmissions immediately. This he did, and was immediately courted by Canadian and United States authorities incensed by the company's attitude, and keen to be involved in a technology that they recognised as having great potential.

Progress in those early days was rapid. When Marconi returned to New York from Southampton in late February on the SS Philadelphia, he maintained readable messages with Poldhu up to 700 miles out by day, and 1,500 at night. The letter "S" was received 2,100 miles out, despite the limited aerial rigged on board.

Although there were theories explaining why radio signals did not ignore the curve of the earth and disappear into space, it was not until 1924 that the existence of the ionosphere was discovered - bouncing them back to the ground. By then, transatlantic wireless communication was commonplace, and the first signal to be sent successfully around the globe - a possibility predicted by Marconi - was demonstrated two years later.

Marconi was born in 1874 in Bologna, Italy, studying Heinrich Hertz's theory of radio there and demonstrating its practice in experiments around the family home. He moved to Britain and filed his first patent in 1896, forming a company in 1897 which became Marconi's Wireless Telegraph Company (eventually Marconi plc) three years later.

The first advertised broadcast in Britain - using a Marconi transmitter - was made in 1920, and the first microwave telephone link was established by Marconi in 1932 between the Vatican and the Pope's summer residence. At that time Marconi was also demonstrating the potential of blind navigation, the forerunner of radar.

Marconi returned to Italy in 1935, and died there in 1937. In a tribute, wireless stations throughout the world observed two minutes silence and the radio spectrum was as silent as it had been forty years before.

¹ Early experiments took place on Salisbury Plain, the Isle of Wight and Bournemouth. In acknowledging the 12 December experiment, King Edward noted earlier ones conducted from the Royal Yacht Osborne in 1898.

² Gordon Bussey is an historical consultant to Marconi plc. His books include "Marcon's Atlantic Leap" published by Marconi Communications and available from the Radio Society of Great Britain's bookshop at www.rsgb.org/shop