On This Day: Marconi Receives First Trans-Atlantic Radio Signal

As a student at the University of Bologna, Guglielmo Marconi studied the theories of Heinrich Hertz, a pioneer in wireless radio transmission. In 1896, soon after graduation, Marconi moved with his Irish-born mother to England, where he set up his first company with an English cousin.

Marconi experimented with sending signals in England, and to France and Ireland. He gained international fame in 1899, when he transmitted the results of the America’s Cup sailing race to a New York newspaper from the deck of a ship.

In 1901, he began working on a way to transmit radio signals across the Atlantic Ocean. He built powerful stations in Poldhu, Cornwall, England and South Wellfleet, Cape Cod, Mass. He later moved his North American station to Signal Hill, St. John’s, Newfoundland, located much closer to England, when he estimated that the signals could not reach Cape Cod.

Many scientists believed that radio signals could not be transmitted such a long distance. The prevailing theory was that a signal could not travel along the curvatures of the Earth for more than a few hundred miles; instead, the signal would continue into space.

At Signal Hill, Marconi and his assistant George Kemp held a telephone receiver and a wire antenna in the air with a kite. On Dec. 10, the Poldhu sent a message, but Marconi could not receive it. Two days later, using the fourth kite of the experiment, Marconi and Kemp at last heard a signal.

“The answer came at 12:30 when I heard, faintly but distinctly, pip-pip-pip,” Marconi later wrote. “I handed the phone to Kemp: ‘Can you hear anything?’ I asked. ‘Yes,’ he said. ‘The letter S.’ He could hear it. I knew then that all my anticipations had been justified. The electric waves sent out into space from Poldhu had traversed the Atlantic—the distance, enormous as it seemed then, of 1,700 miles—unimpeded by the curvature of the earth.”

Though Marconi’s experiment had succeeded, he was wrong to believe that the signal had traveled along the curvature of the Earth. Instead, as his critics believed, the signal was headed into space until it struck an atmospheric layer of ions that deflected back down toward St. John’s.

In studying Marconi’s success, American engineer Arthur Kennelly and British physicist Oliver Heaviside independently theorized the existence of the ionosphere, which became known as the Kennelly-Heaviside layer.

When the success of the experiment became known, it was not considered good news by the Anglo-American Telegraph Company, which had spent a great deal of money installing undersea cables and had received a monopoly on telegraph transmissions from the Newfoundland government. The company threatened to sue if Marconi continued to receive telegraph transmissions, so Marconi, at Canada’s invitation, moved to a new site on Cape Breton Island.