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Marconi recebe sinal de radio sobre
o Atlântico
1901
Late in the nineteenth century, Guglielmo Marconi
began experimenting with electromagnetic waves to send signals. At that
time, the telegraph wire was the quickest way to get messages from here
to there, using Morse code. He designed a transmitter to send and a receiver
to detect radio waves. By the end of the century Marconi had managed to
send signals over several miles with no wires, and the idea was taking
hold with naval officials. In 1898 he sent a wireless message 18 miles.
In 1900 he patented his system.
On December 12, 1901, Marconi attempted to send the first radio signals
across the Atlantic Ocean, in spite of predictions that the radio waves
would be lost as the earth curved over that long distance. He set up a
specially designed wireless receiver in Newfoundland, Canada, using a coherer
(a glass tube filled with iron filings) to conduct radio waves, and balloons
to lift the antenna as high as possible. The signals were sent in Morse
code from Poldhu, Cornwall, in England. Marconi later wrote about the experience:
Shortly before midday I placed the single earphone to my ear and started
listening. The receiver on the table before me was very crude -- a few
coils and condensers and a coherer -- no valves, no amplifiers, not even
a crystal. But I was at last on the point of putting the correctness of
all my beliefs to test. The answer came at 12: 30 when I heard, faintly
but distinctly, pip-pip-pip. 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. The result meant much more to me than the mere
successful realization of an experiment. As Sir Oliver Lodge has stated,
it was an epoch in history. I now felt for the first time absolutely certain
that the day would come when mankind would be able to send messages without
wires not only across the Atlantic but between the farthermost ends of
the earth.
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