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 On this day in engineering history, Guglielmo Marconi announced that he had received the first transatlantic radio signal during three days of wireless experiments. On December 12, 1901, the Italian inventor claimed that his wireless telegraphy facility in St. John's, Newfoundland (now part of Canada) had received faint but repeated signals from a high-power, spark-transmitter station at Poldu, Cornwall, England. The transmissions, which repeated the Morse code for the letter "S", convinced Guglielmo Marconi that transatlantic wireless communications were possible – and potentially profitable. Critics, however, disputed the inventor's claim because Marconi failed to provide independent confirmation of the reported reception.
On December 11, 1901, Guglielmo Marconi watched as workers raised an antenna supported by a kite and balloons high over Signal Hill in St. John's, Newfoundland (top left). Meanwhile, across the Atlantic and 2100 miles away, associates in Poldu, Cornwall, England readied a new spark-transmitter station which, unlike its battery-powered predecessors, used a 35-kW alternator. Designed by J.A. Fleming, the inventor of the vacuum tube rectifier, the transmitter consisted of a two-stage circuit. The transmitting antenna was a fan with 54 vertical wires which were joined at their lower ends and connected to the transmitter's feed line. The top of this fan was approximately 200-ft. wide and suspended about 160 feet above the ground.
In earlier experiments, Marconi's Poldu facility had transmitted radio signals as far as several hundred miles. Encouraged by these results, the Italian inventor now instructed his associates to transmit Morse code for reception 2100 miles away in Newfoundland. Between 11:30 AM and 2:30 PM St. John's time, the Poldu facility transmitted messages at 820 kHz with five-minute breaks. As historian Henry M. Bradford explains, however, "Marconi could hardly have picked a worse combination of frequency and time of day for the transatlantic experiment". During the day, the D-layer of the ionosphere absorbs much of the energy from radio waves in this frequency band. As listeners of AM radio stations can attest, long-distance reception is better at night.
So did Guglielmo Marconi receive the first transatlantic radio signal in December of 1901? Although Henry Bradford claims that "descriptions of the receiving equipment used are sketchy", he speculates that Marconi did not receive a radio signal on the first day of testing (December 11), when accounts indicate that a tuned receiver was used. Nevertheless, Bradford does believe that Marconi heard something on December 12, 1901 – but not at 820 Hz. "Spark transmitters were notorious for the broadband emissions", the historian explains, "and it is quite possible that the spectrum of the Poldu transmitter contained significant power in the HF (short wave) band."
Resources:
http://www.sparkmuseum.com/BOOK_FLEMING.HTM
https://en.wikipedia.org/wiki/Guglielmo_Marconi
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Re: December 12, 1901: The First Transatlantic Radio Signal?
