He received the first trans-Atlantic radio signal on December 12 1901 in St Johns, Newfoundland, Canada using a 400-foot kite-supported antenna for reception. The transmitting station in Poldhu, [[Cornwall] used a spark-gap transmitter to produce a signal with a frequency of approximately 500KHz and a power of 100 times more than any radio signal previously produced. The message received was three dots, the Morse code for the letter S.
Dr. [Jack Belrose]? has recently contested this, however, based on theoretical work as well as an actual reenactment of the experiment; he believes that Marconi heard only random atmospheric noise and mistook it for the signal. Marconi didn't achieve fully reliable transatlantic communication until 1907.