In 1820, the earliest radio communication machine, Oster published the "Oster experiment" for the first time to reveal the physical phenomenon that electric current can produce magnetism. In 1831, Faraday discovered the law of electromagnetic induction. In 1873, the theory of electromagnetic field was put forward by Maxwell. He also described some basic properties of electromagnetic wave. On this basis, Hertz successfully excited high frequency in the wire in 1888, and measured the electromagnetic field around the wire. This experiment proved the theory of the existence of electromagnetic wave.
Telegrams and telephones transmit information through wires between them. In 1895, Marconi used radio waves to send a Morse code message over an open space. Inspired by the Hertz experiment, people began to study the radio communication using electromagnetic wave to transmit information, and did a lot of experiments for this purpose, but the results have not been successful. Until May 7, 1895, Alexander, a Russian physicist