The Establishment of Radio Communication

The year 1897 was important in radio history: Marconi filed for patents on a wireless system, and Lodge developed the theory of tuning as applied to radio circuits. Marconi, perhaps more than any other, deserves the credit for placing radio communication on a commercial basis. During this same year signals were transmitted from shore to a ship 18 miles away. By 1900 radio telegraphy was becoming reasonably well established and was rapidly proving its great value. In 1901 Marconi received signals across the Atlantic.

The coherer, previously mentioned, was used as a detecting device for many years. In 1902 Marconi invented an improved magnetic detector which superseded the coherer and had wide application until the advent of the two-electrode thermonic tube, the crystal, and the electrolytic detectors. The two-electrode tube is of special importance and was employed as a detector by Fleming in 1904. In 1906 de Forest invented the "audion" or triode vacuum-tube amplifier, an event outstanding in the history of communication.²⁸ The Marconi interests initiated regular transatlantic telegraph service in 1907.

The systems thus far traced in this brief consideration were for tele-graphic communication only. Radio telephony is based on the work of Fessenden, who in 1902 developed a system of modulating radio frequencies with the voice. In 1915 engineers of the Bell System succeeded in telephoning from Arlington to Hawaii, and from Arlington to Paris.²⁵ In 1920 the first commercial radio stations were installed for connecting two land telephone systems. This was between the mainland and Santa Catalina Island off the coast of California. In 1927 a transatlantic radio-telephone circuit was opened providing a connection between the telephone systems of Europe and America. Other radio links with important European centers followed. Similar telephone connections have been made from the United States to South and Central America, to Bermuda, to Hawaii, and to the Orient. European countries have extensive commercial radio service with distant trade centers, Many ships at sea are connected by radio for commercial two-way telephone service. Similar service is provided with certain trains. Experimental conversations have been held with aircraft in flight to determine the possibilities of establishing regular commercial telephone service. Radio-telephone connections are provided in certain areas between coastal and harbor craft and between motor vehicles and the telephone network.

Radio broadcasting was inaugurated²⁹ by Conrad in 1920, using a system of amplitude-modulated waves. The so-called superheterodyne radio-receiving set, so widely used since about 1930, was developed by Armstrong. He also perfected a system of frequency modulation³⁰ in about 1936.

From the early dreams and investigations of Alexander Graham Bell and other communication pioneers has grown a vast international communication system, serving to bind together the scattered peoples of the world. This system may fulfil the vision of a distinguished telephone engineer, the late John J. Carty, who said:

"I have the faith that we shall some day build up a great world telephone system making necessary to all nations the use of a common language which will join all the peoples of the earth into one brotherhood."