Radio Broadcast (May-Oct 1922)

200 Radio Broadcast and appreciated. It is with this idea in mind that the following brief story of the wireless telegraph has been written. The earlier name for communication between two stations without the use of connecting wires was the wireless telegraph, but for reasons to be shortly pointed out the term radio telegraph or radio communication is now generally used and preferred. There are three closely allied developments in the growth of the radio of to-day, all of which contributed their share toward our knowledge of the art. The first has to do with the early attempts to carry on ordinary telegraph communication without wires, the earth's surface forming the conducting medium between the two stations. A great deal of work was done in this field by many workers; the reward for a successful solution would have been great as it might have made unnecessary, to some extent, the very expensive cables being installed for transoceanic telegraphy. This scheme of using the earth for conductor found application during the war just past for communication from the front line trenches and is well known to those acquainted with the work of the Signal Corps, where it goes by the abbreviation of its French name, T.P.S. (Telegraphie Par Sol). THEN THE IDEA OF INDUCTION WAS TRIED A second line of work used no conducting medium whatsoever between the two stations; comparatively slow change of current in one coil was used to induce currents in another coil in the vicinity and these induced currents, by some prearranged code, were used to convey information. This work was begun in England and the United States at about the same time, by independent workers; it did not apparently promise much success at the time, but with our present knowledge of the art it seems that some of the experimenters missed the real solution of the problem by a very narrow margin. This scheme has recently received much public notice because of its application to the guiding of vessels into a harbor during the night or in a fog, when ordinary methods of navigation are not available. In this method of navigation, a cable laid in the channel is traversed by alternating current and coils placed on the sides of the vessel's hull receive induced currents from the cable and the navigator can maneuver his vessel by the relative strengths of the signals received on the two sides. The third line of work involved the same gen eral idea as the foregoing, but the changes of current were thousands of times as rapid as those formerly used; instead of using the ordinary phenomena of induction, as explained by Faraday and Henry, a new concept of radiated power was invoked and with this step taken, success was assured. As long as the communication between the two stations depended upon the induction ideas of Faraday and Henry the possible separation of the two stations was but a few times the dimensions of the coils used at the stations; when high frequency radiated power was utilized, the possible distance of communication was increased thousands of times and made feasible the transmission of signals between any two points located upon the surface of the earth. THE FIRST EXPERIMENTS BY STEINHEIL In 1837 Professor Steinheil, of Munich, while making some experiments with the telegraph apparatus ordinarily using two wires, one for the outgoing current and another for the return, found that it was possible to dispense with one of the two wires hitherto thought necessary, and use only one wire. This one wire was connected, at the transmitting end through battery and key, to large plates buried in the earth and at the receiving end it was similarly connected to ground through whatever type of receiving apparatus was used. He thus showed that the ordinary one wire telegraph system of to-day, using the earth as the return was possible. This experience evidently aroused Steinheil's imagination, as he suggested, in 1838, when discussing the results of his experiments, that it might be possible to carry on communication with no connecting wires at all between the two stations! PROFESSOR morse's WIRELESS In 1842, Professor Morse in America, actually did establish telegraphic communication between two stations on the opposite banks of a river, there being no wires at all crossing the river. Along one bank of the river he laid a wire in which were contained his sending battery and key; this wire terminated in two metal plates placed in the river itself. These plates were separated from each other by a distance greater than the width of the river. A similar wire and set of plates was used on the opposite sideof the river, the plates on one bank being opposite those on the other. The receiving galvanometer was inserted in series with this