Wireless Telegraphy - Something of the Principle of Electric Waves

The Marconi System Uses the Atmosphere as a Conductor — Nikola Tesla at Work on a System Using the Earth.

It may be said that a certain kind of electricity tends to travel like waves made by dropping a stone in a pond — in all directions. But it travels fartherest and with least resistance In those directions where it finds the best conductors for it. Some substances are better conductors than others. Glass and rubber are nonconductors, so called, as you may see by looking at the rubber covering of wires on the street car system or the glass insulators, on a telegraph pole. Metals, such as iron, steel and copper, are first-class conductors, and that is why wire is used for telegraph and telephone and electric light purposes. Water and the earth are conductors of electricity and so is the atmosphere. When Benjamin Franklin, by his famous experiment with the kite, proved that lightning is nothing but electricity; he also proved that the atmosphere is a conductor, for a bolt of lightning may travel many miles before striking the earth. Mere space, finally, is a conductor of electricity, as you can prove by passing a current through a vacuum.

As soon as one comprehends that electrical waves can move in space without the conventional wire conductors, it is evident that the question of telegraphy with wires or without wires must depend largely upon the transmitting and receiving apparatus. Wires hitherto have been used because with the apparatus available for sending and receiving electric currents, they have afforded the best results; Indeed, for considerable distances they afforded the only results that could be depended upon. Even with wire as a conductor, far more delicate receiving instruments have to be used on an Atlantic cable than on a circuit between Springfield and Buffalo. Now Marconi is by no means the first one to experiment with wireless telegraphy. Many men have been working at the problem for years. And essentially their problem has been to perfect apparatus at one end which would generate electric waves strong enough to travel long distances with mere space as the conductor, and apparatus at the other end sensitive enough to receive and record those waves.

The transmitting and receiving apparatus thus far developed is complicated, and one needs some techical knowledge to understand it. You will read much about Hertzian waves in this connection. Hertzian waves are waves of electricity. Hertz was a German professor, who died in 1894. He was the first man to prove by experiment that whenever in any circuit electromagnetic changes are brought about, as when an induction coil is in action, the disturbances are transmitted in all directions, bringing about similar changes in neighboring conductors. His great work was to show that these disturbances are transmitted by means of vibration of the luminiferous ether (which is assumed by physicians to fill all space) and also show the character and measures the velocity of those waves. The wireless telegrapher, therefore, first generates Hertzian waves of electricity into space. Gen. Greely, head of the United State Army Signal Service, in describing the transmitter used by the Signal Corps in experiments over two years ago, reported that he used a coil in oil "energized by a threequarter horsepower rotary transformer, furnishing 125 volts, alternating potential," an arrangement making "a very powerful and efficient source of Hertzian radiation." Marconi used at that day a Ruhmkorff coil. According to present methods, the Hertzian waves are transmitted by the generator through a wire to the top of a high pole, and that is where the jumping-off place is.

From the top of the pole, the Hertzian waves are radiated off into space. About one-fifth of a horsepower is necessary to send them 60 miles to sea, and a 1,000 mile range, it is said, ought not to require much more than three and one-half horsepower, provided the energy can be utilized. To send the waves across the Atlantic, the problem of transmission is a question of propelling force. The Hertzian waves follow the curvature of the earth.

Marconi improved the receiving apparatus by discovering or inventing what is known as the "decoherer," which consists of a ball working on an arm attached to the armature of an electromagnet in the circuit of the "coherer," of receiver. But that aside. Enough has been said to show that this apparatus, both sending and receiving, is highly technical, and difficult to be understood in detail by one who is no electrician, or has never witnessed experiments in wireless telegraphy. Suffice it to say that when Marconi, the other day in Newfoundland, received the wireless message from the coast of England, he flew a kite in the air, and from the kite was suspended a wire connecting with his receiving instrument. The Hertzian waves has passed over the ocean from the tall pole on the English coast, and had struck the wire on the kite in Newfoundland. The electric vibrations were thus transmitted to Marconi's delicately adjusted receiver, and read by him exactly as they had been sent across 1,800 miles of ocean.

Marconi's system uses the atmosphere as a conductor. Nikola Tesla, it is understood, is experimenting on a system that uses the earth as a conductor. It seems safe to predict that science will completely master the field of wireless communication through long distances before many years have passed. Evidently the experimenters are only in the infancy of the art. — Springfield Republican