Wireless Telegraphy

New Zealand Tablet, 27 February 1913, Page 11

Wireless Telegraphy

As wireless telegraphy grips the imagination of men more and more by its ever-growing wonders, so does the marvel increase that its inventor developed and achieved his epoch-making idea when he was in age but a schoolboy, and expected to do no more than study his lessons and enjoy himself. Guglielmo Marconi studied at the Universities of Bologna and Padua, and when only 15 years old, on his father's estate near Bologna,- Italy, plunged enthusiastically into the dreamlands of electricity. In the next few years he headed straight for one of its great mysteries, the socalled Hertzian waves, or electrical impulses, which could travel through air without the use of a wire. In 1895, when he was only twenty years old, his advanced knowledge on this obscure subject inspired him with the theory that these waves could be sent out and received at will, and in that year he had constructed the first wireless apparatus, whose efficiency astonished even his enthusiasm. "...-< Wireless telegraphy under the masterful hand of Guglielmo Marconi sprang into commercial success'in a remarkably short space of time. Prior to 1895, electro-magnet-'c waves had been discovered, and men of many countries bad experimented with them, but it remained for Marconi to see that these waves could be harnessed and made the servant of man, that they could be made to transmit intelligence from ship to shore and from one continent to another. The waves or vibrations that make wireless telegraphy possible are in many respects similar to those of light. They travel at the same tremendous speed of 186,330 miles a second. There are several ways of producing these waves, but the one in common use is called the spark method. Briefly, it is this: An induction coil or high-tension transformer is connected

to an electric-current supply so as to produce a spark across' an air space. By "opening or closing an ordinary telegraph key the operator causes a spark of longer or shorter duration to jump across the air space. This spark produces the vibrations by virtue of its oscillatory character. In other words, it acts similarly to a straight spring drawn back and suddenly released. It vibrates to and fro until its energy is exhausted and the rate at which it vibrates is determined by its. length. By varying the rate of vibration longer or shorter waves may be produced. By means of a device, called the oscillation transformer, the vibrations are transferred from the primary circuit to the aerial or masthead wire, always conspicuous at any wireless-telegraph station, thus performing the same function relative to the sparkgap circuit that a radiator does to a steam-heating boiler. That which is called ' tuning ' has to do with the adjustment of the wave length of the aerial wire to that of the closed circuit. In this manner a receiving station may be tuned to a transmitting station or, in other words, the instruments of the former so adjusted that they w ; ll be more sensitive to the waves from the latter than to those from other stations. In the receiving system the same aerial wire and a smaller oscillation transformer are used, "but in lieu of the spark gap we have the detector. This detector may consist of a special form of glow lamp, called an oscillation valve, or of a mineral or crystal such as silicon or carborundum, or other devices. Llowever constructed, the various detectors serve the purpose of causing an intermittent current to flow through the operator's telephone receivers, thus producing audible dots and dashes, corresponding to the shorter or longer duration of the impulses sent out by the transmitting station. This brief account describes with fair accuracy the commercial, tuned wireless system of to-day.' At the present time there may be found stations a thousand miles up. the Amazon River working 500 miles over land through the virgin forest, and huge commercial stations flashing thousands of words daily across the broad Atlantic, and yet the art is still in its infancy.