CALLING ALL NATIONS -- 1941

WONDERS OF RADIO

WONDERS OF RADIO, Page 424 (cont.)

Pages: (1) (2) (3) (4) (5)

By Ellison Hawks, writing in the Popular Science Mechanical Encyclopedia, Popular Science Publishing Company, Inc., New York, 1941, p. 423 - 459.

as part of the circuit. That it was possible to complete an electrical circuit through the ground appears to have first been discovered by Winkler, of Leipzig. In 1746 he discharged Leyden jars through an insulated wire laid along the bank of the River Pleiss, the waters of which formed the return half of the circuit. Later in the same year he successfully transmitted over a distance of two miles, using the ground as a return circuit. Subsequently, there were numerous other instances in which the ground return was employed, as in I747 when an Englishman, Dr. (afterwards Sir William) Watson transmitted an electric current over a single wire 2,800 ft. in length and followed this by transmitting over a distance of two miles, in each case using the ground as a return.

WATER AS A CONDUCTOR

In 1811 the eminent German scientist, Sommering, of Munich, who was experimenting with a form of telegraph, used water in place of wires to conduct the current for telegraphic purposes. He found that when the conducting wires were cut and the ends separated by an interval of water in wooden tubs, the current completed the circuit exactly as though the wires had not been cut. It was further found that the signals ceased when the water in the tubs was connected by a wire. As two separate bodies of water are not often to be found together in natural conditions, Sommering came to believe that his suggested method was impractical. Although his system had thus only a brief life, it was the earliest practical method proposed for wireless communication.

In I838 Dr. C. A. Steinheil, of Munich, made an accidental discovery of some importance. He endeavored to improve upon Sommering's tub-of water experiment by using the ground as a means of conduction, entirely dispensing with both wires. Steinheil was one of the greatest pioneers of the electric telegraph in Europe, and he endeavored to use as telegraphic conductors the two lines of a railway track between Nuremberg and Furth. As far as the original purpose was concerned, the experiment was a failure owing to the impossibility of obtaining a sufficiently good insulation between the two rails to enable the current to travel from one station to the other, there to be picked up by suitable apparatus.

When he failed in these experiments, however, Steinheil determined to use the ground instead of a second wire, having noticed its great conductibility in his endeavors to obtain perfect insulation of the two rails. By using the "earth battery," as it was called, for telegraphic purposes, he introduced a method that, universally adopted, effected a very considerable economy in both wire and labour.

Having succeeded so far in eliminating one of the wires and using the ground battery, he carried out further experiments and he is credited with the first intelligent suggestion of a wireless telegraph, based on his observation of galvanic excitation of the soil round his ground wires. It only depended, he decided, on the laws governing this excitation, whether it was possible to dispense with the return wire altogether.

STEINHEIL'S GALVANIC EFFECT

Steinheil admitted that in practice the suggestion "only holds for small distances, and it must be left to the future to decide whether we shall ever succeed in telegraphing at great distances entirely without metallic connection." Later, he pointed out that "the spreading of the galvanic effect is proportional, not to the distance of the point of excitation, but to the square of this distance. So that, at a distance of 50 ft. (please see the next page)

(page 424)

The amazing Mr. Edison. Wireless communicating patent using an electostatic based inductance scheme granted December 29, 1891. Patent Number 465,971. This illustration is not part of Hawks' article but is meant to help in understanding the points he makes later on.

http://www.popsci.com (external link)

Click here for a selection from Weisman's RF & Wireless. Easy to read, affordable book on wireless basics. (12 pages, 72K in .pdf)