He also devised a simple apparatus to detect the presence of these waves—that is, to receive them, which he called a resonator, and this was a cut wire ring with a little brass ball on each of its ends as shown in the following diagram. Now when Hertz set his induction coil going, streams of sparks were set up in the spark-gap of the oscillator and electric oscillations, or high-frequency currents, surged from one of the copper plates to the other and back again, and these sent out trains of electric waves through the ether.
By holding his resonator, or as we would call it now, his detector, at a little distance from his sending apparatus, when the latter sent out the electric waves they would set up electric oscillations, or currents of high frequency, in the ring detector and these in turn would make a stream of little sparks jump across the gap between the balls.
Here, then, was a complete wireless sending and receiving apparatus, but it would work only a short distance, probably not over 100 feet. But Hertz was not trying to invent a wireless telegraph; all he wanted to and did do was to prove that there were long electric waves and there his work ended.
After Hertz had shown how long electric waves could be set up by the sparks of an induction coil, other scientific chaps went to work to get up a better scheme to detect them. In 1890 Edouard Branly, of France, discovered that when metal filings were put in a tube and electric waves were allowed to fall on them the resistance of the filings was lowered, and Sir Oliver Lodge, in 1894, found that this was caused by the filings being drawn closer together, that is, they cohered. By connecting a coherer (see the diagram) as he called the filings detector, to a galvanometer and a dry-cell he was able to detect the presence of electric waves up to distances of 500 feet.
A year later Popoff, of Russia, made a receiver for studying electric storms—lightning is only gigantic electric sparks—and this consisted of a coherer, a battery, a relay and an electric bell. Popoff connected one side of the coherer with a wire which he ran up into the air, or aerial wire as we call it now, and the other side of the coherer he grounded, as shown in the diagram. This was the first time that an aerial wire and a ground had ever been used in connection with a coherer. With this apparatus Popoff was able to hear the coming of storms for hours before they appeared above the horizon.
About this time Guglielmo Marconi, who was only 20 years old, was going to the University at Bologna, Italy. Prof. Righi who lectured on physics there was repeating Hertz’s experiments and used Branly’s coherer for detecting the electric waves. This set Marconi to thinking and it was not long before he had an experimental wireless set of his own, thus becoming the first wireless kid.