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Popov Radio System
Nina Borisova
A Quantum Leap for Waves
It was Heinrich Hertz who first obtained man-made electromagnetic waves in his experiments in 1888/89 with a spark generator (Ruhmkorff coil with linear vibrator), the wave character of the spark discharge creating short-lived electromagnetic waves. The waves thus produced were received by a resonator located a short distance away from the generator’s aerial. At the moment when the resonator picked up the waves, hardly perceptible sparks were produced in the resonator gap that could be detected using a magnifying glass.
In early 1889, Popov attended a meeting of the Russian Physical-Chemical Society at which the St. Petersburg Professor N. G. Yegorov reproduced Hertz’s experiments, but in a manner that Popov felt to be insufficiently graphic. It took him only a few months to build a more compact and effective device to demonstrate Hertz’s experiments, which he then gradually improved on, so that by 1894 he had constructed a working transmitter that generated electromagnetic waves based on Hertz’s vibrator and using a Ruhmkorff coil. The receiver was more of a problem. In his search for a reliable receiver and indicator for the electromagnetic waves, Popov experimented with Geissler’s gas discharge tubes and a special version of Crookes’ radiometer. The results were unsatisfactory, and Branley’s radio-controlled conductor and Lodge’s receiver, although known at the time, were still in the experimental stage.
The radio-controlled conductor (Branley tube) was invented by the French engineer Edouard Branley in 1890 during his search for parallels between medicine and physics, in this case the capacity of tubes filled with metal filings to act as a conductor in the same way as nerves. The Branley tube was made of glass with metal outlets at each end filled with metal filings. The conductivity of these filings was many times higher if they were exposed to electrical charges, causing them to stick to each other. In order to return the tube to its original condition, it had to be shaken. It was the British physicist Oliver Lodge who first demonstrated the relationship between the conductivity of the Branley tube and electromagnetic waves. He extended the Branley tube by adding a mechanical construction that regularly shook the filings, known as the “trembler,” controlled by a separate clockwork mechanism independently of the electromagnetic waves received. Lodge called his indicator a coherer.
Like Hertz’s early experiments, hardly had Lodge’s paper been published in the journal Electrician in July 1894 than his experiments with the coherer were repeated by physicists around the world, but only Popov was able to obtain a practical result. In 1895 he created a system in which the device was mounted on a wooden base and placed in a metal cage to screen it from electrical interference. The aerial used was either a vertical length of wire or an asymmetrical vibrator with a parabolic mirror. The circuit proposed by Popov was also used for thunderstorm detectors and telegraph transmission.
This was the first transmission and reception system for remittent electronic waves suitable for the reliable communication of information in the history of telecommunications. The method became the prototype for the subsequent first generation of wireless communication systems. The next stage of the development of radio communications was the work of Guglielmo Marconi, who achieved world-wide recognition and was awarded the Nobel Prize in 1909, a development that Alexander S. Popov did not survive to see, his death occurring in 1905.