Radio research

His first research into radio was to make some scientific sense out of the behaviour of coherers, those enigmatic radio detectors used in the first years of radio telegraphy. His success earned him a Doctor of Science degree from the University of London in 1901. This study of coherers was extended into a comprehensive study of crystal detectors and from there into all technical aspects of wireless. As the Dictionary of National Biography puts it, "Eccles was in close contact with nearly every aspect of the subject, as research worker, member of advisory committees, president of learned societies, writer of articles and textbooks, patentee and expert witness. For many years he was the leading (and almost the only) independent physicist working in the field of radio science. "

One spin-off from his crystal-diode research was the crystal oscillator. In about 1909/10, he discovered ways of making crystal detector circuits oscillate and suggested that "under certain conditions a rectifying detector could become a generator of oscillations and conversely a generator of oscillations could be used as a rectifier." One writer has over-enthusiastically suggested that Eccles could therefore be regarded as the grandfather of the transistor. In fact, Eccles had discovered that a contact between two pieces of galena could produce a negative resistance and that, as with electric arcs, this could generate oscillations. He did not have a prototype transistor, but he may" have had a very early tunnel diode.

When the triode began to gain wider use, just before WW1, Eccles was soon studying its applications. It is said that he was one of the first to represent its action algebraically in terms of the self-and mutual conductance of its electrodes (1919/20) and he used the triode in a variety of circuits. It was during this work that the Eccles/Jordan multivibrator was invented. Several circuit configurations seem to have been stu­died "for obtaining various types of continuously acting relay," and patents were taken out by the Admiralty in 1918. This would imply that the work was performed under Admiralty contracts during the war. Because of his Quaker beliefs, it is said, Eccles was himself reluctant to patent his inventions.

Eccles and Jordan did other fascinat­ing work for the Admiralty. In unpublished memoirs, Eccles recalled the use of a triode to sustain the vibrations of a tuning fork. This work, published in began in 1914. The aim was to use the harmonics of a vibrating tuning fork to evade a Telefunken patent which "covered all forms of back-coupled triode circuit and dominated the future of radio" - an interesting nicety, considering the patent was held by a foe. The result was,"a generator of remarkable constancy," which when "combined with a phonic motor" gave a "precision clock." This precision clock was then combined with a known method of picture transmission to give, in 1918, "a secret method for the transmission of naval signals.²"

Another Eccles-Jordan idea was to connect two triode oscillators to produce wavelengths as short as seven metres using ordinary receiving triodes. "The apparatus was invented in 1916 at the request of the War Office and the patent was later bought by the Marconi Company and used in their short-wave beam stations," wrote Eccles. A separate account refers to a 60MHz short-wave transmitter designed by Eccles in 1915 and tested by the French Army for short-distance work. The signals were picked up in Syria and may have been the first indication of the long-distance possibilities of short-wave radio.

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