Wireless: From Marconi's Black Box to the Audion (review)

The contents of Guglielmo Marconi's black box were the components he brought from Italy in 1897 when he traveled to London to interest the British authorities in his work and to seek his first patent. Taken individually those components were not remarkable, but, as William Preece told an audience at the Royal Institution, "Marconi has produced from known means . . . a new system of telegraphy that will reach places hitherto inaccessible." Sungook Hong's aim in this book is to probe "the substance and context" of scientific and engineering practice in the early years of wireless. In his first chapter he sets out the physical background to wireless in the work of Heinrich Hertz and others who had produced and detected Hertzian waves, and then describes Marconi's early work in detail. The second chapter addresses the dispute about the first demonstration of wireless telegraphy—Marconi or Oliver Lodge? Hong comes down firmly in favor of Marconi.

The theme of the third chapter is "grafting power technology onto wireless telegraphy" and John Ambrose Fleming, Marconi's scientific adviser, becomes a central figure in the story. Hong has written elsewhere about Fleming, but here he draws on his notebooks and other previously unpublished material. The greatest distance over which Marconi had sent radio signals was about two hundred miles. He needed far more power to signal across the ocean. Fleming, a professor of electrical engineering at University College, London, had earlier been a consultant to Edison at the Holborn Viaduct power station in London, and to the Edison and Swan United Electric Light Company. He had also conducted research on Ferranti transformers and thus knew about the problems of generating and switching heavy alternating currents at high voltages. His collaboration was vital to Marconi's successful transmission of a signal across the Atlantic in December 1901.

Fleming's role as Marconi's adviser ceased for a time after the "Maskelyne affair" of 1903. Nevil Maskelyne was a rival wireless investigator who later introduced the Poulsen arc as a radio-frequency wave generator. While a demonstration of Marconi's latest equipment was being prepared at the Royal Institution for a lecture by Fleming, Maskelyne sent a message from his own transmitter which was picked up on the Marconi receiver and included this remark: "There was a young fellow of Italy, Who diddled the public quite prettily." Although Maskelyne did not disrupt the actual lecture, he had shown that it was possible to interfere with messages sent by wireless—which was unfortunate for Fleming, because Fleming was seeking to demonstrate that with their latest "tuned" system such interference was impossible. The incident undermined Marconi's confidence in Fleming, and they parted company.

Resuming his own research at University College, Fleming made two inventions connected with wireless. One was his cymometer, an instrument for measuring wave length. Far more significant, however, was the thermionic valve, which could rectify high-frequency alternating currents. It arose from Fleming's earlier research in electric lighting. All carbon filament lamps tend to blacken in use as carbon is evaporated from the filament and deposited on the cooler glass bulb. With direct current the blackening is concentrated on one side of the lamp. Fleming had been studying this phenomenon, known as the "Edison effect," in the late 1880s and found that if an additional electrode were included in the bulb a current could then flow between the filament and that extra electrode, but in one direction only. With the thermionic valve to his credit, Fleming resumed his role as scientific adviser to the Marconi Company in 1905. The following year Lee De Forest announced the audion, or triode valve, which was Fleming's valve with a further electrode included between the filament and Fleming's extra electrode. This device could function both as an amplifier and as an oscillator, enabling wireless telegraphy to make rapid...