Musical Thunderstorms

Radio Record, Volume IV, Issue 11, 26 September 1930, Page 3

Musical Thunderstorms

Interesting Short-wave Phenomenon. HE General WDlectric Company, Schenectady, New York, forwarded the following information to Mr. R. Leslie Jones, Wellington. It should prove of great interest to readers :- "Musical thunder, accompanied by a vivid electrical display, has been encountered by radio engineers of the G.E.C. in their investigations near Schenectady of high-powered, shortwave broadcasting. In these miniature thunder storms, which oceur during any kind of weather, daylight or darkness, clear or overcast skies, the thunder is converted into music which corresponds to the input of the radio microphone. WGY_ engineers have solved the problem of handling 200 kilowatts of power modulated, on long waves, but new difficulties are presented in the use of powers above 15 kilowatts on the short-waves. In using powers up to 15 kilowatts in the an- _ tenna no unusual phenomenon has been a al observed, but when it was first attempted to increase the power to 35 kilowatts in the antenna vivid coronas flashed, wavering like ghostly spectres in mid-air. "This corona demonstration did not appear as long as the carrier alone was on, but as soon as the engineers attempted to modulate, the are was struck in the surrounding air. This are generally started about three or four feet from the antenna and shot upward four feet in the air. Since the power supplying the are was moduvated with music the are alternately collapsed and built up in size corresponding to the modulation. This acdon set up air wave vibrations similar co thunder, but instead of the roar and roll of thunder it was a musical sound similar to the music being broadcast. Men working 300 or 400 feet away thought they were hearing the output of a giant loudspeaker. If the are were allowed to continue it moved out toward the end of the antenna, due to movement of the hot gases, arced across the _ insulators, eracking them open, and finally the intense heat melted the copper and enused the antenna to drop. The trouble was solved in two ways. Antenna wire of larger diameter was adopted, and a large corona plate or half-sphere was placed on each end of the antenna. These measures reduced the voltage gradient at the wire surface due to the increased radius of curvature of conducting surface. It is now possible to get 35 kilowatts of power, modulated 100 per cent. in the antenna without wasteful and destructive coronas."