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Radio Digest, November, 1930, page 101:

Scientific  Progress  of  the  Radio  Arts

By  Howard  Edgar  Rhodes,  Technical  Editor

Experiments  with  High  Power
THE  WESTINGHOUSE Electric and Manufacturing Company was recently granted permission by the Federal Radio Commission to experiment with broadcast transmitter power up to 400 kilowatts, which is eight times as much power as is used by the largest existing broadcasting stations. These experiments will be made at the new KDKA station being built near Saxonburg, Pa.
    Success of these experiments will depend largely upon a new tube designed by Westinghouse engineers. This tube is rated at 200 kilowatts, it is six feet high, and weighs 60 pounds. Quite a tube! In operation it is necessary to cool the tube, in the same manner that an automobile motor is cooled, by means of circulating currents of cold water.
    Approximately five tons of cooling water must be passed through the water jacket of the tube each hour it is in operation--one hour's operation of the tube would heat enough water to supply the requirements of an average home for several weeks.
    Whenever a broadcasting station desires to increase its power, or make experiments with the use of high power, someone always seems to raise the cry of "super-power", forgetting that the only reason that a station desires more power is to improve its service to the public. When the term "super-power" is applied to a large power station, such as is to be erected in South Carolina, with a capacity of 200,000 kilowatts. The phase has some significance. Back in 1924 Mr. David Sarnoff very sensibly suggested that broadcasting stations using considerable amounts of power could more properly be referred to as "long range stations".
    After all, the success of any station depends largely upon its ability to supply a large number of listeners with a signal strong enough for satisfactory reception at all times of the year. This means that the signal must be strong enough to override local noise and static, for no simple, cheap, and effective device to eliminate static has ever been invented--not that such a device wouldn't be of great utility!
    The Institute of Radio Engineers, an organization which numbers among its members many of the most prominent Radio engineers throughout the country, has laid down some very specific recommendations regarding the mest desirable location of broadcasting stations. These recommendations include one to locate a broadcasting station at such a distance from the nearest populous center as to make the interference produced by the station negligible in comparison with its service area. Although the recommendations are based on definite technical considerations, they really consider the old adage, "the greatest good to the greatest number".
200 kilowatt vacuum tube