The large plates at the right and the coil at the top handle the enormous radio frequency energy generated at this point. They compose the tank condenser of this transmitter and are made of aluminum. According to E.B. Landon, chef operator of the transmitting station, the water must be tested frequently to protect the tubes and the cooling system. Ordinary city water cannot be used because it contains lime and other minerals which form harmful scale in the coils. At the KDKA station this ultra-soft water is pumped to an outdoor cooling pool before going to the cooling coils and the tubes.
Hot water coming from the station circulatory system enters the pool through a fountain-like spray.
After cooling in the pool, it is pumped through the same circuit again. An idea of the capacity of the cooling problem may be obtained from the statement that approximately five tons of cooling water must be passed through the water jacket of the cube each hour it is in operation. This water cools the tube in the same manner as water in an automobile cools the motor. One hour's operation of the tube would heat enough water to supply the domestic requirements of the average home for several weeks. While of course these AW-200 tubes will only be used to generate high frequency power for radio stations, an appreciation of the power capacity of one of these tubes can best be gained by a comparing familiar household devices.