Nikola Tesla Books
126 HIGH FREQUENCY APPARATUS The rotor is a disc of ½ in. aluminum, 6 in. in diameter, and having 12 semi-circular sections removed from its periphery, thus leaving a series of 12 teeth, each tooth presenting a surface of ½ x ½ in. to the stationary electrode mounted on either side. The rotor disc is fitted to a fibre bushing and this bushing is mounted upon the shaft of a small alternating current fan motor, which should have a speed of approximately 1,800 r.p.m. The stationary electrodes are lengths of 3/8 in. zinc rod threaded and tipped with large discs of fibre to serve as adjusting knobs to vary the gap between the electrodes and the disc. The entire apparatus is mounted upon a substantial base of dry wood. The Stationary Spark Gap.-This gap may be a stock one purchased from a wireless dealer or it may be constructed to order. The design given in Fig. 1 covers a gap of substantial proportions and one that is designed for continuous operation. The gap consists essentially of the two nickel steel or silver electrodes, mounted upon threaded rods, and supported by square brass pillars of suitable proportions. One of the threaded rods is fitted with a large fibre handle for purposes of adjustment. Radiators consisting of discs of brass separated by washers are mounted in back of the electrodes in order that the latter may be cooled. The construction is so clearly shown in the drawings that no further description is deemed necessary. The Oscillation Condenser.-The condenser comprises four units of .01 mfd. capacity each, so arranged that they may be connected in multiple one at a time by closing the three single pole knife switches mounted on the top of the cabinet. The connections are clearly shown by the diagram in Fig. 4.
