High Frequency Apparatus Page 202

202 HIGH FREQUENCY APPARATUS The transformer requires a current of from 40 to 50 amperes at full load and the leads from the stage pocket must necessarily be of heavy cable. The stage cable used in connection with motion picture arcs is admirably adapted to this purpose and the outfit should include from 50 to 100 feet of this cable. Connection between the transformer secondary and the rotary spark gap electrodes may be made with the high tension cable used in the ignition circuit of automobiles. This cable is to be fitted with substantial lugs as in use it will have to be connected and disconnected a great many times. The oscillation circuit comprising spark gap, condenser and primary of oscillation or high frequency transformer should be connected with the cable. Prevention of Kick Back.-The ground connection shown in the diagram is of the utmost importance as without it high voltage surge back through the transformer wires will be almost sure to puncture the insulation of the transformer. To further protect the latter and to safeguard the house wiring, a protective condenser should be connected across the transformer primary at the point where the line wires are connected. This condenser is made by joining two 2-mfd. telephone condensers in series across the line and grounding the neutral point or wire that connects the two. For the sake of simplicity, the spark gap is shown as a stationary one rather than a rotary. The connections are, of course, the same for the two. When all has been connected up, the spark gap electrodes may be adjusted to the point where they just miss the rotating member and the gap motor started. For this first test, the primary clip of the oscillation transformer may be placed on the center turn to permit of variation in