High Frequency Apparatus Page 98

98 HIGH FREQUENCY APPARATUS inserted in one lead from the gap to the primary of the Oudin or Tesla, while the other connection from the primary goes back to the gap. When the current is applied, the ball of the Oudin or the discharger of the Tesla should give out a large brush discharge of purplish fire. If the first trial does not result in this, try a variation of the primary turns of the oscillation transformer. This, together with a variation of the spark gap, will serve ultimately to bring the apparatus to the point of resonance. The Tesla coil will give a full 16 in. spark with the ½ k.w. transformer described in the early part of this chapter. The spark from the oscillation transformer is perfectly harmless if taken through a metal rod grasped firmly in the hand. No sensation of shock whatever will be experienced. If the discharge touches the bare skin, the current will leave a blister if applied for any length of time in one spot. Aside from this unpleasantness, no direful results may be expected. Whenever the apparatus is operated, the ground connection shown in Fig. 15 should be religiously made. This connection will protect the windings of the low frequency Fig. 15.-Diagram of connections