High Frequency Apparatus Page 83

KICKING COIL APPARATUS 83 3 ence to the diagram in Fig. 2. For direct current work, the large kicking coil is left in the circuit, while for use on alternating currents, it is short circuited with the singlepole, single-throw switch shown in the illustration. The letters "A.C." and "D.C." should be plainly stamped beneath the respective clips of the switch as indicated in the diagram to prevent possible confusion. The capacity of the condenser is varied as may be found necessary by means of the copper strips which are forced into the clips projecting from the condenser case. In operating the apparatus, the adjusting knob of the interrupter should be in the "open" position. Turn the current on and screw the contact in gradually. As soon as contact is made, the interrupter will begin to vibrate and a sputtering spark will form at the break of contact. The operation should start with about half of the condenser capacity thrown in and with half of the turns of the Oudin coil primary in use. Perhaps a spark will be in evidence at the ball terminal of the oscillation transformer if the ground terminal is brought up to within a couple of inches of the ball. If not, try an adjustment of the capacity in the condenser or a variation of the primary turns. This will show some improvement and the operator may then screw in the vibrator contact a bit further; a considerable increase in length and thickness of spark will result. A further adjustment of capacity or inductance and a tentative tightening of the contact will tune the apparatus perfectly until the maximum results are obtained. Electro-therapeutic Work.-The outfit described is admiraby adapted for light X-Ray and vacuum tube work. If a D'Arsonval current is desired for auto-condensation, the builder is strongly advised to make a second oscillation transformer in which the primary has five turns and the secondary ten turns of copper ribbon. This coil may be