High Frequency Apparatus Page 43

THE SPARK GAP 43 To counterbalance the disadvantages enumerated, we may say that the results obtained with this form of gap are remarkable. The high frequency discharge from a Tesla or Oudin coil operated with it is astonishing; instead of the thin, wiry discharge or spark, we get a flaming, white discharge that can best be compared with the flame from a very high potential, low frequency transformer. The high frequency discharge is not silent, however, but it partakes of a loud crashing hiss. For electro-therapeutic work, the quenched gap is splendid, providing it is properly. designed, built, and cared for. The X-Ray current is particularly energetic and for auto-condensation, where a high discharge rate is imperative, the milli-amperage may reach 1400 without great discomfort to the patient. So, the reader will see that even with all of its many troublesome features, the quenched gap is well worth building, if for purposes of experiment only. The Rotary Quenched Gap.-For radio telegraphy, a high pitched note is highly desirable as this spark can be distinguished from the atmospheric crashes and other extraneous sounds so often heard in the telephones of a radio receiver. The ordinary rotary gap gives this note and works well. The 500-cycle alternating current sent into a special transformer and used to discharge across a quenched gap works even better but the 500-cycle current is a thing not to be attained by the average experimenter. Along came a chap a few years ago with a combination of quenched and rotary gap that threatened to displace the 500-cycle sets for, by means of his transmitter, the ordinary 60-cycle current could be sent into the apparatus and be made to produce a clear-cut musical note with every possible advantage of the quenched gap and with many additional advantages as well. In the rotary quenched gap, the rotating electrode