Sphere gap discharge voltages at high frequencies

The paper describes a series of experiments made by the authors to determine the values of steady high-frequency, high-voltage currents required to discharge between seven-inch copper spheres in air, at ordinary temperatures and barometric pressures. A 15-kw. arc generator was used as the source of high-frequency sustained high voltage, and the apparatus employed in securing and measuring currents of 123,000, 255,000 and 612,500 cycles is described in detail. The sphere-gap standard consisted of electrolytic copper spheres mounted on the ends of brass tubes in treated wooden frames, and the gap lengths were accurately determined by means of calipers and micrometer screw or steel scale. The results obtained are given in Tables II and III and are also charted in curves I and II, Fig. 5. The 123,000-cycle values show a right line relation between sphere gaps and discharge voltage, which line, when extended, passes through the origin. The high-frequency voltages are almost uniformly 4.5 kv. below the 25-cycle voltages observed by Chubb and Fortescue.