Effects of the U.S. High-altitude Nuclear Test Series of 1962 on Radio Propagation

THIS communication lists observations made in Melbourne of some high-frequency transmissions and the very-low-frequency standard frequency transmission NPM from Hawaii on 19.8 kc/s during the American test series at Johnston Island in 1962. The July 9 explosion was in the megaton region but the October–November bombs were stated to be sub-megaton. Decreases in high-frequency signal-level which occurred were immediate, that is, less than the receiving system response time (about 1 sec). NPM phase shifts were advances, as measured by the retardation observed during the ensuing period until the normal phase pattern was re-established. In each case the advance occurred well within the time constant of the very-low-frequency receiving system (9 sec). In one case (November 1, 1962) NPM signal-level increased after the explosion.