Low frequency electromagnetic radiation 10-900 cycles per second

During the period of July 10 to September 15, 1955, detection of electromagnetic signals in the frequency range 10 to 900 cycles per second was undertaken. Loops and a vertical antenna were used in a site remote from man-made interference. The spectrum was analyzed with a narrow bandwidth (2 to 6 cycles per second) amplifier. Indicated diurnal patterns show a maximum around local midnight. The peak in the band lies in the region 40 to 200 cycles per second. During one period of several hours, a large increase in narrow band energy was seen near 33 cycles per second. The possibilities of this being radiation at the gyrofrequency of the sodium ion is discussed.