Recent Investigations on the Propagation of Electromagnetic Waves

Since the summer of 1922, quantitative measurements have been carried out on the signal strengths of the American high power stations WQK and WSO, using an objective measuring method. The object of these measurements is to study the propagation of electromagnetic waves. It has been shown that these phenomena can be studied only by continued measurements. Curves are presented showing the field strengths on three successive days and nights once each month for the year February, 1923-January, 1924. In view of the agreement of the calculated values of field strength and the values actually found at night, it is concluded that the night value is to be regarded as the normal one and the day value as the abnormal or disturbed one. An explanation of the diminution of field intensity is given by assuming that the atmosphere is "electrically turbid" by day in consequence of the heating of the earth and the resulting vertical motion of masses of heated air. The waves are refracted, absorbed or reflected (and hence weakened) at the boundary surfaces of air masses of different densities. Diurnal and annual variations of field intensity can be readily explained by this theory. It was not possible to establish any difference between field intensity in a large city and in nearby open country. The derivation of a universally applicable formula giving the field strength, while taking account of all absorption losses, is regarded as impossible at present.