Local Reflection of Wireless Waves from the Upper Atmosphere

Abstract

IN some recent experiments carried out for the Radio Research Board of the Department of Scientific and Industrial Research, measurements have been made of the diurnal variation of the signals received at Cambridge from the stations of the British Broadcasting Company. During the day-time these signals have been found to be fairly constant, but night-time variations of intensity have been measured at distances from the transmitter so short as 50 miles. For example, the signals from London at Cambridge are found to be constant during the day; but, at about sunset, variations, which are often of a periodic character, begin, and continue through the dark hours. In this case the mean night value is very little different from the day value. For more distant stations (for example, Bournemouth) the phenomena are different. During the day the signal is weak and constant; but after sunset the intensity increases and, though variable, the signal maxima may be several times the day value. In this case the variations in signal intensity are larger, less rapid, and less markedly periodic than in the case of the London signals.