Some measurements of the reflexion coefficient of the ionosphere for wireless waves

Abstract

The first measurements of the attenuation of wireless waves in the ionized regions of the upper atmosphere were made by Appleton and Ratcliffe in 1930. The results of their measurements were expressed in terms of the "reflexion coefficient" of the reflecting region, this coefficient being so defined as to be a measure of the total absorption suffered by the atmospheric wave in its passage from the sender to the receiver. It was pointed out that in order to estimate the reflexion coefficient it is necessary to know (l) the intensity of the waves starting out in an upward direction from the transmitting station towards the ionized regions, and (2) the intensity of the waves coming down to the ground after deviation by the region. The intensity of the waves at the receiver may readily be found, but it is much more difficult to measure the intensity of the waves leaving the sender. In the experiments of Appleton and Ratcliffe, the calculated value of the latter factor was used. In recent papers by one of us an account has been given of measurements of the amplitude of wireless waves retracted by the ionized regions of the earth's atmosphere. In these papers the development of the Breit and Tuve method for this purpose has been described and its advantages emphasized. The chief advantage of the method is that the waves which have been once reflected by the ionized regions may be received separated from those which have been more than once rejected between the ionized regions and the surface of the earth, thus permitting the reflexion coefficient to be directly calculated from the relative amplitude of these waves. Since, however, it is not always possible to observe double reflexions it is desirable to calibrate the apparatus so that the reflexion coefficient may be calculated from the amplitude of the first reflexion. A method of doing this is described in this paper.