On a method of determining the state of polarisation of downcoming wireless waves

Abstract

In recent papers an account has been given of the application of certain experimental methods to the study of the characteristics of wireless waves deviated through large angles by the upper atmosphere. Observations by these methods have shown that, for wave-lengths of the order of 300 to 500 metres the downcoming waves possess, in general, components of electric force both in and at right angles to the plane of propagation and that somewhat similar changes of intensity take place in both components during the dark hours; but information on the nature of the polarisation ( i. e ., on the numerical values of the constants of ellipticity) has been lacking. Such information would be of interest from two standpoints. In the first place it has been shown that, if the electrical carriers in the upper atmosphere are of electronic mass, the influence of the earth’s magnetic field would be such as to cause the reproduction of magneto-optical phenomena for wave-lengths within the wireless spectrum. In such a case we might expect to find some relation between the measured constants of ellipticity and the direction of transmission with reference to the earth’s magnetic field. Secondly, a matter of practical interest, since all recent experimental work has confirmed the original suggestions of Eckersley and Bellini that the errors experienced in coil direction finding are due to the presence of a component of electric force at right angles to the plane of propagation, and, since signal variations are due to the component in the plane of propagation, we might expect some correlation between directional errors and fading, if the downcoming ray is of sensibly constant polarisation. Attempts to find such a correlation have been made by Reich but with negative results.