Further investigations of very long waves reflected from the ionosphere

Abstract

In a previous paper Best, Ratcliffe and Wilkes (1936) described two kinds of measurement made on waves of length 18.8 km. (frequency 16 kc./sec.) emitted from the British Post Office sender GBR situated at Rugby. In the first kind of measurement the interference pattern produced at the ground by the superposition of the ground wave and the downcoming wave was investigated over a range of distances from 65 to 145 km. from the sender in a fine running east from Rugby. From the observed positions of the maxima and minima of this ground interference pattern it was concluded that the waves were probably reflected from a height of about 74 km. on a September day, although, because of uncertainties in assigning the order of interference to the different maxima, the possible reflexion heights of approximately 62 and 85 km. could not be definitely excluded. The results were interpreted on the assumption that reflexion took place at a horizontal surface without change of phase. In § 2 of the present paper we describe an extension of these measurements to greater distances. At first the measurements were extended to the sea along the line running east from Rugby, and later were continued to greater distances on a line running north from Rugby. These measurements enabled us to take a further step in resolving the ambiguity in the determination of the reflexion height, and to compare the propagation characteristics in a northerly and an easterly direction.