HF Radio Wave Absorption in the Nighttime : Part II. Measurements of the Field Intensity of HF Radio Waves by Means of Narrow Band Receivers (Reports of the Japanese Antarctic Research Expedition)

Abstract

Narrow-band receivers developed for receiving exclusively the JJY signal in the presence of interferences by the other standard frequency waves with an identical carrier frequency are used since 1967 for the observation of HF radio wave absorption on board the ship of the Japanese Antarctic Research Expedition. This paper summarizes the technicality of the receiver, and presents the results of measurements obtained in the 10th JARE (Nov., 1968-Apr., 1969) by means of the receiver. Dependence of the ionospheric absorption in the nighttime on the solar activity was confirmed quantitatively by the same analysis as that given in Part I (1971) of this paper.