デッカ電波の長距離伝搬特性-II : 北九州チェン…II

Abstract

During the year 1973-1975, five observations on Decca frequencies for 72 hours composed of decometer reading and accompanying with field strength measurements were made at three sites in the Inland Sea (Seto-Naikai). The experiments described in the paper lead the conclusions suggesting some interesting behavior of Decca radio waves. In both signal strength and ambient noise seasonal variation did not change clearly that were obtained by field strength meter with 1kHz bandwidth. Since the field strength in daytime were nearly constant through the observations at Ooshima and Yuge/Hiroshima where is 192km and 293km from master station respectively, the ground wave could be ascertained at two sites. Observed field strength versus distance was found to be a little more attenuated than Norton's theory, thereafter it is suggested that it is due to the propagation effects of multi-islands topography and mountain path in Kyushu island. Decometer readings of each pattern in daytime at Ooshima and Yuge/Hiroshima were enable to assume nearly constant (Table 5). Accordingly the authors considered that these results established repeatability and reliability of the system. In night, the lane slips on decometer occurred frequently in the range of such unexpected phenomenon. To the contrary, the lane slip could not be found at Kagoshima where is the same distance of Yuge from master station. Analysis of difference on the phenomenon taken place at two sites could not introduce the accurate conclusion. However, the authors could demonstrate that the difference of propagation path will only be due the directional difference north/south to east/west.