航行用100kHz電波帯の伝搬特性の解析とそれらによる船位精度の改善…VII : デッカ・システム-II

抄録

The present paper is construced by the eight monitoring records of the Japan Maritime Safety Agency over the Kita Kyushu Decca Chain during three years (1969-1972). And the other experiments were made to assist the analysis of these results above in Kagoshima Bay. The daytime phase difference deviations of each pattern of monthly mean at monitoring sites were variable respectively, its fluctuated range was set about ±10 cel normaly, and 30 cel range or more occured sometimes in special sites. It was considered that this phenomenon might be due to the skywave contamination, because the ground constant and the refractivity of atmosphere would not affect the propagation condition in such amplitude of phase fluctuation. These monitoring sites were situated in lighthouse where standed on the top of high cliff and faced seaside generally. The author examined that making the data apply to the Decca correction table at the surface of seawater off the coast. Moreover, in this examination, the range free from the effect was observed. The field strength and phase difference were obtained inhomogeneously and unsmoothly from sea to land and from sea to mountain. The difference of Decometer reading taken between land and sea is correct when derived from propagation mode above. The error presumably reduced in accordance with the increase of the distance from the coast. The correlation between the meteorological effects and the variation of phase difference pattern was also discussed. 16 (Purple), 4 (Red) and 3 (Green) were picked up during this period for example, and the analyses were based on variation of monitoring site simultaneously over five sites. The purple pattern is the most sensitve to the front approaching and the perfect correlation was admitted. The range of the effect on the phenomenon was observed to be within 100nmi from transmitting station.