1972 Volume 47 Pages 13-21
In fall of 1971, the evaluation test of the Kita-Kyushu Decca chain was simultaneously conducted at four site in the western parts of the Seto Naikai which is similiar to that of 1970. Moreover field strengths of the master station (85kHz) were measured at two points of the fours with continuous recordings. The principal conclusions obtained during two years can be summarized as follows ; 1) The phase deviations of all patterns varied from year to year and from site to site. 2) The big deviation (about 1 lane or more) was obtained at the site (Nada) where, closed to the bush hill. 3) To the contrary, the fluctuation of the phase difference at each site changed at constant rate, this suggesting the annual rateexist. 4) The field strengths observed were associated markedly with the theoretical value of day and night respectively, in addition, the close agreement was also shown between the phase fluctuation of the Purple pattern calculated and the strength at Nagahama observed. 5) Since the sudden change on the field strength at pre-sunrise effect was continued to 78° of solar zenith angle, all the nocturnal phase difference variations did not set the steady state of the groundwave condition. In order to reduce the effect of the nocturnal phase variations the method like the differential OMEGA was applied. The accuracy of the LOP will be able to improved 30% or so.
