The Communications Potentialities of the Trade Wind Inversion Duct, Analysis of Project Neptune Data

摘要

The analysis of propagation data for the trade wind duct shows that signals are strongly trapped and propagate with relatively low attenuation at the eastern end of the trade wind belt. At the western end, on the other hand, the attenuation rate is higher, varying from day to day from relatively low values characteristic of duct propagation to values typical of classical tropospheric scatter propagation. The overall average of the measured attenuation rates for the entire path from Dakar to Puerto Rico was 8.9 decibels per 100 nautical miles. Height gain is definitely present at the eastern end of the trade wind belt. The optimum height is just below inversion level, and the magnitude of signal enhancement ranges from 5 to 20 decibels. Height gain usually is not evident at the western end of the trade wind belt. In particular, the signal above the duct remains relatively strong, so that a broad range of heights is suitable at this end of the path. From the analysis of fading rates, lower bounds for the signal power correlation of 900 feet horizontally and 60 feet vertically are deduced. Consequently, the full gain of antennas having such large apertures may be realized and the bandwidth of the signal should be large. Since the fading rate is found to be roughly independent of distance, antenna gain and bandwidth should not diminish markedly with distance. Recommendations are given for additional experiments to refine the deductions from the data. (Author)