Ground Wave Propagation on Mixed-Paths through Urban Areas

Medium-frequency (MF) ground wave propagation is playing one of the most important roles for a long distance communication. When the surface impedance of the earth along the propagation path changes the ground wave propagation is influenced strongly as it occurs when the radio wave traverses a border from an urban area to a suburban area or viceversa [1]-[4]. The measurements of the ground wave propagation in the urban areas have shown the unexpected high attenuation in some parts of cities and the anomalous variation pattern of the field strength with distance [2], [5][9]. In this paper, we shall examine both experimentally and theoretically the ground wave propagation over the mixed-paths which traverse first the open area along which one can see the transmitting antenna, then the built up area along which the density of the man-made objects is very high, and finally the medium density area. We will show that the experimental results, obtained in the measurements performed in Kanto area including the city of Tokyo in Japan, agree very well with the three-section mixed-path theory [1], [3], [4], [7]-[9].