11.4.3 Other Factors
Type of terrain. Surface waves follow gradual variations in terrain with little additional loss. However, large or abrupt changes in elevation can introduce screening effects that reduce range. Vegetation cover also contributes additional attenuation, particularly when wet. Sparse bushland introduces modest additional loss, whereas dense jungle can severely attenuate surface-wave signals due to absorption within the foliage. In practical link assessment, ground type, terrain profile, and vegetation must therefore all be considered.
Polarization. Surface-wave propagation is effective primarily for vertically polarized waves. A horizontally polarized electric field is strongly attenuated at the ground boundary because induced currents in the surface effectively short-circuit the field component parallel to the ground. Consequently, surface-wave systems employ vertical polarization, requiring vertical antennas for both transmission and reception.
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