line-of-sight wave

direct wave

direct wave
Direct and indirect waves.
An electromagnetic wave that travels directly from a transmitting antenna to the receiving antenna along a straight line. Direct waves are responsible for part, but not all, of the signal propagation between two antennae when a sight line connecting the antennae lies above the ground. The surface (ground) wave and the reflected wave also contribute to the overall signal at the receiving antenna. Also called a line-of-sight wave or a space wave, it is prevalent in frequencies above 30 MHz.
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