In mountainous terrain, why is antenna placement critical for line-of-sight communications?

• A. Terrain blocks paths; elevated roosts reduce shadowing and multipath, improving reliability
• B. Elevation has no effect on line-of-sight
• C. Shadowing cannot occur in mountain terrain
• D. Multipath is not a concern for VHF/UHF

Answer: (A)

Line-of-sight propagation is the governing factor for VHF/UHF links, and mountainous terrain can easily block the direct path between antennas. Elevating the antennas puts the radiating and receiving points above the terrain obstacles, opening a clear line of sight and expanding the radio horizon. This reduces shadowing, the signal loss caused by obstacles in the path, and also lessens the impact of multipath reflections from surrounding terrain that can cause fading. Elevation helps keep the first Fresnel zone clear, which improves link reliability. So, choosing elevated locations for antennas in mountains directly improves LOS reliability and overall communication performance.