Plain-language answer: Line-of-sight propagation is the direct and near-direct path between antennas, influenced by radio horizon, terrain, Fresnel clearance, diffraction, and refraction.
Why it changes the path
Raising either antenna can improve coverage more than modest extra power, but visual sight alone does not remove reflection or obstruction loss.
What to observe
Check height and terrain at both ends, frequency, polarization, feed-line loss, and Fresnel clearance.
The common mistake
Treating the optical horizon as an exact radio cutoff.
Planning boundary
Propagation models and field regions depend on frequency, geometry, terrain, atmosphere, polarization, antenna pattern, and measurement distance. Use them to plan and compare—not to guarantee a contact or installed range.
