A radio wave in the process of propagation in space occupies a volume in the form of an ellipsoid of revolution with a maximum radius in the middle of the path, which is called the first Fresnel zone. Within this zone there should be no objects that absorb, reflect or scatter radio waves. (Any metal, reinforced concrete structures, houses, trees, etc.)
It is perfectly acceptable to narrow the Fresnel zone to 80%. Losses of a signal at the same time are quite admissible.
Related links:
- Fresnel zone - WikiPedia;
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