Height extends the line-of-sight horizon
A higher antenna can see farther over Earth curvature. The geometric approximation in kilometers is 3.57 × (sqrt(tower height) + sqrt(device height)) when heights are in meters.
Radio refraction can extend the apparent horizon
A common planning approximation uses an effective Earth radius of 4/3, giving a coefficient near 4.12. Weather and atmospheric structure can produce different real refraction.
Horizon is not the same as usable coverage
Terrain, clutter, antenna tilt, frequency, power, device sensitivity, interference and carrier design can reduce service well inside the calculated horizon.
Frequently asked questions
How far is the radio horizon for a 30 m tower?
With a 1.5 m device height, the geometric horizon is about 23.9 km and the standard 4/3-Earth radio estimate is about 27.6 km.
Does a taller tower always improve mobile coverage?
Height can improve line of sight, but antenna tilt, capacity, interference and the intended coverage area still govern network design.
Why is actual coverage shorter than the result?
The equation only models Earth curvature. Buildings, hills, trees, frequency, antenna patterns and receiver limits add real losses.