Radio Horizon Calculator

How it works

The distance to the horizon of one antenna of height h is the square root of 2 × k × R × h, where R is the Earth radius (6371 km) and k the refraction factor. With k = 4/3 this is about 4.12 × √h kilometres for h in metres. The maximum line-of-sight range between two antennas is the sum of their horizons.

This is the limit over smooth ground. The real range also depends on hills and obstacles: see the coverage map to calculate it over real terrain, and the guide on radio horizon and antenna height.