How far can two stations talk on VHF/UHF, line-of-sight? Antenna heights in, realistic range out.
Use ~6 ft for an HT in someone's hand; hundreds of feet for a repeater on a ridge or tower.
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maximum radio line-of-sight range between the two stations
Radio waves bend slightly with the atmosphere, so the radio horizon is ~15% beyond the visual one: d(mi) ≈ 1.41 × √h(ft) per station; ranges add.
This is best-case over smooth terrain — a ridge in the path beats any math. Check a terrain profile for real paths.
Range grows with the square root of height: 4× the height only doubles the range. Get above the local clutter first; after that, altitude is expensive.
Tropospheric ducting, knife-edge diffraction, and meteor scatter all break this rule — that's what makes VHF fun.