Line-of-Sight Range (Space Wave) (d_max ≈ √(2 R h_t) + √(2 R h_r))

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d_max ≈ √(2 R h_t) + √(2 R h_r)

What each symbol means

SymbolWhat it stands for
RRadius of Earth (≈ 6.4×10⁶ m in standard problems)
h_rHeight of receiving antenna above ground (m)
h_tHeight of transmitting antenna above ground (m)
d_maxMaximum line-of-sight distance between transmitting and receiving antennas (m)

When to use this

Flat Earth + optical LOS geometric model; neglects atmospheric refraction unless problem states effective Earth radius.