Free Space Path Loss (FSPL):

$FSPL_{dB} = 20 \log_{10}(R_{km}) + 20 \log_{10}(f_{MHz}) + 32.44$

Friis Equation (Logarithmic / dB form):

$P_r (dBm) = P_t (dBm) + G_t (dBi) + G_r (dBi) - FSPL_{dB} - L_{misc}$

This ideal equation assumes free space propagation with no multi-path, reflections, or atmospheric absorption.