[ G = \frac4\pi A\lambda^2 \eta_a ] where (A) = aperture area, (\eta_a) ≈ 0.5–0.7 for typical horns. [ G = \frac4\pi A\lambda^2 \eta_a ] where

Waveguide - Antennas

[ G = \frac4\pi A\lambda^2 \eta_a ] where (A) = aperture area, (\eta_a) ≈ 0.5–0.7 for typical horns.