Antenna Calculator

Antenna gain is the ratio of the power radiated in its main direction to the power that an isotropic antenna (theoretical reference) would radiate with the same input power. It is expressed in dBi (relative to isotropic) or dBd (relative to dipole). A half-wave dipole has a gain of 0 dBd = 2.15 dBi.

The effective area (Aeff) is given by Aeff = (lambda^2 x G) / (4 x pi), where lambda is the wavelength in meters and G is the linear gain. For a dipole at 900 MHz (lambda = 0.333 m) with a gain of 1.64 (2.15 dBi), Aeff = (0.111 x 1.64) / 12.566 = 0.0145 m^2 = 145 cm^2.

The -3 dB beamwidth (half-power) is the angle at which the radiated power drops to half (-3 dB) of its maximum value. For a high-gain directive antenna, the beamwidth is narrow (5-10 degrees). For a typical sector antenna: 65 degrees in azimuth and 7 degrees in elevation. The empirical gain-beamwidth relationship: G (dBi) approx 10 x log10(32400 / (az_bw x el_bw)) for a lossless antenna.