How is parabolic antenna gain calculated?

Gain = η·(π·D/λ)², where D is the diameter, λ the wavelength and η the aperture efficiency. In dB: G(dBi) = 10·log10(η) + 20·log10(π·D·f/c).

What aperture efficiency should I use?

Real dishes run about 50–70%. 55% is a common default for a prime-focus dish; high-performance Cassegrain feeds can reach 65–70%.

What is half-power beamwidth?

HPBW is the angular width where the radiated power falls to half (−3 dB) of the peak. For a dish it is roughly 70·λ/D degrees — bigger dishes and higher frequencies give narrower, more directional beams.

Why does doubling the diameter add 6 dB?

Gain scales with diameter squared, and 10·log10(2²) = 6 dB. Likewise, doubling the frequency also adds about 6 dB of gain for the same dish.

Parabolic Antenna Gain & Beamwidth Calculator

Free parabolic antenna calculator. Enter dish diameter, frequency and aperture efficiency to get gain in dBi, the −3 dB half-power beamwidth, linear gain and effective aperture. Useful for satellite, microwave and point-to-point links.

Find the gain (dBi), beamwidth and effective aperture of a dish antenna.