Antenna Gain Calculator
Calculate the gain of a parabolic dish antenna from its diameter and operating frequency using the standard aperture formula.
m
GHz
%
Gain
41.0 dBi
Gain (linear)12,507
Approx Beamwidth1.46 °
Gain vs Dish Diameter
How Parabolic Antenna Gain is Calculated
Antenna gain measures how effectively the dish concentrates energy compared to an isotropic radiator.
Formula
G = eta x (pi x D / lambda)^2
G(dBi) = 10 x log10(G)
Where D is diameter, lambda is wavelength (c/f), and eta is aperture efficiency (typically 0.5 to 0.7).
The beamwidth approximation is theta = 70 x lambda / D degrees.
Example Calculation
A 1.2 m dish at 12 GHz with 55% efficiency.
- 01Wavelength: 0.3 / 12 = 0.025 m
- 02pi x D / lambda = 3.1416 x 1.2 / 0.025 = 150.8
- 03G linear = 0.55 x 150.8^2 = 0.55 x 22,741 = 12,508
- 04G dBi = 10 x log10(12508) = 40.97 dBi
- 05Beamwidth: 70 x 0.025 / 1.2 = 1.46 degrees
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