Antenna Gain Calculator

Because gain depends on the aperture's physical size measured in wavelengths, not in meters. Raising Frequency shortens the wavelength while Aperture Width and Aperture Height stay fixed, so the same reflector becomes electrically larger and Gain climbs steeply -- this calculator's Gain rises monotonically with Frequency across its full 1 MHz to 100 GHz range at any fixed aperture and efficiency. This is why a small satellite-TV dish at 12 GHz achieves gain that would require an enormous antenna at VHF frequencies.

50-65% is typical for a well-designed parabolic reflector with a standard feed, which is why that range is called out in the Antenna Efficiency field's help text. Higher-quality reflectors with optimized feeds and low surface error can reach into the 65-70% range, while a poorly illuminated or badly blocked aperture can fall well below 50%. Raising Efficiency always raises this calculator's Gain output at fixed frequency and aperture size, since effective aperture is simply efficiency times physical aperture.

No -- it is a widely used engineering approximation for a parabolic reflector's half-power beamwidth, not an exact solution of the antenna's radiation pattern. The constant is commonly cited as 70 for a fairly typical illumination taper, though other references use values from roughly 58 to 70 depending on the assumed taper and reflector shape. This calculator applies the 70λ/D form independently to Aperture Width and Aperture Height, which approximates the beamwidth of a rectangular-aperture antenna such as a horn rather than a perfectly circular dish.

Yes -- Horizontal Beamwidth is inversely proportional to Aperture Width across this calculator's entire 0.01 m to 50 m range at any fixed frequency, because the 70λ/D approximation puts the aperture dimension directly in the denominator. The same relationship holds between Aperture Height and Vertical Beamwidth. A physically larger aperture always trades a wider footprint for a narrower, more concentrated beam.

dBi (decibels relative to an isotropic radiator) compresses gain's enormous working range -- from roughly unity for a small element to tens of thousands for a large dish -- onto a compact logarithmic scale that's easier to add and subtract in a link budget. This calculator reports both: Gain (Linear) is the raw ratio (4π × effective aperture / λ²), and Gain in dBi is simply 10 × log10 of that same linear value.