This tool computes the Antenna Gain using:
- Antenna Factor (units: dB/m)
- Frequency of operation (units: Hz/kHz/MHz/GHz)
Antenna Gain Formula
Gain (dBi) = 20*Log10(9.73/(λ*(10)AF/20))
- λ = Wavelength = c/f, where c is the speed of light and f is the frequency
- AF = Antenna Factor
It is the ratio of the electric field E (units: V/m or μV/m) to the voltage V (units: V or μV) induced across the terminals of an antenna.
The units are dB-per-meter or dB/m.
💡 A higher value of Antenna factor means an electric field induces a smaller voltage across the antenna. This implies or results in a lower value of antenna gain.
At 915 MHz,
- AF = 10 dB/m, the Antenna Gain is 19.45 dBi
- AF = 30 dB/m, Antenna Gain is -0.55 dBi
At a higher frequency of 2450 MHz for an AF of 10 dB/m, the Gain is 28 dBi.
The gain increases with frequency as according to the equation, it is inversely proportional to the wavelength. The wavelength at 2450 MHz is smaller than at 915 MHz (Frequency to Wavelength Calculator).
 Antenna Factor on Wikipedia