Gain

What is Gain?

The gain of an antenna is the relative increase in radiation at the maximum point expressed as a value in dB above a standard. The standard to which other antennas are compared is usually a ½-wavelength dipole. The standard antenna is given a reference gain of 0dBD (zero decibel referenced to dipole). This comes from:

<math> \mbox{gain} = 10 \times \log \left( \frac {Pe}{Pi} \right) </math>

Where Pe is effective radiated power and Pi is input power

An antenna with the effective radiated power of three times the input power would therefore have a gain of:

Pe = 3, Pi = 1

<math> 10 \times \log \left( \frac {3}{1} \right) = 4.77\mbox{dBD} </math>