Antenna Gain
Antenna gain is a measure of how much the antenna concentrates the energy fed to it in a particular direction relative to a reference antenna; it is written in dBi or dBd. An antenna is a passive component and produces no power: every dB gained in one direction is taken from other directions. Gain works to the same degree both when transmitting and when receiving.
Gain arises from the shape of the radiation pattern. An antenna that presses energy into the horizontal plane loses it upwards and downwards; in return it gains a few dB in the horizontal. As gain increases the beam narrows and aiming the antenna becomes critical.
- Low gain (0–3 dBi): wide coverage, insensitive to orientation. Suitable for a moving operator and variable geometry.
- Medium gain (5–9 dBi): adds range in the horizontal plane, but turns into loss if there is a height difference between receiver and transmitter.
- High gain (above 10 dBi): intended for links between two fixed points, not suitable for a mobile remote control.
In crane and construction machine applications the operator walks around the receiver, sometimes standing at a lower level, sometimes higher up. In this geometry a high gain antenna creates dead zones instead of increasing range. The right decision is to take a low gain antenna away from metal and place it higher.
Context in which this term is used: 433 MHz or 2.4 GHz?