When a wireless signal is low and being influenced by heavy interference, it might be possible to upgrade the antennas to create a more solid wireless connection. To determine the strength of an antenna, we refer to its gain value.
An antenna's gain is a measure of how well the antenna will send or pick up a radio signal. The gain value is measured in decibels-isotropic, or dBi. The gain value of an antenna is a unit of comparison to a referencethat reference being an isotropic antenna. An isotropic antenna is an antenna that sends signals equally in all directions (including up and down). An antenna that does this has a 0dBi gain.
An antenna's rating (gain) is the difference between the 0db isotropic antenna and the actual antenna rating. As an example, a wireless antenna advertised as a 15-dBi antenna is 15 times stronger than the hypothetical isotropic antenna.
The initials "dB" reference decibels, and the "i" references the isotropic antenna. dBi is a unit measuring how much better the antenna is compared to isotropic signals.
When looking at wireless antennas, remember that a higher gain rating means stronger sent and received signals. In terms of performance, the rule of thumb is that every 3dBi of gain added doubles the effective power output of an antenna.updated