dBi

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The performance of the system's antennas, however, are measured in decibels specified with respect to some standard reference element such as the "isotropic radiator" of a dipole. (An isotropic radiator is an imaginary, ideal transmitting antenna that radiates a signal equally well in all directions—theoretically a sphere. The sun is often given as an example of an isotropic radiator.) One of the actual measurement units is dBi, which means "decibels isotropic" or "gain over isotropic"—a measurement of signal gain often used in radio antenna design, which refers to signal gain in an isotropic radiator. Such an imaginary perfect antenna is a point suspended in space far from the Earth, with nothing nearby to interfere with the signals as they expand in perfect spheres.

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