How much gain does an antenna have compared to a half-wavelength dipole if it has 6 dB gain over an isotropic radiator?

An isotropic radiator is a theoretical, mathematically perfect point source that radiates energy equally in all directions in a perfect sphere. A standard half-wavelength dipole, however, does not radiate equally in all directions; its inherent physical shape creates a radiation pattern that gives it a gain of approximately 2.15 dB over an isotropic radiator (dBi). To convert an antenna's gain from isotropic gain (dBi) to dipole gain (dBd), you must subtract the dipole's inherent 2.15 dB advantage. The standard formula is: dBd = dBi - 2.15. Given an antenna with a stated gain of 6 dBi, simply subtract 2.15. The calculation (6 - 2.15) yields 3.85 dBd. Distractor values like 8.15 dB usually come from incorrectly adding the conversion factor instead of subtracting it.