GeneralG9C04
How does antenna gain in dBi compare to gain stated in dBd for the same antenna?
B
Answer
Antennas and feed lines
Type
A
Gain in dBi is 2.15 dB lower
B
Gain in dBi is 2.15 dB higher
C
Gain in dBd is 1.25 dBd lower
D
Gain in dBd is 1.25 dBd higher
Answer Notes
Antenna gain is always expressed as a comparison to a reference antenna. The abbreviation 'dBi' refers to an isotropic radiator, a theoretical point source that radiates equally in all directions. 'dBd' refers to a standard half-wave dipole.
Because a standard dipole inherently concentrates its energy into a figure-eight pattern rather than a perfect sphere, it already has a natural gain of 2.15 dB over a theoretical isotropic radiator. Therefore, the numerical value for gain in dBi will always be 2.15 dB higher than the same antenna's gain in dBd.
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How do the lengths of a three-element Yagi reflector and director compare to that of the driven element?
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