Question
How does antenna gain in dBi compare to gain stated in dBd for the same antenna?
Answer Options
- 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
Correct Answer: B
Explanation
Antenna gain is measured relative to a reference antenna, either a hypothetical isotropic radiator (dBi) or a half-wave dipole (dBd). Since a half-wave dipole is a real antenna, it has an inherent gain of 2.15 \text{ dB} over the theoretical isotropic radiator.
Therefore, to compare the two units, you must add 2.15 \text{ dB} to the dBd figure to get the dBi figure. Consequently, the Gain in dBi is 2.15 \text{ dB} higher than the gain in dBd for the exact same antenna, as the dBi reference is lower.
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