Antenna A has a gain of 11dBi, and antenna B has a gain of 8dBi, so how much greater is the gain of antenna A than antenna B?

Question

Options

• A3dB
• B3dBi
• C3dBd
• Dnot sure

• A
  74% (32)
• B
  5% (2)
• C
  7% (3)
• D
  14% (6)

Explanation

When subtracting two antenna gain values, the reference suffix cancels out - just like canceling units in algebra. 11 dBi − 8 dBi = 3 dB, a dimensionless ratio expressing how much stronger one signal is relative to the other.

Why B (3 dBi) is wrong: "dBi" is an absolute measurement referenced to an isotropic radiator. Once you take the difference between two dBi values, the isotropic reference cancels, so the result cannot be dBi.

Why C (3 dBd) is wrong: "dBd" references a half-wave dipole antenna. Neither antenna in the problem is expressed in dBd, and even if they were, the difference would still resolve to plain dB, not dBd.

Why D is wrong: The math is straightforward subtraction; there is a definite answer.

Memory tip: Think of it like unit cancellation - dBi minus dBi leaves dB, just as meters minus meters leaves a plain number. Whenever you compare two gains of the same type, the suffix drops off and you're left with just dB.

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