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For the same antenna, how does gain in dBi compare with gain in dBd?

dBi is 2.15 dB higher than dBd.

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  1. Gain in dBi is 2.15 dB lower
  2. Gain in dBd is 1.25 dBd lower
  3. Gain in dBi is 2.15 dB higher ✔

Why: dBi compares gain to an isotropic radiator and dBd compares it to a dipole. A dipole has 2.15 dBi of gain, so the dBi figure is 2.15 higher.

Huh, didn't know that: Two three-element Yagis stacked half a wavelength apart in free space give about 3 dB more gain than one.

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References

Answer: Gain in dBi is 2.15 dB higher. dBi compares gain to an isotropic radiator and dBd compares it to a dipole. A dipole has 2.15 dBi of gain, so the dBi figure is 2.15 higher.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    B. Gain in dBi is 2.15 dB higher
    Checked 2026-10-11.
  2. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    B. Approximately 3 dB higher
    Checked 2026-10-11.

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