Antenna Factor (AF) ↔ Antenna Gain
Convert between antenna factor (AF, dB/m) and antenna gain (dBi) at a given frequency (50 Ω, free space).
Worked example
(Frequency 100 MHz) Antenna factor AF 8.06 dB/m, Antenna gain 2.15 dBi
Formula
AF(dB/m) = 20·log₁₀(f[MHz]) − G(dBi) − 29.79
50 Ω system, free-space reference
How it works
Antenna factor converts the receiver input voltage to incident field: E(dBµV/m) = V(dBµV) + AF(dB/m). For a given gain, AF rises with frequency, hence AF = 20·log₁₀(f[MHz]) − G(dBi) − 29.79.
Practical tipThis is the ideal free-space relation. In real tests always use the AF from the antenna calibration certificate; use this calculator as a sanity check on certificate values, for example to spot an implausible gain.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10