Antenna Factor and Gain Calculations

Antenna Factor and Gain Calculations — EMC Tool

Enter the desired frequency and any one of the remaining fields. The tool will calculate the rest. * Valid only for 50 ohm systems.

Works like the reference tool: change Frequency and one of (AF, Gain dBi, Gain numeric) and the remaining values update. Uses the attached formulas and \(\lambda=c/f\).

Frequency (MHz)

Must be > 0.

Antenna Factor (dB/m)

Enter AF OR Gain dBi OR Gain numeric.

Gain (dBi)

If you enter Gain dBi, AF will change automatically.

Gain (numeric)

If you enter Gain numeric, AF will change automatically.

Frequency	—	(MHz)
Antenna Factor	—	(dB/m)
Gain	—	(dBi)
Gain	—	(numeric)

Formulas (50 Ω systems)

\[ AF = 20\log_{10}\!\left(\frac{9.73}{\lambda \sqrt{G_{\mathrm{num}}}}\right) \] \[ G_{\mathrm{num}}=\left(\frac{9.73}{\lambda\,10^{AF/20}}\right)^2 \] \[ G_{\mathrm{num}} = 10^{G_{\mathrm{dBi}}/10} \qquad G_{\mathrm{dBi}} = 10\log_{10}(G_{\mathrm{num}}) \] \[ \lambda = \frac{c}{f},\quad f = (\mathrm{MHz})\times 10^6,\quad c=299792458\ \mathrm{m/s} \]

Input rule used: Frequency is always required. The tool uses the first non-empty among: AF → Gain(dBi) → Gain(numeric). Clear a field if you want another one to drive the calculation.

Definitions & Illustration

Concept overview

Antenna Factor (AF) / Correction Factor

Antenna Factor (or correction factor) is defined as the ratio of the incident electromagnetic field to the output voltage from the antenna and the output connector.

Gain (dBi)

Gain (dBi) is the ratio of the signal received or transmitted by a given antenna as compared to an isotropic antenna. Antenna gain is achieved by making the antenna directional.

* These equations are stated as valid for 50 Ω systems.

Directional antennas concentrate energy, increasing gain (dBi) compared to an isotropic radiator (0 dBi).

Antenna Factor and Gain Calculations