This tool calculates the Antenna Factor (**AF**) from the Antenna Gain (**G**) and Frequency of operation (**f**).

**Formula**

**AF = 20*Log _{10}(9.73/(位鈭欸))**

where,

**位 = c/f**

**c** is the speed of light, **f** is the operating frequency and **位** is the wavelength

and

**G** is the linear value of Antenna Gain relative to that of an isotropic antenna.

**How to use the Calculator**

Enter

- Antenna gain (in dBi) – this is typically provided by manufacturers in the data-sheet
- Frequency of operation (in MHz)

Example calculation: for a gain of **8 dBi** and frequency of **915 MHz**, the Antenna Factor is **21.50 dB/m**.

Increasing the antenna gain to **12 dBi** at the same frequency gives a lower value of **AF = 17.5 dB/m**

**Background**

Antenna Factor is the ratio of the electric field **E** (units: V/m or 渭V/m) to the voltage **V** (units: V or 渭V) induced across the terminals of an antenna. It is a measure of how much energy is captured by the antenna.

**For a fixed value of E, a higher Antenna Factor implies a smaller effective voltage. This translates to a lower antenna gain in dBi. **

The units are dB-per-meter or **dB/m**.

**Notes**

The equation for Antenna Factor takes the effect of impedance mismatch into account and only applies under the following conditions

- When the receiving antenna is in the far field of the transmitter
- Impedance is 50 ohm
- Antenna and incident field is matched in terms of polarization