Antenna Gain Calculator

Understanding Antenna Gain Calculator

Antenna gain measures how well an antenna focuses energy in a particular direction compared to an isotropic radiator. Higher gain means more focused radiation.

How to use this calculator

1. Enter the antenna directivity, usually given as a unitless ratio or sometimes converted from dB.
2. Enter the radiation efficiency as a decimal or percent, depending on how the calculator asks for it.
3. Check the calculated gain in dBi to see the antenna's effective directional performance.
4. Use the result to compare antennas or estimate link performance in your design.

The formula explained

The formula computes gain from directivity and efficiency, so it shows how much of the antenna's directional focus is actually usable after losses. Since gain is the product of \(\eta\) and \(D\), lower efficiency reduces the final gain.

• G = antenna gain
• \(\eta\) = radiation efficiency
• D = directivity

Step by step method

1. Find the directivity \(D\) of the antenna.
2. Write the efficiency \(\eta\) as a decimal, such as \(0.80\) for \(80\%\).
3. Multiply \(\eta\) by \(D\) using \(G = \eta \times D\).

Worked example

Problem. An antenna has directivity \(D = 8\) and efficiency \(\eta = 0.75\). Find the gain.

1. Substitute the values into the formula: \(G = 0.75 \times 8\).
2. Multiply: \(G = 6\).
3. So the antenna gain is \(6\) in linear units, which corresponds to its gain value before any dB conversion.

Tips and common mistakes

• Make sure efficiency is entered as a decimal if the calculator does not ask for a percent. For example, \(85\%\) should be \(0.85\).
• Do not mix up directivity and gain, because gain includes efficiency while directivity does not.

Frequently asked questions