Baluns

A balun is short for "balanced to unbalanced", and refers to a device that converts a balanced signal into an unbalanced one, and vice versa. In amateur radio, a balun is often used to connect an antenna, which is usually tuned, to an unbalanced transmission line, such as a coaxial cable.

Balun types

There are several types of balun, designed for different applications and antenna configurations. Each type has its own advantages and disadvantages, and choosing the right balun will depend on the specific application.

Numbers, such as 1:1, 1:4, 4:1, 1:9, 9:1, refer to the balun's transformation ratio. This ratio indicates the relationship between antenna impedance and transmission line impedance.

Balun 1:1: This type of balun has a transformation ratio of 1:1. This means there is no change in impedance between the antenna and the transmission line. It is generally used to connect a balanced antenna (such as a dipole antenna) to an unbalanced transmission line (such as coaxial cable) without changing the impedance.

Balun 1:4 and 4:1: These baluns have transformation ratios of 1:4 and 4:1, respectively. A 1:4 balun is used to adapt a 50-ohm antenna impedance to a 200-ohm transmission line, while a 4:1 balun does the opposite, adapting a 200-ohm antenna impedance to a 50-ohm transmission line. These baluns are often used with long-wire or V-shaped antennas.

9:1 and 1:9 baluns: These baluns have transformation ratios of 9:1 and 1:9, respectively. A 9:1 balun is used to adapt a 50-ohm antenna impedance to a 450-ohm transmission line, while a 1:9 balun does the opposite. These baluns are often used with non-resonant antennas, such as non-resonant long-wire or T-shaped antennas.

It's important to note that choosing the right balun depends on the antenna impedance and the transmission line you're using. It's also crucial to understand that using a balun with the wrong transformation ratio can result in poor impedance matching, which can reduce the efficiency of your antenna system.