difference between balanced line and unbalanced line

This page on balanced line vs unbalanced line describes difference between balanced line and unbalanced transmission line types. Link to types and basics of transmission line is also mentioned.

A transmission line is a 2-wire cable which connects transmitter/receiver parts of wireless system with the antenna. The purpose of transmission line is to carry RF energy from one end to the other.

Usually antenna is located outdoor for best RF signal reception and equipments are located indoor to have protection against environmental factors such as rain, wind, dust etc.

There are two types of wire transmission line viz. balanced line and unbalanced line.

Balanced Line

balanced line

The figure-1 depicts balanced type of transmission line. Balanced line is constructed using two parallel conductors which are spaced about 1/2 inch to several inches. Insulating spacers are used to keep the wires separated. These spacers are made using ceramic or plastic materials.

The term "balanced line" means same amount of current flows in each wire with reference to ground. The direction of current in one wire is 180 degree out of phase with the current in the other wire. In balanced line, none of the wires are connected to the ground.

Unbalanced Line

unbalanced line

The figure-2 depicts unbalanced coaxial type of transmission line. In this type of unbalanced line, one conductor is connected to the ground.

As shown in the figure, coaxial cable (i.e. coax) consists of solid center conductor surrounded by plastic insulator(e.g. teflon). Over the insulator there is another conductor made of fine wires. At outer cover is made of plastic which protects the fine wire braid shield.

Coaxial cable is unbalanced line because current in center conductor is referenced to braid. The braid conductor is connected to the ground. Coaxial cables are available in various sizes starting from 1/4 inch to several inches.

Out of the two transmission line types, coaxial cable is widely used.

Transmission line, microstrip line and coaxial line

Types and basics of transmission line
Types and basics of microstrip line
Types and basics of coaxial line

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