A feed line is a cable that transmits radio signals to a receiver or transmitter from a radio antenna. The feed line connects the antenna with the transmitter, receiver, or transceiver and is commonly used in wireless communication and broadcasting antenna systems. It transmits radio frequency energy from the antenna to the receiver. When properly operated, it does not emit any energy.

Techopedia explains Feed Line:

A feed line is a specialized cable that connects an antenna to the transmitter or receiver in a wireless or radio communication system.

The most commonly used feed lines include:

1. Coaxial cable: Comprising four components – the conductive center wire, the plastic insulation surrounding the wire, the copper shielding on the insulation, and the tough outer covering.

2. Twin-lead: A wire enclosed in plastic, marked at the same distance along the entire line.

3. Ladder line: Also known as the parallel conductor feeding line, it consists of two conductors separated by insulating bars.

4. Waveguides: Used for microwave frequencies.

Feed lines are made from specialized cables because they carry the radio frequency voltage. The antenna and feed line must have the same characteristic impedance to efficiently transfer RF power. If the impedances are not matched, RF energy will be reflected back toward the transmitter, leading to energy waste and excessive heating of the transmitter. An antenna tuner can be used to make the necessary changes for energy transfer.

When using feed lines, it’s important to keep in mind:

– Signal loss increases with frequency.

– Signal loss also increases for longer feed lines, as signal resistance increases along with the feed line length.

This post was written by Justin Tidd, Director at Becker Mining Communications! For over 15 years, Becker Communications has been the industry’s leader in radio communication in tunnels and electrical mining communication systems. As they expanded into surface mining, railroads, and tunneling they added wireless communication systems, handheld radios, tagging, and tracking systems, as well as gas monitoring.


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