Practical Feed Lines: All You Need to Know

This post contains affiliate links, and I will be compensated if you make a purchase after clicking on my links, at no cost to you.

A cable that feeds radio signals by carrying them from radio antennas to transmitter/receivers is a practical feed line. You can call it a bridge that connects an antenna to the receiver, transceiver, or a transmitter.

This is highly used in broadcasting and wireless systems. Thus, you must know about this important component.

How does a practical feed line work?

Practical feed lines or feeders are transmission lines connecting the radio’s antenna to the transmitter/receiver. On the transmitting end, it feeds the RF current from the transmitter to the radio’s antenna. This is when the signals are sent in the form of radio waves.

This radio wave induces a little RF Voltage at the receiving antenna, which is further transferred to the receiver. This is how the signal is transferred through practical feed lines. They play a crucial role in carrying the generated energy between radio and antennas.

The quality of the practical feed line is also an important factor to consider. It doesn’t matter if you are working at HF, UHF or a VHF, any deterioration of quality might cause inconveniences in your ham radio.

Why must you carefully choose a practical feed line?

A feeder or feed line serves the basic purpose of carrying the RF voltage between two ends. Thus, its efficiency is important to maintain a stable communication. These feed lines are made up of specialized cables and possess a characteristic impedance.

This particular impedance must compliment the impedance of the antenna for successful and efficient signal transmission. However, when the impedance of the feeder you attach does not match, then the RF energy reflects the transmitting antenna.

After operating for some time, it will cause overheating in the transmitter and a considerable waste of energy. This condition is called Standing Wave. This is when you might require a tuner to make further adjustments to restore efficiency.

What must you follow while operating a feed line?

Coaxial cables, twin feed line, waveguide, and ladder line are some of the commonly used practical feed lines. Though their exterior is weatherproof and quite reliable, you must take care of some points in particular while operating them.

Firstly, when the radio frequencies increase, the signal loss also increases considerably. Thus, while choosing a practical feed line for high-frequency emission, you must choose the one designed for minimum signal loss.

Secondly, you must carefully match impedance to avoid standing waves, as discussed earlier. Lastly, the signal loss increases with the length of the feed line. This occurs as the resistance increases with length. Thus minimum usable length must be used.

Summing up

Practical feed lines are one of the most crucial components of a wireless communication system. Before choosing the best coaxial cable or a waveguide, it is important to check the intended purpose of the feed line.

Once you make sure that you follow all the necessary cautions while operating a feed line, it will produce desired results. Also, an ideal connection will ensure power efficiency and little or no wastage of energy.


Recommended Reading: