Question: Is A Balun Needed For A Dipole Antenna?

What does a dipole antenna look like?

A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods.

Most commonly it consists of two conductors of equal length oriented end-to-end with the feedline connected between them.

Dipoles are frequently used as resonant antennas..

How long is a dipole antenna?

Dipole Antenna Length. When determining how long to make each leg of a Dipole antenna, dividing the frequency in MHz into 468 will give the overall length. To find the half wave, divide that number by two. This will give you the length of each leg of the antenna.

How do you feed a dipole antenna?

Feeding a dipole antenna. Ideally, a half-wave dipole should be fed using a balanced transmission line matching its typical 65–70 Ω input impedance.

Why is a balun used in an antenna?

Radio and television To avoid feed line radiation, baluns are typically used as a form of common mode choke attached at the antenna feed point to prevent the coaxial cable from acting as an antenna and radiating power.

When should I use an antenna balun?

Baluns. A Balun is used to “balance” unbalanced systems – i.e. those where power flows from an unbalanced line to a balanced line (hence, balun derives from balance to unbalanced). As an example, consider a coaxial cable connected to a half-wave dipole antenna shown in Figure 1.

What balun do I need for a dipole?

Use a 1:1 Tuner Balun. Use as short a coaxial cable as in a multi-band dipole system. Vertical or Horizontal Loop: The best balun for operation far from resonance is a 1:1 ratio current Tuner Balun.

Is a dipole balanced or unbalanced?

Antennas can be balanced or unbalanced. A balanced antenna is symmetrical about the feed point (e.g. a dipole) whereas an unbalanced antenna is not systematical about the feed point (e.g. a Windom). In the real world all antennas are unbalanced to some degree.

Why is coaxial cable unbalanced?

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.

Does a dipole have to be straight?

Dipole antennas need not be installed in a horizontal straight line. They are generally tolerant of bending, sloping or drooping as required by the antenna site. Remember, however, that dipole antennas are RF conductors.

Do I need a balun on my dipole?

Paul, a dipole does not *have* to have a balun. Having one may help prevent RF from coming down the line into the shack and may improve the radiation characteristics of the dipole, but I’ve run dipoles connected straight to coax without a problem. Put one up without a balun and see how it works for you.

What is a 4 to 1 balun?

A 4:1 balun has four times the balanced impedance as unbalanced impedance. Balanced and Unbalanced. Balanced lines and loads, by definition, have equal voltages from each terminal to ground. Each balanced terminal or conductor must also carry precisely equal and exactly out-of-phase currents.

What is a balanced antenna?

A balanced antenna has symmetry about the feed point, for example a dipole. A balanced feed system has two conductors carrying equal but opposite voltages. This would be twin-wire ladder-line, window line or similar. An unbalanced feed usually has one conductor grounded. Typically this would be a coaxial cable.

How do you make a simple dipole antenna?

It is very easy to create a simple 1/2 wave dipole, all you need is some lengths of wire such as the core of some mains flex or even a straightened out metal coat hanger, some co-ax cable and a connector for your scanners antenna input (usually BNC or SMA).

How do I choose a balun?

Select a balun closest to the antenna feedpoint impedance (you’ll have to get this from textbooks or modeling), and use it at the feedpoint or where the feedline from the antenna ends. Be sure the feedline between the balun and antenna feedpoint matches the antenna impedance as closely as possible.

How do you attach a balun to an antenna?

Just trace the flat wire to where it connects to the antenna. Often times there are screws connecting the flat wire. Disconnect them and connect the screws through the metal rings on the balun/adapter and you’re done. Just run a coaxial cable to the home from that point.

Can a balun go bad?

Since a balun is a passive device, and if you don’t run more power than it is rated for through it, it should last forever unless it gets physically damaged.