A balun is a type of transformer: it’s used to convert an unbalanced signal to a balanced one or vice versa. Baluns isolate a transmission line and provide a balanced output. A typical use for a balun is in a television antenna. The term is derived by combining balanced and unbalanced.
When should I use an antenna balun?
Baluns are used in many areas to transition between balanced & unbalanced scenarios: one key area is for radio frequency, RF applications for antennas. RF baluns are used with many antennas and their feeders to transform a balanced feed or line to an unbalanced one.
Why do you need a balun?
The main reason to use a balun is to reduce the feedline radiation. Feedline radiation can distort the radiation part of the antenna-the direction we want the RF to travel. This can produce nulls in the pattern directions that nothing can be transmitted or received.
What is the work of balun?
This transformer is known as a balun, and they are in operation in anything from telephone lines to transmitters. Baluns are used both to sort out the flow of AC signals and make the necessary impedance transformation between coaxial cable, which has a low impedance, and balanced loads, which have higher impedances.
How do I know if I need a balun?
Firstly, we will need a balun to use a balanced line feeder or balanced antenna in any case as radios today are not presenting a balanced output. The next point is the effect that any close by objects have on the balanced feed line, walls, buildings in general, towers, all metal objects, ground, everything!
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.
Does a balun reduce noise?
Whilst a balun is usually associated with reduced unwanted transmission line radiation (eg. from the feedline and power cord), a balun can also help minimise unwanted noise picked up by your feedline.There are many sources for design and construction of simple baluns on the internet.
How do you attach a balun to an antenna?
Usually you would make a loop with the end of the antenna wire through the eyelet and then wrap the loose end around the antenna wire. The pig tail lead from the balun is then wrapped around the antenna wire and soldered.
Why is coax considered unbalanced?
Coaxial cable is unbalanced line because current in center conductor is referenced to braid. The braid conductor is connected to the ground.Out of the two transmission line types, coaxial cable is widely used.
Is a balun needed for a dipole antenna?
The use of a balun will prevent the coax radiating any power or picking up any noise. In many practical situations it is possible to operate the dipole satisfactorily without one, but there may be a slight increased risk of interference if one is not used. Simple baluns can be bought from antenna suppliers, or made.
What is the difference between a balun and a transformer?
Baluns convert between balanced and unbalanced lines, and RF transformers perform impedance matching, voltage or current step-up or step-down, and DC-isolation between two circuits.
What is balun ratio?
Normally a balun has a 1:1 impedance ratio between its input and output sides. By modifying the design of the balun, it is possible to have other impedance ratios. Examples: 4:1, 6:1, 9:1, etc. In these cases, we also refer to these at Transmission Line Transformers (TLT).
Is a loop antenna balanced or unbalanced?
The feed point impedance of a full wave loop antenna is theoretically in the vicinity of 100 ohms and requires a 2:1 impedance transformer to match with 50 ohm line or a 1.5:1 transformer to match with 75 ohm cable. These transformers are unbalanced (coax input) to balanced (loop output) (also called 2:1 baluns).
What is a 1 1 balun used for?
Key uses for the 1:1 current-balun: a) is to marginalize the inverted-L current in the transmission-line feeding a dipole-antenna. This will prevent a radiating Feedline and prevent distorting the antenna’s radiation pattern. There will be some flux in the core but it’ll be minor due to the small current causing it.
What is a 9 1 balun used for?
These are sometimes known as a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50? (unbalanced) coaxial input, hence UnUn.
Do you need a 1 1 BalUn?
If a dipole antenna is fed with a coaxial cable from the transceiver it is always recommended to use a BalUn. BalUn means: Balanced to Unbalanced. This enables us to adapt an unbalanced fed system (coaxial cable) to a balanced antenna system (dipole antenna). The 1:1 BalUn 800 Watt is suitable for QRO use.
Who is W8JI?
Tom Rauch, W8JI, is one of the most renowned antenna authorities of our times. He has an outstanding web site where he shares his knowledge with all of us who are willing to take the time and read it, AND he was the chief architect of the portfolio of Balun products sold by DX-Engineering in the states.
Why are the ham bands so noisy?
It comes mainly from noise from atmospheric discharges which are always taking place somewhere in the world and are propagated by the ionosphere. There is also the noise coming from space usually called galactic or cosmic noise.
Do antenna baluns go bad?
That balun is usually the thing that goes bad. It’s pretty durable and works well, but most baluns are simply printed circuit boards and with enough hot and cold weather, they can crack. At the same time, some of the wiring that connects parts of the antenna together or connects to the balun can crack.
What is the difference between a balanced and unbalanced antenna?
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.
What are basic differences between balanced line and imbalanced line?
Unbalanced transmission uses one signal wire that carries the voltage. The ground wire acts as a reference point. Balanced transmission uses two signal wires that both carry the voltage but the signal on one of them is phase-shifted by 180°, so it is exactly inverted.
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