How does an UnUn work?

How does an UnUn work?

A Balun is used to match a balanced line to an unbalanced line. An Unun is used to match an unbalanced line to another unbalanced line. This is a 4:1 Current Balun. That means it can match a 200ohm antenna to a 50 feed line.

What is an UnUn for antennas?

An unun is an impedance transformer, usually 4:1 or 9:1 , which matches an unbalanced antenna to a feedline. A 9:1 transformer is often used for an end-fed half wave antenna.

What does a 1 1 UnUn do?

The RU-1:1 is a 1:1 Unun intended to help remove unwanted RF from the coax cable shield. It is normally used as a common-mode RF choke for short coax cable runs or non-resonant antennas.

How do you test for UnUn?

You want to test the UnUn so one easy way to do that is to place a 450 non inductive resistor across the output of the UnUn and an antenna analyzer to the input. Now sweep the UnUn. Don’t expect to get a perfect 1 to 1 SWR from 6 to 160 meters.

What is the difference between a balun and a UnUn?

The major difference between them is that baluns are designed to match impedances between balanced and unbalanced circuits, whereas ununs provide impedance matching between two unbalanced circuits.

What is the difference between a UnUn and balun?

Why is a balun used?

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.

Is a balun the same as a choke?

You can use either a 1:1 balun or a choke balun at the feed point of the antenna or where the balanced part of the system meets the unbalanced part. The choke balun usually does the same thing as a regular 1:1 current balun but adds the high impedance path to the common mode currents too.

What is the input impedance of a transmission line?

If Z L is equal to the characteristic impedance Z 0 of the transmission line, then the input impedance Z i n will be equal to Z L. Otherwise Z i n depends on both Z L and the characteristics of the transmission line.

What’s the difference between an autotransformer and an unun?

The term “unun” simply means unbalanced to unbalanced and requires no specific impedance ratio. On the other hand an autotransformer is an unun also, and can have an impedance transformation depending on tap point. As a matter of fact, the technically correct term for what is usually called an unun is an autotransformer.

Which is the impedance of a terminated lossless transmission line?

Equation 3.15.2 is the input impedance of a lossless transmission line having characteristic impedance Z 0 and which is terminated into a load Z L. The result also depends on the length and phase propagation constant of the line. Note that Z i n ( l) is periodic in l.

When to use an unun on a coax cable?

They are often used with “untuned” verticals to limit the extreme VSWRs that would otherwise occur on the coax feedline – and therefore the cable losses – on some bands. A properly designed UnUn should do nothing other than alter the antenna impedance by a fixed ratio.