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What is an Unun: RF Antenna Unun

Posted:04:17 PM January 24, 2024 writer: iotbyhvm


An Unun, short for Unbalanced to Unbalanced, is a type of transformer used in RF antenna systems to match impedance between an unbalanced antenna and an unbalanced transmission line. It is designed to convert the impedance of the antenna to a value that is better suited for the transmission lines. Which helps in improving the signal transfer. Impedance matching is important in RF systems to minimize signal reflections and maximize power transfer. When the impedance of the antenna and the transmission line are not properly matched. It can lead to signal loss, distortion, and reduced efficiency.

An Unun consists of two windings, primary and secondary, wound on a ferrite core. The primary winding is connected to the unbalanced antenna, while the secondary winding is connected to the unbalanced transmission line. The ratio of the number of turns in the primary and secondary windings determines the impedance transformation ratio. When RF energy is applied to the primary winding, it induces a voltage in the secondary winding. This voltage is then transmitted to the transmission line, allowing for efficient signal transfer. The Unun effectively matches the impedance of the unbalanced antenna to that of the unbalanced transmission line, minimizing signal reflections and maximizing power transfer.

Let us understand the unun meaning. Ununs are an essential component in RF antenna systems, providing impedance matching and efficient signal transfer between unbalanced antennas and unbalanced transmission lines. Their ability to operate over a wide range of frequencies, compact design, and convenience make them a popular choice for various applications of RF. By implementing Ununs in your RF antenna system, you can ensure optimal signal performance, minimal signal loss, and enhance overall efficiency. Whether you are a radio enthusiast, a professional in this field, or you have a curiosity about RF technology, understanding the role of Ununs in antenna systems is key to achieving reliable and high-quality signal transmission and reception. In this section, you will understand the meaning of Unun.

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Antenna UNUN applications

An antenna unun serves as a type of RF transformer designed to connect two different impedance levels, particularly when dealing with unbalanced lines. Coaxial cables are commonly used as unbalanced feeders. They consist of a central conductor and an outer screen with the screen typically grounded. However, balanced feeders have two ungrounded lines which ensures equal and opposite signals cancel each other out, preventing power radiation.

Antennas can exhibit balanced or unbalanced characteristics. A dipole, for instance, is a balanced antenna since neither of its feed point sections is grounded. Conversely, antennas like end-fed wires or vertical antennas utilize the ground as part of the antenna, requiring an unbalanced feeder like coaxial cable. When there's a need for impedance transformation at the antenna's feed point, an unun comes into play.

Quarter-wave vertical antennas often present a feed impedance of around 20Ω, which is incompatible with the typical 50Ω coaxial feeder cable. To address this, an autotransformer, functioning as an unun, is incorporated into the base assembly. This unun matches the 20Ω impedance of the vertical antenna with the 50Ω impedance of the coaxial feeder. Ununs employed for matching quarter-wave vertical antennas are usually integrated into the base of commercially manufactured vertical antennas and are not often seen as separate components. In the case of end-fed wire antennas, there is a growing trend of bringing them directly into the radio room and interfacing them through an antenna tuning unit. This setup allows for effective matching and tuning of the antenna system.

Basic concept of the end fed half wave EFHW antenna

For optimal performance and to minimize RF energy exposure in inhabited spaces, the recommended approach is to install an end-fed wire in an open area, away from occupied regions. The antenna is then connected to a coaxial cable for feeding. The feed impedance of an end-fed wire, especially with the rising popularity of end-fed half-wave antennas, necessitates a method of matching the feeder to the antenna at its feeding point. This matching process is achieved through the use of a device called an unun.

Basic Unun Concepts

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Difference between Balun and Unun

When it comes to radio frequency (RF) systems and antennas, you may have come across the terms "balun" and "unun." These devices play an important role in matching impedance and ensuring efficient signal transmission. Let us understand "what are baluns" and Difference between Balun and Unun (unun vs balun). Below, you'll find a comparison chart that outlines the main characteristics and functions of both devices:





(balun vs unun)

A balun is a type of transformer that converts balanced signals to unbalanced signals, or vice versa.

An unun is a type of transformer that matches an unbalanced input to an unbalanced output, or vice versa.

Signal Conversion

Converts between balanced and unbalanced signals.

Matches unbalanced signals between different impedance levels.


Typically used for impedance transformation between different types of transmission lines or antennas.

Primarily used for impedance matching purposes.


Commonly used in radio frequency (RF) systems, such as antennas, to ensure efficient signal transmission.

Often employed in audio systems, such as connecting an unbalanced audio source to a balanced input.


Can have different configurations, such as 1:1, 1:4, or 1:9, depending on the specific needs of the system.

Typically has a 1:1 configuration, but can also have other ratios depending on the application.

Core Material

Usually made of ferrite or powdered iron cores.

Commonly made of ferrite cores, but can also be air-core or other materials depending on the requirements.

Common Designs

Common balun designs include the voltage balun and the current balun.

Common unun designs include the voltage unun and the current unun.


Used to eliminate common mode noise, improve signal quality, and prevent signal loss.

Used to match impedance levels, reduce reflections, and optimize signal transfer.

Signal Balance

Ensures the balance of the signal by canceling out noise and interference.

Does not focus on signal balance, but rather on impedance matching.

As you can see from the table above, what are baluns? and baluns vs ununs have different purposes and functions. While baluns are primarily used for converting between balanced and unbalanced signals, ununs are focused on impedance matching. Both devices play important roles in various applications, such as radio frequency systems and audio systems. Understanding the differences between baluns and ununs is important for selecting the appropriate device for your specific needs. Whether you're working with antennas, transmission lines, or audio equipment, choosing the right transformer will ensure optimal signal transmission and performance.

What is an Unun?

Unun, also known as unbalanced-unbalanced, is a device used to match impedance in unbalanced transmission lines. They are designed specifically for unbalanced lines. It is commonly used when there is a need to match the impedance of an unbalanced antenna to the impedance of the transmission line. Ununs come in different configurations, such as a 1:1 unun or a 9:1 unun. These ratios indicate the transformation ratio, reflecting the difference in impedance between the input and output sides of the device. The choice of the unun ratio depends on the specific requirements of the antenna and transmission line.

An unun is a type of transformer that matches impedance between unbalanced components, typically an unbalanced antenna and an unbalanced transmission line. The name "Unun" itself denotes its purpose – transforming an unbalanced system to another unbalanced system. The key function of an unun is to ensure efficient energy transfer between the antenna and the transmission line by adjusting the impedance to minimize signal reflections.

Ununs are used when there is a need to match impedance in unbalanced transmission lines, commonly in situations where the impedance of the antenna does not align with the impedance of the transmission line. By using an unun, the impedance can be adjusted to ensure efficient signal transfer and minimize signal loss. One example of using an unun is in long-wire antennas. These antennas often have high impedance, which may not match the impedance of the transmission line. By using an unun with the appropriate transformation ratio, the impedance can be matched, resulting in better signal transmission and reception.

Key features of Ununs include:

  1. Transformer Design: Ununs consist of a transformer with specific winding ratios designed to match the impedance of the antenna to that of the transmission line. The winding ratio determines the transformation of impedance, allowing for effective signal transfer.
  2. Configurations: Ununs come in various configurations based on the required impedance transformation. Common configurations include 1:1, 4:1, 9:1, and others, each serving different purposes in antenna systems.
  3. Core Material: The core material used in Ununs is crucial for their performance. Ferrite cores are commonly employed due to their high permeability and ability to handle RF frequencies effectively.
  4. Frequency Range: Ununs are designed to operate across a wide frequency range, making them versatile for different antenna setups. The specific frequency range depends on factors such as core material, winding configuration, and construction quality.
  5. Balanced to Unbalanced Transition: Ununs bridge the gap between unbalanced antennas and unbalanced transmission lines, ensuring a smooth transition of signals without significant reflections or loss.
  6. Compact and Lightweight: Ununs are often compact and lightweight, making them suitable for various applications, including portable setups and field operations.
  7. Weather Resistance: In outdoor installations, Ununs are designed to be weather-resistant, providing durability and reliability even in challenging environmental conditions.


In summary, Ununs play an important role in RF antenna systems for several reasons. Ununs contribute to impedance matching, ensuring that the antenna's impedance aligns with that of the transmission line. This alignment optimizes signal transfer and minimizes signal loss. Ununs are designed for broadband operation, capable of functioning across a wide range of frequencies. This versatility makes them well-suited for various RF applications, providing efficient performance across different frequency bands. Additionally, Ununs stand out for not requiring extensive ground radials for proper operation, offering a more convenient and flexible option for RF antenna installations. Lastly, their compact and lightweight design makes Ununs easy to integrate into different antenna systems, whether for portable or fixed installations, further enhancing their appeal in the realm of RF technology.

Baluns and ununs are both crucial devices in RF systems and antenna setups. While baluns are used to convert between balanced and unbalanced signals, ununs are employed to match impedance in unbalanced transmission lines. Understanding the differences between these devices and knowing when to use each one is crucial for ensuring optimal signal transmission and maintaining signal integrity. Baluns and Ununs share the common goal of impedance transformation; the distinction lies in their applications and the types of systems they address. Baluns bridge the gap between balanced antennas and unbalanced transmission lines, whereas Ununs focus on matching impedance between unbalanced components.

As technology continues to advance and the demand for efficient communication systems grows, understanding the nuances of components like Ununs becomes increasingly important. These devices not only enhance the performance of antenna systems but also play a vital role in ensuring reliable and seamless communication across diverse scenarios. As we continue to explore new frontiers in communication technology, the role of Ununs is likely to become even more prominent, contributing to the evolution of efficient and reliable antenna systems.


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