What is the impedance of a coaxial cable

Coaxial cables are one of the most used cables for transmitting radio frequency from one place to another. More commonly known as “Coax cables,” these are electrical cables that can easily transmit RF signals. These are extremely easy to install and do not require professional installation, and are durable for connecting antenna facilities to your desired place.

Coax cables are commonly used for residential and as well as for commercial use. There are many types of them that come in different sizes and diameters, some of which are the RG-58, RG-59, RG-6, and RG-213.

When selecting the best coaxial cable for use, impedance is taken as the first consideration for the desired type. Impedance plays a huge role in the selection and working of any kind of coaxial cable.

Both homeowners and businesses prefer coaxial cables. The reason is that these cables are very effective in transmitting the radio frequency signals quickly without any interference or damage to the wire. The signals are easily transmitted because of the shielded design of the cable, which allows quick transfers.

The components of a coaxial cable all work together to transmit the signals effectively. To know how impedance affects the working, you first need to understand how coax cables work.

Working of a coaxial cable

Coaxial cable consists of several layers or components, and you need to understand each one of them to know how coaxial cable works.

A center conductor, which in most cases is a thin copper wire. This copper wire is the main channel of transmission, which allows audio signals and video signals to pass through it, and then ultimately be transferred to the place where you want. The central conductor wire is often thin and covered by three different layers, which provide insulation and protection.

The dielectric plastic insulator covers the thin copper wire and is thicker than all of the layers of the coax cable. It surrounds the copper wire and provides basic insulation.

A critical layer that helps transmit signals effectively is the layer that covers the plastic insulator. It is a braided mesh made up of copper and sits above the plastic insulator. The copper mesh helps to protect the cable against electromagnetic interference. If that happens, the signal can be disrupted, and the copper mesh helps prevent that.

The outermost layer of the cable is a plastic jacket that protects the copper cable and the other layers surrounding it. It makes sure that no physical damage occurs during the transmission.

These layers are essential for signal transmission. While the signal may be carried out by the copper wire only, the external layers are extremely important to help reduce any kind of signal loss or other interference with the signal. Moreover, the final and outermost layer helps keep the inner layers physically compact.

The dielectric layer provides some protection and insulation while the other two layers help keep the transmission going. Together, they transfer data quickly without any difficulty.

What is the impedance of a coaxial cable

Different coaxial cables are used for various tasks, and one distinguishable factor of those is the impedance. Therefore, the first consideration in the selection process is usually finding out the impedance of the wire, as it directly impacts the transmission. Hence, it becomes one of the most important parameters when selecting the coaxial cable that best suits your needs.

Impedance is the value of resistance that is encountered by the signals which proceed from the coaxial cable. When the impedance is low, more waves pass through the coax cable because of little resistance, and similarly, when the impedance is high, waves have more difficulty passing through the cable as there is a lot more resistance.

The impedance must match the source and the load to ensure that the transmission is occurring as expected. The source is referred to as the transmitter, and the load here is the antenna. By confirming an optimum balance between the source and the load, maximum signals can be transferred through the cable.

All feeders which are used for signal transmission have a characteristic impedance that directly affects its working. For coaxial cables, the primary standard for impedance is 75 Ω and 50 Ω. Both of these impedances are applicable in most standard coaxial cables.

The 50 Ω coaxial cables have a different use than the 70 Ω cables. It is pretty clear that more transmissions can occur through a 50 Ω cable than a 70 Ω cable. So, the 50 Ω cables are used primarily for commercial and professional purposes, such as businesses, because of their increased productivity. Large companies which need quick signal transmission use these cables.

On the other hand, the 70 Ω coax cables are used chiefly for domestic purposes. Homeowners use them for TV signal transmission as well as VHF FM applications.

To clearly understand the difference between these two impedances, we need to know that a 50 Ω cable gives the minimum loss for a weight that is already provided. In contrast, the 75 Ω cable gives the minimum weight for a loss that is already provided.

Again, these two are the standard impedances for coax cables, but you can get other impedances that suit your needs, too. These are used in specialist applications that require an impedance other than 75 or 50 ohms.

Specialist applications such as computer installations require greater impedances, which are sometimes even more than 125 ohms. Still, you can use coax cables with impedances of 25, 125, or 95 ohms for other specialist applications.

The importance of impedance of coax cables

Different systems require different impedances, and it is crucial that you choose a coax cable with an impedance that best suits your needs.

Impedance determines the balance between the system, which then defines the level of power or data transfer and the level of standing waves. It is important that you find out which impedance would be the best for your system and then get a coax cable accordingly.


Knowing the key factor that differentiates between the types of coaxial cables is crucial, and it helps you choose the best coax cable for your requirements. The impedance of a coax cable is clearly defined in this article, and once you have read it, you will know how important it is and how it affects the wiring system.

Next time you are going to purchase the coax wires, skim through this article again and get yourself familiar with the impedance of a coax cable.