What is a coaxial cable? A simple explanation of the basics you need to know

Coaxial cables play an important role in our daily lives and business environments, including communication and data transmission, but we may not have many opportunities to learn more about their structure, functions, and types.

In this article, we will explain the basics of coaxial cables, as well as their types and standards. Learn the basics about coaxial cables and deepen your understanding of how to choose the right cable and how to use it.

What is Coaxial Cable?

A coaxial cable is a type of coated wire used for electrical communications such as video. The official name of a coaxial cable is "foamed polyethylene insulated vinyl sheath coaxial cable," and it has the advantage of being able to transmit high-frequency signals efficiently.

Here we will explain the uses and benefits of coaxial cables.

Applications of coaxial cables

Coaxial cables are used in the following applications and locations:

• High-speed communications such as LAN and CATV
• Pulling in from a TV receiving antenna
• Broadcasting stations and relay stations
• Transmission of audio, video and microwave signals
• 監視カメラ

Coaxial cables have a central conductor, an outer conductor, and an insulator between them, which provides effective protection against electromagnetic interference (EMI) and radio frequency interference (RFI), making them widely used in TV antennas, cable TV wiring, satellite communications, internet connections, and more.

Coaxial cables are also highly durable. The outer coating protects the internal conductor from physical damage, allowing them to maintain reliable performance even in harsh environments. For example, they can be used safely in places susceptible to external influences, such as antenna cables installed outdoors or wiring that passes through the walls of buildings.

Advantages of Coaxial Cable

In addition to extremely low signal loss and high durability, coaxial cables have many other advantages.

Coaxial cables have excellent cost performance. One of the advantages of coaxial cables is that the material and installation costs can be kept low compared to optical fiber cables. Therefore, when building large-scale networks or for use in ordinary homes, high-quality communications can be achieved while reducing costs.

Another advantage of coaxial cables is their high compatibility. Many existing devices and connected equipment use coaxial cables, so they can be easily connected when introducing new equipment. This high compatibility has the advantage of making it easy to expand and update the system.

Coaxial cable structure

Coaxial cables are made up of several layers arranged in a specific order, each with a specific function. At the center is a metal wire called the "center conductor," usually made of copper or aluminum. The center conductor's role is to directly transmit the signal.

Around the central conductor is an "insulator" made of insulating materials such as polyethylene or fluororesin. The insulator is a protective layer to prevent the signal from leaking or being subjected to external interference. On the outside of that is a braided copper wire called the "outer conductor (shield)," which protects the signal from external electromagnetic waves and prevents the internal signal from leaking out.

Additionally, there is an "outer jacket" on the outside of the outer conductor. It is usually made of a durable material such as polyvinyl chloride (PVC) or polyethylene, and its role is to protect the entire cable from physical damage and environmental factors. The outer jacket increases the cable's durability and allows it to be used for a long time.

The multi-layer structure of coaxial cable as described above improves signal transmission efficiency and makes it possible to minimize external interference.

How coaxial cables transmit electronic signals

When a coaxial connector is attached to a coaxial cable, it becomes possible to transmit high-frequency electrical signals. A coaxial connector is a component that connects a coaxial cable to a device. To connect a coaxial cable and a coaxial connector, the following points must be in contact:

• Coaxial cable (inner conductor) and coaxial connector (center contact)
• Coaxial cable (outer conductor) and coaxial connector (main body)

Coaxial cables are characterized by having a central conductor and an outer conductor arranged on the same axis. This arrangement allows for highly efficient transmission of electronic signals while minimizing the effects of electromagnetic waves.

Electronic signals are transmitted by applying a voltage to the central conductor. This change in voltage is transmitted as an electronic signal and is then processed again as a signal at the receiving end. In the case of high-frequency signals, the structure of the coaxial cable makes use of the skin effect, which allows for efficient transmission. The skin effect is the phenomenon in which high-frequency current flows close to the surface of the conductor, reducing signal loss.

In addition, coaxial cables have a constant characteristic impedance, which reduces signal reflection and distortion and enables stable transmission. The characteristic impedance is determined by the cable design and usually follows standards such as 50 ohms or 75 ohms.

Types of Coaxial Cables

There are various types of coaxial cables for different applications. Among them, the following two standards are widely used.

• JIS standard: Japanese Industrial Standard
• MIL standard: US military procurement standard

We will explain the characteristics of each.

JIS standards

JIS (Japanese Industrial Standards) are standards that guarantee the quality and performance of coaxial cables used in Japan. Coaxial cables that comply with JIS standards are highly reliable and safe as industrial products, and are suitable for use in specific applications and environments. JIS standards stipulate detailed specifications such as the cable outer diameter, conductor material, type of insulation, and shield structure. This ensures compatibility between products and enables stable performance.

JIS standard coaxial cables are widely used mainly in Japan for communication infrastructure, broadcasting systems, industrial measuring instruments, etc. For example, cables that comply with JIS standards are used in a variety of situations, including receiving television broadcasts, connecting to the Internet, and even in video surveillance systems.

Furthermore, by complying with JIS standards, manufacturers are required to control the quality of their products. As a result, it is possible to minimize product variation and maintain consistent performance. Products that comply with JIS standards are also highly reliable, comparable to international standards.

JIS standard coaxial cables are designed to be adaptable to specific environmental conditions and applications, and some products meet special requirements such as heat resistance, cold resistance, and corrosion resistance. Therefore, one of the strengths of JIS standard cables is that they can continue to perform well even in hot and humid places or low-temperature regions.

MIL standard

MIL (Military Inspection Standards) are military specifications established by the United States Department of Defense to ensure the quality and performance of coaxial cables suitable for military applications. These specifications are intended for use in harsh environmental conditions and situations where high reliability is required, where durability and signal integrity are extremely important. Coaxial cables that comply with MIL specifications perform well even under harsh conditions such as extreme temperature changes, vibration, humidity, and corrosion.

Specific MIL standards include MIL-C-17 and MIL-DTL-17. These standards specify detailed requirements for cable construction, materials, electrical properties, mechanical properties, etc. For example, the MIL-C-17 standard is characterized by strict criteria for the materials of the outer shield and the properties of the inner insulation.

Furthermore, MIL-standard coaxial cables are widely used in fields where reliability is required, such as medical equipment, industrial equipment, as well as in the aerospace and defense fields. Unlike regular commercial cables, MIL-standard cables are required to continue providing stable performance over a long period of time.

In addition, MIL-standard coaxial cables go through a rigorous testing and certification process before being released to the market, so users can have high confidence in their quality and performance. Therefore, the demand for MIL-standard coaxial cables is increasing not only in military applications but also in a wide range of industrial fields.

Summary

This time, we introduced basic knowledge about the structure and types of coaxial cables. Coaxial cables are an important technology that are widely used in various fields, such as home and business networks, television broadcasting, and communication systems.

I hope that this article has helped you to gain a basic understanding of coaxial cables and to gain knowledge that will be useful in your actual operations. Let's understand the basics of coaxial cables and gain the knowledge to be able to choose them yourself.