What are coaxial cables? Structure and types of coaxial cables

1.2 What are coaxial cables?

A coaxial cable is a type of cable designed to efficiently transmit electrical signals, particularly high-frequency signals. Thanks to this capability, coaxial cables are widely used in applications such as television antennas, internet connections, wireless communications, and video surveillance systems.

A key advantage of coaxial cables is their excellent shielding performance, which minimizes the impact of external interference and reduces signal loss during transmission. In addition, coaxial cables offer good mechanical flexibility, making them easy to install in confined spaces or along complex routing paths. This combination of performance and ease of installation is why coaxial cables are highly valued in both commercial and industrial applications.

1.3 Structure of coaxial cables

The main components of a coaxial cable include: inner conductor, insulating dielectric, outer conductor/shield, and outer sheath.

• Inner conductor: The inner conductor is typically made of copper wire. In most cases, it is a single solid conductor. However, for certain applications - such as when the cable is subject to repeated flexing or when extremely low insertion loss is required - coaxial cables may be designed with a stranded (multi-wire) conductor.
• Insulating dielectric: Between the inner conductor and the outer conductor is the insulating dielectric layer. This dielectric not only maintains the physical separation between the two conductors but also determines many of the key electrical characteristics of the cable. The dielectric may be solid or semi-air spaced. This structure can take the form of long hollow tubes within the dielectric material, a spiral wrap of dielectric tape, or a foam construction, in which air makes up a significant portion of the material. The most commonly used materials include PE, foam PE, and Teflon (PTFE).
• Outer conductor / metallic shield: The outer conductor is typically made of a braided copper shield, which provides the cable with flexibility and mechanical pliability. If the outer conductor is solid, the cable becomes much less flexible, except in certain specialized designs such as semi-rigid coaxial cables. To enhance shielding effectiveness, some coaxial cables use double or even triple layers of braided shielding. This is usually achieved by layering braided shields on top of one another or by combining them with copper foil or metallic tape. Increasing the shielding layers significantly reduces external interference pickup and signal radiation leakage.
• Outer sheath: This layer has no electrical function, but it serves to protect the cable from dirt, moisture, and mechanical damage such as abrasion or impact. A wide variety of materials are used, selected according to the environmental conditions of use, including resistance to solvents, abrasion resistance, moisture resistance, and the ability to withstand different operating temperature ranges.

Coaxial cables have been a fundamental part of communication infrastructure for decades. Their ability to reliably transmit data over long distances makes them indispensable across a wide range of industrial sectors.

• Cable television and broadband internet: Despite the rapid growth of fiber optics, coaxial cables continue to play a key role in delivering cable TV and broadband internet services. They provide high bandwidth and stable signal transmission and are particularly effective in rural and suburban areas.
• Security and surveillance systems: Thanks to their strong resistance to electromagnetic interference, coaxial cables ensure clear and stable video signals. In industrial environments, they are used to connect multiple cameras across large facilities, helping to enhance operational safety and monitoring efficiency.
• Satellite and radio communications: Satellite antennas and radio transmission equipment rely on coaxial cables to carry signals from the antenna to the receiver. This application is especially critical in remote areas and in military operations, where reliable long-distance communication is essential.
• Industrial automation and control: In factories and production lines, coaxial cables are used to transmit control signals and data between machinery and central control systems. Their high durability and effective shielding help reduce downtime and maintenance costs.
• Telecommunication: Coaxial cables are used in backbone and distribution networks, connecting base stations, data centers, and local exchanges. This ensures high-speed data flow and network reliability, supporting the rapid development of 5G technology and IoT devices.

Explore the HELUKABEL product portfolio for industrial communication and building automation

3.3 Twinax cables

This type of cable has a structure similar to a coaxial cable, but instead of a single center conductor, it contains two conductors. Twinax is used for short-distance, high-speed signal transmission, typically in network equipment with SFP+ interfaces, servers, and data centers.

3.4 Triax cables

Triax cable has a structure similar to a standard coaxial cable but includes an additional insulation layer and a second outer conductor/shield.

Compared to conventional coaxial cables, Triax is more expensive, but in return it offers higher bandwidth and superior noise immunity. This type of cable is commonly used in professional broadcast production and in environments with strong EMI.

3.5 Semi-rigid cables

Semi-rigid cables use a PTFE dielectric and a solid metal shield instead of a braided shield. This construction provides superior dielectric properties, helping to improve signal transmission performance at high frequencies.

However, compared to fully rigid cables, semi-rigid cables are limited in terms of physical size and operating frequency range. As a result, they are mainly used in precision RF applications with moderate power requirements.

Among the various types of coaxial cables available, RG coaxial cable is considered the most common and widely used on the market. Thanks to clearly standardized specifications covering construction, impedance, and electrical characteristics, RG cables provide stable and reliable signal transmission across a wide range of environments and applications.

4.1 What are RG coaxial cables?

RG cable, also known as Radio Guide cable, is a type of coaxial cable with military origins, first developed during World War II. The designation “RG” stands for Radio Guide, a term used within the U.S. military’s radio frequency (RF) cable classification system.

RG coaxial cables are designed for the transmission of radio frequency signals and are available in many different variants, each with specific technical characteristics tailored to particular applications. These applications range from telecommunications and broadcast radio–television systems to specialized instrumentation and control systems.

4.2 MIL standards

MIL standards (Military Specifications and Standards) are a system of standards issued by the U.S. Department of Defense and are widely applied to ensure the performance and quality of coaxial cables.

At first glance, MIL part numbers may appear complex, but in reality, each element of the designation carries a specific technical meaning. Once the structure of the part number is understood, it becomes possible to accurately identify the cable’s characteristics and its intended application.

5.4 SAT coaxial cables

SAT coaxial cables are used to connect a satellite antenna to a TV receiver or to a cable television (CATV) system. In some installations, the cable may be used in combination with intermediate amplifiers, splitters, or switching devices to maintain signal quality over longer distances or across multiple connections.

This type of cable always features a standard impedance of 75 ohms and is available with various shielding configurations, allowing it to meet different EMI protection requirements and installation conditions for specific system applications.

SAT COAXIAL CABLE ALG (40151)

SAT/BK COXIAL CABLE A+ (400197)

SAT COXIAL CABLE (40021)