Understanding Coaxial Cable: A Comprehensive Guide

Coaxial Cable, often referred to as coax, is a vital component for the telecommunications industry. This includes high-grade lines and sub-fiber cables that cable television operators, telephone companies, and Internet service providers use to transmit data, video, and voice communications with their customers.

This guide explains coaxial Cable in detail, including its structure, types, applications, advantages over other cables (including those considered superior), and disadvantages.

What is Coaxial Cable?

Coaxial Cable, also known as coax cable, is a type of Cable used to carry electrical signals at high frequencies along a conductor surrounded by an outer conductor. It differs from traditional wires in that it has multiple layers of insulation around its signal-carrying core, shielding the signals from external interference, such as walls or floors.

The core conductor is surrounded by a dielectric insulator, which is, in turn, enclosed by a metallic shield. This shield considerably blocks electromagnetic interference (EMI) and avoids signal loss. As a result, the signal can still be reliably transmitted over long distances of wire.

Structural Features of Coaxial Cable

Commonly known as coax cable, coaxial Cable plays a vital role in telecommunications, enabling data, video, and voice communications to travel from providers such as cable television companies, telephone carriers, and internet service providers to their customers.

This guide provides a comprehensive understanding of coaxial Cable, covering its structure, categories, applications, advantages, and disadvantages.

What is Coaxial Cable?

A coaxial cable is a transmission line that carries high-frequency electrical signals with low loss. It differs from traditional cables in that it comprises multiple layers of insulating material that shield and protect the signal-carrying core.

Inside the Cable, a copper wire passes through a dielectric layer and is enclosed by an aluminum or plastic sheath. This structure effectively inhibits electromagnetic interference (EMI) while minimizing signal attenuation over long distances, ensuring reliable long-distance transmission.

Structural Features

Coax consists of four main parts:

1. Core Conductor: The inner conductor is typically solid (see skin effect for high-frequency signals), while hollow copper tubes or copper-clad aluminum bars are used. Copper-clad aluminum wires are recommended for distribution networks or backbone lines to reduce weight and cost while maintaining optimal transmission performance.
2. Dielectric Insulator: The insulating material may be polyethylene, polypropylene, polyvinyl chloride (PVC), or fluoroplastics. Polyethylene is widely used because of its low loss (at a frequency) and outstanding processing performance.
3. Braided Shield (Outer Conductor): The braided shield acts as both the transmission circuit of the conductor and shielding. There are three kinds of structures:
   • Tubular Metal: Made by longitudinal soldering copper or aluminum foil or by extruding and drawing seamless copper tubes. This structure ranks first in shielding performance but has poor flexibility.
   • Aluminum-Plastic Composite Foil Longitudinal Overlap: This material exhibits a good shielding effect and is relatively low-cost to produce.
   • The combination of Braided Shield and Aluminum-Plastic Composite Foil Longitudinal Overlap provides good flexibility and reliable joints, making it widely used.
4. Protective Plastic Layer: Black polyethylene, with its excellent weather resistance, is preferred for outdoor cables. Light-colored polyethylene is used for aesthetic reasons for indoor cables.

Functionality

Coaxial Cable conducts alternating current (AC), meaning the current direction reverses multiple times per second. Ordinary wires act as antennas and radiate energy when carrying high-frequency currents, leading to signal loss and leakage.

The unique coaxial cable design addresses this issue by utilizing the inner conductor to carry the signal and the outer conductor to shield it from external electromagnetic fields. The dielectric material between the conductors ensures consistent impedance along the Cable’s length, optimizing signal transmission.

Specific Classifications

Coaxial Cable is divided into several categories based on its characteristics and applications:

Standard Coaxial Cable

It is widely used in communication, broadcasting, and television. It offers high bandwidth, stable signal transmission, and strong anti-interference capabilities, making it suitable for cable TV and broadcast television.

RG Series

Standardized for video signal transmission and computer network connections. The RG series is renowned for its stable impedance and long transmission distances, making it suitable for long-distance video surveillance and network transmission. Common types include RG-59 (short-distance), RG-6 (medium-to-long-distance), and RG-11 (long-distance).

Low-Loss Coaxial Cable

Used for high-frequency signal transmission, featuring low-loss insulation and high-quality conductor materials. It is widely used in wireless, satellite, and other fields, improving signal transmission quality and distance.

High-Temperature Coaxial Cable

Designed to operate in high-temperature environments using high-temperature-resistant materials. They are used in aerospace, military equipment, and other fields requiring high-temperature signal transmission.

Lightning Protection Coaxial Cable

It uses unique materials and structural designs to prevent lightning interference and damage to signal transmission. It is used in radars, communication base stations, and other locations that require lightning protection.

Submarine Coaxial Cable

They are used for underwater communication and feature unique waterproof materials and structural sealing designs. They are also used in submarine optical cables, marine observation, and other underwater communication needs.

The Types of Connectors

Coaxial cable connectors come in various types, each designed for specific applications and frequency ranges. Some common types include:

• Bayonet Neill-Concelman (BNC): Used for television, video, and radio signals under 4GHz.
• Threaded Neill-Concelman (TNC): Used for telephony applications with frequencies up to 12 GHz.
• SubMiniature version A (SMA): Used in mobile phones, Wi-Fi antennas, microwave systems, and radios with frequencies up to 18GHz.
• SubMiniature version B (SMB): Used in telecommunications hardware.
• Quick-locking SMA (QMA): Rapid-opening SMA connectors for industrial and communications electronics use.
• Radio Corporation of America (RCA): Used with audio and radio signals, often found on older TV sets.
• F Connector: Commonly used for digital and Cable TV applications using RG-6 or RG-59 cables.

Applications

Coaxial Cable is widely used across various industries and applications, including:

• Television: Transmits the signal for a television set, with cable TV using 75-ohm RG-6 coaxial Cable.
• Internet: Carries internet signals, often via RG-6 cable.
• CCTV: Used in Closed Circuit Television (CCTV) systems, RG-59 and RG-6 cables are well-suited for the job.
• Video: RG-6 is a medium for digital video transmission, while RG-59 is suitable for lossless analog video transmission.
• HDTV: High Definition Television (HDTV). It uses an RG-11 coaxial cable for higher signal transmission.

Advantages

Coaxial Cable offers several advantages over other types of transmission media:

• Low Signal Loss: Enables efficient signal transmission over long distances.
• High Bandwidth: Supports a wide frequency range, suitable for transmitting high-bandwidth signals such as video and voice, as well as low-frequency, data-intensive applications.
• Strong Anti-Interference Capability: With excellent EMI/RFI protection, the signal remains clean and intact.
• Long Transmission Distance: It transmits signals over long distances with minimal degradation, making it ideal for telecommunications and broadcasting applications.
• Versatility: Can be used in various applications, including cable television, internet connections, closed-circuit television surveillance systems, and telecommunications networks.

Disadvantages

Despite its many advantages, coaxial Cable also has some limitations:

• Cost: It can be more expensive than similar transmission media, such as twisted-pair Cable or fiber-optic Cable.
• Bulkiness: This type of Cable is bulkier and less flexible than most others, making it unsuitable for tight spaces or applications that require significant mobility during installation.
• Complexity of Installation: Installing coaxial Cable may require special tools and techniques, especially in outdoor or long-distance installations.
• Limited Bandwidth: Although it offers higher bandwidth than twisted-pair copper cable, it still falls short of optical fiber’s capacity, which can theoretically carry all data ever produced.
• Susceptibility to Damage: This device may be vulnerable to physical damage, such as cuts or kinks, that can affect its transmission.

Interference Issues

Coaxial cables can experience various types of interference, including signal leakage, external noise, and electromagnetic interference (EMI). Signal leakage occurs when electromagnetic fields penetrate the Cable’s outer shielding, resulting in signal loss. External signals may also leak through the insulation, causing additional interference.

FAQs

• How to dress coaxial cables on a telephone pole？
  Use cable ties and spacers to secure the Cable, ensuring minimal stress on the connector.
• What size coaxial Cable is for exterior use?
  RG6 cables are commonly recommended for outdoor applications due to their weather-resistant properties.
• How many ohms are in the RG-58 coaxial cable?
  RG-58 cables typically have an impedance of 50 ohms.
• How do you test coaxial Cable?
  Use a multimeter or cable tester to check continuity and signal strength.
• How to join coaxial cables?
  Use coaxial couplers or compression connectors for a seamless connection.

Conclusion

Coaxial Cable is a versatile and reliable transmission medium used in telecommunications, broadcasting, and networking. Its unique design provides low signal loss, high bandwidth, and strong anti-interference capabilities, making it ideal for transmitting high-frequency signals over long distances. While it has limitations in cost and bulk, its numerous advantages make it an essential component of modern communication systems.

As technology evolves, coaxial Cable remains critical for ensuring reliable, efficient signal transmission across various industries and environments.

Need help with your customized coaxial cables or consulting solutions?

Romtronic is China’s leading and most innovative professional cable assembly manufacturer and wire harness factory. We have 29 years of experience in OEM and ODM services for medical, industrial, and automotive cables, and can provide technical support and customer service.

Contact the experts at Romtronic today by calling +86 199-2816-5824 or emailing us at info@romtronic.com.

If you need to know more about RF connectors, please click to view RF Connector Basics.

Apple Liu

Apple Liu is Romtronic’s Marketing Manager, focusing on business growth across the Asian market. With a background in International English and eight years of sales experience in the electronic cable and harness industry, she brings both in-depth industry knowledge and a global outlook to her role.

In addition to leading market strategy, Apple Liu also oversees content development and editorial work—crafting clear, engaging messaging that reflects Romtronic’s values and technical strengths. She is passionate about digital engineering and is committed to strengthening Romtronic’s brand presence and innovation in a competitive global landscape.