Coaxial Cable: Advantages and Disadvantages

Coaxial cable has been a widely used medium for transmitting data, particularly in TV, internet, and radio broadcasting. Its unique design helps minimize signal loss and interference, making it ideal for high-frequency signals.

In this guide, we will explore the key advantages and disadvantages of coaxial cables to help you understand their role in modern communication systems.

What is Coaxial Cable?

Introduction

Coaxial cable is a type of electrical cable used for transmitting radio frequency (RF) signals.

It is the most common transmission line used to transmit electrical energy from one location to another. For example, it’s used to connect a transmitter to an antenna.

The signal propagation is in the form of TEM (Transverse Electromagnetic) mode.

It is widely used in telecommunications, internet connections, and cable TV networks.

Structure of Coaxial Cable

As shown in Figure 1, coaxial cable consists of two conductors which are separated by a dielectric material. The center conductor and outer conductor (e.g., shield) are configured to form concentric cylinders with a common axis, hence the name.

The center conductor is constructed using solid or seven-strand conductors. The materials commonly used include copper, silver-plated copper, copper-clad aluminum, copper-clad steel, etc. The outer conductor uses multiple small aluminum or copper conductors. A dielectric layer separates these two conductors. It is made using materials such as polyethylene, polypropylene, fluorinated ethylene propylene, etc. Many coaxial cables use an additional insulating outer sheath or jacket.

Figure 1: Coaxial Cable

Working

Coaxial cables work by transmitting electrical signals through the inner conductor while the outer shield blocks interference from outside sources. The dielectric layer keeps the signal intact by maintaining an electric field between the core and the shield. Since the signal travels through the central conductor, the shielding minimizes signal loss and external interference, making it ideal for long-distance and high-frequency transmission.

Types of Coaxial Cable

There are several types of coaxial cables, each suited for specific applications. Some of the most common types include the following:

• RG-6: This is the most commonly used coaxial cable for TV, satellite, and internet connections. It has a thicker core, which allows for better signal transmission over longer distances.
• RG-59: Typically used for short-distance video signals, RG-59 has a thinner core than RG-6, making it less efficient for high-frequency transmission but more flexible.
• RG-11: RG-11 cables are used in industrial and outdoor installations due to their thicker core and superior signal transmission capabilities over long distances.
• Hardline Coaxial Cable: Often used in high-frequency applications, such as cable TV distribution, these cables have a solid metal outer conductor and offer excellent shielding and low signal loss.
• Tri-axial Cable (Triax): This type of cable has an additional layer of insulation and shielding, making it ideal for applications where extra protection from interference is needed.

Advantages of Coaxial Cable

Due to its unique structure, there are numerous advantages of coaxial cable as follows:

1. Due to the skin effect, coaxial cable is used in high-frequency applications (> 50 MHz) using copper-clad materials for the center conductor. The skin effect is a result of high-frequency signals propagating along the outer surface of the conductor. It increases the tensile strength of the cable and reduces weight.
2. The cost of coaxial cable is relatively low.
3. The outer conductor in coaxial cable is used to improve attenuation and shield effectiveness. This can be further enhanced with the use of a second foil or braid known as a jacket. The jacket is used as a protective cover from the environment and makes the overall coaxial cable flame retardant.
4. It is less susceptible to noise or interference (EMI or RFI) compared to twisted-pair cable.
5. It supports high bandwidth signal transmission compared to twisted-pair cable.
6. It is easy to wire and easy to expand due to flexibility.
7. It allows high data transfer rates with coaxial cable having better shielding materials.

Disadvantages of Coaxial Cable

While it offers several benefits, below are key disadvantages of Coaxial Cable which helps us take the right purchase decision as per our requirements.

1. The thicker design, especially in high-quality cables, makes coaxial cables less flexible and harder to route through tight spaces compared to alternatives like twisted-pair cables.
2. It is expensive to install for longer distances due to its thickness and stiffness.
3. As a single cable is used for signal transmission across the entire network, in case of failure in one cable, the entire network will be down.
4. Security is a great concern as it is easy to tap the coaxial cable by breaking it and inserting a T-joint (of BNC type) in between.
5. It must be grounded to prevent interference.
6. While they are shielded from external interference, coaxial cables can still suffer from signal degradation over time due to wear and tear or damage to the outer insulation.
7. Coaxial cables experience signal loss over long distances, which requires signal boosters or repeaters for extended transmission.
8. With the growing demand for fiber-optic cables, which offer faster data transmission speeds and greater capacity, coaxial cables are being phased out for some applications.

Conclusion

Coaxial cables offer a reliable and cost-effective solution for transmitting high-frequency signals, making them a popular choice in telecommunications and broadcasting. Apart from the advantages listed, they have disadvantages in terms of flexibility, distance, and signal degradation over time. While alternatives like fiber-optic cables are gaining popularity, coaxial cables still serve critical roles in various industries.

FAQs: Frequently Asked Questions and Answers on Coaxial Cable

Question-1: What is a coaxial cable used for?

Answer-1: Coaxial cables are primarily used for transmitting high-frequency signals in applications like cable TV, internet connections, and radio communications.

Question-2: What are the main types of coaxial cables?

Answer-2: The main types include RG-6 (used for TV and internet), RG-59 (used for short-distance video), RG-11 (used for long-distance communication), and hardline coaxial cables for industrial use.

Question-3: How does coaxial cable work?

Answer-3: Coaxial cables transmit electrical signals through a central conductor, while a surrounding shield blocks external electromagnetic interference, ensuring signal integrity.

Question-4: What are the advantages of coaxial cable?

Answer-4: Coaxial cables offer high bandwidth, durability, and resistance to electromagnetic interference, making them ideal for long-distance, high-frequency transmissions.

Question-5: What are the disadvantages of coaxial cable?

Answer-5: Coaxial cables are bulky, less flexible, and experience signal loss over long distances. They can also be more expensive than twisted-pair cables.