1.5 Compare and contrast transmission media and transceivers
Wired Media
📘CompTIA Network+ (N10-009)
What is a Coaxial Cable?
A coaxial cable (often called coax cable) is a type of electrical cable used to transmit data, voice, or video signals. It gets its name “coaxial” because the inner conductor and outer shield share the same central axis — “co” means together, and “axial” means axis.
It is designed to carry high-frequency electrical signals with low interference and signal loss over medium distances.
🔹 Structure of a Coaxial Cable
A coaxial cable has four main layers that protect the signal and reduce interference:
- Inner Conductor:
- This is the core wire that carries the electrical signal.
- It’s usually made of copper or aluminum for good conductivity.
- Dielectric Insulator:
- A plastic layer that surrounds the inner conductor.
- It keeps the signal stable and maintains the proper distance between the conductor and the shield.
- Metallic Shield:
- A braided or foil shield that protects the signal from electromagnetic interference (EMI) from other devices or cables.
- This layer also helps prevent signal leakage.
- Outer Jacket:
- The protective plastic cover that shields all inner layers from physical damage, moisture, and heat.
🔹 How Coaxial Cable Works
When data travels through a coax cable, it moves as electrical signals along the inner conductor.
The shield layer blocks external electromagnetic signals from interfering with the data transmission and also prevents the data signal from radiating out.
Because of this design, coaxial cables are more resistant to interference and can carry signals longer distances compared to unshielded twisted-pair (UTP) cables.
🔹 Common Types of Coaxial Cables
Different coaxial cables are used depending on the signal type and distance.
Here are the most common types you should know for the exam:
| Type | Characteristic Impedance | Typical Use |
|---|---|---|
| RG-6 | 75 ohms | Used for broadband internet, cable television, and digital video connections |
| RG-59 | 75 ohms | Used for shorter distance video or CCTV connections |
| RG-58 | 50 ohms | Used for older Ethernet networks (10Base2, also known as Thinnet) |
| RG-8 | 50 ohms | Used in older thick Ethernet networks (10Base5, also known as Thicknet) |
🧠 Note for the exam: The impedance value (measured in ohms) defines how much resistance the cable has to alternating current (AC).
Network systems are designed to match impedance values — mismatched impedance can cause signal reflection and data loss.
🔹 Connectors Used with Coaxial Cables
Coax cables use special connectors to attach to networking devices or wall outlets.
Here are the most common ones:
| Connector | Description | Common Use |
|---|---|---|
| BNC (Bayonet Neill–Concelman) | Has a twist-and-lock mechanism | Used in older Ethernet networks (10Base2) and some video systems |
| F-type | Screws on tightly for a secure connection | Commonly used for cable TV and broadband internet |
| N-type | Large, threaded connector | Used for long-distance, high-frequency connections such as wireless antennas |
🔹 Advantages of Coaxial Cable
- Good resistance to EMI: The shielding protects data signals from interference.
- Supports higher bandwidth than UTP: Can carry more data over longer distances.
- Durable and reliable: The outer layers provide physical protection.
- Can carry multiple types of data: Supports both analog and digital signals (e.g., TV, Internet, CCTV).
🔹 Disadvantages of Coaxial Cable
- Thicker and less flexible: Harder to install and manage compared to twisted-pair cables.
- More expensive: Costs more than UTP cables.
- Limited scalability: Not suitable for modern high-speed networks like fiber optics.
- Shared medium: In older networks, multiple devices on one coax cable could cause collisions if two signals were sent at the same time.
🔹 Coaxial Cable in Networking Environments
Coaxial cables are less common in modern LANs but still play a role in specific IT environments, such as:
- Broadband Internet (Cable modems): Coaxial cables connect modems to ISP networks.
- Video and CCTV Systems: Used to connect cameras and recording systems.
- Wireless Antenna Connections: Used for RF (radio frequency) and microwave signals.
- Legacy Ethernet (10Base2 / 10Base5): Once used in early Ethernet networks before twisted-pair and fiber took over.
🔹 Signal Distance and Performance
| Coax Type | Max Distance | Bandwidth/Speed |
|---|---|---|
| RG-58 (10Base2) | ~185 meters | 10 Mbps |
| RG-8 (10Base5) | ~500 meters | 10 Mbps |
| RG-6 (Broadband) | Up to several hundred meters | High-speed digital/video data |
🔹 Coaxial Cable vs. Twisted-Pair vs. Fiber Optic
| Feature | Coaxial Cable | Twisted-Pair Cable | Fiber Optic Cable |
|---|---|---|---|
| Transmission Medium | Electrical signals | Electrical signals | Light signals |
| Speed | Medium | Medium | Very high |
| EMI Resistance | High | Medium to low | Very high |
| Distance | Medium | Short | Long |
| Cost | Medium | Low | High |
| Common Use | Broadband, CCTV, older Ethernet | LANs, phones | WANs, high-speed backbones |
🔹 Exam Tip (Important for Network+ N10-009)
✅ Remember these key points for the exam:
- Coaxial cables use copper and transmit electrical signals.
- RG-6 and RG-59 = 75-ohm cables (TV, broadband).
- RG-58 and RG-8 = 50-ohm cables (Ethernet).
- BNC and F-type are the most commonly used connectors.
- Shielding helps prevent EMI and signal loss.
- Coaxial cable is less common in modern networks but still used for broadband and RF applications.
🧭 Summary
- Coaxial cable is a shielded copper cable designed to carry electrical signals with low interference.
- It’s built with a central conductor, insulating layer, shield, and outer jacket.
- Although not widely used in new LAN installations, it remains essential in broadband, video, and RF systems.
- Knowing the types (RG-6, RG-59, RG-58, RG-8) and connectors (BNC, F-type) is crucial for the CompTIA Network+ exam.
