Coaxial Cable Construction: A Complete Breakdown

Published by Wassalat Technical Team

Have you ever wondered what's inside a coaxial cable? Behind the simple black jacket lies a sophisticated engineering design that makes high-frequency signal transmission possible.

This comprehensive guide takes you layer by layer through the construction of coaxial cables—explaining what each component does, what materials are used, and why every layer matters for performance.

Overview: The Four Layers

Every coaxial cable consists of four main layers working together to transmit signals with minimal loss and interference:

Center Conductor

The center conductor is the heart of the coaxial cable. It carries the electrical signal from the source to the destination.

Conductor Materials

Solid vs Stranded Conductors

Conductor Size (AWG)

The conductor size is measured in AWG (American Wire Gauge). Lower numbers = thicker wire.

• RG-6 – 18 AWG (1.02 mm diameter)
• RG-59 – 22 AWG (0.64 mm diameter)
• RG-11 – 14 AWG (1.63 mm diameter)
• RG-58 – 20 AWG (0.81 mm diameter)
• LMR-400 – 13 AWG (1.80 mm diameter)

Dielectric Insulation

The dielectric (or insulator) separates the center conductor from the shield. It's one of the most important layers for signal quality.

Dielectric Materials

Why Foam Dielectric is Better

Foam dielectric is used in RG-6 and RG-11 because:

• Lower signal loss – More air means less signal absorption
• Faster signal speed – Higher velocity of propagation
• Lighter weight – Foam is lighter than solid plastic
• Better bending – Foam is more flexible

Metallic Shield

The metallic shield is what makes coaxial cables special. It blocks interference from entering the cable and prevents signal leakage.

Shield Types

1. Braided Shield

Construction: Woven copper or aluminum wires

Coverage: 60% to 95%

Advantages: Flexible, excellent for mobile applications

Disadvantages: Can have gaps (interference can leak through)

2. Foil Shield

Construction: Thin aluminum foil wrapped around the dielectric

Coverage: 100%

Advantages: Complete coverage, excellent high-frequency protection

Disadvantages: Less flexible, can tear

3. Combination Shield

Construction: Foil + Braid

Coverage: ≈100%

Advantages: Best of both worlds, excellent protection

Disadvantages: More expensive, thicker

4. Solid Copper Tube

Construction: Solid copper outer conductor

Coverage: 100%

Advantages: Ultimate shielding, lowest loss

Disadvantages: Rigid, expensive

Shield Coverage Comparison

Outer Jacket

The outer jacket protects the cable from physical damage, moisture, UV rays, and chemicals.

Jacket Materials

Jacket Color Codes

While not standardized, common jacket colors indicate specific applications:

• Black – Outdoor, UV-resistant
• White – Indoor residential
• Blue – CCTV, security
• Orange – High visibility, power
• Yellow – Plenum-rated
• Green – Audio/video
• Red – Critical/fire alarm

Shielding Types Explained

1. Single Shield (Foil or Braid)

Construction: One layer of foil OR one layer of braid

Performance: Basic protection, adequate for most residential use

Common Use: RG-6 (basic), RG-59

2. Dual Shield (Foil + Braid)

Construction: Foil wrapped around dielectric, braid over foil

Performance: Good protection, suitable for most installations

Common Use: RG-6 (standard)

3. Triple Shield (Foil + Braid + Foil)

Construction: Foil + Braid + Foil

Performance: Very good protection, reduced interference

Common Use: RG-6 (premium)

4. Quad Shield (Foil + Braid + Foil + Braid)

Construction: Foil + Braid + Foil + Braid

Performance: Maximum protection, minimal interference

Common Use: RG-6 (satellite, high-interference areas)

5. Double-Braid Shield

Construction: Two layers of braid (no foil)

Performance: Excellent protection, flexible

Common Use: LMR-400, LMR-600, RG-8

Material Comparison

Different materials offer different performance characteristics. Here's how they compare:

Manufacturing Process

Coaxial cables are manufactured through a precise, multi-step process:

1. Wire Drawing – Copper wire is drawn to the correct thickness
2. Conductor Manufacturing – Solid or stranded conductor is produced
3. Dielectric Extrusion – Plastic is extruded over the conductor
4. Foil Application – Aluminum foil is wrapped around the dielectric
5. Braid Braiding – Wire braid is woven around the foil
6. Jacket Extrusion – Outer jacket is extruded over the shield
7. Testing – Cable is tested for impedance, continuity, and loss
8. Spooling – Cable is wound onto spools for shipping

Quality Indicators

How can you tell if a coaxial cable is high quality?

What to Look For

Red Flags to Avoid

• CCA conductor – Inferior performance, higher loss
• Loose braid – Poor shielding, interference susceptibility
• No branding – Unidentified cable, unknown quality
• Brittle jacket – Poor quality material, crack risk
• Missing specifications – Manufacturer hiding poor performance

Frequently Asked Questions (FAQ)

1. What is the most important layer in a coaxial cable?

All layers are important, but the dielectric and shield have the biggest impact on signal quality. The dielectric determines loss, and the shield determines interference rejection.

2. What is the difference between solid and stranded conductor?

Solid conductor is a single wire (better for permanent installations, lower loss). Stranded conductor is multiple wires twisted together (more flexible, good for patch cables).

3. Why is foam dielectric better than solid?

Foam dielectric contains air bubbles that reduce signal loss. Signals travel faster and lose less power through foam than solid plastic.

4. What does "quad-shield" mean?

Quad-shield means the cable has four layers of shielding: two layers of foil and two layers of braid. This provides maximum protection against interference.

5. Can I use outdoor coaxial cable indoors?

Yes. Outdoor cable (PE jacket) can be used indoors. However, indoor cable (PVC jacket) should NOT be used outdoors because it lacks UV and moisture resistance.

6. What is plenum-rated cable?

Plenum-rated cable has a fire-retardant jacket that produces less smoke when burned. It's required by building codes for installation in air circulation spaces.

7. What is the best conductor material?

Solid bare copper is the best conductor material, offering the lowest resistance and best performance. However, it's also the most expensive.

8. Does cable color affect performance?

No. Color is purely for identification and aesthetics. It doesn't affect electrical performance.

9. How can I tell if my cable has a copper or CCA conductor?

Scratch the conductor with a knife. If you see silver (steel) or white (aluminum) underneath, it's CCA or CCS. Solid copper is copper all the way through.

10. What is the minimum bend radius for coaxial cable?

Most coax has a minimum bend radius of 6-10 times the cable diameter. For RG-6, this is about 2-3 inches. For RG-11, it's about 4-6 inches.

11. Can coaxial cable be installed underground?

Yes, but you need "direct burial" rated cable with a PE jacket and often a gel filling to prevent moisture ingress.

12. Why is my coaxial cable stiff?

Stiffness is usually due to a solid conductor or thick shield. Some cables are intentionally stiff for permanent installations. Flexible cables use stranded conductors.

? Related Articles

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• What Is a Coaxial Cable?
• 50 Ohm vs 75 Ohm Coax
• RG6 vs RG11
• RG58 vs RG59
• Coaxial Cable Connectors Guide
• Browse Coaxial Cables →

Last Updated: July 2026

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