How to Make a Coaxial Cable: Steps, Materials, Tools, and Best Practices

Why Proper Tools Matter

Using incorrect tooling can cause:

• Dielectric deformation
• Impedance mismatch
• Shield damage
• Voltage breakdown

For connectorized assemblies, tooling must match ferrule OD exactly.

How Is a Coaxial Cable Made?

A coaxial cable is manufactured through a precise, multi-stage process that builds its layers in perfect concentric alignment. The steps include conductor drawing, dielectric extrusion, shielding application, jacket extrusion, and final electrical and mechanical testing. Every stage affects the cable’s impedance, attenuation, flexibility, and long-term reliability. High-frequency coaxial cables—such as RG316, RG400, and LMR-type—require even tighter tolerances because small geometry errors can cause reflections and signal loss.

Below is a detailed breakdown of how coaxial cable production works from raw materials to finished cable.

1. Center Conductor Manufacturing

The center conductor is the core signal path and must be manufactured with exact diameter tolerance.

1.1 Material Preparation

Common conductor types include:

• Solid bare copper (low loss; stable impedance)
• Stranded copper (high flexibility; often used in patch cables)
• Silver-plated copper (better high-frequency conductivity)
• Copper-clad steel (CCS) (cost-effective for CATV and long-distance cables)

1.2 Wire Drawing Process

Copper rods are fed through multiple carbide dies, gradually reducing diameter to the exact specification.

Critical parameters include:

• Diameter tolerance (often ±0.01 mm)
• Surface smoothness (prevents micro-arcing)
• Resistance uniformity (affects attenuation)

1.3 Annealing

For stranded conductors or flexible cable types, annealing softens the copper to improve bending characteristics.

2. Dielectric Extrusion

The dielectric maintains spacing between the conductor and shield—key to controlling impedance (50 Ω or 75 Ω).

2.1 Material Options

• Solid PE (Polyethylene) – stable, economical
• Foam PE – lower dielectric constant, reduces attenuation
• PTFE / FEP – high temperature, high-frequency stability
• Low-loss foam fluoropolymers – used in LMR-style cables

2.2 Extrusion Process

A high-precision extruder coats the conductor with dielectric material while maintaining perfect concentricity.

Important performance factors:

• Dielectric thickness tolerance
• Cell-structure uniformity (in foam types)
• Moisture control – trapped moisture increases signal loss

2.3 Concentricity Control

Concentricity must typically be within 90–95% to avoid impedance mismatch.

Poor concentricity → increased VSWR → higher reflection → degraded RF performance.

3. Shielding Application

The shielding layer prevents interference, leakage, and maintains the coaxial geometry.

3.1 Foil Shielding

An aluminum or copper foil is longitudinally wrapped around the dielectric.

• Provides 100% coverage
• Essential for high-frequency RF stability
• Often bonded to the dielectric for better adhesion

3.2 Braided Shielding

Copper or tinned copper braid is applied using a braiding machine.

Key variables include:

• Braid density (%) – often 60%, 80%, or 95%
• Number of carriers and ends
• Braid angle – affects flexibility and coverage

Higher coverage improves EMI resistance but reduces flexibility.

3.3 Dual or Triple Shielding

Used for low-loss, low-EMI applications:

• Foil + braid
• Foil + braid + foil
• Double braid + foil

This structure is common in LMR-series, RG6Q (quad-shield), and professional RF cables.

4. Outer Jacket Extrusion

The outer jacket protects the cable from mechanical wear, chemicals, heat, and UV exposure.

4.1 Material Options

• PVC – general purpose, flexible
• PE – outdoor UV resistance
• FEP – high-temperature, chemical-resistant
• TPE – flexibility + abrasion resistance
• LSZH – low-smoke zero halogen for aerospace/medical environments

4.2 Extrusion Process

The shielded dielectric core passes through a second extrusion machine that applies the jacket under controlled pressure and temperature.

Critical factors:

• Uniform thickness
• Smooth surface finish
• Proper adhesion without crushing the shield
• OD tolerance (affects connector compatibility)

5. Final Quality Testing

Each batch of coaxial cable undergoes strict electrical and mechanical tests before shipment.

5.1 Electrical Tests

• Impedance (50 Ω / 75 Ω)
• Capacitance
• Attenuation per meter
• Return loss (VSWR)
• Shielding effectiveness (dB)
• Dielectric strength – high-voltage breakdown

5.2 Mechanical & Environmental Tests

• Outer diameter tolerance
• Bend radius endurance
• Tensile strength
• Shield adhesion
• Temperature cycling
• Flame and oil resistance (if applicable)

Testing ensures the cable performs correctly at the rated frequency range.

Table: Coaxial Cable Production Stages

Why Precision Matters in Coaxial Cable Manufacturing

Small deviations at any step can cause measurable RF issues:

• 0.05 mm dielectric error → impedance shift
• 5% braid coverage reduction → EMI ingress
• Poor concentricity → high VSWR
• Jacket deformation → connector mismatch

This is why professional coaxial manufacturers follow strict material control, calibrated extrusion systems, and 100% electrical testing.

How to Assemble a Coaxial Cable with Connectors?

Assembling a coaxial cable requires precise stripping, correct handling of the dielectric and shielding, and proper attachment of the connector using crimping, compression, or soldering. A correct assembly ensures stable impedance, low VSWR, and reliable long-term mechanical performance. Even minor mistakes—like braid strands touching the center conductor or improper pin depth—can result in noise, intermittent connection, or RF failure.

To assemble a coaxial cable, cut the cable cleanly, strip each layer to the specified dimensions, fold back the shielding, insert the center conductor into the connector pin, place the ferrule over the braid, and secure the connector using crimping, compression, or soldering. Inspect the joint for proper alignment, continuity, and mechanical stability to ensure low-loss, interference-free performance.

1. Required Tools and Components

Proper tools protect the cable structure and ensure consistent assembly quality.

Essential Tools

• Precision coax stripper (adjustable blade depth)
• Coax cable cutter
• Crimping tool (with correct die size)
• Compression tool (for RG6/RG59 F-type connectors)
• Soldering station (for certain SMA, N-type, or U.FL assemblies)
• Heat gun and heat-shrink tubing
• Multimeter or continuity tester

Connector Components

Depending on connector type (SMA, BNC, N-type, MMCX, F-type), assemblies typically include:

• Connector body
• Center pin (crimp or solder)
• Ferrule (crimp sleeve)
• Insulator interface

2. Standard Strip Dimensions

Different cable types require specific strip lengths to maintain proper impedance and connector fit.

Strip Dimension Table

Note: Always refer to the connector’s datasheet for exact values.

3. Step-by-Step Coaxial Cable Assembly Process

Step 1: Cut the Cable Cleanly

Use a sharp coax cutter to avoid deforming the dielectric.

A crushed dielectric causes:

• Impedance shift
• Increased insertion loss
• Poor RF performance

Step 2: Strip the Outer Jacket

Use a coax stripper set to the correct blade depth.

Avoid cutting into:

• Shield braid
• Foil
• Dielectric layer

Damaging these layers weakens shielding integrity.

Step 3: Prepare the Shielding

Proper shield handling determines EMI performance.

Braid Preparation

• Fold braid strands backward evenly over the jacket
• Remove the foil only if required by connector design
• Ensure no stray braid wires touch the center conductor

Dielectric Check

• Surface should be smooth
• No dents or scoring
• Exact diameter for interference-fit connectors

Step 4: Install the Center Pin

(For connectors like SMA, N-type, BNC)

Two methods:

• Crimp-style pin: Insert conductor into pin, then crimp using the correct die.
• Solder-style pin: Tin the conductor, heat-pin barrel, insert conductor, and finish with a clean solder joint.

Correct center pin depth is critical. Too long → won’t seat. Too short → intermittent connection.

Step 5: Insert Cable into the Connector Body

Push firmly until:

• The dielectric bottoms out inside the connector
• The pin enters the mating interface smoothly
• The braid sits evenly between ferrule and connector body

Avoid twisting during insertion—twisting can damage foil layers.

Step 6: Crimp, Compression, or Solder the Connector

Crimp Method (BNC, SMA, N-Type)

• Slide ferrule onto braid
• Use the exact crimp die size (e.g., 0.128″, 0.213″)
• Apply a full, even crimp (oval shape indicates incorrect die use)

Compression Method (F-Type)

• Insert cable into F connector
• Use compression tool to lock connector securely
• Produces reliable weatherproof joints for RG6/RG59

Solder Method (Certain SMA/U.FL)

Used for high-frequency or micro-miniature connectors.

• Requires flux control
• Avoid excess solder (can wick into dielectric)

Step 7: Final Inspection

Verify:

• No stray braid strands
• Pin protrusion matches connector spec
• Ferrule crimp is firm and uniform
• Cable does not twist or wobble in connector
• Conductivity passes continuity test

A well-assembled connector will have:

• Low VSWR
• Stable mechanical retention
• Proper electrical contact

4. Why Correct Assembly Technique Is Critical

Improper technique leads to significant RF and mechanical problems.

Common Assembly Errors

Impact on Performance

• Higher insertion loss
• Poor return loss (VSWR > 1.5)
• EMI leakage
• Mechanical pull-out failure
• Overheating during high-power RF operation

Correct assembly preserves the designed impedance, shielding effectiveness, and long-term stability.

5. Connector Types and Their Assembly Differences

Micro-coax connectors require extremely controlled assembly due to small diameter (1.13 mm, 1.37 mm).

6. Best Practices for Reliable Coax Assembly

• Always match ferrule size to cable OD
• Avoid crushing or bending the dielectric during handling
• Maintain shielding coverage as close to 100% as possible
• Trim braid cleanly—no long strands
• Use heat shrink for strain relief in high-vibration environments
• Follow connector manufacturer’s strip dimensions exactly
• Use calibrated crimp tools for repeatable results

What Problems Occur When a Coaxial Cable Is Made Incorrectly?

Manufacturing errors lead to electrical and mechanical issues.

Common Issues

• Impedance mismatch
• High attenuation
• Poor shielding → EMI ingress
• Dielectric deformation
• Connector pull-out

Root Causes

• Poor concentricity
• Wrong dielectric material
• Low-coverage braid
• Incorrect ferrule dimensions
• Excessive stripping force

This is why quality control is essential.

How Sino-Conn Supports Custom Coaxial Cable Manufacturing