What Causes Coaxial Cable Failure? Common Problems and How to Fix Them

The causes of coaxial cable failure range from moisture ingress and corrosion to excessive bending, crushed dielectric material, damaged shielding, connector defects, vibration, and improper cable selection. Because these problems affect RF performance in different ways, effective coaxial cable troubleshooting starts by identifying the type of failure.

Start with the symptoms you can observe. The way a cable behaves often provides the first clue to what has failed. This is especially important when evaluating custom RF cable assemblies, since their specialized lengths, connectors, and configurations can introduce application-specific failure points.

These failure modes are often interconnected. For this reason, effective coaxial cable troubleshooting should not rely on a single test.

1. Excessive Signal Loss or Insertion Loss

Excessive signal loss occurs when a coaxial cable attenuates the RF signal more than expected for its length and operating frequency. It typically appears as reduced transmitted or received power and may worsen at higher frequencies. The first step naturally is to determine the causes of RF signal loss.

Possible Causes:

• Moisture ingress or corrosion

• Damaged or poorly installed connectors

• Excessive cable length

• Dielectric or conductor damage

• Severe bending or crushing

• Using a cable with excessive loss for the operating frequency

Likely Fix:

Measure insertion loss, preferably S21 with a VNA, across the intended frequency range and compare it with the cable specification. This helps distinguish actual cable damage from normal attenuation or incorrect cable selection. Then apply the fixes listed below.

• Replace damaged or moisture-contaminated cable

• Repair or re-terminate faulty connectors

• Shorten the cable run where possible

• Use a lower-loss cable for high-frequency applications

• Replace cable that has been permanently crushed or deformed

2. Impedance Mismatch, High VSWR, and Poor Return Loss

Impedance mismatch occurs when part of the coaxial cable assembly no longer maintains the intended characteristic impedance, typically 50 Ω or 75 Ω. This creates signal reflections, which appear as higher VSWR and poorer return loss and can reduce power transfer through the RF system.

Possible Causes:

• Crushed or deformed cable

• Bend radius violations

• Dielectric deformation

• Incorrect connector installation

• Damaged connectors

• Mixing 50 Ω and 75 Ω components

• Manufacturing or termination defects

• Moisture affecting dielectric properties

Likely Fix:

Measure S11, return loss, or VSWR with a VNA to confirm the mismatch. TDR or distance-to-fault testing can help locate a specific impedance discontinuity along the cable. Then apply the fixes listed below.

• Replace crushed or permanently deformed cable

• Reterminate or replace defective connectors

• Use correctly matched cable and connector impedances

• Correct bend-radius or installation issues

• Replace moisture-damaged cable

3. Open-Circuit Coaxial Cable Failure

An open-circuit failure occurs when the electrical path through the center conductor or shield is interrupted. It can cause complete signal loss or, if the break is only partial, intermittent RF performance.

Possible Causes:

• Conductor fracture

• Flex fatigue

• Failed solder joint

• Poor crimp

• Connector separation

• Severe tensile stress

Likely Fix:

Use a continuity or resistance test to confirm the open circuit. TDR testing can help locate the break if it is somewhere along the cable rather than at the connector. Then apply the fixes listed below.

• Re-terminate the connector if the break is at the termination

• Repair or replace a failed solder or crimp connection

• Replace the cable if the internal conductor is broken

• Improve strain relief if excessive pulling or flexing caused the failure

4. Short-Circuit Failure

A short-circuit failure occurs when the center conductor makes electrical contact with the outer conductor or shield. This can cause complete signal loss or severe degradation in RF performance.

Possible Causes:

• Poor connector installation

• Stray braid strands

• Crushed dielectric

• Excessive mechanical deformation

• Damaged connector

• Manufacturing defect

Likely Fix:

Check center-to-shield resistance first to confirm the short. TDR or VNA measurement can help determine whether the fault is located at the connector or elsewhere along the cable. Then apply the fixes listed below.

• Re-terminate the connector if the short is confined to the termination

• Remove stray braid strands or correct connector assembly errors

• Replace damaged connectors

• Replace the cable assembly if internal deformation or dielectric damage caused the short

5. Intermittent RF Cable Assembly Failure

An intermittent RF cable assembly failure occurs when the cable performs normally under some conditions but loses performance when moved, flexed, or vibrated. These failures can be difficult to diagnose because the assembly may appear normal during a static test.

Possible Causes:

• Conductor fatigue

• Partially broken shield

• Loose RF connector

• Poor crimp

• Damaged solder joint

• Repeated flexing

• Vibration

• Connector mating wear

Likely Fix:

Perform a controlled flex test while monitoring S11 or S21, inspect the connector interfaces, and compare performance with a known-good cable assembly to confirm the fault. Then apply the fixes listed below.

• Replace fatigued or internally damaged cable

• Reterminate or replace faulty connectors

• Repair poor crimps or solder joints where appropriate

• Improve strain relief

• Reduce excessive flexing or vibration at the cable connection

6.Coaxial Cable Shielding Failure

A coaxial cable shielding failure occurs when the cable still transmits RF but no longer adequately contains or rejects electromagnetic energy. This can lead to increased noise, greater EMI susceptibility, RF leakage, and degraded performance near interference sources.

Possible Causes:

• Broken braid

• Foil damage

• Corrosion

• Abrasion

• Crushed cable

• Poor connector shield termination

• Incomplete 360° shield connection

Likely Fix:

Start with a physical inspection of the cable and connector terminations, then use appropriate RF or EMI testing to confirm whether shielding performance has degraded. Then apply the fixes listed below.

• Replace cable with internal shield damage

• Re-terminate connectors with poor shield contact

• Repair or replace corroded connector components

• Replace crushed or abraded cable

• Ensure proper 360° shield termination at the connector

7. Moisture-Related Coaxial Cable Failure

Moisture can trigger several types of coaxial cable failure at once because it affects both the conductive and insulating parts of the assembly. Water ingress can increase attenuation, promote corrosion, degrade connectors, alter dielectric properties, and create impedance discontinuities that lead to poor return loss or intermittent RF performance.

Possible Causes:

• Damaged or cracked cable jacket

• Poor weather sealing

• Loose or improperly installed connectors

• Condensation

• Long-term exposure to rain, humidity, or saltwater environments

Likely Fix:

Inspect the cable and connectors for signs of moisture, corrosion, or compromised sealing, then verify performance with insertion-loss and return-loss measurements. If water has penetrated the dielectric, replacement is usually more reliable than repair. Then apply the fixes listed below.

• Replace moisture-contaminated cable

• Replace or re-terminate corroded connectors

• Restore proper weather sealing

• Repair damaged jacket sections only if internal contamination has been ruled out

• Use outdoor-rated cable and sealing methods in exposed installations

8. Thermal and High-Power Coaxial Cable Failure

Thermal failure occurs when a coaxial cable or connector operates beyond its safe power or temperature limits. Excess heat can increase insertion loss, destabilize performance, damage the dielectric, and eventually cause permanent failure.

Possible Causes:

• RF power above the cable rating

• Excessive connector loss

• Poor VSWR causing localized power dissipation

• Inadequate thermal management

• Excessive ambient temperature

Likely Fix:

Check the cable’s power rating, connector condition, operating temperature, and VSWR to determine whether excessive heating is coming from overload, mismatch, or a lossy connection. Then apply the fixes listed below.

• Use a cable assembly with a higher power rating

• Replace damaged or high-loss connectors

• Correct impedance mismatches that are increasing VSWR

• Improve cooling or thermal management

• Reduce exposure to excessive ambient temperature

9. Poor High-Frequency Performance

A coaxial cable may perform normally at lower frequencies but degrade as frequency increases. At higher frequencies, small discontinuities, connector defects, dielectric damage, and conductor losses become more significant, leading to higher insertion loss or poorer return loss.

Possible Causes:

• Connector discontinuities

• Cable deformation or tight bends

• Excessive insertion loss

• Dielectric damage

• Poor termination

• Cable or connector not rated for the operating frequency

Likely Fix:

Sweep the cable across its full operating frequency range with a VNA and review both S11 and S21. This helps identify whether the problem is caused by reflections, excessive transmission loss, or unsuitable component selection. Then apply the fixes listed below.

• Replace damaged or deformed cable

• Reterminate or replace defective connectors

• Use cable and connectors rated for the required frequency

• Shorten the cable run where practical

• Upgrade to a lower-loss RF or microwave cable assembly

10. Phase or Amplitude Instability

Phase or amplitude instability occurs when the electrical performance of a coaxial cable changes with movement, temperature, or mechanical stress. This is especially important in microwave, test, radar, and other phase-sensitive RF systems where even small changes can affect accuracy or system performance.

Possible Causes:

• Repeated cable flexing

• Temperature cycling

• Connector movement

• Mechanical stress

• Dielectric instability

• Changes in conductor or shield geometry

Likely Fix:

Monitor phase and amplitude with a VNA while flexing the cable or changing its temperature. If the measurements shift beyond the required tolerance, the assembly is no longer stable enough for the application. Then apply the fixes listed below.

Possible fixes:

• Replace mechanically fatigued cable

• Improve strain relief and cable routing

• Replace loose or unstable connectors

• Use phase-stable cable for flexing applications

• Use cable designed for the expected temperature range

How to Troubleshoot Coaxial Cable Failure

A good troubleshooting process starts with simple physical checks, then moves to electrical and RF measurements if the problem is not obvious. Before testing, disconnect power where appropriate and confirm the cable type, connector type, length, and operating frequency.

1. Inspect the Cable and Connectors: Look for kinks, crushing, jacket damage, corrosion, loose connectors, bent contacts, and failed weather sealing. Pay particular attention to areas near connectors, cable ties, sharp bends, and entry points into equipment. 

2. Check Continuity and Shorts: Use a multimeter to check center-conductor continuity from end to end and verify that the center conductor is isolated from the shield. Test the shield separately if possible.

3. Measure Insertion Loss and Return Loss With a VNA: Use S21 to check transmission or insertion loss and S11 to evaluate reflections and return loss. Compare the results from RF test equipment with the cable manufacturer’s specifications or with a known-good cable of the same type and length.

4. Use TDR Testing: TDR testing coaxial cables can help locate opens, shorts, and impedance discontinuities by measuring reflected pulses and estimating the distance to the fault. Set the correct cable velocity factor in the TDR so the distance calculation is accurate.

5. Test Across the Actual Operating Frequency Range: Always test across the cable’s intended frequency band. Check for increasing insertion loss, sharp reflection peaks, or unstable readings as frequency rises. If the cable is used outdoors, repeat testing after movement, temperature changes, or exposure to moisture.

6. Compare With a Known-Good Cable: When possible, temporarily replace the suspected cable with a cable known to work correctly. If the system immediately returns to normal, the original cable or one of its connectors is likely defective.

Should You Repair or Replace a Failed Coaxial Cable?

Some coaxial cable failures can be corrected at the connector or termination, while internal cable damage usually requires replacement. Use the type and location of the fault to guide the decision.

How to Prevent Coaxial Cable Failure

Preventing coaxial cable failure starts with correct cable selection and careful installation. The cable should match the system’s impedance, frequency range, power requirements, and environmental conditions.

• Follow the specified minimum bend radius

• Use proper strain relief near connectors

• Apply the correct connector torque

• Weather-seal outdoor connections

• Support cables to prevent crushing or excessive movement

• Use the correct 50 Ω or 75 Ω impedance

• Choose cable and connectors rated for the operating frequency

• Stay within the cable’s power-handling limits

• Use materials suitable for temperature, moisture, UV, and chemical exposure