Troubleshooting Common Issues with Coax Cables: Causes, Tests and Fixes

Overview: why coax troubleshooting matters

Coaxial cable remains widely used for RF, CCTV, satellite and broadband links because of its shielding and predictable impedance. However, coax cables can suffer signal loss, interference, connectors failing, or physical damage. This guide on troubleshooting common issues with coax cables explains symptoms, simple tests, and repairs tailored for South African makers, students and technicians who need reliable local supply and fast turnarounds.

Typical applications and common symptoms

• Satellite or TV: picture breakup, pixelation, or no signal.
• CCTV: intermittent or noisy video, flicker, or colour loss.
• Broadband/Internet over coax: slow throughput, frequent drops.
• RF test setups: unexpected attenuation, impedance mismatch or high SWR.

Quick visual and physical checks

Start with simple inspections: look for kinks, crushed sections, or exposed centre conductors. Check connectors (F-type, BNC, N) for bent pins or loose fittings. Test by swapping in a known-good patch lead where possible to narrow the problem to cable, connector or equipment. Local branches often stock replacement connectors and patch leads for same-day pickup-see collections for parts and accessories here.

Tools you should have

• Multimeter (continuity and short checks)
• Coax cable tester or time-domain reflectometer (TDR) for advanced fault location
• Signal meter (satellite/CCTV) and a spectrum analyser for RF work
• Proper crimping tools, BNC/F/IEC/N connectors, and dielectric scissors

Basic electrical checks

Use a multimeter to verify continuity on the centre conductor and that the shield is continuous to ground. Also check for shorts between centre and shield. Follow Ohm's law and power considerations when working with active equipment: V = I * R. For passive coax links, focus on resistance and continuity rather than power dissipation.

Common fault table: symptoms, likely causes and first actions

Cable types and important specs

Knowing the cable type (RG-6, RG-59, RG-11, or professional foam-dielectric variants) helps set expectations for attenuation and bandwidth. RG-6 is common for satellite and broadband; RG-59 is older and higher loss for long runs. For higher-frequency RF or long-distance links, choose lower-loss variants. Comparing coax cables for network communication can help pick the right grade. Communica stocks a range of coax and connectors across categories-browse brands and categories here.

Testing methods and step-by-step diagnostics

Follow a methodical approach: isolate, swap, measure. Begin by disconnecting the cable at both ends and testing continuity from centre to centre and shield to shield. Then check for shorts between centre and shield. Use a simple coax tester for quick pass/fail checks. For precise fault location on buried or long runs, a TDR will show distance to the fault.

Wiring diagrams and connector checks

Standard F-type and BNC connections are straightforward but must be fitted correctly: centre conductor straight, dielectric trimmed not crushed, and shield folded back evenly. Example ASCII wiring for an F connector:

Cable end:
  | shield (braid) \
  | dielectric  --- centre conductor |
Connector fit:
  centre conductor -> pin
  shield -> connector body

A poorly fitted connector can introduce impedance discontinuities leading to reflections and signal loss. If you see high SWR or reflected power in RF setups, re-terminate or replace the connector and retest.

Calculations and practical examples

Attenuation is often given in dB per metre at a reference frequency. Use the formula to estimate signal loss: Loss(dB) = dB/m * length(m). Example: an RG-6 with 0.05 dB/m at 100 MHz over 30 m gives 1.5 dB loss. In many South African installations, acceptable losses depend on original signal level; aim to keep total loss under the margin your receiver requires. If replacing an RG-59 with RG-6 reduces loss and resolves picture issues, it may be worthwhile.

Repair techniques and when to replace

• Re-terminate connectors using proper tools to restore reliable contact.
• For localized jacket damage, cut out the section and use a new connector or splice kit; maintain characteristic impedance.
• Replace entire runs when there are multiple crushes, moisture ingress, or excessive length-related loss.

Local considerations: availability, lead times and cost examples

In South Africa, lead times and stock vary by branch. For urgent repairs, check stock and collection options at the Samrand head office or nearby branches for same-day pickup; branch details and trading hours are available here. Typical replacement patch leads or connectors can range from around ZAR 30-ZAR 200 depending on type and brand (prices are indicative; check current stock). For project or educational budgets, buy bulk cable reels or student kits from the Collections index here.

Troubleshooting checklist

• Swap in a known-good cable to isolate fault.
• Check continuity centre and shield; test for shorts.
• Inspect and re-terminate connectors with correct tooling.
• Measure attenuation or use TDR for distance-to-fault on long runs.
• Weatherproof outdoor joints and replace water-damaged cable runs.

Further learning and sourcing parts

For students and makers, practising proper termination and using low-loss cable where appropriate improves outcomes. Communica stocks a broad range of connectors, test equipment and cables suitable for hobbyist and professional use-browse the categories to compare options here. For company procurement, Communica provides VAT invoices and account quoting to assist with institutional purchases; see About Us for company details here.

Sources

• Coaxial cable overview - Wikipedia
• Understanding coaxial cable losses - RF Solutions
• Testing coaxial cable - Cabling Installation & Maintenance
• Communica branches & trading hours - Communica