AIS Antenna Cable Loss Explained

AIS antenna cable loss is an important part of any AIS installation. A good AIS transceiver and antenna can still perform poorly if the coaxial cable run is too long, the wrong cable type is used, or the connectors are badly fitted.

This guide explains how cable loss affects AIS performance, why cable length matters, and how to choose suitable marine coax cable for AIS, VHF and marine communication antenna installations.

What Causes AIS Antenna Cable Loss?

AIS antenna cable loss happens when signal strength is reduced as it travels through the coaxial cable between the AIS transceiver and antenna. All antenna cable has some loss, but poor cable selection, long cable runs and bad connectors can make the problem much worse.

This is especially important on sailboats and yachts where masthead antennas often require long cable runs through the mast and back to the navigation station.

Why Cable Loss Matters for AIS Performance

AIS operates using marine VHF frequencies, meaning antenna height, cable quality and connector installation all affect real-world range.

In practical terms, poor cable installation can lead to:

• Reduced AIS transmission range
• Weaker AIS reception from nearby vessels
• Intermittent or unreliable AIS performance
• Reduced benefit from masthead antenna mounting
• Difficult fault finding during installation

If the antenna is mounted high but connected using poor cable or badly fitted connectors, much of the range benefit can be lost before the signal reaches the antenna.

RG58 vs RG213 vs Low-Loss Marine Coax

The correct cable depends on the length of the run, vessel layout and installation requirements. Short cable runs may use smaller coax, while longer masthead installations usually benefit from lower-loss cable.

RG58 Cable

RG58 is commonly used for shorter marine antenna cable runs. It is flexible and easier to route, but it is not usually the best choice for long masthead AIS or VHF antenna installations where signal loss becomes more important.

RG213/U Cable

RG213/U is a heavier coaxial cable often selected for medium marine antenna cable runs. It generally offers lower loss than RG58 and is better suited to installations where cable length is greater.

RG214/U Cable

RG214/U may be used where a more robust coaxial cable is required for longer or more demanding marine communication installations.

LMR400 and LMR600 Cable

LMR400 and LMR600 are low-loss cable options often used for longer communication runs, including V-SAT, TVRO and other marine RF systems. They may be considered where reduced signal loss is important and the installation allows for larger cable routing.

View our marine cable assemblies for AIS, VHF and marine communication installations.

Cable Length and Signal Loss

Longer cable runs create more signal loss. This is why masthead AIS antenna installations need careful planning. A high antenna position can improve AIS range, but a poor cable run can reduce the benefit.

Long masthead cable runs are especially important to consider when deciding whether a separate AIS antenna is required or if an AIS splitter system will be used.

When planning an AIS antenna cable route, consider:

• Total cable length from AIS unit to antenna
• Cable type and loss characteristics
• Number of connectors or joins
• Routing through masts, lockers or conduits
• Waterproofing and strain relief
• Future access for inspection or replacement

For masthead installations, cable selection should be considered at the same time as antenna mounting position. See our Where to Mount an AIS Antenna guide for related installation advice.

Connector Quality and Installation

Connectors are a common weak point in marine AIS and VHF antenna systems. A good cable can still perform badly if connectors are poorly fitted, corroded or not sealed correctly.

Common connector issues include:

• Poor crimp or compression fitting
• Water ingress at deck or mast connections
• Loose RF connectors
• Incorrect connector type
• Corrosion in exposed marine environments

Marine antenna cable connections should be installed carefully, checked during commissioning and protected against saltwater exposure where required.

Common AIS Cable Mistakes

1. Using RG58 on long masthead runs – flexible but not ideal where cable length is high.
2. Adding unnecessary joins – every join introduces another potential loss or fault point.
3. Poor connector fitting – one of the most common causes of weak AIS performance.
4. Ignoring water ingress – moisture inside coaxial cable can seriously affect signal quality.
5. Routing cable without strain relief – movement and vibration can damage cables over time.
6. Choosing antenna height without considering cable length – height helps, but cable loss still matters.

Recommended AIS Cable and Antenna Equipment

• Marine cable assemblies
• AIS antennas and compatible marine VHF antennas
• AIS splitters
• AIS transceivers
• Marine antenna mounts and fittings
• AIS antenna for boats guide
• Where to mount an AIS antenna guide
• AIS Splitter vs Dedicated AIS Antenna guide

AIS Antenna Cable Loss: Final Thoughts

Managing AIS antenna cable loss is essential for reliable AIS performance. Cable type, cable length, connector quality and antenna mounting position all affect how well the system performs in real marine conditions.

For short cable runs, smaller coaxial cable may be acceptable. For longer masthead installations, lower-loss marine coax and properly fitted connectors are usually a better choice.

If you are unsure which cable assembly is suitable for your AIS or marine VHF installation, contact F&C Marine for practical guidance based on your vessel type, antenna position and cable route.

For further technical information about AIS systems and marine radio communications, see the International Telecommunication Union (ITU).