This em-trak B400 AIS upgrade proposal has been prepared for Light Horse, a 40ft sailing yacht currently fitted with an older Raymarine Class B AIS system, a masthead VHF antenna and an Echomax XS Active radar target enhancer.

The objective is to improve AIS transmission performance without adding another closely spaced VHF antenna at the masthead. Our recommendation is to install an em-trak B400 AIS Class B transceiver together with an em-trak S300 VHF antenna AIS splitter , allowing the vessel’s masthead VHF antenna to be shared between the AIS and marine VHF radio.

em-trak B400 AIS Upgrade Objectives

Assessment of the Existing Installation

The yacht has an estimated mast height of approximately 50ft and an estimated masthead-to-navigation-station cable route of around 62ft, or 18.9m. The existing masthead equipment includes a VHF antenna, wind instrument and Echomax XS Active, with the radar scanner installed lower on the mast.

Adding a second AIS antenna close to this equipment would create unnecessary installation complexity. The more appropriate solution is to use a suitable active splitter and share the primary masthead antenna.

This approach is discussed in more detail in our guide comparing an AIS splitter versus a dedicated AIS antenna . Antenna spacing, height and RF interaction should also be reviewed against established marine AIS and VHF antenna placement principles.

Recommended AIS Installation Package

AC Antennas N163F Masthead Mount

The proposed CX4-3 masthead antenna requires a rigid and corrosion-resistant mounting arrangement. The AC Antennas N163F marine antenna mast mount is the recommended bracket for this proposal.

The N163F is manufactured from SS304 stainless steel and is designed as an angle bracket for marine antenna installations. It includes 5/8-inch and 1-inch mounting-hole options.

Before installation, the masthead surface, fixing positions, cable exit route and clearance from the wind instrument and Echomax unit should be checked.

View AC Antennas N163F

Why We Recommend the em-trak B400

The em-trak B400 provides a substantial upgrade from an older Class B AIS installation. It is suited to a navigation-station installation where the unit can be viewed and accessed by the skipper.

The installation can be integrated with compatible onboard equipment using NMEA 0183 or NMEA 2000 , subject to confirmation of the yacht’s existing navigation network and available connections.

The B400 should be mounted below decks in a protected, ventilated position with sufficient clearance for its power, data, GNSS and VHF connections.

Optional Chart Display Capability

The em-trak B400 includes its own colour display for viewing AIS targets, vessel information, course, speed and collision-avoidance data without relying entirely on the yacht’s main chartplotter.

Compatible chart data can also be added to the B400, allowing AIS targets to be viewed against a chart background directly on the unit.

For this installation, the B400 should still be treated primarily as an AIS transceiver and dedicated AIS display. The yacht’s existing Raymarine chartplotter would remain the principal navigation display.

Why Use the em-trak S300 AIS Antenna Splitter?

The em-trak S300 VHF antenna AIS splitter allows the AIS transceiver and marine VHF radio to use the same masthead VHF antenna. This avoids the need to install a second AIS whip in close proximity to the existing antenna and Echomax unit.

A splitter installation must be correctly wired, powered and tested. The antenna feed connects to the splitter’s VHF antenna port, with separate outputs feeding the VHF radio and B400 AIS transceiver.

Further practical guidance is available in our marine AIS splitter installation guide .

Recommended Coaxial Cable: 20m RG213/U

Richard’s estimated cable route is approximately 62ft, or 18.9m. Supplying exactly that amount would leave little allowance for the actual route through the mast, deck entry, bends, securing points and navigation-station service loops.

We therefore recommend supplying 20 metres of RG213/U 50-ohm coaxial cable. RG213/U offers lower loss and greater mechanical strength than lightweight RG58, while remaining a practical choice for this length of masthead VHF and AIS installation.

The cable should be supplied with one PL-259 UHF plug already fitted. The opposite end should remain unterminated during routing, with a second compatible PL-259 plug supplied loose and fitted after the cable has passed through the mast conduit, cable gland and internal route.

Cable attenuation is particularly important on long masthead runs. See our guides to AIS antenna cable loss and the differences between RG58, RG213, RG214 and LMR400 cable .

Proposed AIS System Architecture

The CX4-3 VHF antenna is secured at the masthead using the AC Antennas N163F mast mount . The antenna then connects through the 20m RG213/U coaxial cable to the S300 splitter. The splitter provides separate connections to the vessel’s VHF radio and em-trak B400 AIS transceiver.

The B400 uses its own dedicated GNSS antenna and connects to the yacht’s navigation system through the appropriate NMEA data interface.

Navigation Station Installation

The B400 should be installed where its display remains visible and accessible, while allowing sufficient space behind the unit for cable routing. The S300 splitter can be installed nearby in a dry, protected location, provided the coaxial cable runs remain practical and properly supported.

em-trak B400 and S300 Wiring Configuration

Installation and Commissioning Checks

The antenna, mast mount, coaxial cable and connectors should be checked before commissioning the new AIS equipment. The N163F bracket must be installed on a suitable rigid masthead surface, with secure fasteners and adequate clearance around the antenna.

Checks should include cable continuity, connector condition, water ingress, antenna performance, bracket security, supply voltage, GNSS reception, AIS transmission and reception, and confirmation that the VHF radio continues to operate correctly through the splitter.

These checks help prevent common marine AIS installation faults and reduce the risk of poor transmission range after the installation has been completed.

Our Yacht Bijou AIS antenna fault investigation also illustrates why antenna and coaxial condition should be verified rather than assumed.

Final Recommendation

For Light Horse, we recommend retaining a single masthead VHF antenna and installing the em-trak B400 through an em-trak S300 active AIS splitter. This avoids adding another transmitting antenna close to the existing masthead equipment while retaining the benefit of maximum practical antenna height.

The proposed package should include:

• em-trak B400 AIS Class B transceiver
• em-trak S300 VHF antenna AIS splitter
• Dedicated external GNSS antenna
• AC Antennas CX4-3 VHF antenna
• AC Antennas N163F marine antenna mast mount
• 20 metres of RG213/U 50-ohm coaxial cable
• One professionally fitted PL-259 UHF plug
• One loose PL-259 plug for termination after cable routing
• Appropriate deck sealing, cable support, fasteners and installation consumables
• Final antenna, mounting, VHF, GNSS and AIS commissioning tests
• Optional compatible chart package for the B400, available at additional cost

This arrangement provides a practical, serviceable and technically appropriate AIS setup for a sailing yacht of this size.

Upgrade Your Yacht’s AIS System

View the recommended em-trak and AC Antennas equipment for the proposed Light Horse AIS upgrade.