GMR™ 18 HD3 Radom

The Garmin GMR 18 HD3 radome is a next-generation HD3 high-definition marine radar. It provides precise target detection and features advanced BlueNet™ connectivity, enabling seamless integration with modern Garmin systems. This radar is designed to ensure reliable monitoring of the maritime environment, even in challenging conditions.

For installation of the Garmin GMR 18 HD3 radome, the following tools are required:

A drillA 9.5 mm (3/8 in) drill bitA 32 mm (1 1/4 in) drill bit (optional, for cable routing)A 4 mm (5/32 in) Allen keyA 13 mm (1/2 in) wrench and a torque wrenchMarine sealant

When choosing the mounting location, several points must be considered:

The radar must be mounted out of reach of people, with the vertical beam above head height. It must be installed high above the vessel's keel line, with minimal obstructions between the vessel and the radar beam. The mounting surface must be flat, parallel to the waterline, and sufficiently robust to support the radar's weight. The radar must be kept away from heat sources such as exhausts and lights. It must not be mounted closer to a compass than the specified safety distance to avoid magnetic interference. Other electronic equipment and cables must be more than 2 m (6 ½ ft) from the radar beam path. GPS antennas must be either above or below the radar beam path. The radar must be at least 1 m (40 in) from any transmitting equipment and cables carrying radio signals (VHF, antennas). It must be at least 2 m (6.5 ft) from SSB radios (single sideband).

If you mount the radar on a coachroof or hardtop, you must raise it sufficiently to avoid interference with the surface. To determine the mounting height, follow these steps:

Measure the distance between the planned mounting location and the farthest forward corner of a rectangular coachroof, or the forward apex of a curved roof. Use the following equation to calculate the mounting height: For measurements in millimeters: (Distance (mm) × 0.222) - 150 = height (mm) For measurements in inches: (Distance (in) × 0.222) - 6 = height (in) For example, if the distance is 2 m (2000 mm) from the roof corner, the mounting height would be (2000 mm × 0.222) - 150 = 294 mm.

Then install a riser or another support so that the radar’s base is equal to or greater than the calculated height.

Yes, it is mandatory to update the software of your Garmin chartplotter when installing the GMR 18 HD3 radome. To get detailed instructions on how to update the software, please refer to your Garmin chartplotter user manual.

The Garmin GMR 18 HD3 radome uses Garmin BlueNet™ network technology and is compatible with Garmin BlueNet devices as well as other devices on the Garmin Marine Network.

Yes, if your boat is equipped solely with Garmin Marine Network devices, you must use a Garmin Marine Network adapter cable to connect the GMR 18 HD3 to your network. If this cable is not included in the product box, you can purchase it separately (Garmin part number 010-12531-01).

The Garmin GMR 18 HD3 radome is a next-generation HD3 marine radar. It provides precise detection and features advanced BlueNet™ connectivity, enabling seamless integration with modern Garmin systems. It is designed to ensure reliable environmental monitoring, even in challenging conditions.

The Garmin GMR 18 HD3 radome housing includes the radome itself, a Garmin BlueNet cable, a mounting template, anti-seize compound, and four M8 x 1.25 x 60 threaded rods with flat washers, spring washers, and hex nuts for installation.

The GMR 18 HD3 radar beam extends vertically 12.5 degrees above and 12.5 degrees below the radome’s radiating element. On vessels with higher bow angles at cruising speed, the installation angle can be slightly adjusted downward using shims if necessary, to direct the beam toward the static waterline.

For installing the Garmin GMR 18 HD3 radome, you will need the following tools:

A drill with 9.5 mm (3/8 in) drill bits and, if needed, 32 mm (1 1/4 in) bits for cable routing. A 4 mm (5/32 in) Allen key. A 13 mm (1/2 in) wrench and a torque wrench. Marine sealant for waterproofing.

When choosing the mounting location for the GMR 18 HD3 radome, several considerations are important:

The radar must be mounted high above the vessel's keel line, with minimal obstructions between the vessel and the radar beam. It must be installed out of reach of people, with the vertical beam above head height. The mounting surface must be flat, parallel to the vessel's waterline, and sufficiently robust to support the radar's weight. Avoid mounting the radar near heat sources, spreaders, or booms. Ensure a minimum safe distance from other electronic equipment and cables to prevent interference.

If you install the radome on a roof or hardtop, it is recommended to use a riser (pedestal or similar structure) to prevent the surface from interfering with the radar signal. The beam extends at 12.5 degrees from the horizontal centerline, so the base of the radome must be high enough for the beam to clear the roof edge. A calculation formula is provided in the installation manual to help determine the required height.

Wiring requirements for powering the GMR 18 HD3 are as follows:

It is recommended to connect the power cable directly to the battery. Route the cable away from moving objects, high-heat sources, doors, and bilges. Do not run power and network cables parallel to other cables (radio antenna lines, other power cables) to avoid interference. If unavoidable, cables must be shielded. If an extension of the power cable is required, use a wire gauge suitable for the length: 2 m (6.5 ft): 16 AWG (1.31 mm²) 4 m (13 ft): 14 AWG (2.08 mm²) 6 m (19.5 ft): 12 AWG (3.31 mm²)

Yes, it is imperative to update the software on your Garmin chartplotter when installing the GMR 18 HD3 radome to ensure system compatibility and optimal operation.

The Garmin GMR 18 HD3 radome uses Garmin BlueNet™ networking technology and is compatible with Garmin BlueNet devices as well as Garmin Marine Network devices.

If your boat is equipped only with Garmin Marine Network devices, you must use a Garmin Marine Network adapter cable to connect the GMR 18 HD3 to your network. This adapter cable (reference 010-12531-01) is usually not included in the product box and must be purchased separately.

Yes, if your boat is equipped with a Garmin BlueNet chartplotter, you must connect the GMR 18 HD3 to an available network port on this chartplotter or on a Garmin BlueNet 20 switch, using the included Garmin BlueNet cable.

The warranty for the Garmin GMR 18 HD3 radome may be voided in the following cases:

If the unit is opened by anyone other than a Garmin-authorized service technician. The device contains no user-serviceable parts. If the power cable is connected without the inline fuse holder and the correct fuse installed, as specified in the product documentation.

No, the Garmin GMR 18 HD3 radome contains no user-serviceable parts inside. To avoid voiding the warranty, the unit must only be opened by a technician authorized by Garmin.