Garmin Fantom 18x vs 24x: size, beamwidth and installation

Fantom 18x suits the more constrained mount; Fantom 24x deserves consideration when the boat can accommodate a larger antenna. Both belong on a shortlist only after the proposed Garmin display and network connection have been confirmed. This is a specification-based choice between two radomes, not a field-test ranking.

#Compare the exact x-series models

Shaded rows contain different values. On a small screen, scroll the table; model names stay visible within it.

Source: Garmin’s Fantom 18x/24x installation instructions, checked 3 October 2026. Consumption depends on operation; the table is not a measured passage average. These figures should not be transferred to older non-x scanners with similar names.

#Why the 24x can earn its space

The larger scanner’s narrower horizontal beam is the principal documented reason to prefer it. That matters when the question is whether close bearings can be distinguished, rather than simply whether a large landmass is visible. A good buying discussion should connect that difference to your regular waters and how you use radar.

It does not establish a universal detection advantage in every sea state. Range, target reflectivity, clutter settings and installation still matter. Ask for a demonstration of the actual display controls and target presentation before choosing an expensive system from specification sheets alone. Screenshots from different conditions cannot substitute for a controlled comparison.

#When the smaller scanner is the better fit

On a yacht, antenna size affects more than appearance. Measure the mounting position with the sail plan and rigging in mind, and include service access. On a small motorboat, check the hardtop structure and whether adding a scanner changes access to lights or other equipment.

A larger antenna is a poor use of money if accommodating it requires a compromised position. Conversely, do not assume the smaller one will fit an existing bracket: use the supplied mounting template and verify fasteners, clearances and cable entry. The model name is not a dimensioned installation drawing.

#Display and power checks

Keep three decisions separate: scanner supply, the network carrying radar imagery, and the heading/position data used by the display. Getting one right does not prove the other two. Garmin’s installation instructions discuss Marine Network and BlueNet connections; follow the path applicable to your exact chartplotter rather than buying an adapter based on connector appearance.

For power planning, use the manufacturer’s electrical limits to size the installation and a realistic operating schedule to estimate daily demand. Record how much time you expect to spend transmitting and in standby. Do not treat transmitter output power as battery consumption. The marine electrical guide explains the wider budget.

#Buy a working installation

Obtain matched Australian quotes for each scanner, including the cable run, supported display connection, mounting, any heading work and commissioning. No Australian sale price was verified for this page, so there is no invented “from” figure. A complete quote should identify GST and excluded labour explicitly.

Choose 18x when a compact installation best fits the boat; choose 24x when its narrower beam addresses a real need and mounting is straightforward. After installation, record alignment, check target tracking with the required inputs and practise switching ranges. If the existing display is incompatible, compare the entire refit against other systems through the comparison directory.

#Translate the beamwidth difference into the installation brief

The 24x’s narrower published native beam can make it worth investigating when target separation matters, but the boat still needs a sound mounting arrangement, correct configuration and a competent operator. The weight and physical envelope belong in the installer’s assessment. Do not add a larger scanner to an existing bracket just because the bolt pattern appears plausible.

Consider two owners. The first has a 32-foot monohull with restricted mast space and a compatible Garmin display. The second has a 50-foot cruiser with a properly assessed arch and more room for service access. The first should price the compact installation carefully; the second can assess whether the larger scanner’s benefit justifies its complete installation. Boat length alone does not settle either decision.

#Read electrical figures as limits, not a passage forecast

The table lists maximum normal-transmit consumption, not a measurement of your radar through an entire passage. As an illustrative upper-bound calculation for that stated mode, 33 W for six hours is 198 Wh. That is about 16.5 Ah at a nominal 12 V before losses; it excludes the display, network, heading source and every other load. Standby time and actual operation change the result. Use the selected manual for circuit design and measure the finished system for passage planning.

A sensible complete quote answers these questions:

• Which exact GPSMAP and software version will display the radar?
• Which network connectors, adapters or gateway are needed?
• Can the chosen mount carry the scanner and preserve specified clearances?
• How will the cable route remain inspectable and protected?
• What alignment, feature checks and crew practice are included?

The lower-cost option is the one that meets the brief at the lower complete cost, not necessarily the one with the lower scanner price. A budget owner should protect the installation and commissioning allowance. A premium owner should also demand an independent navigation fallback: another Garmin screen sharing the same power and network does not solve every common failure. Use the budget comparison to rank that expenditure.