Marine Radar Buying Guide: Radome vs. Open Array, Range and Doppler
Quick answer: For most recreational boats from about 20 to 40 feet, an 18 to 24 inch radome is the right radar. Choose an open array (3.5 feet and up) if you run a larger boat, travel long distances at night, or need to separate targets that are close together. Modern solid-state, Doppler-capable radars start instantly, show moving targets in color, and are the best choice if your chartplotter supports one. Make sure the radar matches your display brand before you buy.
Radar is the one instrument that sees through fog, rain and darkness. It shows other boats, channel markers, land and squalls whether they carry AIS or not. If you run early mornings, cross inlets in fog, fish offshore or run home after dark, radar turns guessing into seeing. This guide covers dome versus open array, power and range, solid-state technology, mounting and the questions to ask before you buy.
Step 1: Radome or open array?
| Radome | Open array | |
|---|---|---|
| Size | About 18 to 24 inch dome | Rotating bar, roughly 3.5 to 6 feet |
| Typical boats | Center consoles, cruisers, sailboats about 20 to 40 feet | Larger cruisers, sportfish, trawlers, commercial |
| Target separation | Good | Better, thanks to a narrower horizontal beam |
| Weight and windage | Light, compact, enclosed | Heavier, needs a sturdy mount and clearance to spin |
| Cost | Lower | Higher |
The longer the antenna, the narrower the beam, and the better the radar can tell two close targets apart, such as a buoy next to a boat.
Step 2: Understand power and range
Radar range is mostly limited by the curve of the earth and how high the antenna is mounted, not just by power. A dome mounted on a T-top will see large targets like ships and shorelines many miles away, but small boats and buoys only at shorter distances. A rated maximum range of 24 or 36 miles is a measure of capability, not what you will see on every target. For most recreational use, 2 to 4 kW traditional radars and today's low-power solid-state radars are plenty.
Step 3: Solid-state and Doppler
- Traditional magnetron radar: proven and affordable, needs warm-up time, and emits higher peak power. Keep people clear of the beam at head height.
- Solid-state (pulse compression) radar: starts almost instantly, uses very low transmit power, and gives sharp close-range detail.
- Doppler target highlighting: colors approaching targets differently from receding ones, so you can spot a boat on a collision course at a glance.
Most major brands now offer solid-state Doppler domes. The catch: they usually only work with that brand's chartplotters.
Step 4: Match it to your display
Most radars connect to a multifunction display from the same brand over that brand's network or ethernet. Before you buy, confirm:
- Your chartplotter supports radar and the specific radar model.
- You have the right data and power cables for the run length from the radar to the helm.
- Your electrical system can supply the radar's power, through a proper fuse or breaker.
No compatible display? Choose a standalone radar with its own screen, or a wireless radar that displays on a tablet.
Step 5: Mount it right
- Height: mount high enough to clear people's heads and see over the bow, typically the T-top, hardtop, arch or mast.
- Level: boats run bow-up. Leaning radar mounts compensate for running angle so the beam does not shoot into the sky.
- Clearance: keep the radar clear of antennas and metal structures that cause shadows or interference.
- Sailboats: mount on the mast or a pole mount with a guard to protect it from sails and lines.
Step 6: Learn to use it
Practice on clear days. Compare what you see on radar to what you see out the window, learn the gain and sea clutter controls, and overlay radar on your chart if your display supports it. Radar is a skill, and the time to learn it is before the fog rolls in.
Our picks by boat and setup
All in stock at Boat Supplies Direct.
No compatible chartplotter: standalone radar
SI-TEX T-760 Compact Color Radar, a complete system with a 4 kW 18 inch dome and its own 7 inch touchscreen.
Radar on your tablet
Furuno 1st Watch Wireless Radar, a dome that sends its picture over Wi-Fi to a compatible tablet. Order the power cable separately.
Furuno networks and serious offshore boats
Furuno DRS6AX 6 kW UHD Digital Radar or the Furuno DRS12AX 12 kW for Furuno NavNet systems. Antenna and cable sold separately.
Mounting
Scanstrut PowerTower 6 inch aft-leaning radar mount, or the forward-leaning version to match your hardtop. Sailors: the Scanstrut LMM-1 Self Leveling Mount.
Frequently Asked Questions
What size radar do I need for my boat?
Most boats from about 20 to 40 feet use an 18 to 24 inch radome. Larger boats and those needing the best target separation choose a 3.5 foot or longer open array.
Is radar worth it on a center console?
If you run in fog, at night, or offshore, yes. Radar shows boats, markers and weather that AIS and your eyes can miss.
What is the difference between a radome and an open array radar?
A radome encloses a small spinning antenna in a dome. An open array is a longer exposed antenna with a narrower beam that separates close targets better, at more cost and weight.
Do I need a chartplotter to use radar?
Most radars display on a compatible chartplotter from the same brand, but standalone radars with their own screen and wireless radars that show on a tablet are available.
How far can boat radar see?
It depends on antenna height and target size. Large targets like ships and land show many miles out, while small boats and buoys appear at shorter range.
What is Doppler radar on a boat?
A feature on modern solid-state radars that colors approaching and receding targets differently, making collision risks easy to spot.
This guide is general information. Radar does not replace a proper lookout. Follow your radar manufacturer's installation and safety instructions.
