ELECTRONICS

Highly potent solid-state radars improve safety at sea.

Solid-state radars have changed the safetyat-sea game with crisp imagery and the ability to pinpoint potential danger ahead.

It’s a common scenario on my home waters: A cargo ship heads south on Puget Sound, its bow aimed for the Port of Seattle’s always-hungry cranes, as a ferry steams west from Edmonds for Kingston and the Kitsap Peninsula. Compounding the situation is Seattle’s notorious rain and fog. While the ships are situationally aware thanks to robust commercial-grade radar and Class A AIS systems, the same isn’t always true of the recreational yachts with older radars. To the yachtsmen, the ship and ferry could appear as a single onscreen blob…provided that the radar can even penetrate the rain. ¶ Fortunately, today’s high-powered solid-state radars can mitigate this potentially confusing situation. ¶ Radar systems have long employed cavity magnetrons to transmit radio-frequency energy in extremely short, high-powered bursts. While effective, radar technology didn’t fundamentally change for recreational mariners until 2016, when multiple manufacturers released fully digital radars that replaced magnetrons with solid-state transistors. These radars broadcast lower-powered bursts of RF energy over significantly longer intervals using pulse-compression technology (think chirp sonar). Critically, solid-state transistors transmit highly predictable frequencies that enable Doppler processing, allowing these systems to color-code targets based on their threat levels (red means danger). ¶ While these radars work well, next-generation solid-state radars are offering higher power and new software features. ¶ Furuno’s first-generation solid-state radar—the radome-enclosed DRS4D-NXT—offered 25 watts of power and Target Analyzer, which delivered color-coded Doppler processing. Furuno’s newest offerings, the open-array DRS12ANXT ($7,430 to $8,275) and the DRS25ANXT ($9,430 to $10,275), offer 100 and 200 watts of power, respectively. Both radars are available with 41-inch, 4-foot or 6-foot arrays transmitting narrow wedges of

RF energy in horizontal beam widths of 2.3, 1.9 and 1.35 degrees, respectively. Like many other Ethernet-enabled sensors, these radars pack their smarts and processing power into the unit’s pedestal and use networked Furuno NavNet TZtouch multi-function displays. ¶ Garmin uses similar architecture and Ethernet connectivity with its radars. Garmin’s first-generation solid-state radars, the GMR Fantom 4 and GMR Fantom 6, employed 4-foot and 6-foot open arrays to deliver 40 watts of power and MotionScope Doppler processing. Additional GMR Fantom radars followed, and Garmin’s latest open-array radars, which are expected to hit the market by the end of this year, will each deliver 250 watts of power and beam widths of 1.8 and 1.25 degrees (depending on antenna). ¶ The transmitted power of Furuno’s and Garmin’s solid-state radars is significantly less than the peak outputs of magnetron units, but Eric Kunz,

Furuno’s senior product manager, says magnetron radars are rated for their peak power transmission, while solid-state radars are rated for their average power output. ¶ “The [total] power transmission between solid-state and magnetron radars is the same, and they both use the same frequency spectrum,” Kunz says. “It’s a different way of creating transmissions, but the result is the same.” ¶ Dave Dunn, Garmin’s director of sales and marketing for marine, agrees. “A 120-watt solid-state radar delivers the same total energy as a 15 kW magnetron-based radar,” Dunn says, explaining that the conversion between solid-state and magnetron radars is (roughly) a factor of 10 and change. “Solid-state radars get better information at greater distances because the RF energy stays on the target longer,” he adds. ¶ Overall, Furuno’s and Garmin’s solid-state radars now deliver the same (or greater) overall power as each company’s highest-end, recreational-level magnetron radars, which offer 25 kW of peak power. ¶ “The overall performance is equal to or better than magnetron-based radars,” Kunz says, adding that while cavity magnetrons need to be replaced after 3,000 to 5,000 hours of use, solid-state transistors typically outlast the radar pedestal’s motor drives. ¶ Both experts also say that narrower beam widths enable higher-resolution imagery. ¶ “I use the analogy of a wide-tip Sharpie marker,” Dunn says. “You can’t draw the picture you can with a narrow-tipped Sharpie.” In radar parlance, this means that beam width is the difference between having a general idea about targets and having a specific picture. ¶ Kunz agrees, adding that target separation is improved: “We’re taking energy and squeezing it into a narrower area. This improves onscreen resolution and puts more-effective radiated power onto the target.” ¶ Solid-state transistors open the door to advanced digital-signal processing, enabling Doppler processing and other features. For example, Furuno’s DRS12ANXT and DRS25ANXT radars are equipped with Furuno’s RezBoost, which can digitally decrease beam width to just 0.7 degrees; Bird Mode, which helps

anglers spot birds using the radar’s gain function; and Rain Mode, which helps mariners peer into squalls. ¶ “Signal processing can discern rain reflections from hardtarget reflections,” Kunz says. “Boaters can see rain, but it doesn’t obscure targets.” ¶ Additionally, Furuno radars have an automatic radar plotting aid that acquires and tracks an unlimited number of potentially dangerous targets. ¶ Garmin’s newest GMR Fantom radars will be equipped with MotionScope Doppler processing and proprietary features such as scan-to-scan averaging and advanced mini-automatic radar plotting aid. Scan-to-scan averaging compares each frame of radar data with its previous radar returns to eliminate intermittent noise and clutter—say, when tracking fast-moving targets, detecting distant shorelines or searching for fishfinding birds—while advanced MARPA automatically acquires and tracks up to 10 targets sans any user input. ¶ Another noteworthy point is that while magnetron radars have “main bang ” blind spots (such as 65 feet for a 25 kW radar), solid-state radars can detect targets as close as 20 feet. Moreover, the radars discussed in this article have a 96-nautical-mile range; however, their long-range performance is limited by how far above the waterline the radar array is physically mounted. The long-range features are likely best used to detect weather systems and birds rather than distant vessels. ¶ So, if you’ve been considering a new radar but have been waiting for the technology to mature, now could be the time to make it happen. As for yachtsmen cruising Puget Sound’s challenging waters, today’s high-power solid-state radars have no trouble color-coding and distinguishing between cargo ships and ferries at ranges that were previously the province of commercial- or military-grade hardware.