Insights: Pinging the Unknown

Looking at the technology that supports modern marine radar.

Sunshine flooded the waters separating California's Catalina Island from Channel Islands Harbor. Capt. Tom Petersen, skipper of the Sea Ray 55 Sundancer Valkyrie, was leading a small flotilla when an unexpected fog bank quashed visibility. Valkyrie carries the latest Raymarine kit (Petersen is a Raymarine Pro Ambassador), including a 12 kW, 6-foot, open-array, high-definition radar, but Petersen's companions weren't electronically fortified. "I sat behind the other boats, watching them on my radar and maintaining radio contact," Petersen said. One boat didn't have radar or autopilot, and the skipper was ignoring his compass. "I told him to keep [maintaining] a certain angle, but he picked up speed and went in the wrong direction. Then, he got scared." Staying calm, Petersen advised the panicked skipper to cut his speed, and he used his radar to wend Valkyrie alongside. "Without radar," Petersen said, "this would have been dangerous."

Raytheon (known to today’s boaters as Raymarine) delivered the world’s first commercial and recreational radar after World War II. Other systems followed, including now-generation ones that use high-definition (HD), broadband and Wi-Fi technologies to improve both radar imagery and user interface. Still, these latest and greatest offerings use traditional radar technology as their basic foundation, so it’s helpful to understand how that technology works before delving into the newest add-ons.

Traditional or “pulse-modulated” radars emit extremely short (typically one microsecond or less) pulses of radio-frequency (RF) energy that are generated by the system’s magnetron and transmitted via a fixed-mount, rotating directional antenna. These pulses move at the speed of light in a narrow, horizontal band before bouncing of targets and boomeranging as an echo. The radar receives the echo and determines the range to a target by measuring the elapsed time between a transmission and an echo’s return; bearing is calculated by measuring the radar antenna’s angle when the echo is received. Finally, the system applies filters to sift out signal noise (e.g., breaking waves or rain) before presenting this imagery on an electronic display.

Pulse-modulated radars cannot simultaneously transmit and receive, so these systems (even modern ones) constantly cycle between modes. Typical pulse-modulated radars transmit some 400 to 4,000 times per second and then spend the majority of their time “listening,” enabling the system to track all targets simultaneously within a 360- degree radius. Pulse-modulated radar can either be enclosed in a radome or use an open-array design; radome units typically draw 40 to 60 watts while providing a maximum range of 24 to 36 miles, while open-array systems typically draw 65 to 240 watts and provide a max range of 64 to 96 nautical miles.

This radar technology clearly works, although it can be difficult to separate and identify densely packed targets. Because of this, manufacturers employ a variety of now-generation technologies — including HD and broadband — to improve radar imagery significantly, but it’s still important to remember that all radar technology suffers attenuation issues in rain.

While the basic physics are the same between pulse modulated and HD systems, today’s manufacturers use technology to narrow the pulse’s horizontal band. Additionally, HD radar employs significantly faster sampling rates while offering a color-coding scheme to bolster target separation. Other HD features include power boost, dual-radar support, bird mode (great for fishing) and dual-range (provides both macro- and micro-level views of surrounding traffic), as well as sophisticated microprocessors that replace analog filters, and that are preprogrammed to “recognize” certain signal noises.

Unlike pulse-modulated radar, broadband radar (including 3G and 4G offerings from B&G, Lowrance and Simrad) uses solid-state, continuous wave technology that transmits RF energy while receiving echoes, all at once. This technology transmits in a continuous linear sweep (think CHIRP sounder technology), which allows the system to extract the maximum amount of information with the minimum amount of noise. Broadband radar has no “main bang” that’s inherent to all pulse- modulated radars. It emits less radiation than traditional radar, and it offers “instant on” functionality, which eliminates the magnetron’s warm-up time. Additionally, 4G broadband radar has beam-sharpening technology with target-separation control that doubles the azimuth resolution, allowing an 18-inch dome to deliver imagery normally found in a 3-foot open array radar.

The latest chapter in radar technology involves wireless units, such as Furuno’s revolutionary, Wi-Fi-based DRS4W 1st Watch Wireless Radar, which debuted last fall. This radar offers a range of 0.125 to 24 nautical miles and is a small, lightweight system providing several advantages while affording a glimpse at radar’s future. Aside from a power cable, the DRS4W operates sans hard-wired connections, simplifying installation. More important, the DRS4W streams its data over the vessel’s Wi-Fi network and displays its imagery on up to two Apple iOS devices, eliminating the need for a radar display and allowing boaters to use familiar touch-screen gestures, rather than memorizing the nuisances of a dedicated screen.

“In the past, you’ve had to have a radar antenna with a large, bulky signal cable coming into and connecting with the proprietary display,” explained Dean Kurutz, vice president of sales, marketing and product planning at Furuno. “Now, we’ve removed both, and we allow you to wirelessly transmit the radar signal to the iOS device.” While the DRS4W was primarily designed for smaller boats, a larger yacht can run a DRS4W as a backup unit; additionally, Kurutz said, a DRS4W can be set up on a tender.

Furuno is the only manufacturer to offer Wi-Fi radar (at the time of this writing), but other brands are expected to join this market, and bigger, more powerful Wi-Fi radar systems are expected. This, hopefully, will lower radar’s barrier of entry, but here the last word belongs to Petersen:

“If you had the choice to buy any one piece of electronics for your boat, get radar. If money and space aren’t an issue,[a] bigger, [more powerful system] really is better.”