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Electronics

Broadband Radar


It’s long past time that the magnetron was consigned to the dust bin of maritime history,” enthused Larry Brandt, a commenter on my electronics blog who is both a professional mariner and a radar tech with experience working on everything from 60-ton 1960’s Air Force sky scanners to the super-compact, super-high-performance solid-state sets that modern airliners use to dodge storm cells. And Brandt was just one of many experts excited about Navico’s introduction of its magnetron-free Broadband Radar in Europe last fall. In fact, even we non-engineer-type boaters can quickly recognize that Broadband Radar is something truly unusual.

For instance, while the three domes pictured above each occupy roughly the same space as an 18-inch scanner powered with a conventional 2-kW magnetron, they transmit at just 0.1 W. Yes, Broadband Radar uses just 1/2000th the peak power of the scanners it replaces and purportedly outperforms, in some ways spectacularly. The dome photo doesn’t show the claimed performance—and even screen shots need explanation—but it does illustrate Navico’s confidence. When delivered this spring, the domes will work with most existing Northstar and Simrad multifunction displays, as well as the new Lowrance HDS Series seen on page 42.

While a 0.1-W radar may sound nuts to boaters, it doesn’t to guys like Brandt who are familiar with the low-wattage, high-end radar that’s long been used by the military and others with deep pockets. Put simply, a microwave signal produced by a semiconductor—the definition of solid-state radar—is so much more precise than one produced by a vacuum-tube magnetron that it takes much less power to bounce it off a buoy or boat and get back a precise echo. What amazes Brandt and others is that Broadband Radar (BR) domes will start at about $1,750, a steal if they perform as promised.

Navico’s very unusual scanner comes with two antennas.

Lowrance product manager Greg Konig acknowledges that BR is not a patented invention per se, but rather a blend of smart engineering and just-now-available components. But he notes that it took five years for Navico to find the performance-value “sweet spot” he’s both proud of and careful to define: Apparently 0.1-W transmitters, though affordable, are a little weak even for solid state, and Konig says that BR is nothing special from about ten miles out to its 24-mile maximum range. But inside ten miles—and especially inside five miles—BR performance is “absolutely unmatched,” he says, and he means that relative to the best 2- and 4-kW HD recreational radars available. What BR apparently has going for it is a range resolution that’s far superior to what’s possible when a magnetron sends out pulses and then stops and listens for their return. In fact, BR uses a solid-state technique called Frequency Modulated/Continuous Wave (FM/CW), which means there are no pulses at all. Indeed, there are two antennas inside the dome, one transmit and one receive. The continuous transmission is slightly modulated so that echo returns are measured not based on pulse timing but on exact frequency timing. The more you know, the stranger BR is, but the result is the ability to distinguish between even small, closely spaced targets like moored boats, pilings, and kayaks, according to Konig.

And that’s not all. The stop/start nature of crude, if powerful, magnetron pulses is why a radar area around your boat is either obscured by noise or blanked out by the digital signal processing chips inside the newer HD radars. BR doesn’t have that problem and can purportedly distinguish targets just ten feet away. Moreover, the high- range resolution means that BR is better at discriminating between wave tops and harder objects, and hence clutter controls are more successfully automated. Plus, solid-state radar scanners turn on instantly—no standby period waiting for the magnetron to warm up—and are intrinsically more stable, which means they need less tuning and tweaking.

This article originally appeared in the March 2009 issue of Power & Motoryacht magazine.

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