Marine Radar has undergone so many changes in the past few years that our concept of how and why we use it – and whether or not we need it – is changing.
When it comes to marine electronics, few things are as expensive, complex, and difficult to interpret as radar, right? While that may have been a defensible statement a few short years ago, today it’s far off the mark. In fact, with today’s latest units you get far more bang for your buck, their auto-settings work far better than they used to, and their displays are far easier to read than they once were.
Radar Basics – Marine Radar
We’ll dig into how and why things have changed so much in just a sec, but first let’s make sure everyone has a solid basic understanding of how exactly marine radar works (you salty types who have been running it for years can skip down a couple paragraphs).
Historically, radar worked by emitting a transmission in the form of high-frequency radio waves via a magnetron, and then listening for the waves to be bounced back (“returns”) after they hit a solid object. Measuring the time difference between the initial transmission and the reception of the returned signals then made it possible for the radar’s digital brain to calculate distance to the target, and display it accordingly on-screen.
Unfortunately, that big burst of power creates something called a “main bang,” an area of interference that can cover 100’ or more immediately around your boat. So while long range performance is excellent, very short ranges are hampered. The good news about main bang is that it drove electronics companies to develop a technology that eliminates it. Instead of using strong bursts of power, newer solid-state units are magnetron-free and use much lower power levels. And instead of calculating the difference between the transmission/reception time delay, they calculate the difference between transmitted and received frequencies. There’s no main bang, target discrimination is excellent, and it’s possible to see a very poor target – like a small buoy – whether it’s 25 feet or 2.5 miles away. The range for this type of radar, however, is often more limited than that of traditional radar and usually maxes out at under 30 or 40 miles.
One other important factoid: many people choose the biggest, most powerful (and usually most expensive) unit possible, to get the most range. This is usually a mistake, however, because radar range is limited by the curvature of the Earth. Functional range isn’t determined by the numbers printed in the unit’s specifications, but by the height of your antenna and the height of the target you’re trying to get a return from. For you mathematical types, here’s the equation that determines radar range: 1.2NM x (square root of antenna height in feet) + 1.2NM x (square root of target height in feet) = Range
For the rest of us, a much simpler way to wrap your head around it is to remember that super-tall stuff is easier to see at a distance because it sticks up real high, and at long distances, shorter stuff disappears. Let’s say, for example, your radar sits 9-feet above the water on your boat’s hard-top, and a vessel 15 miles away has a tower standing 36-feet above the water’s surface. You’ll never see it, no matter how potent and expensive your radar may be. Why? Let’s feed those numbers into our equation. Start with 1.2 x 3 (the square root of 9, which is the height of your radar antenna). That makes 3.6. Now account for the other boat’s height of 36-feet and multiple 1.2 by 6 (the square root of 36) and you get 7.2. Add the two figures together, and you have 10.8. No matter what, the boat remains out of radar range until you’re 10.799999 (etcetera) miles away. Period.
Newer Is Better
Now for the good news: newer radar not only do away with main bang and get a serious target discrimination boost, they also benefit from modern man’s zeal for developing algorithms. You no longer commonly need to twist one dial for sea clutter, another for rain clutter, and another for sensitivity until you find the perfect mix to see a relatively clean radar screen – your MFD is now smart enough to do all that for you. In the same way that fishfinder auto-settings have become vastly improved over those we had a decade ago, today’s radar auto-settings rarely let you down. Added bonus: since that radar image is no longer wired to its own display but instead gets routed to your MFD at the helm, overlaying that radar on a digital chart is a piece of cake. That alone takes much of the guesswork out of interpreting what all those blips and blobs are.
Like they say on TV: But wait, there’s more!
Add in features like Doppler and integration with AIS, which have become commonplace in the market, and reading that screen becomes even easier. Targets can be color-coded for levels of collision danger, vectors can be displayed, and AIS-active boats can be identified with speed and course.
I know that you’re thinking: all this new tech is going to cost me an arm and a leg, right? Well, not really. Today’s low-end units still go for under $1,500 and even the high-end units, which often integrate both the potent magnetron-based radar and the newer solid-state versions, rarely exceed five or six grand. While that’s not exactly cheap, in today’s dollars it’s basically the same as we paid for old-tech radar with a stand-alone screen a decade ago – so your bang for the buck has only grown stronger.
Choices, Choices, Choices
Which radar is the best for you? This may sound like a cop-out, but we really mean it: generally speaking all of the big manufacturers are making radar that’s so good it’s hard to complain about any of them. As each company has added this perk or that one, the others follow so rapidly that it’s hard to put your foot down and say which is the most “advanced” at any given point in time. Pricing is incredibly competitive, as are warranties and hardware quality. So when upgrading or expanding a systems you should feel safe opting for the radar that matches whatever gear you already have on your boat. Just make sure that you do in fact upgrade or expand. Because when it comes to radar, having a modern unit aboard gives you a serious leg up.
Get more great boating information, tips and reviews from BD’s Lenny Rudow.