Radar: the magic bullet of navigation. It lets you see in the dark and fog, and gives you accurate and early information about the bearing of objects, distant or lurking.

But it can't do a thing for you if you aren't using it effectively.

Just ask the pilot of the Cosco Busan. The container ship struck the Bay Bridge in San Francisco in a thick fog in 2007, causing an oil spill that killed more than 2,000 birds. Among the federal charges filed against the pilot was failure to use the ship's radar while approaching the bridge.

The most important thing to remember about radar is that it changes the rules – literally. The United States Inland Rules and the International Regulations for Preventing Collisions at Sea (COLREG) have specific sections on the use of radar, and even recreational boat captains have been held responsible for not using their radar correctly when a crash occurs. If your boat has "fitted and operational" radar, you are required to have it on and to use it.

FRANK MUMMERTOn occasion you should inspect your installation for security.What exactly does "fitted and operational" mean? It involves the installed position of your radar, but there's more to it than just that simple explanation. Before you can properly use your unit, you should really understand not just the full meaning of that phrase, but also what the rules say.

RULES FOR A REASON

Rule 6 deals with the definition of "safe speed," and almost half of it covers vessels equipped with operational radar. It requires the operator to take into consideration the characteristics and limitations of the unit; the effect of weather and sea state on the radar; and the quality of information that can be received by it. In effect, you are responsible for knowing how to operate and interpret the radar.

Rule 19 covers the conduct of vessels in or near areas of restricted visibility and specifies what actions to take. Section D says, "a vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists." If you believe this is happening, you need to "take avoiding action in ample time," and that action should "avoid an alteration of course to port for a vessel forward of the beam, other than for a vessel being overtaken, and alteration of course toward a vessel abeam or abaft the beam."

By contrast, if you don't have operational radar but hear a fog signal apparently forward of your beam, the rules say that you must slow down, and even come to a complete stop.

POSITIONING THE RADAR

Because of the requirements for radar to be "fitted and operational," the location of the console is important. When my wife and I bought Rockhopper, our Morgan 452 ketch, the radar unit, a Furuno CRT, was at the navigation table. This made it handy for navigation, but reduced our ability to use it for plotting and collision avoidance. With the engine running, communication between the navigation station and the helm was difficult at best. If I ran the boat solo, having to run back and forth between the two reduced my ability to maintain good plots. If only two of us were on board and we were running in restricted visibility, one of us had to be continuously at the helm while the other was at the radar below. This left no one to act as a good lookout on the bow.

FRANK MUMMERTHere's an example of how not to install radar: The beams are right at the helsman's feet.Ty and Suzanne Giesemann of Liberty, a Morgan 46 sloop, provided a better approach. They installed an LCD radar in the cockpit so that the person at the helm could monitor the autopilot and the radar, while the second person was free to roam the deck, serving as eyes and ears away from the engine.

We installed a Raymarine LCD radar/chartplotter on Rockhopper at the helm, putting the radome on the main mast, but leaving the Furuno at the navigation station and its radome on the mizzenmast. This allows us to keep an eye on traffic, even when we are at anchor, by using the radar-watch feature, which activates the radar periodically, sweeping the horizon and shutting down if it doesn't detect anything within range. It also gives us a backup in the event the Raymarine unit fails. The downside is that the power requirements of the Furuno and the interference between the two units prevent us from running them simultaneously.

Note how above, I mention that we installed the radome on the main mast. Radar beams contain high-intensity energy, which can be harmful. In his excellent book Radar for Mariners, David Burch discusses possible short- and long-term effects of being "in the beam." Short-term exposure to most commercial small-boat radar is probably not dangerous, but long-term or direct, up-close exposure can have undesired effects, some of which are not fully understood.

The key to reducing any danger is antenna placement. Ideally, the radome should be high enough in the rigging, on a radar arch or on a cabin roof, that the beam never touches any crewmembers. As the radar beam moves away from the radome, it starts to expand, somewhat like the light beam from a flashlight. Therefore, even if the antenna array is placed above the height of the tallest crewmember when standing directly under the antenna mount, the beam may expand enough to expose someone standing in the bow, bringing in the anchor or serving as lookout. Sailboats generally don't have this problem, since the radome can be mounted on the mast. Small powerboats, especially center consoles, can have a much harder time finding a spot high enough to avoid exposing the crew.

In addition, the higher the radome is mounted, the more weight it puts in the rigging, which can affect stability. While a complete discussion of stability to beyond the scope of this article, mounting the radome at the desired location temporarily and moving around on the sides of the boat can give an idea of how much the additional weight can affect stability. If there is any doubt, working with a professional installation expert or rigging specialist can provide input on possible location choices. If the boat is already "tender" or prone to rolling, it may be necessary to put some weight low in the boat to offset the effect of the radome.

FRANK MUMMERTTechnology has come a long way.LEARNING RADAR

In the commercial marine world, deck crewmembers must show successful completion of a radar operator's course to operate vessels of more than 500 gross tons. recreational boaters have no such requirement. However, the United States Power and Sail Squadrons offer some helpful radar information in their coastal navigation and marine electronics courses, and the American Sailing Association has added a radar endorsement course to its offerings.

One of the easiest ways to get training is through the Starpath School of Navigation, www.starpath.com a marine training and software company headquartered in Seattle. Run by David and Mark Burch, it specializes in subjects like celestial navigation, weather forecasting and radar operation through classroom, home study and private instruction. The radar course is centered around Radar for Mariners, which includes a pair of radar simulators on a CD-ROM. They replicate the old-style CRT-type radar display and a newer, integrated LCD radar/chartplotter, allowing students to practice the plotting and ranging techniques that David Burch explains in the book. (The book can be purchased as part of the course or separately.)

The course also involves a series of online classes, with reading assignments and homework involving the radar simulator. Finished assignments are sent to Starpath electronically, where they are graded and returned with feedback. Upon completion of the course, you can coordinate with a local library to take a final examination and, upon passing, receive a certificate. Having the certificate may bolster your argument if you ever have to prove in court that you were operating your radar correctly.

But while documentation of your experience and training are important, even the best-trained mariners occasionally misinterpret the radar screen. The key to ensuring you understand what the radar is telling you is constant practice in good weather. Don't wait until you get into a situation where you need to use your radar to break out the book.