If you participated in the Boaters' Parade of Lights last month, you might have a better appreciation for the value of RADAR. Traveling a crowded waterway at night is no fun. The potential for collision is all around and the distraction of background lights, a festive and distracted crew, the wake of dozens of boats, and the occasional boat whose overloaded generator suddenly goes pitch-black doesn't make the challenge any easier. Dimly lit boats, ATONS, bridges, docks, and the marsh - all await for a stealthy encounter on the journey home.

But a crowded holiday is not the only occasion where RADAR comes in handy. Any situation which obstructs a captain's vision calls out for a tool that can pierce through the vale - whether it be darkness of night, fog, sleet, snow, rain, or even smoke. Having a strong search light helps in the dark, but is only reflected back in other forms of visual obstruction.

If you do elect to add a RADAR to your wish list, there are a few things you should consider. RADAR units are composed of an antenna, which alternates rapidly between transmitting and receiving signals, a data recorder, processor, and a display monitor. One of the biggest reasons for dissatisfaction comes from buying an antenna that is too small. The longer the antenna arm, the narrower the beam angle, and the better the unit will be able to discern objects and paint a clear images. (The price tag gets longer, too.) Also required, is sufficient power to punch through a thick fog (more bling). But buying a cheap unit may leave you so frustrated that you won't use it.

Another source of disappointment arises when a small boat owner buys a unit, hoping to see long distances away. RADAR operates on line of sight. Given the limits imposed by the curvature of the earth, the distance that a RADAR unit can "see" is proportional to the height above water that it is mounted. The formula is distance = 1.22 X the square root of the height. So a unit mounted 36 feet high will "see" 1.22 X 6, or 7.32 miles, while one mounted 9 feet high will only "see" 4.66 miles.

Is your boat only 4 feet off the water? Your range will be less than 3 ½ miles. But, is that so bad? If you can't get out of the way of something 3 miles away, you have other issues. Let's face it, while it is useful to know what lies 50 miles away, the main reason we have RADAR is to avoid things close by that we would normally be able to see.

RADAR doesn't reflect well off of water or wood, but does reflect off of earth and metal quite well. That is generally a good thing. We don't want it to reflect off of water. We do want it to "paint" the sides of the creek. But failing to "see" wooden pilings or boats can be a problem. There are limitations to what your RADAR can do, and units have a number of controls that you must be able to adjust if you are going to operate your unit safely. You should know how to change from standby to transmit, adjust the zoom level, the offset, and various gain controls.

You should take the time to read your manual and understand how to use extra features like Variable Range Markers (VRM) and Electronic Bearing Lines (EBL). How to change between North-Up and Heading- or Course-Up Displays. How to superimpose your RADAR output onto your chartplotter display (if so configured). How to display waypoints and data from your GPS onto the monitor, and how to use MARPA (if so-equipped).

MARPA (Mini Automatic Radar Plotting Aid) is a really cool feature found on moderately priced units and above. This handy feature allows you to click on a return and allow the unit to "acquire" the target. Once acquired, the RADAR will follow the target and constantly calculate the closest point of approach, alarming you if it gets too close. This has great value when traveling offshore, where targets sometimes get lost or forgotten in the clutter and waves.

Displays come in two flavors - CRT and LCD. The latter is larger, waterproof, and more visible in bright sunlight. A recent invention allows you to plug an antenna directly into a laptop, via a USB port. Software on the laptop turns your computer into a RADAR monitor. Definitely worth looking into.

One caveat. If you do own a RADAR unit and it is in working order, you are required by COLREG rules to monitor it to avoid collisions and should you have an accident, you will be held to a higher level of accountability. But don't let that stop you. If you have one and know how to properly use it, the chance of having an accident in limited visibility will be significantly reduced.

Ready to start shopping? Visit our local boating stores and electronics installers and ask lots of questions to find the right unit for your boat. Merry Christmas.