There are now products on the market that improve the chance of being seen within a safe margin. One of these is the Sea-me Active Radar Enhancer. The main benefits are as follows:
Greater detection range
The strength of a radar signal falls off rapidly with distance. In the case of a passive reflector this degradation takes place over a distance equal to double the range (radar to target and back) whereas in the case of an active device, which is itself a transmitter, it only falls off over the return distance - and from a much higher amplified signal level. This means that an active device, has a greater detection range than the typical passive reflector.
A more consistent return
Ships today use a system known as ARPA (Automatic Radar Plotting Aid). This enables the radar to emit an alarm when it acquires a target within its guard zones and thus to alert the watchkeeper. Target acquisition will only take place if the radar receives returns on at least 50% of scans. Two factors contribute to a consistent return - the strength of the returned signal and, because small boats yaw and heel, particularly in rough seas, the evenness of the return.
Better performance in clutter
Performance in clutter (rain and wave) is all about signal strength. The single fact that an enhancer emits a stronger signal means that it performs better in clutter.
Better performance at heel
The effectiveness of a passive reflector falls off rapidly as the boat heels, as you would expect of a device which is effectively a mirror reflecting in a single direction. An active device shapes the beam to provide an effective return even when the boat is heeled.
Ship detection alert
Passive reflectors cannot give you any warning that you have been struck by a radar signal indicating that there is a ship in your area. An enhancer being active, knows when it has received a signal and can alert you with a flashing light, and if required, audibly..
Are you a poor reflector?
The modern yacht or motor cruiser is most likely to be built of GRP and to be inherently a poor reflector of radar signals. Since radar is the most effective pair of eyes on board a ship, having a long range and being largely impervious to fog and darkness, it is important that we do whatever we can to improve the probability that our vessel will be visible to radar. It is worth remembering that the visibility problem occurs not only in fog and mist but also at night - boats under 20m LOA are only required to carry lights with a visible range of 3nm, a distance which will be covered by a ship making 20 knots in 9 minutes.
Be seen and be safe
The prime purpose of a Radar Target Enhancer is to increase the probability that your vessel will be seen on the radar of commercial shipping. It aims to achieve this by returning an improved radar signal. It is worth noting that one radar is, to all intents and purposes, invisible to another. It must be noted that a radar enhancer does not obviate you from your responsibility under the International Regulations for the Prevention of Collisions at Sea to both keep a good lookout and to take whatever action is required to avoid a collision.
