Furuno DRS4DNXT radar

David Pugh assesses Furuno’s claim that its DRS4D-NXT ‘packs the performance of an open-array radar in a compact 24in radome’

Radar for small boats has moved on by leaps and bounds in recent years. For a long time conventional pulsed radar was king, but the tumbling cost of solid-state electronics and digital processing has driven manufacturers to seek new solutions, citing lower power, lighter weight and better resolution among their aims – although one can’t help but wonder if lower manufacturing costs might play a part too.

None of the technologies are really new, as the military and commercial markets have explored them all at various times, but the ability to cost-effectively manufacture them for private use is in itself revolutionary. so, which is the time taken for the radar to switch from transmit to receive.

Pulsed radar units are heavy owing to the magnetron which develops the pulse, and the high voltage power supply to drive it. This can pose a power problem as a 4kW scanner/plotter combo will draw up to 4A, and have a warm-up time of a minute. However, their real drawback is that the power and frequency of a magnetron cannot be altered: the only thing that can be is the pulse width. A long pulse has more energy than a short one at the same power, and is therefore better at picking up

targets: however, a long pulse may fail to resolve the difference between two targets on the same bearing at similar ranges. As a result, pulsed radars compromise by using long, high-energy pulses at long range and shorter ones at closer ranges.

Resolving targets close together at the same range is also a challenge, and is dependent on beam width. The purpose of the antenna is to form a searchlightlike beam and rotate it around, a bit like a lighthouse. The bigger the scanner the sharper the beam and the better the target bearing separation. Narrower beam widths improve resolution, but the only way to achieve this with a traditional scanner is to make the scanner bigger.