PBO Sketchbook

Where best to mount a radar? Dick Everitt’s illustrated guide

A. The radar horizon is just over the visual horizon, so if we mount the radar scanner at about 20ft (6m) we should see a buoy at 6 miles, and another vessel’s radar reflector mounted at 20ft (6m) at about 12 miles. Bigger things like ships and mountains, which poke above the horizon, will show up at a much greater range.

B. Mounting the scanner where the lowers meet the mast is a good stable position and looks right. But make sure it doesn’t mask any mast-mounted deck floodlights.

C. If it’s too high the weight and the windage will create too much movement.

D. I’ve seen a couple of boats with scanners that can be hoisted on tracks in fog. But they must be very rigid so as not to spoil the display accuracy.

E. Some boats mount them at the side to be clear of sweeping sails.

F. Mizzen masts are ideal provided the scanner is clear of loose topping lifts.

G. Radar struts are a practical solution, but make sure the scanner is not in line with the boom. Otherwise, if you have a target to starboard, the bounced signal could show a phantom one to port as well.

H. Strut kits are available with bracing bars, cable glands and adapters to fit sloping surfaces.

I. radars don’t work too well if they are pointing into the sea, so if you intend to be on one tack for several days it might be worth considering a mount that can be pinned at an angle.

J. Oil-damped, self-levelling brackets are also available, to mount a strut on the backstay.

K. Motorboats don’t have any running rigging to foul the antenna, so can have a large, open array that gives much better target definition.

L. Even though the vertical beam angle is 25˚ some installers like to tip the front of the antenna down a few degrees to allow for the bow rising when she’s on the plane.

M. I’ve also seen these tipped scanners in RIBs and on flybridges – but I’m not sure I’d want my head that close to the transmitter for hours on end.