Correspondence Received: Radar reflector – correction

24th February 2017

Correspondence Received: Radar reflector - correction

Initial Report

Dear CHIRP,

In the Video Broadcast bulletin No.1 you make the point that a yacht can be lost in the sea clutter and show an octahedral radar reflector at the top of a mast. Please note the reflector in the picture is incorrectly mounted and will not produce a strong return signal. Perhaps you could correct this in your next bulletin.

Incorrectly mounted reflector

 In response: CHIRP worked with the reporter to find definitive guidance to support the claim.

In 2007, the UK’s MAIB commissioned a report: “Performance Investigation of Marine Radar Reflectors on the Market”. They found that, in the upright position, the Radar Cross Section (RCS) performance peaks are very large for a small reflector, the drawback with this reflector mounted in this fashion is the very large nulls between the peaks and performance gets worse as the elevation angle is increased. In the ‘catch rain’ position, the RCS has lower peaks but is more balanced with azimuth angle variation and is more consistent over the elevation range. This opinion is supported by the Transport Canada publication “Radar Reflectors on Small Vessels” which states the axis of the reflector should be tilted 45 degrees to obtain optimal reflection, and recommends that the preferred orientation of mounting should be clearly marked on the reflector.

Correctly mounted reflector

CHIRP Comment:

In addition to fitting a radar reflector, fitting a “transmit and receive” AIS system is a prudent course of action; especially if transiting busy shipping areas. In any event, small boaters should keep a very good lookout and not simply rely on equipment to ensure they will be seen – which, in all probability, they may not be in the sea clutter. Remember the Mk I eyeball is still the best collision avoidance device!!!

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