A radar reflector only needs to be used at times of limited visibility.
Vessels such as trailer boats often give very poor echoes on a ship’s radar, especially in rough seas. These can be even poorer from fibreglass and timber vessels.
They are simply a piece of metal arranged to return radio waves and can be purchased from boat chandleries or even home-made.
A radar reflector does not have to be displayed permanently, only in times of reduced visibility. Radar waves do not penetrate through swells so it is best, when necessary to display the radar reflector, to have it as high as possible, maybe on a boat hook in a rod holder or if on a yacht, hoist it up the mast with a halyard.
The Marine and Safety (Motor Boats and Licences) By-Laws 2023 require vessels of all lengths that operate outside sheltered waters to carry a radar reflector. In general terms, sheltered waters extend two nautical miles to seaward of land unless otherwise specified in the Marine and Safety (Limits of Operational Areas of Vessels) By-Laws 2013).