This set of radio direction finding (RDF) equipment comprises a Homer marine radio receiver with headphones, a hand-held directional aerial that incorporates a Sestrel sighting compass and a shortwave converter (which was mainly used for receiving time signals). The equipment was originally used by Sir Alec Rose when he sailed around the world in the ‘Lively Lady’ in 1968.

RDF uses radio waves to help fix a vessel’s position. The receiver picks up the signal from a transmitter whose location is known, and with the directional aerial is able to determine the bearing of that transmitter. If bearings are taken from the signals of several different transmitters, the vessel’s position can be plotted on a chart. RDF was developed for use in navigation in the 1920s and was found to be particularly useful for navigation close to shore, up to about 25 miles (40 km) from land.