Type 281 radar

The Type 281 radar was a British naval early warning radar developed during World War II. It replaced the Type 79 as the Royal Navy's main early warning radar during the war.

The prototype system was mounted on the light cruiser HMS Dido (37) in October 1940. This radar used a frequency of 90 MHz, a beamwidth of 35°, and a wavelength of 3.5 metres. It required separate transmitting and receiving antennas that were rotated by hand. For long-range warning the radar used a 15 microsecond pulse at a power level of 350 kW that gave a detection range up to 110 nmi for aircraft. For tracking surface targets it used a 2–3 microsecond pulse at 1 MW that gave a range up to 12 nmi. A second set was installed in January 1941 aboard the battleship HMS Prince of Wales (53) and production began of another 57 sets with the first deliveries occurring the following month.

Type 281B consolidated the transmission and receiving antennas while the Type 281BP radar had the short pulse feature removed. It was fitted with improved receivers that increased the maximum detection range for an aircraft at 20000 ft to 120 nmi. At lower altitudes, ranges declined to 90 nmi at 10000 ft and 65 nmi at 5000 ft. The Type 281BQ was a Type 281BP fitted with power rotation, at 2 or 4 rpm, and equipped with a plan position indicator. After the end of the war, the Type 281 was replaced by the Type 960 radar.