Type 281 radar
Encyclopedia
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
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 antennae 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 nautical miles (203.7 km) for aircraft. For tracking surface targets it used a 2–3 microsecond pulse at 1 MW that gave a range up to 12 nautical miles (22.2 km). A second set was installed in January 1941 aboard the battleship
and production began of an another 57 sets with the first deliveries occurring the following month.
Type 281B consolidated the transmission and receiving antennae 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 foot to 120 nautical miles (222.2 km). At lower altitudes, ranges declined to 90 nautical miles (166.7 km) at 10000 foot and 65 nautical miles (120.4 km) at 5000 foot. 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.
Early warning radar
An early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate...
developed during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. It replaced the Type 79
Type 79 radar
The Type 79 radar was a British naval early warning radar developed before World War II. It was the first radar system deployed by the Royal Navy....
as the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
's main early warning radar during the war.
The prototype system was mounted on the light cruiser
Light cruiser
A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...
in October 1940. This radar used a frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of 90 MHz, a beamwidth
Beamwidth
In telecommunication, the term beamwidth has the following meanings:1. In the radio regime, of an antenna pattern, the angle between the half-power points of the main lobe, when referenced to the peak effective radiated power of the main lobe....
of 35°, and a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of 3.5 metres. It required separate transmitting and receiving antennae 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 nautical miles (203.7 km) for aircraft. For tracking surface targets it used a 2–3 microsecond pulse at 1 MW that gave a range up to 12 nautical miles (22.2 km). A second set was installed in January 1941 aboard the battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...
and production began of an another 57 sets with the first deliveries occurring the following month.
Type 281B consolidated the transmission and receiving antennae 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 foot to 120 nautical miles (222.2 km). At lower altitudes, ranges declined to 90 nautical miles (166.7 km) at 10000 foot and 65 nautical miles (120.4 km) at 5000 foot. The Type 281BQ was a Type 281BP fitted with power rotation, at 2 or 4 rpm, and equipped with a plan position indicator
Plan position indicator
The plan position indicator , is the most common type of radar display. The radar antenna is usually represented in the center of the display, so the distance from it and height above ground can be drawn as concentric circles...
. After the end of the war, the Type 281 was replaced by the Type 960 radar.