Nomenclature

These sets were initially numbered as wireless telegraph (w/t) sets, but a distinguishing prefix of "2" was soon added. Metric sets were numbered in the 28x and 29x series. When centimetric sets arrived with the advent of the cavity magnetron

Cavity magnetron

The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field. The 'resonant' cavity magnetron variant of the earlier magnetron tube was invented by John Randall and Harry Boot in 1940 at the University of...

, they were numbered by subtracting 10 from the metric type number they were based on (e.g. the metric Type 284 was replaced by the centimetric Type 274). This was not always possible however, as Types 271 - 274 were already in use for original centimetric sets, thus some metric sets in the Type 28x range had 20 subtracted (e.g. the metric Type 282 was replaced by the centimetric Type 262). Aerial outfits were given a three letter identifier that began with "A".

Suffixing letters indicated the following;

• B - conversion of sets with separate transmitting
  Transmitter
  In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
  
   (Tx) and receiving
  Receiver (radio)
  A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
  
   (Rx) antennas to single antenna operation.
• M, P, Q - major set modifications
• R - addition of range-taking panel
• U - modification to suit coastal operations
• W - modification to submarine use
• X, Y, Z - experimental modifications

ASV II

Type	Aerial outfit	Peak power Effective radiated power In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...  (kW Kw kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada... )	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...  (MHz)	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...  (mm)	In service
ASV II		7	176		1940

The first successful Air to Surface Vessel (ASV) radar. ASV II radar allowed Aircraft Carrier

Fleet Air Arm

The Fleet Air Arm is the branch of the British Royal Navy responsible for the operation of naval aircraft. The Fleet Air Arm currently operates the AgustaWestland Merlin, Westland Sea King and Westland Lynx helicopters...

 based RN Swordfish

Fairey Swordfish

The Fairey Swordfish was a torpedo bomber built by the Fairey Aviation Company and used by the Fleet Air Arm of the Royal Navy during the Second World War...

 to locate and attack the German battleship Bismarck in May of 1941, from the carriers Victorious

HMS Victorious (R38)

HMS Victorious was the second Illustrious-class aircraft carrier ordered under the 1936 Naval Programme. She was laid down at the Vickers-Armstrong shipyard at Newcastle-Upon-Tyne in 1937 and launched two years later in 1939...

 and Ark Royal

HMS Ark Royal (91)

HMS Ark Royal was an aircraft carrier of the Royal Navy that served during the Second World War.Designed in 1934 to fit the restrictions of the Washington Naval Treaty, Ark Royal was built by Cammell Laird and Company, Ltd. at Birkenhead, England, and completed in November 1938. Her design...

.

ASV III

Type	Aerial outfit	Peak power Effective radiated power In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...  (kW Kw kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada... )	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...  (MHz)	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...  (mm)	In service
ASV III/XI		50		100	1943

The first successful airborne microwave radar. This radar was used on both the Swordfish and Barracuda

Fairey Barracuda

The Fairey Barracuda was a British carrier-borne torpedo- and dive bomber used during the Second World War, the first of its type used by the Royal Navy's Fleet Air Arm to be fabricated entirely from metal. It was introduced as a replacement for the Fairey Swordfish and Fairey Albacore biplanes...

 aircraft. High resolution centimetric radar could detect even small objects, such as the periscope or snorkel of a submerged submarine, making it a highly efficient tool for ASW

Anti-submarine warfare

Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

. The Mk XI was a further development exclusively for the Fleet Air Arm.

Type 79

Type	Aerial outfit	Peak power Effective radiated power In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...  (kW Kw kw or KW may refer to:* Kuwait, ISO 3166-1 country code** .kw, the country code top level domain for Kuwait* Kilowatt* Self-ionization of water Kw* Cornish language's ISO 639 code* Kitchener–Waterloo, Ontario, Canada... )	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...  (MHz)	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...  (mm)	In service
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....		70	42.8	7,000	1938

Based on the Type 79 w/t, first fitted to HMS Sheffield

HMS Sheffield (C24)

HMS Sheffield was one of the Southampton sub class of the Town-class cruisers of the Royal Navy during the Second World War. She took part in actions against several major German warships. Unlike most Royal Navy ships of her time, her fittings were constructed from stainless steel instead of the...

 then HMS Rodney then HMS Curlew

HMS Curlew (D42)

HMS Curlew was a C-class light cruiser of the British Royal Navy. She was part of the Ceres group of the C class of cruisers.She was laid down by Vickers Limited on 21 August 1916, and launched on 5 July 1917, being commissioned into the navy on 14 December 1917. In common with most of her...

  (40 sets ordered)

Type 86

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
86M	APH

Fore-runner to Type 286.

Type 262

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
262	APE	30	9,670	31

Centimetric fire-control set for 40 mm Bofors

Bofors 40 mm gun

The Bofors 40 mm gun is an anti-aircraft autocannon designed by the Swedish defence firm of Bofors Defence...

 weapons. Fitted to Close Range Blind Fire (CRBF) director and STAAG weapon mount. Dish antenna spun off-centre at high speed to produce scanning cone, target lock and blind fire possible.

Type 267

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
267	APT	100	214	1,400

Air warning set for submarines replacing Type 291W.

Type 268

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
268	AQN	40	9,386	32

Small vessel millimetric target indication and navigation.

Type 271

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
271		5	2,997	100	March 1941
271P		90	2,997	100	1943
271Q		90	2,997	100	1943

Type 271 was the original naval centimetric target indication radar, later fitted with 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...

. Modifications P and Q were known as the "Centimetric Mark IV". IT had separate Tx and Rx aerials, small parabolic dishes stacked on top of each other, and referred to as "cheese" after their shape. The antenna array was carried in distinctive protective perspex "lantern", and initially had to be fitted directly onto the radar office roof due to limitations in coaxial cabling

Coaxial cable

Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...

 (until suitable waveguide

Waveguide

A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...

s had been developed.) The Type 271 was a vitally important war weapon, as for the first time it allowed escort ships to reliably detect surfaced U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s or even just their periscope

Periscope

A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....

s. First fitted on HMS Orchis

HMS Orchis (K76)

HMS Orchis was a that served in the Royal Navy during World War II.-North Atlantic Trade Convoy Escort:In March 1941, Orchis was the first ship fitted with the very successful 10-cm wavelength Type 271 Radar enabling detection of a surfaced submarine at 5000 yards or a submarine periscope at 1300...

. (350 sets ordered) It was fitted widely to escort vessels of corvette

Corvette

A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft or fast attack craft , although many recent designs resemble frigates in size and role...

 and frigate

Frigate

A frigate is any of several types of warship, the term having been used for ships of various sizes and roles over the last few centuries.In the 17th century, the term was used for any warship built for speed and maneuverability, the description often used being "frigate-built"...

 size.

Type 272

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
272		90	2,997	100	1941

"Centimetric Mark III" target indication set. Carried in distinctive protective perspex "lantern". For vessels of destroyer and cruiser size.

Type 273

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
273	AQN	90	2,997	100	1941

"Centimetric Mark IV" target indication set. This set was based on the Type 271, but was intended for major warships of cruiser and battleship size. It used side-by-side 3 feet (914.4 mm) wide cheese antennas that were carried in a distinctive protective perspex "lantern". In the Battle of the North Cape, HMS Duke of York

HMS Duke of York (17)

HMS Duke of York was a King George V-class battleship of the Royal Navy. Laid down in May 1937, the ship was constructed by John Brown and Company at Clydebank, Scotland, and commissioned into the Royal Navy on 4 November 1941, subsequently seeing service during the Second World War.In...

 identified the target of Scharnhorst

German battleship Scharnhorst

Scharnhorst was a German capital ship, alternatively described as a battleship and battlecruiser, of the German Kriegsmarine. She was the lead ship of her class, which included one other ship, Gneisenau. The ship was built at the Kriegsmarinewerft dockyard in Wilhelmshaven; she was laid down on 15...

 at 45000 yards (41,148 m) using her Type 273 set.

Type 274

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
274	AUM	500	3,294	91	1944

Centimetric replacement for Type 284. Main armament ranging and shot-spotting set for cruisers and 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...

s. "Double cheese" antennas.

Type 275

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
275		400	3,526	85	1944

Centimetric replacement for Type 285. Destroyer

Destroyer

In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

 main armament and capital ship secondary fire control set. Fitted to directors HACS

HACS

HACS, an acronym of High Angle Control System, was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 onwards and used widely during World War II...

 Mark VI and Mark 6M and modified American Mark 37. Separate Tx and Rx dishes.

Type 276

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
276	AUS / AUJ	500	2,997	100	1944

"Centimetric Mark V" target indication set with continuously rotating antenna. Reduced 4 feet (1.2 m) antennas in aerial outfit AUS.

Type 277

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
277P	AUK	400	2,997	100	1943
277Q	ANU	500	2,997	100	1944

"Centimetric Mark V" target indication set with steerable antenna. Aerial Outfit AUK was a parabolic dish, ANU was a cropped paraboloid. Fitted on a "nodding" mount, often used as a height finding set. Superseded in service by Type 278 height finder in County class destroyer

County class destroyer

The County class was a class of guided missile destroyers, the first such vessels built by the Royal Navy. Designed specifically around the Sea Slug anti-aircraft missile system, the primary role of these ships was area air-defence around the aircraft carrier task force in the nuclear-war...

.

Type 279

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
279 Type 279 radar The Type 279 radar was a British naval early warning radar developed during World War II from the Type 79.-External links:*...		70	39.9	7,450	1940
279M		70	39.9	7,450	1941

Follow on from Type 79, metric air warning set. Had separate Tx and Rx antennas, combined in Type 279M to single antenna operation. This set also had a secondary surface search with surface and aerial gunnery capability and used a Precision Ranging Panel, which passed accurate radar ranges directly to the HACS

HACS

HACS, an acronym of High Angle Control System, was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 onwards and used widely during World War II...

 table (analog computer).

Type 280

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
280		25	85	3,500	1940

Metric air warning set with separate Tx / Rx antennas. Based upon Army

British Army

The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 GL Mark I set, fitted to C class cruiser

C class cruiser

The C class was a group of twenty-eight light cruisers of the Royal Navy, and were built in a sequence of seven classes known as the Caroline , Calliope , Cambrian , Centaur , Caledon , Ceres and Carlisle classes...

s converted to anti-aircraft ships. This set used a Precision Ranging Panel, which passed accurate radar ranges directly to the HACS

HACS

HACS, an acronym of High Angle Control System, was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 onwards and used widely during World War II...

 table (analog computer).

Type 281

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
281 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....	AQB	350	85	3,500	1940

Metric air warning set with separate Tx / Rx antennas. Type 281B had combined Tx / Rx antenna. First fitted to HMS Dido

HMS Dido (37)

HMS Dido was the name ship of her class of light cruisers for the Royal Navy. She was built by Cammell Laird Shipyard , with the keel being laid down on 26 October 1937. She was launched on 18 July 1939 and commissioned on 30 September 1940.-Mediterranean:On 18 August 1942 Captain H. W. U...

 then HMS Prince of Wales This set also had a secondary surface search and gunnery capability and used a Precision Ranging Panel. The Type 281 ranging system allowed the user to select either a 2000yd to 14000yd or a 2000yd to 25000yd range display with range accuracies of 50 or 75yds RMS, respectively.

Type 282

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (cm)	In service
282		25	600	50	1941

Centimetric ranging set for Bofors 40 mm and "multiple pom-pom" fire control. Fitted on Bofors mounting Mark IV "Hazemeyer" and "Pom-pom Director Mk IV"

Pom-Pom Director

-History:The Vickers 40mm "Pom-Pom" Antiaircraft mounting was introduced to the Royal Navy in the early 1930s. The mounting was capable of a tremendous volume of fire but the crew had great difficulty in aiming the mounting due to the smoke and vibration created by the guns...

, twin Yagi antenna

Yagi antenna

A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element and additional parasitic elements...

s. Type 282 used a mechanical ranging panel and a 0-5000yd display. Type 282M increased transmission power to 150KW, used a 0 - 6000yd display and introduced Beam Switching, while Type 282P introduced a Precision Ranging Panel.

Type 283

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (cm)	In service
283		25	600	50	1942

Main armament anti-aircraft barrage fire control set fitted to "barrage director" for cruiser 6 inches (152.4 mm) and battleship guns. This set used a Precision Ranging Panel and was used to fire the guns automatically using the Automatic Barrage Unit.

Type 284

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (cm)	In service
284	ASF	25	600	50	1940
284M	ASF	150	600	50	1941
284P	ASF	150	600	50	1942

Main armament ranging and shot-spotting set for cruisers and battleships with lobe switching

Lobe switching

Lobe switching is a method used on early radar sets to improve tracking accuracy. It used two slightly separated antenna elements to send the beam slightly to either side of the midline of the antenna, switching between the two to find which one gave the stronger return, thereby indicating which...

 beginning with Type 284M to increase accuracy of bearing readings. Prototype fitted on HMS Sardonyx. HMS Southdown received first production set. Used by HMS Suffolk

HMS Suffolk (55)

HMS Suffolk was a County class heavy cruiser of the Royal Navy, and part of the Kent subclass. She was built by Portsmouth Dockyard, Portsmouth, UK), with the keel being laid down on 15 November 1924...

 to shadow Bismarck

German battleship Bismarck

Bismarck was the first of two s built for the German Kriegsmarine during World War II. Named after Chancellor Otto von Bismarck, the primary force behind the German unification in 1871, the ship was laid down at the Blohm & Voss shipyard in Hamburg in July 1936 and launched nearly three years later...

. Type 284P was instrumental in the Battle of the North Cape, effectively allowing HMS Duke of York

HMS Duke of York (17)

HMS Duke of York was a King George V-class battleship of the Royal Navy. Laid down in May 1937, the ship was constructed by John Brown and Company at Clydebank, Scotland, and commissioned into the Royal Navy on 4 November 1941, subsequently seeing service during the Second World War.In...

 to sink Scharnhorst

German battleship Scharnhorst

Scharnhorst was a German capital ship, alternatively described as a battleship and battlecruiser, of the German Kriegsmarine. She was the lead ship of her class, which included one other ship, Gneisenau. The ship was built at the Kriegsmarinewerft dockyard in Wilhelmshaven; she was laid down on 15...

 blind.

Type 285

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (cm)	In service
285		25	600	50	1941
285M		150	600	50	1941
285P		150	600	50	1942

Ranging set for anti-aircraft fire control, fitted to HACS directors and rangefinder-directors and used ranging panel L12. Type 285 with six element Yagi antenna with separate Tx / Rx. Type 285P with five element Yagi antenna with combined Tx / Rx function. The Type 285M could provide accurate ranges via the mechanical ranging panel, L12, and bearing information using lobe switching, but height finding was primitive and had to be calculated using maximum signal indication. As such it could not achieve a target lock, and could not offer blind fire capability. Type 285P introduced a Precision Ranging Panel and had 25yd RMS range accuracy.

Type 286

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
286M	ATQ		214	1,400	1940

Metric target indication set based upon RAF ASV (Air to Surface Vessel) Mark II set. Type 286M had fixed antennas, with a central Tx and an Rx on either side to give some indication of contact bearing. The antennas were fixed, scanning being achieved by conning the ship. Type 286PU and Type 286W were fixed antennas sets for coastal vessels and submarines respectively. Type 286PQ had a steerable combined Tx / Rx antenna from the Type 291 set.

Type 290

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
290		100	214	1,400

Metric target indication set, replacement for Type 286.

Type 291

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
291		100	214	1,400	1941

Metric air warning sets. Original Type 291 had a hand-steered antenna, replaced by Type 291M with power training and plan position indicator. U and W variants for coastal craft and submarines respectively.

Type 293

Type	Aerial outfit	Peak power (kW)	Frequency (MHz)	Wavelength (mm)	In service
293M	AUR	500	2,997	100	1945
293P	AQR	500	2,997	100	1945
293Q	ANS	500	2,997	100	1945

"Centimetric Mark V" target indication set, shared transmitter with Type 276 / Type 277 sets. Stabilised "cheese" antenna, 6 feet (1.8 m) diameter in outfit AUR, upgraded to 8 feet (2.4 m) in Type 293P (replaced all Type 293 and Type 276 sets) and to 12 feet (3.7 m) in Type 293Q.

Precision Ranging Panel

The Precision Ranging Panel (PRP) was an electromechanical transmission and calculating system. The PRP allowed for accurate range determination, range rate determination using radar, and accurate transmission of radar ranges and range rates to fire control computers. The PRP used an electronic timing signal and pip matching to provide very accurate ranges. It also used a power follow up to continuously transmit the correct range rate as long as the target maintained a steady course and speed. The PRP was adapted from the British Army GL, Gun Laying, radar system, and first went to sea in 1939 aboard several C class AA cruisers, using the Type 280 radar. By 1941 the PRP was a common feature on the Type 280, 279 and 281 radars, and by late 1941 began to appear on the type 282P, 284P and 285P radar systems.

Mechanical Ranging Panel

The Type 282, 282M, 285, and 285M radars used a mechanical ranging panel that used a mechanical cursor placed over the ranging display, to estimate range and automatically transmitted the calculated range to either the HACS or FKC

Fuze Keeping Clock

The Fuze Keeping Clock was a simplified version of the Royal Navy's High Angle Control System analogue fire control computer. It first appeared as the FKC Mk1 in destroyers of the 1938 Tribal class, while later variants were used on sloops, frigates, destroyers, aircraft carriers and several...

fire control computer. Type 285 used Ranging Panel L12 and this also featured range rate estimation with power follow up so that the ranging panel would continue to transmit the correct range without operator intervention as long as the target maintained a steady course at a constant speed.

External links

• The RN Radar and Communications Museum