Radar warning receiver

Radar warning receiver (RWR) systems detect the radio emissions of radar systems. Their primary purpose is to issue a warning when a radar signal that might be a threat (such as a police speed detection radar or a fighter jet's fire control radar) is detected. The warning can then be used, manually or automatically, to evade the detected threat. RWR systems can be installed in all kind of airborne, sea-based, and ground-based assets (such as aircraft, ships, automobiles, military bases). This article is focused mainly on airborne military RWR systems; for commercial police RWR systems, see radar detector.

Depending on the market the RWR system is designed for, it can be as simple as detecting the presence of energy in a specific radar band (such as police radar detectors). For more critical situations, such as military combat, RWR systems are often capable of classifying the source of the radar by the signal's strength, phase and waveform type, such as pulsed power wave or continuous wave with amplitude modulation or frequency modulation (chirped). The information about the signal's strength and waveform can then be used to estimate the most probable type of threat the detected radar poses. Simpler systems are typically installed in less expensive assets like automobiles, while more sophisticated systems are installed in mission critical assets such as military aircraft.

The top end of the aircraft's vertical stabilizer contains a Radar warning receiver, part of the Rafale's SPECTRA self defense system


The RWR usually has a visual display somewhere prominent in the cockpit (in some modern aircraft, in multiple locations in the cockpit) and also generates audible tones which feed into the pilot's (and perhaps RIO/co-pilot/GIB's in a multi-seat aircraft) headset. The visual display often takes the form of a circle, with symbols displaying the detected radars according to their direction relative to the current aircraft heading (i.e. a radar straight ahead displayed at the top of the circle, directly behind at the bottom, etc.). The distance from the center of the circle, depending on the type of unit, can represent the estimated distance from the generating radar, or to categorize the severity of threats to the aircraft, with tracking radars placed closer to the center than search radars. The symbol itself is related to the type of radar or the type of vehicle that carries it, often with a distinction made between ground-based radars and airborne radars.

The typical airborne RWR system consists of multiple wideband antennas placed around the aircraft which receive the radar signals. The receiver periodically scans across the frequency band and determines various parameters of the received signals, like frequency, signal shape, direction of arrival, pulse repetition frequency, etc. By using these measurements, the signals are first deinterleaved to sort the mixture of incoming signals by emitter type. These data are then further sorted by threat priority and displayed.

The RWR is used for identifying, avoiding, evading or engaging threats. For example, a fighter aircraft on a combat air patrol (CAP) might notice enemy fighters on the RWR and subsequently use its own radar set to find and eventually engage the threat. In addition, the RWR helps identify and classify threats—it's hard to tell which blips on a radar console-screen are dangerous, but since different fighter aircraft typically have different types of radar sets, once they turn them on and point them near the aircraft in question it may be able to tell, by the direction and strength of the signal, which of the blips is which type of fighter.

A non-combat aircraft, or one attempting to avoid engagements, might turn its own radar off and attempt to steer around threats detected on the RWR. Especially at high altitude (more than 30,000 feet AGL), very few threats exist that don't emit radiation. As long as the pilot is careful to check for aircraft that might try to sneak up without radar, say with the assistance of AWACS or GCI, it should be able to steer clear of SAMs, fighter aircraft and high altitude, radar-directed AAA.

SEAD and ELINT aircraft often have sensitive and sophisticated RWR equipment like the U.S. HTS (HARM targeting system) pod which is able to find and classify threats which are much further away than those detected by a typical RWR, and may be able to overlay threat circles on a map in the aircraft's multi-function display (MFD), providing much better[1] information for avoiding or engaging threats, and may even store information to be analyzed later or transmitted to the ground to help the commanders plan future missions.

The RWR can be an important tool for evading threats if avoidance has failed. For example, if a SAM system or enemy fighter aircraft has fired a missile (for example, a SARH-guided missile) at the aircraft, the RWR may be able to detect the change in mode that the radar must use to guide the missile and notify the pilot with much more insistent warning tones and flashing, bracketed symbols on the RWR display. The pilot then can take evasive action to break the missile lock-on or dodge the missile. The pilot may even be able to visually acquire the missile after being alerted to the possible launch. What's more, if an actively guided missile is tracking the aircraft, the pilot can use the direction and distance display of the RWR to work out which evasive maneuvers to perform to outrun or dodge the missile. For example, the rate of closure and aspect of the incoming missile may allow the pilot to determine that if they dive away from the missile, it is unlikely to catch up, or if it is closing fast, that it is time to jettison external supplies and turn toward the missile in an attempt to out-turn it. The RWR may be able to send a signal to another defensive system on board the aircraft, such as a Countermeasure Dispensing System (CMDS), which can eject countermeasures such as chaff, to aid in avoidance.

RWR types in service

See also


  1. ^ http://www.dtic.mil/descriptivesum/Y2000/Navy/0603270N.pdf

The AN/ALQ-128 Electronic Warfare Warning Set is a Electronic countermeasure receiver manufactured by Magnavox and used on the F-15C/D/E. The system, along with the Loral AN/ALR-56C radar warning receiver, is used to give the ALQ-135(V), the F-15s automatic countermeasure system, information through radar warning suites that allows it to provide active jamming against enemy radar threats.


The AN/ALR-2002 Radar Warning Receiver is designed to warn an aircraft's crew of potentially hostile radar activity. British Aerospace Australia was the sole contractor for the AN/ALR-2002 Australian indigenous System

The AN/ALR-2002 Radar Warning Receiver is a threat warning system for tactical aircraft and was designed for the F-111, the Royal Australian Air Force (RAAF) F/A-18 Hornet and S-70 Blackhawk Helicopters. The system was designed to detect, identify and display radars and radar-guided weapon systems. The system also co-ordinates its operation with jammers.

The AN/ALR-2002B comprises the following units:

Four Quadrant Receivers

A Low-Band Receiver

A Data Processor

A Track and Interface Processor, and

A Colour Threat DisplayAs of 2006, the Australian Defence minister has accepted a recommendation to stop development of the ALR-2002B variant for the F/A-18, the RAAF will most likely install the US Navy deployed Raytheon ALR-67(V)3 instead. The ALR-67(V)3 is currently fitted to the F/A-18 E/F Hornet and some F/A-18 C/D Hornet aircraft. The decision was based on integration, programmatic (cost & schedule), political (internal to DMO) and performance issues. [1]

Continued development and deployment of the ALR-2002B variant, for use with transport and rotary wing aircraft, is still expected to continue.

AN/ALR-67 Radar Warning Receiver

The AN/ALR-67 Radar Warning Receiver is designed to warn an aircraft's crew of potentially hostile radar activity. It is an airborne threat warning and countermeasures control system built to be successor to the United States Navy's AN/ALR-45. Northrop Grumman Corporation's Electronic Systems sector (Rolling Meadows, Illinois) was the main contractor for the AN/ALR-67(V) and (V)2. Raytheon Electronic Warfare Systems (Goleta, California) was the main contractor for the AN/ALR-67(V)3.

Aung Zeya-class frigate

Aung Zeya class frigate is a class of frigates operated by the Myanmar Navy. The ship was built locally with Indian assistance. The lead ship of the class is named for Aung Zeya (Alaungpaya), the founder of Konbaung Dynasty of Burma (Myanmar).As of 2014, the lead ship (F-11) is the only ship in this class.


Beryoza literally meaning "birch tree" in Russian, may refer to

Russian-language name of Byaroza, a town in Belarus

Beryoza, call sign of Samara Airlines, Russia

SPO-15 Beryoza, a Russian radar warning receiver

Beryoza River, Russia

T-80UD "Beryoza", a Russian tank T-80 model

Heroine-class submarine

The Heroine class are a variant of the Type 209 diesel-electric attack submarine developed by Howaldtswerke-Deutsche Werft (HDW) of Germany, currently in service with the South African Navy.

IAR 99

The IAR 99 Șoim (Hawk) is an advanced trainer and light attack aircraft capable of performing close air support and reconnaissance missions. The IAR 99 replaced the Aero L-29 Delfin and Aero L-39 Albatros as jet trainer of the Romanian Air Force. The aircraft is of semi-monocoque design, with tapered wings and a swept back tail unit. A large blade-type antenna installed beneath the nose on the port side of the fuselage gives the IAR 99 trainer a distinctive appearance.

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Leigh Light

The Leigh Light (L/L) was a British World War II era anti-submarine device used in the Battle of the Atlantic. It was a powerful (22 million candela) carbon arc searchlight of 24 inches (610 mm) diameter fitted to a number of the British Royal Air Force's Coastal Command patrol bombers to help them spot surfaced German U-boats at night.Early night operations with the new Air-to-Surface Vessel radar (ASV) demonstrated that the radar's minimum range of about 1 kilometre (0.62 mi) meant that the target was still invisible when it disappeared off the radar display. Efforts to reduce this minimum were not successful, so Wing Commander Humphrey de Verd Leigh hit upon the idea of using a searchlight that would be switched on just when the target was about to disappear on radar. The U-boat had insufficient time to dive and the bombardier had a clear view of the target. Introduced in June 1942, it was so successful that for a time German submarines were forced to switch to charging their batteries during the daytime, when they could at least see aircraft approaching.Germany introduced the Metox radar warning receiver in an effort to counter the combination of ASV and Leigh Light. Metox provided the submarine crew with early warning that an aircraft using radar was approaching. Because the radar warning receiver could detect radar emissions at a greater range than the radar could detect vessels, this often gave the U-boat enough warning to dive. Having expected this, the Allies introduced the centimetric ASV Mk. III radar, regaining control of the battle. Although the German Naxos countered these radars, by this time the U-boat force was already damaged beyond repair.

List of Harrier variants

This is a list of variants of the Harrier Jump Jet family of V/STOL ground attack fighter aircraft.

Low-probability-of-intercept radar

A low-probability-of-intercept radar (LPIR) is a radar employing measures to avoid detection by passive radar detection equipment (such as a radar warning receiver (RWR), or electronic support receiver) while it is searching for a target or engaged in target tracking. This characteristic is desirable in a radar because it allows finding and tracking an opponent without alerting them to the radar's presence. This also protects the radar installation from anti-radiation missiles (ARM).

LPI measures include:

Power management and high duty cycle (long integration times)

Wide bandwidth (or Ultra-wideband)

Frequency Agility, and frequency selection

Advanced/irregular scan patterns

Coded pulses (coherent detection)

High processing gain

Low sidelobe antennas

Metox radar detector

Metox, named after its manufacturer, was a pioneering high-frequency radar warning receiver (RWR) manufactured by a small French company in occupied Paris. It was tuned to receive the 1.5 m signals used by many British radars of the early and mid-WWII era, notably the ASV Mk. II radar used by RAF Coastal Command to attack U-boats. It is not clear whether the design was German or French or both. It was installed on German U-boats starting in 1942 and used until the end of the war.From July 1940 onwards, the British fitted the RAF Mk II AI (Airborne Interception) radar into Coastal Command aircraft for use as the MkII "1½-metre ASV". The radar's known AI weaknesses — problems due to land clutter and inability to determine height effectively, which caused its failure in night fighters — were no handicap in this new role. With two range scales, 0–9 mi (0–14 km) and 0–36 mi (0–58 km), it could detect surfaced U-boats at up to 12 mi (19 km) and land at up to 70 mi (110 km), though a typical U-boat detection range was 5 mi (8.0 km). The radar had a fairly crude display by today's standards, but was able to give the range and an approximate direction within an arc either side of the aircraft heading. Returns were lost in sea clutter once the aircraft was within about 1 mi (1.6 km) of the U-boat, but usually by then, the aircraft was within visual range—and the U-boat was well into a crash dive.

To counter this, Wing Commander Humphry de Verde Leigh developed the Leigh light, effectively a powerful floodlight steered by the ASV radar. This allowed ASV radar equipped aircraft to search for U-boats at night. The U-boat was initially tracked by the radar with the light following the radar track but switched off. Once the returns were lost, the light would be switched on and the U-boat would be bathed in light and very vulnerable. The first successful attack was on the U-502 on 5 July 1942. The sudden light was often the first indication that the U-boat had been found and the Leigh light was initially very successful, particularly in the Bay of Biscay.

Metox was the German answer to the British radar. Metox sets received the transmitted pulses from the ASV and rendered them as audible beeps. It enjoyed the usual advantage of radar detectors over radar in that the signal is direct and only had to travel one way whereas the radar has to detect the very weak reflection from the submarine. Most radars increase the number of pulses and decrease the width of the pulses when switched to a shorter range, the shorter pulse widths allow the radar to look at closer objects. The Metox exploited the fact that once the radar operator changed the range indication from 36 miles (58 km) to 9 miles (14 km), the pulse repetition frequency of the radar's transmitter doubled. Radar cannot detect any reflections returned earlier than half a pulse width so when the U-boat was closer than 9 miles (14 km) the operator would change to the shorter scale. If the Metox set started beeping at twice the rate, the U-boat knew that they had been detected. By the time the aircraft was close enough to the U-boat's position to energise the Leigh light, the U-boat was well under the water. As a bonus, the Metox set would also provide warning in excess of visual range in daylight.

In December 1942 British codebreakers regained the ability to decipher messages encrypted with naval Enigma machines. The Germans noticed the resulting uptick in spotted U-Boats. Based on their confidence in the Enigma machine, as well as the testimony of a captured British bomber pilot, the Germans came to the erroneous conclusion that the Allies had developed a means for detecting emissions produced by the Metox itself. The executive officer of U-230, Captain Herbert Werner, said of Metox, "Then, on August 3 [1943], we received a message from Headquarters which had a greater impact on our lives than any since the beginning of the Allied offensive. ALL U-BOATS. ATTENTION. ALL U-BOATS. SHUT OFF METOX AT ONCE. ENEMY IS CAPABLE OF INTERCEPTING. KEEP RADIO SILENCE UNTIL FURTHER NOTICE."

Metox was eventually countered by a version of the 10 centimetre H2S radar, which Metox could not detect and once again the Leigh light forced U-boat crews to refuse to run surfaced at night. Even during the day the new radar was easily able to detect a submerged U-boat's periscope or snorkel, assuming they were deployed, which earlier radars employing longer wavelengths could not do.

Metox was superseded by the Naxos receiver that was capable of detecting 10 cm wavelength (3 GHz) H2S signals, but unable to detect the even higher, 10 GHz frequency of the American development, the H2X radar.

Naxos radar detector

The Naxos radar warning receiver was a World War II German countermeasure to X band microwave radar produced by a cavity magnetron. Introduced in September 1943, it replaced Metox, which was incapable of detecting centimetric radar. Two versions were widely used, the FuG 350 Naxox Z that allowed night fighters to home in on H2S radars carried by RAF Bomber Command aircraft, and the FuMB 7 Naxos U for U-boats, offering early warning of the approach of RAF Coastal Command patrol aircraft equipped with ASV Mk. III. A later model, Naxos ZR, provided warning of the approach of RAF night fighters equipped with AI Mk. VIII radar.

Orange Harvest

Orange Harvest was an ESM receiver fitted to marine patrol Avro Shackletons during the Cold War.

Orange Harvest was an S band and X band radar warning receiver, capable of giving a directional bearing to surface ships or submarines that were transmitting radar emissions. Although less precise than the Shackleton's main ASV.21 search radar, it could give a greater detection range, provided that the target was emitting. As a passive system, it also had the advantage that it did not betray the aircraft's presence to its target.

A particular target would be the I band RLK-101 Albatros (NATO Snoop Tray) and MRK-50 Snoop Pair radars used by the early Soviet nuclear submarines. As these boats could now run continually submerged, without even needing to snorkel, they were increasingly difficult to detect by previous methods, such as Autolycus or search radar.

Electrically there were two quite separate systems: wide- and narrow band, but sharing the same external antenna housing. The wide band receiver was made by Rank in Plymouth. The narrow band receiver derived from an early ELINT receiver called 'Breton', developed in Comets by 51 Squadron.

The external antenna for Orange Harvest was the distinctive white dielectric 'spark plug' carried on the upper surface of the Shackleton. This 'spark plug' has often been mis-identified as an insulator for a HF long-wire antenna running to the aircraft's tail. It is actually self-contained, and at a wavelength far shorter than would use long wires. The Shackleton did carry HF antennae, but these were supported by two small metal masts, just ahead of Orange Harvest. The structural fitment for Orange Harvest was a metal plinth built into the fuselage, at approximately the previous dorsal turret position. The large antenna was fastened to this. As the antenna causes significant drag, it was sometimes removed and only the plinth was evident. This was more common in the 1960s ASW era, rather than the later AEW period.

The interior display for Orange Harvest was a 3" cathode ray tube, in front of the C operator.Orange Harvest was introduced with the Shackleton MR.3 Phase II in 1961. After the replacement of Shackleton with Nimrod MR.1 in the ASW role, Orange Harvest continued with the Shackleton AEW.2 aircraft of 8 Squadron RAF from 1972 to 1991.

Project Kahu

Project Kahu was a major upgrade for the A-4K Skyhawk attack aircraft operated by the Royal New Zealand Air Force (RNZAF) in the mid-1980s. The project was named after the Kāhu or New Zealand harrier.

SAS Queen Modjadji

SAS Queen Modjadji is a variant of the Type 209 diesel-electric attack submarine developed by Howaldtswerke-Deutsche Werft (HDW) of Germany, currently in service with the South African Navy. She was named after the South African Rain Queen on 14 March 2007 by the ships sponsor, Mrs. Rita Ndzanga, at a ceremony in Emden, Germany.

Thales Spectra

SPECTRA (Système de Protection et d'Évitement des Conduites de Tir du Rafale (literally: System of Protection and Avoidance of enemy Fire-Control for Rafale) or "Self-Protection Equipment Countering Threats to Rafale Aircraft") was jointly developed by Thales Group and MBDA for the Dassault Rafale fighter aircraft, now in service with the French Air Force and Navy.

The full SPECTRA integrated electronic warfare suite provides long-range detection, identification and accurate localisation of infrared homing, radio frequency and laser threats. The system incorporates radar warning receiver, laser warning and Missile Approach Warning for threat detection plus a phased array radar jammer and a decoy dispenser for threat countering. It also includes a dedicated management unit for data fusion and reaction decision.The SPECTRA system consists of two infrared missile warning sensors (Détecteur de Départ Missile Nouvelle Génération). A new generation missile warning system (DDM NG) is currently being developed by MBDA. The DDM NG delivered its first in flight images in March 2010 and will be available on the Rafale from 2012. DDM NG incorporates a new infrared array detector which enhances performance with regard to the range at which a missile firing will be detected (with two sensors, each equipped with a fish-eye lens, DDM NG provides a spherical field of view around the aircraft). The DDM-NG also offers improved rejection of false alarms and gives an angular localisation capability which will be compatible with the future use of Directional Infrared Counter Measures (DIRCM).Thales Group and Dassault Aviation have mentioned stealthy jamming modes for the SPECTRA system, to reduce the aircraft's apparent radar signature. It is not known exactly how these work or even if the capability is fully operational, but it may employ active cancellation technology, such as has been tested by Thales and MBDA. Active cancellation is supposed to work by sampling and analysing incoming radar and feeding it back to the hostile emitter out of phase thus cancelling out the returning radar echo.

Type 965 radar

The Type 965 radar was VHF (P band) long range aircraft warning radar used by warships of the Royal Navy from the 1960s onwards. The Type 965M, Type 965P, Type 965Q and Type 965R were improved versions; the Type 960, 965M and 965Q used the single bedstead AKE(1) aerial, whilst the Type 965P and 965R used the double bedstead AKE(2) aerial.The various versions of the Type 965 radars all had the limitation that they could not detect moving targets with a land mass behind them; this was a major disadvantage during the 1982 Falklands War, which ultimately led to the loss of HMS Coventry. Similarly the Type 965 could not detect aircraft flying low; the two Argentine Navy Super Étendards that caused the loss of HMS Sheffield were not detected by Type 965R radar when they were flying at 98 feet (30 m), but were shown as contacts by HMS Glasgow's Type 965R radar when they popped up to 120 feet (37 m) above sea-level at 45 nautical miles (83 km), though it was the UAA1 radar warning receiver that drew attention to the contacts.The Type 965M and 965P had a narrower beam (12° horizontal) than the preceding Type 960 (35° horizontal). The narrower beam was needed for air direction. The Type 965Q and 965R were improvements on the 965M and 965P respectively; these had a moving target indicator (MTI) mode to suppress clutter; though Friedman states that they lacked any provision for moving target indication.The Type 965 radars used radio frequencies that were also used by television stations, and therefore caused interference with television (and vice versa) if used near land in Europe. Type 965 was superseded by the Type 1022 radar, which did not have this disadvantage.

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