Dowding system

Air Defence systemcommand and control system
Kermit Tyler, concluded the radar site had spotted the bombers and failed to pass on the warning. The Japanese attack went unopposed. It was only through the combination of all of the elements of the Dowding system that an effective defensive network was created. Peter Townsend later noted that: "The Germans knew about British radar but never dreamed that what the radar 'saw' was being passed on to the fighter pilot in the air through such a highly elaborate communications system." During the early war period, the Luftwaffe consistently underestimated the value of the system.

Anti-aircraft warfare

anti-aircraftanti-aircraft gunair defense
Multiple transmitter radars such as those from bistatic radars and low-frequency radars are said to have the capabilities to detect stealth aircraft. Advanced forms of thermographic cameras such as those that incorporate QWIPs would be able to optically see a Stealth aircraft regardless of the aircraft's Radar Cross-Section (RCS). In addition, Side looking radars, High-powered optical satellites, and sky-scanning, high-aperture, high sensitivity radars such as radio telescopes, would all be able to narrow down the location of a stealth aircraft under certain parameters.

Tizard Mission

British mission, led by TizardSir Henry TizardTizard delegation
Radar and the Tizard Mission. Bowen's account from Radar World. Detailed description of the Mission - La Physique au Canada Nov/Dec 2001.

Terrain-following radar

terrain following radarterrain-followingTerrain Following
Terrain-following radar (TFR) is a military aerospace technology that allows a very-low-flying aircraft to automatically maintain a relatively constant altitude above ground level and therefore make detection by enemy radar more difficult. It is sometimes referred-to as ground hugging or terrain hugging flight. The term nap-of-the-earth flight may also apply but is more commonly used in relation to low-flying military helicopters, which typically do not use terrain-following radar. The technology was originally developed by Ferranti for use with the TSR-2 aircraft. The system works by transmitting a radar signal towards the ground area in front of the aircraft.

Radio spectrum

bandradio bandspectrum
Radar applications use relatively high power pulse transmitters and sensitive receivers, so radar is operated on bands not used for other purposes. Most radar bands are in the microwave part of the spectrum, although certain important applications for meteorology make use of powerful transmitters in the UHF band. *WARC bands Longwave AM Radio = 148.5 kHz – 283.5 kHz (LF). Mediumwave AM Radio = 525 kHz – 1710 kHz (MF). Shortwave AM Radio = 3 MHz – 30 MHz (HF). Bandplan. Bandstacked. Cellular frequencies. DXing. Frequency allocation. Geneva Frequency Plan of 1975. North American Regional Broadcasting Agreement. Open spectrum. Radio astronomy. Scanner (radio). Two-way radio. U-NII.

SS Normandie

NormandieSS ''NormandieUSS ''Lafayette
An early form of radar was installed to prevent collisions. The rudder frame, including the 125-ton cast steel connecting rod, was produced by Škoda Works in Czechoslovakia. A less known technical novelty was, for the inaugural Atlantic crossing, the testing of a “radar” then called "Obstacle detector" built by Henry Gutton (SFR). Coincidently, the US coastal Artillery had also used the ship to test the detection capability of a thermal “radar,” the SCR-263T. The luxurious interiors were designed in Art Déco and Streamline Moderne style. Many sculptures and wall paintings made allusions to Normandy, the province of France for which Normandie was named.

Massachusetts Institute of Technology

MITM.I.T.Massachusetts Institute of Technology (MIT)
In electronics, magnetic core memory, radar, single electron transistors, and inertial guidance controls were invented or substantially developed by MIT researchers. Harold Eugene Edgerton was a pioneer in high speed photography and sonar. Claude E. Shannon developed much of modern information theory and discovered the application of Boolean logic to digital circuit design theory. In the domain of computer science, MIT faculty and researchers made fundamental contributions to cybernetics, artificial intelligence, computer languages, machine learning, robotics, and cryptography.

Pathfinder (RAF)

Pathfinder ForcePathfinderPathfinders
In the era before the widespread use of radar and the techniques needed to guide fighters to their targets with radar, night bombing would render the bombers vulnerable only if they were picked up by searchlights, a relatively rare occurrence. Offsetting the advantages of night bombing was the understanding that identifying the targets and attacking them accurately would be much more difficult. This meant a night bomber force was only useful against very large targets, like cities, and was one of the reasons daylight bombing was considered.


laserslaser beamlaser light
Gould's notes included possible applications for a laser, such as spectrometry, interferometry, radar, and nuclear fusion. He continued developing the idea, and filed a patent application in April 1959. The U.S. Patent Office denied his application, and awarded a patent to Bell Labs, in 1960. That provoked a twenty-eight-year lawsuit, featuring scientific prestige and money as the stakes. Gould won his first minor patent in 1977, yet it was not until 1987 that he won the first significant patent lawsuit victory, when a Federal judge ordered the U.S. Patent Office to issue patents to Gould for the optically pumped and the gas discharge laser devices.


armed forcesdefensedefence
During the war, significant advances were made in military communications through increased use of radio, military intelligence through use of the radar, and in military medicine through use of penicillin, while in the air, the guided missile, jet aircraft, and helicopters were seen for the first time. Perhaps the most infamous of all military technologies was the creation of the atomic bomb, although the exact effects of its radiation were unknown until the early 1950s. Far greater use of military vehicles had finally eliminated the cavalry from the military force structure.


searchlightssearch lightspotlight
Although searchlights remained in use throughout the war, the newly developed radar proved to be a far more effective locating device, and Japanese radar development lagged far behind that of the US. Searchlights were first used in the First World War to create "artificial moonlight" to enhance opportunities for night attacks by reflecting searchlight beams off the bottoms of clouds, a practice which continued in the Second World War. The term "artificial moonlight" was used to distinguish illumination provided by searchlights from that provided by natural moonlight, which was referred to as "movement light" in night-time manoeuvers.

United States Naval Research Laboratory

Naval Research LaboratoryU.S. Naval Research LaboratoryNRL
The same polymer films are used in Los Angeles-class submarine radomes to repel water and enable radar operation soon after surfacing. Scientists at NRL frequently contribute theoretical and experimental research on novel materials, particularly magnetic materials and nanomaterials and thermoplastic. The first modern U.S. radar was invented and developed at NRL in Washington, DC in 1922. By 1939, NRL installed the first operational radar aboard the USS New York, in time for radar to contribute to naval victories of the Coral Sea, Midway and Guadalcanal. NRL then further developed over-the-horizon radar as well as radar data displays.

Side looking airborne radar

side-looking airborne radarside-looking radarSLAR
Synthetic aperture radar refers to a method for improving the azimuth resolution (not range resolution). * Radar imaging \tau = duration of the (may be compressed in matched receiver) radar pulse. c_0 = speed of light. \gamma = depression angle. \lambda = wavelength. L = antenna length (in direction of flight). \rho = slant range. H = height of the platform. Radartutorial. "A Sideways Glance" a 1966 Flight article on SLAR.

Stealth technology

stealthstealthyinvisible aircraft
Dielectric composite materials are more transparent to radar, whereas electrically conductive materials such as metals and carbon fibers reflect electromagnetic energy incident on the material's surface. Composites may also contain ferrites to optimize the dielectric and magnetic properties of a material for its application. Radiation-absorbent material (RAM), often as paints, are used especially on the edges of metal surfaces. While the material and thickness of RAM coatings can vary, the way they work is the same: absorb radiated energy from a ground or air based radar station into the coating and convert it to heat rather than reflect it back.

Radar cross-section

radar cross sectionradar signatureRCS
All other factors being equal, the plane will have a stronger signal from the side than from the front so the orientation between the Radar station and the target is important. The relief of a surface could contain indentations that act as corner reflectors which would increase RCS from many orientations. This could arise from open bomb-bays, engine intakes, ordnance pylons, joints between constructed sections, etc. Also, it can be impractical to coat these surfaces with radar-absorbent materials. The size of a target's image on radar is measured by the radar cross section or RCS, often represented by the symbol σ and expressed in square meters. This does not equal geometric area.


heavier-than-airheavier-than-air flightheavier-than-air aircraft
The avionics comprise the aircraft flight control systems and related equipment, including the cockpit instrumentation, navigation, radar, monitoring, and communications systems. The flight envelope of an aircraft refers to its approved design capabilities in terms of airspeed, load factor and altitude. The term can also refer to other assessments of aircraft performance such as maneuverability. When an aircraft is abused, for instance by diving it at too-high a speed, it is said to be flown outside the envelope, something considered foolhardy since it has been taken beyond the design limits which have been established by the manufacturer.

Radar altimeter

radio altimeterradar altimetryelectronic altimeter
Radar altimeters are an essential part in ground proximity warning systems (GPWS), warning the pilot if the aircraft is flying too low or descending too quickly. However, radar altimeters cannot see terrain directly ahead of the aircraft, only that below it; such functionality requires either knowledge of position and the terrain at that position or a forward looking terrain radar. Radar altimeter antennas have a fairly large main lobe of about 80° so that at bank angles up to about 40°, the radar detects the range from the aircraft to the ground (specifically to the nearest large reflecting object).

Reflection (physics)

Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. Reflection of light is either specular (mirror-like) or diffuse (retaining the energy, but losing the image) depending on the nature of the interface. In specular reflection the phase of the reflected waves depends on the choice of the origin of coordinates, but the relative phase between s and p (TE and TM) polarizations is fixed by the properties of the media and of the interface between them.

Electronic countermeasure

electronic countermeasuresECMelectronic attack
Basic radar ECM strategies are (1) radar interference, (2) target modifications, and (3) changing the electrical properties of air. Interference techniques include jamming and deception. Jamming is accomplished by a friendly platform transmitting signals on the radar frequency to produce a noise level sufficient to hide echos. The jammer's continuous transmissions will provide a clear direction to the enemy radar, but no range information. Deception may use a transponder to mimic the radar echo with a delay to indicate incorrect range. Transponders may alternatively increase return echo strength to make a small decoy appear to be a larger target.

Bawdsey Manor

Air Ministry Research Establishment
From 1937 Bawdsey was operational as the first of the RDF (radar) Chain Home, and during World War 2 also acquired Chain Home Low and Coast Defence/Centimetric equipment for tracking enemy ships. It continued as a radar station through most of the Cold War. Demolition of the 10 towers began in the 1960s, and all are now gone. Bawdsey Manor continued as an RAF base through the Cold War and Bloodhound Missiles were sited on the cliffs until the Bloodhound force ceased operations in 1990, when all the missiles were withdrawn to RAF West Raynham. RAF Bawdsey was closed in 1991.

Active radar homing

active radarARHactive radar seeker
Active radar homing (ARH) is a missile guidance method in which a missile contains a radar transceiver (in contrast to semi-active radar homing, which uses only a receiver) and the electronics necessary for it to find and track its target autonomously. NATO brevity code for an air-to-air active radar homing missile launch is Fox Three. There are two major advantages to active radar homing: Many missiles employing passive homing have an additional capability: if the target does attempt to use noise jamming, the missile can home in on the target's radiation passively (home-on-jam). This makes such missiles practically immune to noise jamming.

Chaff (countermeasure)

chaffWindowchaff rocket launchers
For over a year the curious situation arose where both sides of the conflict knew how to use chaff to jam the other side's radar but had refrained from doing for fear of their opponent replying in kind. Window rendered the ground-controlled Himmelbett (canopy bed) fighters of the Kammhuber Line unable to track their targets in the night sky and the early UHF-band versions of the airborne intercept Lichtenstein radar (following the capture of a Ju 88R-1 night fighter by the British in May 1943) useless, blinding radar-guided guns and spotlights dependent on the ground-based radar.

Vessel traffic service

VTSmaritime vessel traffic controlVessel Traffic Control System
Typical VTS systems use radar, closed-circuit television (CCTV), VHF radiotelephony and automatic identification system to keep track of vessel movements and provide navigational safety in a limited geographical area. The VTS guidelines require that the VTS authority should be provided with sufficient staff, appropriately qualified, suitably trained and capable of performing the tasks required, taking into consideration the type and level of services to be provided in conformity with the current IMO guidelines on the subject.


amplifiersamplificationelectronic amplifier
It made possible long distance telephone lines, public address systems, radio broadcasting, talking motion pictures, practical audio recording, radar, television, and the first computers. For 50 years virtually all consumer electronic devices used vacuum tubes. Early tube amplifiers often had positive feedback (regeneration), which could increase gain but also make the amplifier unstable and prone to oscillation. Much of the mathematical theory of amplifiers was developed at Bell Telephone Laboratories during the 1920s to 1940s.

Corner reflector

radar reflectorcorner cubecorner-cube
Radar corner reflectors are designed to reflect the microwave radio waves emitted by radar sets back toward the radar antenna. This causes them to show a strong "return" on radar screens. A simple corner reflector consists of three conducting sheet metal or screen surfaces at 90° angles to each other, attached to one another at the edges, forming a "corner". These reflect radio waves coming from in front of them back parallel to the incoming beam. To create a corner reflector that will reflect radar waves coming from any direction, 8 corner reflectors are placed back-to-back in an octahedron (diamond) shape.