
#REDIRECT Radar
:''This article is about the device. For the fictional character in ''M*A*S*H'', see Corporal Walter (Radar) O'Reilly.'' [[Image:Radar antenna.jpg|right|thumbnail|250px|This long range radar antenna (electronics) (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon.]] ''RADAR'' is an acronym for RAdio Detection And Ranging or Radio Angle Detection And Ranging. It is a system used to detect, range (determine the distance of), and map objects such as aircraft and rain. Strong radio waves are transmitted, and a receiver listens for any echo_(phenomenon)es. By analysing the reflected signal, the reflector can be located, and sometimes identified. Although the amount of signal returned is tiny, radio signals can easily be detected and amplification. Radar radio waves can be easily generated at any desired strength, detected at even tiny powers, and then amplified many times. Thus radar is suited to detecting objects at very large ranges where other reflections, like sound or visible light, would be too weak to detect. ==Principles== ===Reflection=== Electromagnetic waves reflect from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or vacuum, or other significant changes in atomic density between object and what's surrounding it, will usually reflect radar waves. This is particularly true of electrically-conductive materials such as metal, making radar particularly well suited to the detection of aircraft and ships. Radar waves reflect in a variety of ways depending on the size of the radio wave and the shape of the target. If the radio wave is much shorter than the reflector's size, the wave will bounce off in a way similar to the way light bounces from a mirror. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas modern systems use shorter wavelengths (a few centimetres) that can image objects as small as a loaf of bread. Radio waves always reflect from curves and angles, in a way similar to glint from a rounded piece of glass. The most reflective targets have 90° angles between the reflections. A surface consisting of three flat surfaces meeting at a single corner, like the corner on a block, will always reflect directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation. For generally the same reasons objects attempting to avoid detection will angle their surfaces in a way to eliminate corners, which leads to "odd" looking stealth aircraft. Electromagnetic waves do not travel well underwater; thus for underwater applications, sonar, based on sound waves, has to be used instead of radar. ===Polarization=== Polarization is the direction that the wave vibrates. Radars use horizontal, vertical, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces, and help a search radar ignore rain. Random polarization returns usually indicate a fractal surface like Rock (geology) or soil, and are used by navigational radars. [[Image:weather radar.jpg|thumb|Brightness can indicate reflectivity as in this 1960 weather radar image. The radar's frequency, polarization, and receiver determine what it can observe.]] ==Distance measurement== ===Transit time=== The easiest way to measure the range of an object is to broadcast a short pulse of radio signal, and then time how long it takes for the reflection to return. The distance is one-half the product of round trip time (because the signal has to travel to the target and then back to the receiver) and the speed of the signal. where c is the speed of light in a vacuum, and is the round trip time. For RADAR the speed of signal is the speed of light, making the round trip times very short for terrestrial ranging. For this reason accurate distance measurement was difficult until the introduction of high performance electronics, with older systems being accurate to perhaps a few percent. The receiver cannot detect the return while the signal is being sent out – there's no way to tell if the signal it hears is the original or the return. This means that a radar has a distinct minimum range, which is the length of the pulse divided by the speed of light, divided by two. In order to detect closer targets you have to use a shorter ''pulse length''. A similar effect imposes a specific maximum range as well. If the return from the target comes in when the next pulse is being sent out, once again the receiver cannot tell the difference. In order to maximize range, one wants to use longer times between pulses, the ''inter-pulse'' time. These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. You could offset this by using more pulses, but this would shorten the maximum range again. So each radar uses a particular type of signal. Long range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. This pattern of pulses and pauses is known as the ''Pulse Repetition Frequency'' (or ''PRF''), and is one of the main ways to characterize a radar. As electronics have improved many radars now can change their PRF. ===Frequency modulation=== Another form of distance measuring radar is based on frequency modulation. Frequency comparison between two signals is considerably more accurate, even with older electronics, than timing the signal. By changing the frequency of the returned signal and comparing that with the original, the difference can be easily measured. This technique can be used in radar systems, and is often found in aircraft radar altimeters. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a sine wave or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared. Since the signal frequency is changing, by the time the signal returns to the aircraft the broadcast has shifted to some other frequency. The amount of that shift is greater over longer times, so greater frequency differences mean a longer distance, the exact amount being the "ramp speed" selected by the electronics. The amount of shift is therefore directly related to the distance travelled, and can be displayed on an instrument. This signal processing is similar to that used in speed detecting doppler effect radar. See also the section on Continuous Wave radar below. == Speed measurement == Speed is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a little memory to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making grease-pencil marks on the radar screen, and then calculating the speed using a slide rule. However there is another effect that can be used to make much more accurate speed measurements, and do so almost instantly (no memory required), known as the Doppler effect. Practically every modern radar uses this principle in the pulse-doppler radar system. It is also possible to make a radar without any pulsing, known as a continuous-wave radar (CW radar), by sending out a very pure signal of a known frequency. Return signals from targets are shifted away from this base frequency via the Doppler effect enabling the calculation of the speed of the object relative to the radar. == Position measurement == Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located. ===Early systems=== :''main article History of radar'' Early systems tended to use omni-directional broadcast antennas, with directional receiver antennas which were pointed in various directions. For instance the first system to be deployed, Chain Home, used two straight antennas at right angles for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by rotation the antenna so one display showed a maximum while the other shows a minimum. One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is subject to the inverse-square law. To get a reasonable amount of power on the "target", the broadcast should also be steered. More modern systems used a steerable parabola "dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combined two radar frequencies in the same antenna in order to allow automatic steering, or radar lock. ===Phased array=== Another method of steering is used in ''phased array radar'', which uses the radio signal's interference with itself. If one were to broadcast a single signal from a large number of antennas, the result will be a single beam with the waves in the rest of space cancelling each other. If the phase of the signal is changed before broadcast, the direction of the beam can be moved because the point of constructive interference will move. Instead of constructing a single large antenna, such a system has a number of small omni-directional antennas referred to as ''elements'', usually arranged in a flat plate. Phased array radars require no physical movement. The beam can be steered by electronically adjusting the phase-shifters to each small antenna element. This means that the beam can scan at thousands of degrees per second, fast enough to irradiate many individual targets, and still run a wide-ranging search periodically. By simply turning some of the antennas on or off, the beam can be spread for searching, narrowed for tracking, or even split into two or more virtual radars. Phased array radars have been in use since the earliest years of radar use in World War II, but limitations of the electronics led to fairly poor accuracy. Phased array radars were originally used for missile defence. They are the heart of the ship-bourne Aegis combat system, and the MIM-104_Patriot, and are increasingly used in other areas because the lack of moving parts makes them more reliable, and sometimes permits a much larger effective antenna. As the price of electronics has fallen, phased array radars have become more and more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is far offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are now limited to roles where cost is the main factor such as weather radars and similar systems. Phased array radars are also valued for use in aircraft, since they can track multiple targets. The first aircraft to use phased array radar was the Mikoyan MiG-31. ==Radar equation== The amount of power ''Pr'' returning to the receiving antenna is given by the radar equation: : where *Pt = transmitter power, *Gt = gain of transmitting antenna, *Ar = effective aperture (area) of receiving antenna, *''σ'' = Radar Cross Section, or scattering coefficient of target, *Rt = distance from transmitter to target, *Rr = distance from target to receiver. In the common case where the transmitter and receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range. This yields: : This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small. Other mathematical developments in radar signal processing include time-frequency analysis (Weyl Heisenberg or wavelet), as well as the chirplet transform which makes use of the fact that radar returns from moving targets typically "chirp" (change their frequency as a function of time, as does the sound of a bird or bat). ==Frequency bands == The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world in the 21st century. They have been adopted in the United States by the IEEE, and internationally by the International Telecommunication Union. Most countries have additional regulations to control which parts of each band are available for civilian or military use. Other users of the radio spectrum, such as the broadcasting and electronic countermeasures (Electronic counter-measures) industries, have replaced the traditional military designations with their own systems. {| border="1" |+ Radar Frequency Bands !Band Name!!Frequency Range!!Wavelength Range!!Notes |- |HF||3-30 Megahertz||10-100 metre||coastal radar systems;'high frequency' |- |P||< 300 MHz||1 m+||'P' for 'previous', applied retrospectively to early radar systems |- |VHF||50-330 MHz||0.9-6 m||very long range, ground penetrating; 'very high frequency' |- |UHF||300-1000 MHz||0.3-1 m||very long range (e.g. ballistic early warning), ground penetrating; 'ultra high frequency' |- |L||1-2 Gigahertz||15-30 centimetre||long range air traffic control and surveillance; 'L' for 'long' |- |S||2-4 GHz||7.5-15 cm||terminal air traffic control, long range weather, marine radar; 'S' for 'short' |- |C||4-8 GHz||3.75-7.5 cm||a compromise (hence 'C') between X and S bands; weather |- |X||8-12 GHz||2.5-3.75 cm||missile guidance, marine radar, weather; in the USA the narrow range 10.525GHz ±25MHz is used for airport radar. |- |Ku||12-18 GHz||1.67-2.5 cm||high-resolution mapping, satellite altimetry; frequency just under K band (hence 'u') |- |K||18-27 GHz||1.11-1.67 cm||from German language ''kurz'', meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz. |- |Ka||27-40 GHz||0.75-1.11 cm||mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz. |- |mm||40-300 GHz||1 - 7.5mm||'millimetre' band, subdivided as below |- |V||40-75 GHz||4.0 - 7.5 mm | |- |W||75-110 GHz||2.7 - 4.0 mm||used as a visual sensor for experimental autonomous vehicles, high-resolution meterological observation |} ==Specific radar systems== *Active Electronically Scanned Array (AESA) *Continuous-wave radar *Doppler radar as weather radar *Millimetre cloud radar *NEXRAD *Passive radar *Pulse-doppler radar *Radar gun traffic and sports radars *Secondary surveillance radar (SSR) *Synthetic aperture radar *X-band radar ==See also== * Types and uses of radar ** Doppler radar ** Imaging radar ** Incoherent scatter ** 3D radar ** SCR-270 radar * History of radar * Magnetron * List of radars * Radio * Similar detection and ranging methods ** Sonar ** LIDAR ==Further reading== * Barrett, Dick, "''[http://www.radarpages.co.uk/index.htm All you ever wanted to know about British air defence radar]''". The Radar Pages. (History and details of various British radar systems) *ES310 "''[http://www.fas.org/man/dod-101/navy/docs/es310/syllabus.htm Introduction to Naval Weapons Engineering.''". (Radar fundamentals section)] * Robert Buderi: ''The invention that changed the world: the story of radar from war to peace'', Simon & Schuster, 1996. ISBN 0-349-11068-9 * Merrill I. Skolnik, Radar Handbook. ISBN 007057913X widely used in the United States since the 1970s. * R.V. Jones, ''Most Secret War''. R.V. Jones's account of his part in British Scientific Intelligence between 1939 and 1945, working to anticipate the German's radar, radio navigation and V1/V2 developments. ==External links== [http://www.radar-france.net The first operational radar in France 1934] * Hollmann, Martin, "''[http://www.radarworld.org/index.html Radar Family Tree]''". [http://www.radarworld.org/ Radar World]. * Penley, Bill, and Jonathan Penley, "''[http://www.penleyradararchives.org.uk/history/introduction.htm Early Radar History] - an Introduction''". 2002. * Buderi, "''[http://www.privateline.com/TelephoneHistory3/radarhistorybuderi.html Telephone History: Radar History]''". Privateline.com. (Anecdotal account of the carriage of the world's first high power cavity magnetron from Britain to the US during WW2.) * Sinnott, D.H., "''[http://www.dsto.defence.gov.au/corporate/history/othr/ The Development of Over-the-Horizon Radar in Australia]''" * USAF Long Range Radar, "''[http://www.rades.hill.af.mil/ 84th Radar Evaluation Squadron]''". US Air Force Squadron responsible for long-range Radar Sensor (both civilian and military) operational availability, counterdrug, search and rescue, and flight safety information assurance to the operations community.. Acronyms Radar ms:Radar
==UK's vs US' contributions== There was a claim on the :Manhattan Project page that radar was invented at MIT. I thought it was at least partly a British invention. Anybody got more details? --User:Robert Merkel :The key individual role (most such inventions are collaborative even if those responsible for the individual contributions never met each other) is credited to Robert Watson-Watt (1892-1973) of Brechin, Angus, Scotland. Moving from the Royal Aircraft Establishment (Farnborough, Hampshire) to the Radio Research Station (later part of the National Physical Laboratory) in Slough, (then in Buckinghamshire, but now now part of Berkshire) and then to a new NPL site at Teddington (then in Middlesex, but now in Surrey), he was asked by the Air Ministry to investigate a counterpart to an alleged German aircraft-killing "death ray". :Concluding that the power needed made it impractical to fry bombers out of the sky, instead on 26 February 1935 he demonstrated the future radar by using the BBC's Daventry (Northamptonshire) short-wave radio transmitter and a receiver and oscilloscpe (housed in a former ambulance in a field seven miles away) to detect a Handley Page Heyford bomber at 27 km. Subsequently head of the Bawdsey research station in Felixstowe (Suffolk), Watson-Watt helped to develop the ring of radar stations established in 1938. He was knighted in 1942. :MIT's role came shortly afterward (1938-1940), developing in collaboration with Canadian researchers a fighter-borne system (the first British airborne experiment had been in September 1937, but still needed development). User:David Parker ==MIT Rad Lab & I. I. Rabi== The following was floating around on the page, probably debris from an incomplete edit. Someone who knows this stuff could probably figure out where it belongs: ''... especially at the Radiation Lab at MIT (I. I. Rabi) and played an important role in the outcome of the war.'' --User:Ortolan88 12:56 Jul 25, 2002 (PDT) : It's from an old version, and has been replaced by a lengthy section of expanded text now. --Anonymous No.I ==General vs military radar== It seems useful to me to split this entry in two: one radar in general, and the other more focused on the military history side of it. I'm thinking of the link I'm about to make in an explicitly military context and seeing an article that doesn't deal with the stuff that it's appropriate to link to until you scroll quite a way down. And it's easy enough to imagine the contrary example, where you want to link to radar from an entry on a completely non-military area - microwave ovens or car safety devices or astronomomy, say. What do people think? User:Tannin 09:26 Jan 26, 2003 (UTC) :On the history section: it's a very good history of British and German developments, but US work deserves more mention, esp the Rad Lab stuff. Also, Watson-Watt gets too much prominence at present: he played an important role in the development of British radar, and an even more important role in the getting-to-say-who-invented-it-afterwards department, to the exclusion of several others. There is an excellent and fairly recent American history of the Rad Lab that covers this in detail. I have it here somewhere, just can't remember the title at the moment. User:Tannin 11:16 Jan 26, 2003 (UTC) : Found it! Added it to main article. User:Tannin ==French early contributions== I should verify but according to some sources the French engineers of the CFS had active research on the radar before ww II, they gave their technology to the British in 1939. User:Ericd There a PD article at http://www.vectorsite.net/ttwiz1.html you can cut and paste as you want. User:Ericd here is a source about French researchs http://sjdangle.free.fr/societe/ponte.htm User:Ericd 12:10 Jan 26, 2003 (UTC) ==Chain home; ''RDF1'' book; WWII Proximity fuse== One of the big achievements of the British WWII radar system was in developing the handling of the information from the radar stations. They started work on this before the system was working fully. Chain Home might have been primitive in many ways but was in use right through WWII and was providing valuable information on V2 launches towards the end of the war. I quite agree that Robert Budari's book on the Rad Lab gives a good overall picture of radar in WWII. The best book that I have found on the British ground based radar system is ... RDF1 by Michael Bragg Published by Hawkhead Publishing ISBN 0953154408 [http://www.net-magic.net/users/w4fok/Radar_Page.htm] It follows the story in chronological order. By the way, the WWII Proximity Fuse was not a true radar (i.e. pulse) device. It used a continuous carrier and the doppler effect to detect its proximity to an aircraft or the ground. User:Jmb ==British (+German?) bias?== The article as it is written is very biased to British (and some German) radar work. As discussed in this article, technological advances seem to end about 1950. This simply isn't true. When we look at the history, we certainly need to include in the early years - 1901 (I think) - Tesla delivers a paper before the Institution of Radio Engineers proposing, for the first time, radar. Maxwell developed the theory, Hertz was the first to show reflections of radio waves at UHF, and Tesla was the first to propose radar. The telemobiloscope of Hulsmeyer is not properly mentioned, and the shortcomings of the telemobiloscope that caused its economic and technical failure are not discussed. It is surely worthy of note that there were no real amplifiers until deForrest developed them and no good power sources for microwaves. The development of the first pulsed radar at the Naval Research Labs in 1924 to measure the height of the ionosphere is also quite worthy of note. Developments in the early 1930s were not only done in Britain and Germany. The SCR-270 was in place and detected the Japanese attack on Pearl Harbor in 1941. US PBY Catalina aircraft detected the Bismarck for the British fleet, and it was this detection that allowed the sinking of the Bismarck. The Bismarck itself had an impressive targeting radar. By the early 1930s, there were excellent researchers in the United States, France, Italy, Russia, Britain, and Germany all working on radar. All achieved impressive results. The development of the SCR-584, which was the first modern anti-aircraft radar, in 1943, revolutionized aerial attacks. The SCR-584 at Anzio had, it is reported, a 70% probability of kill, eliminating German air attacks. The airborne ground mapping radars, which reached their WWII height with the H2S and the H2X, should also be a part of this history. This is true not just because they were the first radars to show ground maps or because of their effectiveness, but because the whole idea of ground mapping from air or space is essentially overlooked in the article. The beginnings of ECM and ESM are also a critical development for radar. After World War II, technology did not stop. Doppler radars came about in the 1960s, medium PRF in the 1970s, and the electronically scanned antenna mostly in the 1980s, a trend still going on today. Ground penetrating radars are another specialty area in which there has been considerable development. Vehicle navigation and anti-collision radars are worth a mention in the article. These are getting to be a big market. There are many CW radars in this subarea, and they do measure range with FM. Well, that's just a few items. I would suggest that someone develop a credible outline for radar, then start fleshing it out. The current article looks like it was written by someone who does not understand the technical material, but has read a British history on the subject. --Anonymous No.II :I agree with the previous post. I did some research on radar history, which has been documented in http://ghj-associates.co.uk/radar_history.html. To summerize my research, radar technology started with Karl Ferdinand Braun around 1897 when he invented oscilloscope tube and improved range of wireless. Marconi tried to steal Braun's patent and in the end Nobel prize for inventing wireless was awarded to both of them. In 1904 Christian Hulsmeyer filed a patent for radar. In 1929 German Navy, Reichsmarine started work on what we know today as sonar. This effort lead to the first magnetron build by Philips and establishing of GEMA, Gesellschaft für Elektroakustische und Mechanische a firm dedicated to radar research. :Dr. Hans Eric Hollmann, who worked on radar in Telefunken, filed some 300 patents on his work. All of Telefunken radar patents were filed in United States also, so any american radar developments were copies of Dr. Hans Eric Hollmann patents. In 1935 first radar was installed on the german ship "Welle". "Home Chain", which british started in 1937 operated on 27 MHz and compared to german radars operating at 125 MHz was a primitive device. In 1937 to 1938 germans installed hundreds of Freya radars as german early warning radar system with the range of between 60 to 120 km. In 1938 a new naval radar system instlaled on the battleship Admiral Graf Spee with a range of 11 miles, which operated on 375 MHz. During the war germany developed Wuerzburg radar to guide night fighters to the british bombers. This and many other radar developments started a jamming war between radar engineers on both sides of English Channel. :British transferred all their radar knowledge to americans in 1940, which started american efforts to build a vaiable radar in what was called "RadLab". "RadLab" designed all american radar devices and at the height of its operation employed 4000 people. I could not establish when the first american radar was produced but from my research it looks like 1941 would be the date. Americans could have purchased some radars from Telefunken in 1939 or even in 1940, since trade between war time germany and the rest of the world was vey active, but again I could not find any proof of that. Radars were also installed on polish bombers in 1939, most likely copies of german radars. From Polish Air Force radar technology most likely traveled to Russians, so it is prudent to assume that both Poles and Russians had german radar designs in 1939. From the first sonar development in German Navy radar was hidden behind a wall of military secresy and even today it is difficult to piece together the real order of events. :For the lack of proof of several important dates I do not feel competent to rewrite anglocentered propaganda of radar history page in Wikipedia, but it would be nice to have somebody with a better knowledge of the subject to present a true story of this fascinating device. :--Anonymous No.III ::Seriously, add or edit a paragraph. It's easy to edit the Wiki one paragraph at a time. You've presented a good bit of information here, why not put SOME of that into the REAL page instead of the talk page. User:Rboatright 19:21, 7 Apr 2004 (UTC) == Frequency range(s) wanted == In the Frequency section, in addition to listings of a couple of 'bad' frequencies/frequency ranges, I would very much like to see an overview of the frequency range(s) used in all kinds of radar applications. That would make the article much more accessible and usable in a reference setting, I think. --User:Wernher 00:57, 26 Jun 2004 (UTC) :Thanks, User:Heron! :-) --User:Wernher 02:44, 5 Jul 2004 (UTC) ==Scientific use of Radar== I'd like to see (or add) a section or a separate page on some of the current scientific uses for radar, particularly in my field of atmospheric/ionospheric research. In the ionosphere#Geophysics entry there is a link to Project HAARP, but there is much more to tell. The Arecibo Observatory was built to be a radar, a fact not obvious from the entry, and there is a handful of ionospheric incoherent scatter radars around the world. In addition, there is a large number of ionosondes and digisondes for automated ionospheric monitoring, and VHF meteor radars and coherent scatter radars for upper atmospheric research, as well as the SuperDARN radar chain of which the UK Cutlass radar is just one pair of stations. There is also the fascinating topic of passive radar, which probably deserves a section or page of its own. I have read the various FAQs and tutorials for contributing to the 'pedia, and I'll be willing to contribute to these sections, if this is of interest. I'd appreciate opinions on structure, though. I.e., add a section or create separate page on scientific radar instruments, etc. Also, should I create an account before starting on such contributions? --Tom Grydeland Tom.Grydeland@phys.uit.no :Thanks for your offer to contribute, Tom. I think we would all welcome your help. Here are my suggestions, which are by no means authoritative. # Get yourself a user account on Wikipedia (see Special:UserLogin). This is not obligatory, and some contributors manage fine without one, but it tends to encourage other users take you more seriously. You can advertise your email address, but many Wikipedians won't use it, preferring to keep all communications on the Wikipedia record. # Add a section to Radar summarising the scientific uses, and then, if you feel like going into more detail, add more articles on the more specialised topics. Personally, I feel that lots of medium-sized articles on the specific areas you mentioned, such as Cutlass, would be more interesting and easier to navigate than a huge amorphous article on "scientific radar", but others might disagree. # Beware of creating articles with ambiguous titles, such as "Cutlass". The convention here is to describe the most common sense of the term (i.e. the knife) in the article of that name, but to add a note at the top or bottom saying "''See Cutlass (radar) for the scientific radar system.''" # Prepare yourself for lots of discussions and perhaps even arguments with other contributors, some better informed than others. Best wishes, -- User:Heron 17:32, 27 Jun 2004 (UTC) ==How to shorten the article since it's well above the 32k limit?== I wanted to make a small change but refrained due to the warning that it's already 38k and should be shortened or split up. Are there any ideas on how to do that? None looked obvious to me, but splitting it up seems prefereable to just shortening it, since all the information looks to be well worth keeping. Maybe split off the frequency bands since that is a very specialized thing that is probably not of interest to most readers, or condense the history section and move the contents to a radar history article? And does this Talk page count against the limit (probably not since it is a separate page, but just verifying)? User:Spalding 12:31, Sep 6, 2004 (UTC) :The 32k limit is a technical thing to work around a bug in some older browsers. If you want to make a small change in the short term, just go ahead. If the article is already 38k, then you won't make the problem any worse by expanding it to 39k. In the longer term, I would agree with splitting off the history section, although I would leave a single-paragraph summary here to satisfy the casual reader. Finally, the Talk page doesn't count towards the 32k. Thanks for taking the trouble to ask. --User:Heron 12:56, 6 Sep 2004 (UTC) Spun ''lots'' material out to more appropiate seperate pages. User:Dan100 13:14, Jan 3, 2005 (UTC) == Radar Intrusion Detection Devices == I would like to see more about the use of radar as intrusion detection devices. I have been researching them as I am a Security Consultant and the literature that is out there is either slim or very old and out-dated. I have been trying to find the frequency range of a paticular device that is used as a short range, low crawl detector. It is a Doppler short-beam radar. The specs do not give a frequency, they give a range of 32 feet and a delay of .5 to 2 seconds. I'm a security specialist, not an engineer. If I happened to have missed this within the pages of this article, forgive me. If not, please guide me.... ALWAYS LEARNING == i don't see the small square == "Several types of radars on the frigate Duquesne, notably a navigation radar (small square) and the big radome which protects the DRBI 23 air sentry radar." - User:Omegatron 17:14, Jan 2, 2005 (UTC) As the picture became 'missing', I've removed it. User:Dan100 13:18, Jan 3, 2005 (UTC) == Radar versus RADAR == Shouldn't we change the title of this page from "Radar" to "RADAR" since RADAR is an acronym?--User:Ptdecker 04:35, 7 Apr 2005 (UTC) There appear to be planty of examples of acronyms written in lower case documented in Wikipedia. --User:Sicooke 20:15, 23 Apr 2005 (UTC) == Request for references == Hi, I am working to encourage implementation of the goals of the Wikipedia:Verifiability policy. Part of that is to make sure articles Wikipedia:Cite sources. This is particularly important for featured articles, since they are a prominent part of Wikipedia. Further reading is not the same thing as proper references. Further reading could list works about the topic that were not ever consulted by the page authors. If some of the works listed in the further reading section were used to add or check material in the article, please list them in a references section instead. The Wikipedia:WikiProject Fact and Reference Check has more information. Thank you, and please [http://en.wikipedia.org/w/wiki.phtml?title=User_talk:Taxman&action=edit§ion=new leave me a message] when a few references have been added to the article. - User:Taxman 19:23, Apr 22, 2005 (UTC) == K band useless? == In the article it says that K-band is useless because of its absorbtion by water vapor. When I went into my friend's car, which has a radar detector, it has a feature that allows the detection of radar detectors in the K-band. I know my knowledge is limited, but nowhere in the article does it mention police radar guns, and these should be placed somewhere in the article. == History == Shouldn't there be at least a short section on the history of radar in this article? I realize there is a seperate article, but it is in dreadful shape, would be nice to see a crisp paragraph or two outlining the history.
wireless communications
See other meanings of words starting from letter:
Words begining with Radar:
RADAR
Radar
Radar
Radar
Radarange
RadarCzar
RadarCzar
Radarmaker
Radars
RADARSAT-1
RADARSAT-2
Radarscope
Radar_ambiguity_function
Radar_Astronomy
Radar_astronomy
Radar_Base,_Texas
Radar_Base,_TX
Radar_cross-section
Radar_Cross_Section
Radar_cross_section
Radar_detector
Radar_gun
Radar_gun
Radar_Jamming
Radar_Love
Radar_networks
Radar_note
Radar_O'Reilly
Radar_Records
Radar_reflector
Radar_Scope
Radar_Tower_Bremerhaven
Radar_warning_receiver
Radar_warning_receivers
RADAR
#REDIRECT Radar
Radar
:''This article is about the device. For the fictional character in ''M*A*S*H'', see Corporal Walter (Radar) O'Reilly.'' [[Image:Radar antenna.jpg|right|thumbnail|250px|This long range radar antenna (electronics) (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon.]] ''RADAR'' is an acronym for RAdio Detection And Ranging or Radio Angle Detection And Ranging. It is a system used to detect, range (determine the distance of), and map objects such as aircraft and rain. Strong radio waves are transmitted, and a receiver listens for any echo_(phenomenon)es. By analysing the reflected signal, the reflector can be located, and sometimes identified. Although the amount of signal returned is tiny, radio signals can easily be detected and amplification. Radar radio waves can be easily generated at any desired strength, detected at even tiny powers, and then amplified many times. Thus radar is suited to detecting objects at very large ranges where other reflections, like sound or visible light, would be too weak to detect. ==Principles== ===Reflection=== Electromagnetic waves reflect from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or vacuum, or other significant changes in atomic density between object and what's surrounding it, will usually reflect radar waves. This is particularly true of electrically-conductive materials such as metal, making radar particularly well suited to the detection of aircraft and ships. Radar waves reflect in a variety of ways depending on the size of the radio wave and the shape of the target. If the radio wave is much shorter than the reflector's size, the wave will bounce off in a way similar to the way light bounces from a mirror. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas modern systems use shorter wavelengths (a few centimetres) that can image objects as small as a loaf of bread. Radio waves always reflect from curves and angles, in a way similar to glint from a rounded piece of glass. The most reflective targets have 90° angles between the reflections. A surface consisting of three flat surfaces meeting at a single corner, like the corner on a block, will always reflect directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation. For generally the same reasons objects attempting to avoid detection will angle their surfaces in a way to eliminate corners, which leads to "odd" looking stealth aircraft. Electromagnetic waves do not travel well underwater; thus for underwater applications, sonar, based on sound waves, has to be used instead of radar. ===Polarization=== Polarization is the direction that the wave vibrates. Radars use horizontal, vertical, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces, and help a search radar ignore rain. Random polarization returns usually indicate a fractal surface like Rock (geology) or soil, and are used by navigational radars. [[Image:weather radar.jpg|thumb|Brightness can indicate reflectivity as in this 1960 weather radar image. The radar's frequency, polarization, and receiver determine what it can observe.]] ==Distance measurement== ===Transit time=== The easiest way to measure the range of an object is to broadcast a short pulse of radio signal, and then time how long it takes for the reflection to return. The distance is one-half the product of round trip time (because the signal has to travel to the target and then back to the receiver) and the speed of the signal. where c is the speed of light in a vacuum, and is the round trip time. For RADAR the speed of signal is the speed of light, making the round trip times very short for terrestrial ranging. For this reason accurate distance measurement was difficult until the introduction of high performance electronics, with older systems being accurate to perhaps a few percent. The receiver cannot detect the return while the signal is being sent out – there's no way to tell if the signal it hears is the original or the return. This means that a radar has a distinct minimum range, which is the length of the pulse divided by the speed of light, divided by two. In order to detect closer targets you have to use a shorter ''pulse length''. A similar effect imposes a specific maximum range as well. If the return from the target comes in when the next pulse is being sent out, once again the receiver cannot tell the difference. In order to maximize range, one wants to use longer times between pulses, the ''inter-pulse'' time. These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. You could offset this by using more pulses, but this would shorten the maximum range again. So each radar uses a particular type of signal. Long range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. This pattern of pulses and pauses is known as the ''Pulse Repetition Frequency'' (or ''PRF''), and is one of the main ways to characterize a radar. As electronics have improved many radars now can change their PRF. ===Frequency modulation=== Another form of distance measuring radar is based on frequency modulation. Frequency comparison between two signals is considerably more accurate, even with older electronics, than timing the signal. By changing the frequency of the returned signal and comparing that with the original, the difference can be easily measured. This technique can be used in radar systems, and is often found in aircraft radar altimeters. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a sine wave or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared. Since the signal frequency is changing, by the time the signal returns to the aircraft the broadcast has shifted to some other frequency. The amount of that shift is greater over longer times, so greater frequency differences mean a longer distance, the exact amount being the "ramp speed" selected by the electronics. The amount of shift is therefore directly related to the distance travelled, and can be displayed on an instrument. This signal processing is similar to that used in speed detecting doppler effect radar. See also the section on Continuous Wave radar below. == Speed measurement == Speed is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a little memory to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making grease-pencil marks on the radar screen, and then calculating the speed using a slide rule. However there is another effect that can be used to make much more accurate speed measurements, and do so almost instantly (no memory required), known as the Doppler effect. Practically every modern radar uses this principle in the pulse-doppler radar system. It is also possible to make a radar without any pulsing, known as a continuous-wave radar (CW radar), by sending out a very pure signal of a known frequency. Return signals from targets are shifted away from this base frequency via the Doppler effect enabling the calculation of the speed of the object relative to the radar. == Position measurement == Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located. ===Early systems=== :''main article History of radar'' Early systems tended to use omni-directional broadcast antennas, with directional receiver antennas which were pointed in various directions. For instance the first system to be deployed, Chain Home, used two straight antennas at right angles for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by rotation the antenna so one display showed a maximum while the other shows a minimum. One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is subject to the inverse-square law. To get a reasonable amount of power on the "target", the broadcast should also be steered. More modern systems used a steerable parabola "dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combined two radar frequencies in the same antenna in order to allow automatic steering, or radar lock. ===Phased array=== Another method of steering is used in ''phased array radar'', which uses the radio signal's interference with itself. If one were to broadcast a single signal from a large number of antennas, the result will be a single beam with the waves in the rest of space cancelling each other. If the phase of the signal is changed before broadcast, the direction of the beam can be moved because the point of constructive interference will move. Instead of constructing a single large antenna, such a system has a number of small omni-directional antennas referred to as ''elements'', usually arranged in a flat plate. Phased array radars require no physical movement. The beam can be steered by electronically adjusting the phase-shifters to each small antenna element. This means that the beam can scan at thousands of degrees per second, fast enough to irradiate many individual targets, and still run a wide-ranging search periodically. By simply turning some of the antennas on or off, the beam can be spread for searching, narrowed for tracking, or even split into two or more virtual radars. Phased array radars have been in use since the earliest years of radar use in World War II, but limitations of the electronics led to fairly poor accuracy. Phased array radars were originally used for missile defence. They are the heart of the ship-bourne Aegis combat system, and the MIM-104_Patriot, and are increasingly used in other areas because the lack of moving parts makes them more reliable, and sometimes permits a much larger effective antenna. As the price of electronics has fallen, phased array radars have become more and more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is far offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are now limited to roles where cost is the main factor such as weather radars and similar systems. Phased array radars are also valued for use in aircraft, since they can track multiple targets. The first aircraft to use phased array radar was the Mikoyan MiG-31. ==Radar equation== The amount of power ''Pr'' returning to the receiving antenna is given by the radar equation: : where *Pt = transmitter power, *Gt = gain of transmitting antenna, *Ar = effective aperture (area) of receiving antenna, *''σ'' = Radar Cross Section, or scattering coefficient of target, *Rt = distance from transmitter to target, *Rr = distance from target to receiver. In the common case where the transmitter and receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range. This yields: : This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small. Other mathematical developments in radar signal processing include time-frequency analysis (Weyl Heisenberg or wavelet), as well as the chirplet transform which makes use of the fact that radar returns from moving targets typically "chirp" (change their frequency as a function of time, as does the sound of a bird or bat). ==Frequency bands == The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world in the 21st century. They have been adopted in the United States by the IEEE, and internationally by the International Telecommunication Union. Most countries have additional regulations to control which parts of each band are available for civilian or military use. Other users of the radio spectrum, such as the broadcasting and electronic countermeasures (Electronic counter-measures) industries, have replaced the traditional military designations with their own systems. {| border="1" |+ Radar Frequency Bands !Band Name!!Frequency Range!!Wavelength Range!!Notes |- |HF||3-30 Megahertz||10-100 metre||coastal radar systems;'high frequency' |- |P||< 300 MHz||1 m+||'P' for 'previous', applied retrospectively to early radar systems |- |VHF||50-330 MHz||0.9-6 m||very long range, ground penetrating; 'very high frequency' |- |UHF||300-1000 MHz||0.3-1 m||very long range (e.g. ballistic early warning), ground penetrating; 'ultra high frequency' |- |L||1-2 Gigahertz||15-30 centimetre||long range air traffic control and surveillance; 'L' for 'long' |- |S||2-4 GHz||7.5-15 cm||terminal air traffic control, long range weather, marine radar; 'S' for 'short' |- |C||4-8 GHz||3.75-7.5 cm||a compromise (hence 'C') between X and S bands; weather |- |X||8-12 GHz||2.5-3.75 cm||missile guidance, marine radar, weather; in the USA the narrow range 10.525GHz ±25MHz is used for airport radar. |- |Ku||12-18 GHz||1.67-2.5 cm||high-resolution mapping, satellite altimetry; frequency just under K band (hence 'u') |- |K||18-27 GHz||1.11-1.67 cm||from German language ''kurz'', meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz. |- |Ka||27-40 GHz||0.75-1.11 cm||mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz. |- |mm||40-300 GHz||1 - 7.5mm||'millimetre' band, subdivided as below |- |V||40-75 GHz||4.0 - 7.5 mm | |- |W||75-110 GHz||2.7 - 4.0 mm||used as a visual sensor for experimental autonomous vehicles, high-resolution meterological observation |} ==Specific radar systems== *Active Electronically Scanned Array (AESA) *Continuous-wave radar *Doppler radar as weather radar *Millimetre cloud radar *NEXRAD *Passive radar *Pulse-doppler radar *Radar gun traffic and sports radars *Secondary surveillance radar (SSR) *Synthetic aperture radar *X-band radar ==See also== * Types and uses of radar ** Doppler radar ** Imaging radar ** Incoherent scatter ** 3D radar ** SCR-270 radar * History of radar * Magnetron * List of radars * Radio * Similar detection and ranging methods ** Sonar ** LIDAR ==Further reading== * Barrett, Dick, "''[http://www.radarpages.co.uk/index.htm All you ever wanted to know about British air defence radar]''". The Radar Pages. (History and details of various British radar systems) *ES310 "''[http://www.fas.org/man/dod-101/navy/docs/es310/syllabus.htm Introduction to Naval Weapons Engineering.''". (Radar fundamentals section)] * Robert Buderi: ''The invention that changed the world: the story of radar from war to peace'', Simon & Schuster, 1996. ISBN 0-349-11068-9 * Merrill I. Skolnik, Radar Handbook. ISBN 007057913X widely used in the United States since the 1970s. * R.V. Jones, ''Most Secret War''. R.V. Jones's account of his part in British Scientific Intelligence between 1939 and 1945, working to anticipate the German's radar, radio navigation and V1/V2 developments. ==External links== [http://www.radar-france.net The first operational radar in France 1934] * Hollmann, Martin, "''[http://www.radarworld.org/index.html Radar Family Tree]''". [http://www.radarworld.org/ Radar World]. * Penley, Bill, and Jonathan Penley, "''[http://www.penleyradararchives.org.uk/history/introduction.htm Early Radar History] - an Introduction''". 2002. * Buderi, "''[http://www.privateline.com/TelephoneHistory3/radarhistorybuderi.html Telephone History: Radar History]''". Privateline.com. (Anecdotal account of the carriage of the world's first high power cavity magnetron from Britain to the US during WW2.) * Sinnott, D.H., "''[http://www.dsto.defence.gov.au/corporate/history/othr/ The Development of Over-the-Horizon Radar in Australia]''" * USAF Long Range Radar, "''[http://www.rades.hill.af.mil/ 84th Radar Evaluation Squadron]''". US Air Force Squadron responsible for long-range Radar Sensor (both civilian and military) operational availability, counterdrug, search and rescue, and flight safety information assurance to the operations community.. Acronyms Radar ms:Radar
Radar
==UK's vs US' contributions== There was a claim on the :Manhattan Project page that radar was invented at MIT. I thought it was at least partly a British invention. Anybody got more details? --User:Robert Merkel :The key individual role (most such inventions are collaborative even if those responsible for the individual contributions never met each other) is credited to Robert Watson-Watt (1892-1973) of Brechin, Angus, Scotland. Moving from the Royal Aircraft Establishment (Farnborough, Hampshire) to the Radio Research Station (later part of the National Physical Laboratory) in Slough, (then in Buckinghamshire, but now now part of Berkshire) and then to a new NPL site at Teddington (then in Middlesex, but now in Surrey), he was asked by the Air Ministry to investigate a counterpart to an alleged German aircraft-killing "death ray". :Concluding that the power needed made it impractical to fry bombers out of the sky, instead on 26 February 1935 he demonstrated the future radar by using the BBC's Daventry (Northamptonshire) short-wave radio transmitter and a receiver and oscilloscpe (housed in a former ambulance in a field seven miles away) to detect a Handley Page Heyford bomber at 27 km. Subsequently head of the Bawdsey research station in Felixstowe (Suffolk), Watson-Watt helped to develop the ring of radar stations established in 1938. He was knighted in 1942. :MIT's role came shortly afterward (1938-1940), developing in collaboration with Canadian researchers a fighter-borne system (the first British airborne experiment had been in September 1937, but still needed development). User:David Parker ==MIT Rad Lab & I. I. Rabi== The following was floating around on the page, probably debris from an incomplete edit. Someone who knows this stuff could probably figure out where it belongs: ''... especially at the Radiation Lab at MIT (I. I. Rabi) and played an important role in the outcome of the war.'' --User:Ortolan88 12:56 Jul 25, 2002 (PDT) : It's from an old version, and has been replaced by a lengthy section of expanded text now. --Anonymous No.I ==General vs military radar== It seems useful to me to split this entry in two: one radar in general, and the other more focused on the military history side of it. I'm thinking of the link I'm about to make in an explicitly military context and seeing an article that doesn't deal with the stuff that it's appropriate to link to until you scroll quite a way down. And it's easy enough to imagine the contrary example, where you want to link to radar from an entry on a completely non-military area - microwave ovens or car safety devices or astronomomy, say. What do people think? User:Tannin 09:26 Jan 26, 2003 (UTC) :On the history section: it's a very good history of British and German developments, but US work deserves more mention, esp the Rad Lab stuff. Also, Watson-Watt gets too much prominence at present: he played an important role in the development of British radar, and an even more important role in the getting-to-say-who-invented-it-afterwards department, to the exclusion of several others. There is an excellent and fairly recent American history of the Rad Lab that covers this in detail. I have it here somewhere, just can't remember the title at the moment. User:Tannin 11:16 Jan 26, 2003 (UTC) : Found it! Added it to main article. User:Tannin ==French early contributions== I should verify but according to some sources the French engineers of the CFS had active research on the radar before ww II, they gave their technology to the British in 1939. User:Ericd There a PD article at http://www.vectorsite.net/ttwiz1.html you can cut and paste as you want. User:Ericd here is a source about French researchs http://sjdangle.free.fr/societe/ponte.htm User:Ericd 12:10 Jan 26, 2003 (UTC) ==Chain home; ''RDF1'' book; WWII Proximity fuse== One of the big achievements of the British WWII radar system was in developing the handling of the information from the radar stations. They started work on this before the system was working fully. Chain Home might have been primitive in many ways but was in use right through WWII and was providing valuable information on V2 launches towards the end of the war. I quite agree that Robert Budari's book on the Rad Lab gives a good overall picture of radar in WWII. The best book that I have found on the British ground based radar system is ... RDF1 by Michael Bragg Published by Hawkhead Publishing ISBN 0953154408 [http://www.net-magic.net/users/w4fok/Radar_Page.htm] It follows the story in chronological order. By the way, the WWII Proximity Fuse was not a true radar (i.e. pulse) device. It used a continuous carrier and the doppler effect to detect its proximity to an aircraft or the ground. User:Jmb ==British (+German?) bias?== The article as it is written is very biased to British (and some German) radar work. As discussed in this article, technological advances seem to end about 1950. This simply isn't true. When we look at the history, we certainly need to include in the early years - 1901 (I think) - Tesla delivers a paper before the Institution of Radio Engineers proposing, for the first time, radar. Maxwell developed the theory, Hertz was the first to show reflections of radio waves at UHF, and Tesla was the first to propose radar. The telemobiloscope of Hulsmeyer is not properly mentioned, and the shortcomings of the telemobiloscope that caused its economic and technical failure are not discussed. It is surely worthy of note that there were no real amplifiers until deForrest developed them and no good power sources for microwaves. The development of the first pulsed radar at the Naval Research Labs in 1924 to measure the height of the ionosphere is also quite worthy of note. Developments in the early 1930s were not only done in Britain and Germany. The SCR-270 was in place and detected the Japanese attack on Pearl Harbor in 1941. US PBY Catalina aircraft detected the Bismarck for the British fleet, and it was this detection that allowed the sinking of the Bismarck. The Bismarck itself had an impressive targeting radar. By the early 1930s, there were excellent researchers in the United States, France, Italy, Russia, Britain, and Germany all working on radar. All achieved impressive results. The development of the SCR-584, which was the first modern anti-aircraft radar, in 1943, revolutionized aerial attacks. The SCR-584 at Anzio had, it is reported, a 70% probability of kill, eliminating German air attacks. The airborne ground mapping radars, which reached their WWII height with the H2S and the H2X, should also be a part of this history. This is true not just because they were the first radars to show ground maps or because of their effectiveness, but because the whole idea of ground mapping from air or space is essentially overlooked in the article. The beginnings of ECM and ESM are also a critical development for radar. After World War II, technology did not stop. Doppler radars came about in the 1960s, medium PRF in the 1970s, and the electronically scanned antenna mostly in the 1980s, a trend still going on today. Ground penetrating radars are another specialty area in which there has been considerable development. Vehicle navigation and anti-collision radars are worth a mention in the article. These are getting to be a big market. There are many CW radars in this subarea, and they do measure range with FM. Well, that's just a few items. I would suggest that someone develop a credible outline for radar, then start fleshing it out. The current article looks like it was written by someone who does not understand the technical material, but has read a British history on the subject. --Anonymous No.II :I agree with the previous post. I did some research on radar history, which has been documented in http://ghj-associates.co.uk/radar_history.html. To summerize my research, radar technology started with Karl Ferdinand Braun around 1897 when he invented oscilloscope tube and improved range of wireless. Marconi tried to steal Braun's patent and in the end Nobel prize for inventing wireless was awarded to both of them. In 1904 Christian Hulsmeyer filed a patent for radar. In 1929 German Navy, Reichsmarine started work on what we know today as sonar. This effort lead to the first magnetron build by Philips and establishing of GEMA, Gesellschaft für Elektroakustische und Mechanische a firm dedicated to radar research. :Dr. Hans Eric Hollmann, who worked on radar in Telefunken, filed some 300 patents on his work. All of Telefunken radar patents were filed in United States also, so any american radar developments were copies of Dr. Hans Eric Hollmann patents. In 1935 first radar was installed on the german ship "Welle". "Home Chain", which british started in 1937 operated on 27 MHz and compared to german radars operating at 125 MHz was a primitive device. In 1937 to 1938 germans installed hundreds of Freya radars as german early warning radar system with the range of between 60 to 120 km. In 1938 a new naval radar system instlaled on the battleship Admiral Graf Spee with a range of 11 miles, which operated on 375 MHz. During the war germany developed Wuerzburg radar to guide night fighters to the british bombers. This and many other radar developments started a jamming war between radar engineers on both sides of English Channel. :British transferred all their radar knowledge to americans in 1940, which started american efforts to build a vaiable radar in what was called "RadLab". "RadLab" designed all american radar devices and at the height of its operation employed 4000 people. I could not establish when the first american radar was produced but from my research it looks like 1941 would be the date. Americans could have purchased some radars from Telefunken in 1939 or even in 1940, since trade between war time germany and the rest of the world was vey active, but again I could not find any proof of that. Radars were also installed on polish bombers in 1939, most likely copies of german radars. From Polish Air Force radar technology most likely traveled to Russians, so it is prudent to assume that both Poles and Russians had german radar designs in 1939. From the first sonar development in German Navy radar was hidden behind a wall of military secresy and even today it is difficult to piece together the real order of events. :For the lack of proof of several important dates I do not feel competent to rewrite anglocentered propaganda of radar history page in Wikipedia, but it would be nice to have somebody with a better knowledge of the subject to present a true story of this fascinating device. :--Anonymous No.III ::Seriously, add or edit a paragraph. It's easy to edit the Wiki one paragraph at a time. You've presented a good bit of information here, why not put SOME of that into the REAL page instead of the talk page. User:Rboatright 19:21, 7 Apr 2004 (UTC) == Frequency range(s) wanted == In the Frequency section, in addition to listings of a couple of 'bad' frequencies/frequency ranges, I would very much like to see an overview of the frequency range(s) used in all kinds of radar applications. That would make the article much more accessible and usable in a reference setting, I think. --User:Wernher 00:57, 26 Jun 2004 (UTC) :Thanks, User:Heron! :-) --User:Wernher 02:44, 5 Jul 2004 (UTC) ==Scientific use of Radar== I'd like to see (or add) a section or a separate page on some of the current scientific uses for radar, particularly in my field of atmospheric/ionospheric research. In the ionosphere#Geophysics entry there is a link to Project HAARP, but there is much more to tell. The Arecibo Observatory was built to be a radar, a fact not obvious from the entry, and there is a handful of ionospheric incoherent scatter radars around the world. In addition, there is a large number of ionosondes and digisondes for automated ionospheric monitoring, and VHF meteor radars and coherent scatter radars for upper atmospheric research, as well as the SuperDARN radar chain of which the UK Cutlass radar is just one pair of stations. There is also the fascinating topic of passive radar, which probably deserves a section or page of its own. I have read the various FAQs and tutorials for contributing to the 'pedia, and I'll be willing to contribute to these sections, if this is of interest. I'd appreciate opinions on structure, though. I.e., add a section or create separate page on scientific radar instruments, etc. Also, should I create an account before starting on such contributions? --Tom Grydeland Tom.Grydeland@phys.uit.no :Thanks for your offer to contribute, Tom. I think we would all welcome your help. Here are my suggestions, which are by no means authoritative. # Get yourself a user account on Wikipedia (see Special:UserLogin). This is not obligatory, and some contributors manage fine without one, but it tends to encourage other users take you more seriously. You can advertise your email address, but many Wikipedians won't use it, preferring to keep all communications on the Wikipedia record. # Add a section to Radar summarising the scientific uses, and then, if you feel like going into more detail, add more articles on the more specialised topics. Personally, I feel that lots of medium-sized articles on the specific areas you mentioned, such as Cutlass, would be more interesting and easier to navigate than a huge amorphous article on "scientific radar", but others might disagree. # Beware of creating articles with ambiguous titles, such as "Cutlass". The convention here is to describe the most common sense of the term (i.e. the knife) in the article of that name, but to add a note at the top or bottom saying "''See Cutlass (radar) for the scientific radar system.''" # Prepare yourself for lots of discussions and perhaps even arguments with other contributors, some better informed than others. Best wishes, -- User:Heron 17:32, 27 Jun 2004 (UTC) ==How to shorten the article since it's well above the 32k limit?== I wanted to make a small change but refrained due to the warning that it's already 38k and should be shortened or split up. Are there any ideas on how to do that? None looked obvious to me, but splitting it up seems prefereable to just shortening it, since all the information looks to be well worth keeping. Maybe split off the frequency bands since that is a very specialized thing that is probably not of interest to most readers, or condense the history section and move the contents to a radar history article? And does this Talk page count against the limit (probably not since it is a separate page, but just verifying)? User:Spalding 12:31, Sep 6, 2004 (UTC) :The 32k limit is a technical thing to work around a bug in some older browsers. If you want to make a small change in the short term, just go ahead. If the article is already 38k, then you won't make the problem any worse by expanding it to 39k. In the longer term, I would agree with splitting off the history section, although I would leave a single-paragraph summary here to satisfy the casual reader. Finally, the Talk page doesn't count towards the 32k. Thanks for taking the trouble to ask. --User:Heron 12:56, 6 Sep 2004 (UTC) Spun ''lots'' material out to more appropiate seperate pages. User:Dan100 13:14, Jan 3, 2005 (UTC) == Radar Intrusion Detection Devices == I would like to see more about the use of radar as intrusion detection devices. I have been researching them as I am a Security Consultant and the literature that is out there is either slim or very old and out-dated. I have been trying to find the frequency range of a paticular device that is used as a short range, low crawl detector. It is a Doppler short-beam radar. The specs do not give a frequency, they give a range of 32 feet and a delay of .5 to 2 seconds. I'm a security specialist, not an engineer. If I happened to have missed this within the pages of this article, forgive me. If not, please guide me.... ALWAYS LEARNING == i don't see the small square == "Several types of radars on the frigate Duquesne, notably a navigation radar (small square) and the big radome which protects the DRBI 23 air sentry radar." - User:Omegatron 17:14, Jan 2, 2005 (UTC) As the picture became 'missing', I've removed it. User:Dan100 13:18, Jan 3, 2005 (UTC) == Radar versus RADAR == Shouldn't we change the title of this page from "Radar" to "RADAR" since RADAR is an acronym?--User:Ptdecker 04:35, 7 Apr 2005 (UTC) There appear to be planty of examples of acronyms written in lower case documented in Wikipedia. --User:Sicooke 20:15, 23 Apr 2005 (UTC) == Request for references == Hi, I am working to encourage implementation of the goals of the Wikipedia:Verifiability policy. Part of that is to make sure articles Wikipedia:Cite sources. This is particularly important for featured articles, since they are a prominent part of Wikipedia. Further reading is not the same thing as proper references. Further reading could list works about the topic that were not ever consulted by the page authors. If some of the works listed in the further reading section were used to add or check material in the article, please list them in a references section instead. The Wikipedia:WikiProject Fact and Reference Check has more information. Thank you, and please [http://en.wikipedia.org/w/wiki.phtml?title=User_talk:Taxman&action=edit§ion=new leave me a message] when a few references have been added to the article. - User:Taxman 19:23, Apr 22, 2005 (UTC) == K band useless? == In the article it says that K-band is useless because of its absorbtion by water vapor. When I went into my friend's car, which has a radar detector, it has a feature that allows the detection of radar detectors in the K-band. I know my knowledge is limited, but nowhere in the article does it mention police radar guns, and these should be placed somewhere in the article. == History == Shouldn't there be at least a short section on the history of radar in this article? I realize there is a seperate article, but it is in dreadful shape, would be nice to see a crisp paragraph or two outlining the history.
Radar
wireless communications
See other meanings of words starting from letter:
R
RA | RB | RC | RD | RE | RF | RG | RH | RI | RJ | RK | RL | RM | RN | RO | RP | RS | RT | RU | RW | RX | RY | RZ |Words begining with Radar:
RADAR
Radar
Radar
Radar
Radarange
RadarCzar
RadarCzar
Radarmaker
Radars
RADARSAT-1
RADARSAT-2
Radarscope
Radar_ambiguity_function
Radar_Astronomy
Radar_astronomy
Radar_Base,_Texas
Radar_Base,_TX
Radar_cross-section
Radar_Cross_Section
Radar_cross_section
Radar_detector
Radar_gun
Radar_gun
Radar_Jamming
Radar_Love
Radar_networks
Radar_note
Radar_O'Reilly
Radar_Records
Radar_reflector
Radar_Scope
Radar_Tower_Bremerhaven
Radar_warning_receiver
Radar_warning_receivers
These materials are based on Wikipedia and licensed under the GNU FDL
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