The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Bibliographic Entry||Result |
|Miller, Rex. Electronics The Easy Way. Hauppauge, NY: Barron's Educational Series, 1988: 284-285.||"That X band radar for police use and for others in the experimental band is 10.525 gigahertz (GHz) or 10,525 MHz. They also use the K band (hand held unit) which is in the gigahertz range. Police radar operates on 24.15 GHz."||10.525 GHz |
|"Radar Applications by Frequency." Encyclopedia Britannica. Chicago: Encyclopaedia Britannica, 1997.||"X band (8 to 12 GHz). This is a band frequently used for shipboard civil marine radar, tracking radar, airborne weather avoidance radar, systems for detecting mortar and artillery projectiles, and police speed meters.||8–12 GHz |
|"Radar Wars: Upping the Ante." Car and Driver. 38, 4. (October 1992): 153.||"The granddaddy of systems is X band radar … X band operates on the narrow channel from 10.500 to 10.550 gigahertz (GHz) … K band appeared in the seventies and quickly became popular in its deadliest form: a hand held gun featuring an instant on switch. K band operates on a higher-frequency channel from 24.050 to 24.250 GHz … In 1989, photo radar appeared on the scene, and it was bad news for motorists--it operated on a frequency that was undetectable by existing radar detectors. The FCC set up a channel for photo-radar from 34.200 to 34.400 GHz, which lies within the wide Ka band … Which brings us to the Stalker, the latest wrinkle in hand-held radar guns. It operates on the Ka band anywhere from 34.200 to 35.200 GHz."||10.500–10.550 GHz |
|Markus, John. Modern Electronic Circuits Reference Manual. New York: McGraw Hill, 1980: 82.||"10.5 GHz RADAR DETECTOR- Picks up CW Doppler traffic signals in X band region at 10.525 GHz and alerts speeding driver with audio tone."||10.5 GHz |
|Hitzeroth, Deborah. Radar: The Silent Detector. Murray Hill, NJ: Lucent, 1990: 62-63.||"Police use two frequencies of radar, K band and X band. K band operates at a frequency of twenty four Gigahertz (one Gigahertz is equal to one billion Hertz). X band radar operates at a frequency of 10 Gigahertz."||10 GHz |
|Lotz, W. Gregory & Robert A. Rinsky. Occupational Exposure of Police Officers to Microwave Radiation From Traffic Radar Devices. Occupational Safety and Health Administration, June 1995.||"The early traffic radar devices were designed to operate at 10.525 gigahertz (GHz), in which electromagnetic energy wave oscillatesat a frequency of 10.525 billion cycles per second."||10.525 GHz|
|Service of Police Radars. Vizma, 1998.||"Working frequency of radiation at measurement of speed (10525 +-30 EHz [sic].)"||10.525 GHz|
The branch of law enforcement that regulates traffic on highwaysand other roads where a certain speed limit must be met uses aradar gun to calculate the speed of the vehicles. Radar is anacronym which stands for radio detection and ranging. Radar worksby transmitting electromagnetic energy in the form of waves intothe environment and detecting the energy reflected by objects.Radar picks up this "echo"and calculates its Dopplershift. Radar is based on the Doppler effect which describes theincreasing frequency of waves on a stationary observer as themoving source heads toward the observer, and likewise a decreasein frequency as the source moves away. The frequency shift thatthis radar gun picks up from the "echo"is directlyproportional to the velocity of the moving object that reflectsthe "echo".
Law enforcement radar guns became popular and set to dailyuse in the early 1970s. Though they emit microwave radiation theyare relatively harmless because they emit only 15 to 50 milliwattsof microwave power which is a considerably small amount sincepower is energy per time. In addition to being low-power devices,radar guns emit waves in a continuous fashion and are known ascontinuous wave (CW) systems. The frequency of the electromagneticwaves emitted by the police radar gun is determined by the FederalCommunications Commission (FCC) and is designated in the X bandor K band. The most common was the radar gun mounted insidethe squad car window or dashboard and lies in the X bandfrequencies of 10.500-10.550 GHz. A handheld version of thisradar gun utilizes the K band frequencies between 24.050-24.250 GHz.
The X band and K band radar guns soon became vulnerableto radar detectors that pick up these frequencies and alert driversof upcoming radar guns. This fact made research of this topicextremely difficult considering the fact that nobody would wantto give away the frequency of these radar guns so that radar detectorscould be created in light of this research. When these devicesbecame open to the public at a cheap price, radar gun designersstarted creating radar guns which utilized the Ka band from34.200 to 35.200 GHz. This frequency band is currentlyundetectable by existing radar detectors and thus makes deviceslike the Stalker and photo-radar very useful. They are very expensivethough and they won't be seen in your local highway trooper'shands any time soon.
Max Lipkin -- 2000
with additional references from Pak Nin Lui -- 1996
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