A radar detector is an electronic device used by motorists to determine if their speed is being monitored. The term originates from early speed-detection technologies, in which police bounced a radio wave off of a moving vehicle with a device that determined the vehicle's speed by the Doppler-effect-moderated change in the wave's frequency. Most of today's radar detectors detect signals across a variety of wavelength bands - usually X, K, and Ka bands.

Newer speed-detection technology uses pulsed laser light (LIDAR, commonly referred to as laser detection) rather than radio waves. Modern "radar detectors" have been adapated to suit that technology, by detecting the infrared light emitted by these new detection methods. LIDAR detection is not nearly as reliable as the detection of radar, since the light is much more focused and often aimed below the windshield level , where the detector is usually mounted. There are many products that are advertised to "scramble" or "absorb" both radar and laser, but many of which are snake oil, such as the products offered by Rocky Mountain Radar.

Despite the advent of LIDAR speed detection, radar remains more prevalent for several reasons, not the least of which are the lower costs of radar (although some insurance companies supply laser guns to police departments for free). Popular radar detector brands include Escort, Cobra, Valentine One and K40; the best consumer models retail for about $299-$399 USD, although more sophisticated (and more expensive) systems exist.

External links

• Howstuffworks.com article on radar detectors
• SpeedZones (SML) A popular radar detector test site.
• Radartest.com Another site that includes popular radar detector tests. This site is very biased because Craig Peterson who runs it hates Mike Valentine who is the inventor of the Valentine One which is the best radar detector.
• Radardetector.co.uk - (UK) information about radar and GPS speed camera detectors.
• Radardetector.net A popular radar detector forum.