Radar detectors are small devices that help identify the presence of radars, such as those used by police to locate cars driving over the speed-limit. Certain types of radar detectors also identify the presence of laser-speed guns, which may be useful for those looking to avoid speed traps that traditional radar detectors may miss. In order to understand how exactly a radar detector works, it’s helpful to understand the manner in which basic radars operate.
Radars are frequently used to identify distance and speed, such as how far away an object is or how fast it is moving. A radar device emits a radio wave, which moves at the speed of light, and bounces back to the radar device when it encounters an object in its path. Based on how long it takes for the radio wave to hit the designated object (for example, a tree at an undetermined distance) and how long it takes the wave to bounce back, the radar device can figure out the distance between the device and the tree.
When a radar is used to detect speed (for example, the rate at which a car is moving), the radio wave frequency of the returned signal is altered because the car is moving. If the car is moving toward the radar device, the return signal has a shorter distance to travel and the radio wave frequency increases. The radar device can then use the change in frequency to determine the speed at which the car is moving. In laser-speed guns, waves of light are used in place of radio waves.
A simple radar detector identifies radar devices based on the radio waves it emits. Essentially, radar detectors simply act as radio receivers, picking up specific frequencies used by radar devices, specifically radar guns used by police to identify and catch speeding cars. Because radar devices used by police cast a wide net of radio waves but only track one specific target, radar detectors in moving cars often pick up on radar radio waves before the car comes within close enough range of the police car to be tracked.
Other, more advanced radar detectors not only detect police radar, but can essentially throw off the reading a police radar receives. In these types of radar detectors, a radio transmitter emits a scrambled signal (called a jamming signal) which takes the original detected signal and adds additional radio signals. When the scrambled signal reaches the radar, the police have trouble getting an accurate speed reading. A similar system exists for laser-speed guns (called lidar) wherein the laser detector emits a scramble beam of light.
Of course, there are different kinds of radar that a radar detector must be sensitive to. An x-band radar has a low-frequency and a high out-put, making it relatively easy to detect from 2 to 4 miles away. However, devices other than police radars generate x-band signals, including garage door openers and microwave towers. K-band radar is most commonly used by police, and has a small wavelength. A k-band police radar can conduct an accurate reading from .5 to 2 miles away, making it difficult for radar detectors to pick up on the wavelength beforehand because of their small wavelength.