How Do Radar Detectors Work?

03rd Nov,2018

Most people are accustomed to going over the speed limit at least a little bit, but it’s something that could get you pulled over at some point. The good radar detectors offer an effective way to prevent costly tickets, and it’s important that you learn how do radar detectors work.

how radar detector works
Image by Radenso.

The Basics – How does a police radar detector work?

Radar uses radio waves to determine the distance of an object to identify its relative location. These devices produce radio waves to pick up on echoes. Any objects that are within a certain distance of the radar detector will bounce back electromagnetic energy. All radio waves travel at the speed of light, allowing the device to determine how far away a given object is by the amount of time the radio signal takes to come back.

A radar detector will scan the area around it for certain signals, specifically the kind that is produced by police speed guns. This type of device is only useful if there is a police officer down the road with a radar gun that is already turned on. When you start getting close, the radar detector will let you know with visual and/or audio indications. That’s basically how radar detectors work.

Understanding Radar Guns

If you want protection against speed traps, it is important to know how radar guns work and not only how radar detector works. The standard radar gun produces radio waves at a very specific frequency. These waves hit a car, bounce off and return to the gun. Assuming the police car is perfectly still, the waves return at the same frequency at which they left. If the car is in motion, the frequency will be significantly higher.

There are a lot of radar detectors that feature special panels that are designed to pick up on beams that come from lidar guns. These guns that some police use are a lot harder to get protection from because of how they are designed. By the time your radar detector notifies you of a lidar gun in use, it’s usually too late. You can, however, get a plastic cover to minimize the reflective properties of your license plate. This is not always effective, but it certainly can be.

Laser Jamming

Most modern radar detectors are designed with radar jammers. There are a series of LEDs that emit a light beam that makes it difficult for police to get an accurate reading of your vehicle’s speed. While not all of these systems are always completely effective, they can help with avoiding speeding tickets when you are on the road.


There is a lot of confusion as to whether or not radar detectors are legal to own/use. As of 2018, the only places in the U.S. that do not allow these devices are the District of Columbia and Commonwealth of Virginia. It is illegal for anyone operating a commercial vehicle to use a radar detector. In this case, a commercial vehicle is any vehicle that exceeds 10,000 pounds. In areas where these devices are illegal, police use Spectre RDD, which are devices uses to identify radar detectors. In Minnesota and California, you cannot have a radar detector mounted on your windshield, but you can have one on a dash mount.

Different Types of Radar

You will find that some of these devices are capable of detecting just one type of radar, while others can pick up on multiple kinds. X-band radar is the low frequency with a high output, and it can be easily identified from 2-4 miles away. There is also K-band radar, which is utilized by a majority of police departments. This type of radar has a short wavelength and can be more difficult to identify in time. Most radar detectors will notify you of a k-band radar within half a mile to two miles away. The longer the wavelength, the easier it is to recognize the signal from a greater distance.

Law enforcement is also deploying a new type of device to detect speeding drivers. This type of detection is called MRCD. It is similar to traffic redlight cameras but has the capability of catching speeding driver then mailing you a ticket if you are over the limit.

Still not sure if you should get a radar detector? check this out:

William Johnson

William Johnson is the owner and founder of He writes about car accessories, with his passion stemming from a deep enthusiasm for all things automotive. His website, RRD, focuses on in-depth reviews of car accessories to help people find the best and latest products in the market.