How Do Radar Detectors Work?

A device used by the drivers to avoid law enforcement officers’ speeds, guns, or speeding tickets is called a radar detector. The police radar detector can detect the speed of gun activity beforehand, which is used by patrol police and hence gives the driver enough time to slow his vehicle down by alerting him. A remote Radar detector is an electronic device capable of radio signals emitted from law enforcers’ speed guns or such radar devices.

Generally, the radar detector can easily detect signal emitting devices like LIGHT DETECTION AND RANGING or LIDR, dopplers, etc. But those devices that do not use radio signals but rather use visual effects to get the vehicle’s speed are tough to be detected by normal radar detectors. An example of such a device is Visual Average Speed Computer And Recorder or VASCAR.

Automatic number plate recognition cameras are also another example of such a device. Radar detectors can not detect VASCAR or ANPR in the daytime as they do not emit any signal or ray. But at night, these devices use infrared lights, which the radar detector can detect easily.

Advanced radar detectors can detect almost any type of speed gun or devices law enforcers use to monitor vehicle speed. Some radar detectors contain GPS, which helps the user to pinpoint places where police radar detector checks speeds most of the time. This article aims to get a sound knowledge of how radar detectors work.

Evolution of Radar Detector System:

The first-ever radar detector named Radar Sentry was first introduced commercially in 1961 in New york. This device was very simple in design and ran on AA batteries. It was supposed to be set on the sun visor of a car. It was very cheap. In 1968 an electronic expert named Dale Smith was charged with a speeding ticket which made him furious. This led him to develop a radar detector which he named FazzBuster.

This device had a simple control system with a warning light on it. It worked fine against the doppler radar laser gun used by the police. Due to the vast use of radar detectors, the speed guns used by the police became less effective, which made the law enforcers frustrated. In 2000 the VG2 gun was introduced. This device was used to detect any radio signal leaked from a radar detector. Another device named Spectre was introduced by Cobra Radar detector company in 2000. It was supposed to detect a radar detector from a 1000-meter range.

Soon after this invention microcontroller was introduced to radar detectors. These microcontrollers replaced transistors and resistors, thus reducing the size of a radar detector. The size and the radar detector were also updated with lots of configuration and a display feature. These small computers ran with software, and this software could have been updated using USB or serial ports, which can be found in modern radar detectors.

These updates could increase the efficiency of the radar detector, whereas, without software, it would have to be the hardware that was supposed to be changed to get desired performance from the radar detectors. Soon digital radar signal processing was introduced and was implemented in radar detectors.

These detectors received the high-frequency signals and converted them into digital signals for proper and accurate analysis. As a result, it gives very few false alarms. That is why digital radar detectors are far superior to analog detectors in these cases. Then GPS was introduced and incorporated with radar detectors along with locations for the false alarm. After GPS, the internet was also incorporated with the detectors so that it can get a real-time view of false alarm locations and real speed camera ticket areas. It helps to continuously update the map of the area the user is traveling.

The user and others can be benefited from this as they will get notified as soon as someone finds a speed ticket location.

Types of Radar Detectors:

  • Corded: These detectors have cords and can be mounted on windshields with suction cups.
  • Cordless: These radar detectors do not have cords and are very easy to install.
  • Remote controlled: These radar detectors are installed in the car permanently. These detectors are not easy to detect as they are installed in such a place in your car so that no one would be able to find them. At Least no easily.

Working Principle:

First, we need to know what radar is. Radar stands for Radio detection and ranging. A radar throws a radio wave in the air, an electromagnetic type of energy. This energy can produce the desired signal in the air at a 3.08 x 108 meters per second speed. This is the speed of light. When transmitted by the radar, these signals travel the radar transmission path, and if there is any object in the path, the signal gets bounced back off the object to the radar again.

This is how radar systems can detect the distance and type of object. The distance can be calculated using the return time of the signal, and the speed can be detected by calculating the variation between the transmitted and returned signal. The returned signal frequency normally increases, which helps to detect the speed.

Now we have a clear idea of how radar systems work. We will learn how radar detectors work following the radar system theory. A radar detector is a kind of radio signal receiving device. It can detect specific frequencies that are transmitted from special radar devices like radar guns that police usually use. As the radar gun throws a signal, the signal then spreads out in the air.

The radar detector can then easily catch and detect that signal, raise the alarm, and show the warning on the display of the radar detector. This way, the radar detector user can easily detect any police unit that is using a speed gun even before getting close to the unit.

In advanced radar detectors, there is also a special transmitter. When this type of radar detector identifies any speed gun unit, it not only notifies the user but also transmits a special signal. This signal then superimposes the return signal of the speed gun and makes it difficult to detect the speeding car.


The radar detector is a nice device that is pretty handy if you want to avoid any speed tickets. Radar detectors are legal to use in almost every country, though some exceptions. In the case of commercial vehicles which weigh above ten thousand pounds and on military bases, radar detectors are illegal to use. But you should always follow and maintain the speed marks on the road. Excessive speed is not good and can cause accidents that may cost your life.

Hopefully, this article will help you to get a proper understanding of how radar detectors work.

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