How Does a Speed Radar Detector Work?

A speed radar detector is a specialized electronic gadget used by certain motorists to detect whether law enforcement or police are monitoring their speed using a radar gun. The radar detector allows the drivers to reduce their speed, and avoid getting a ticket for over speeding. The development of radar detectors proves that law bending has become prevalent and widely accepted. Introduced in the 70s, radar detectors have gained popularity, and become a must–have accessory for most speed junkies.

Certain countries have outlawed the processing or use of radar detectors or jammers. Drivers caught using such devices face traffic ticket violations and fines, seizure of the gadgets, or both. The premise for prohibition is that a driver who uses the device is more likely to over speed, thus posing a greater risk to other motorists and pedestrians, than a driver who does not use the device. However, a 2001 research conducted by Ipsos MORI, a market research organization based in the UK, suggested that users of the radar detector posed a 28 percent lower possibility of accident.

How a Speed Radar Detector Works

The first step in understanding how a radar detector works is by knowing what exactly the device detects, i.e., radar. The basic speed gun used by law enforcement is a combination of a radio receiver and transmitter in one unit. The transmitter fluctuates an electrical current upwards and downwards at a certain frequency, generating electromagnetic energy that travels through the air as a wave. It also has an amplifier that enhances the intensity of the energy, as well as an antenna that broadcasts the energy into the air. On the other hand, the receiver performs the opposite, by picking up electromagnetic waves using the antenna, and converting them into an electrical current.

Radar uses radio waves to detect and monitor objects, and give an indication of how far away an object is, by emitting a concentrated wave and listening for the echo. Radio waves move through the air at the speed of light; therefore, a radar device can calculate how far an object is, based on the duration it takes for the signal to return.

When it comes to measuring speed, radar technology uses the Doppler shift. Radio waves have a certain frequency, just like sound waves. When the car and the radar gun are both still, the original signal and the echo have the same frequency, with each section of the reflected signal mirroring the original signal; however, when the car is moving, the signal frequency changes, thus, the reflected signal creates different wave patterns, based on the direction and speed the car is travelling.

The radar gun can calculate the velocity of a car that is moving away from it or towards it, based on the frequency changes. Sometimes, police use a radar gun while inside a moving police car. In this case, the speed of the police car must factor in the calculation. For example, if the gun detects that the other car is moving away at 30 miles an hour and the police car is moving at 50 miles an hour, then the target must be moving at 80 miles an hour.

A speed radar detector is able to detect a radar gun based on the radio waves it emits. In simple terms, a radar detector acts as a radio receiver, and picks up specific radar device frequencies. Since police radar guns cast a wide radio wave net while tracking a single target, other motorists with radio detectors in their cars can detect radar radio waves before they come within range of the police car.

Law enforcement has added new detectors that use light instead of radio waves to try to stay a step ahead of people who use radar detectors. Unfortunately, certain types of detectors are able to detect the presence of laser speed guns; in fact, the more advanced radar detectors can even throw off the readings that a radar gun receives.