Electronic Devices: How Radar Detectors Work

Radar detectors work by looking for radar signals sent by police radars and finding them before they can illuminate the speeding car.

Radar detectors work by looking for radar signals sent by police radars and finding them before they can illuminate the speeding car. Police radar units send a series of radar pulses and calculate the speed based on how long it takes two consecutive pulses to reach the radar gun after reflecting off the car in question. Radar detectors search for these pulses by using superheterodyne design and attempt to find the pulses before they have the opportunity to reflect off the car where the radar detector is located. Superheterodyne design is used by the radar detectors to locate the radar pulses even when the pulses are not strong enough to reflect back to the radar gun. A signal that mixes with any incoming radar pulse producing a lower frequency that is easy to detect. This design also allows detectors to detect pulses around curves or over hills and can extend the range straight ahead.

Radar detectors have to be able to locate different types of radars. The X-band radar is the easiest to detect due to a lower frequency and higher power output. Detecting this radar can vary from 2 to 4 miles depending on the terrain, temperature and amount of humidity, but the X-band radar can only accurately read speeds from a distance of ½ mile or less. The downfall with using a radar detector to locate a X-band radar is that police radars are not the only source of X-band signals. Garage door openers, microwave intrusion alarms, microwave towers, and other high-tech equipment can set off the radar detector as well.

The K-band radar is the most common police radar today. These radar waves have a relatively small wavelength making them easily absorbed by water molecules in the air. The effective clocking range of these radars is about ¼ of a mile up to 2 miles, depending on terrain, weather and other factors. With this type radar, by the time the detector alerts you, the radar has already clocked your speed. The detector may actually work to your advantage if the police radar clocks the cars in front of you and happens to set your radar detector off.



Ka Photo Cop and Ka wide-band radars allow for a predetermined speed that will trigger the camera when a vehicle approaches it at the predetermined speed. The photo will show the front of the vehicle, license plate, driver's face, date, location and time. These units can clock and photograph up to 200 vehicles per hour. The effective range of these radar cameras is 120-3000 feet and transmits a continuous signal, making it a plus for radar detectors. The film from these cameras is developed and the speeders get their ticket mailed to them ordering them to pay the fine for speeding. Radar detectors can usually detect these radar cameras ¼ to ½ a mile away.

Ka super wide-band is the stalker radar gun. This radar gun is capable of FCC licensing of any frequency in the Ka-band between 33.4 GHz to 36.0 GHz. Because of this, radar detectors that only detect X, K and photo radar will not detect these. Radar detectors have been developed with the technology that will sweep all the Ka-band frequencies as well as protection against X, K and photo radar.

Laser radars allow for more accurate identification of a specific vehicle and the amount of time needed for clocking a car is less than half a second and are accurate for up to 1 ½ miles. These radars also have drawbacks, which include expense, use from a stationary position, do not work behind glass and accurate aiming requires using a tripod or having a steady hand. Because of these drawbacks, there are still not many of these radars on police cars yet.

There are radar detectors available for all of these radars. Determining which one is right for you is the tricky part even though they all perform the same task in pretty much the same way.

© High Speed Ventures 2011