How Radar Detectors Work

Jamming Signals

I­n the last section, we looked at conventional radar detector, which pick up police radar with a simple radio receiver. This sort of detector is a completely passive device: It simply recognizes the presence of radar. More sophisticated detectors actually take an active role in eluding the police. In addition to the basic receiver, these devices have their own radio transmitter, which emits a jamming signal. Essentially, the signal replicates the original signal from the police radar gun, but mixes it with additional radio noise. With this information added, the radar receiver gets a confusing echo signal, and the police can't make an accurate speed reading.

Modern detectors may also include a light-sensitive panel that detects the beams from lidar guns. These devices are more difficult to evade than traditional radar because the beam is much more focused and it doesn't carry well over long distances. By the time a detector recognizes the presence of the laser beam, the car is most likely in the beam's sights already. Some speeders try to get around these systems by reducing the reflectivity of their car. A black surface reduces reflectivity because it absorbs more light. Drivers can also get special plastic covers that reduce the reflectivity of license plates. These measures reduce the effective range of the lidar system, but not the range of the driver's detector. With this extra time, a speeder might be able to slow down before the lidar gun can get a read on his or her speed.

Speeders may also use a laser jammer. This works basically the same way as a radar jammer. In addition to a light-sensitive panel, the detector has its own built-in light emitting diodes (LEDs) that produce a light beam of their own. When this beam shines on the lidar system, the receiver can't recognize any reflected light and so can't get a clear speed reading.

It's important to note that none of these systems are 100 percent effective; even with a top-of-the-line detection and jamming system, the police still might catch you speeding. Also, since police periodically introduce new speed-monitoring technology, a detector might suddenly become outdated. Whenever this happens, the fully equipped speeder has to dump everything and pick up all new equipment.

Of course, there is always one surefire way you can avoid speeding tickets, no matter what technology the police come up with: slow down!

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