You probably know the basics of radar detectors: They detect radar – so you can find out where speed is being monitored and escape highway traps, slow down, and generally avoid getting pulled over or being given a speeding ticket. And while we’ve provided you with a list of the best radar detector reviews to look through, we haven’t actually talked much about how the detector works. A little tech talk can go a long way.
Law enforcement and other organization tend to use both lasers and radar when track vehicle speeds. The radar option is very simple: It shoots out a pulse of radio waves, then uses a receiver to pick up on the waves that bounce back. By comparing the timing and speed of the waves (you may have read about this before as the common Doppler Effect, used in many fields), the radar can tell how quickly something is approaching – and you’ve got a speed reading. Several different radio frequencies are used by police for these purposes. Meanwhile, laser versions (sometimes called Lidar, which hasn’t really caught on for obvious reasons) use infrared beams of light that can measure space very, very quickly and put together a snapshot of how fast a vehicle is traveling.
Radar detectors, meanwhile, use similar types of receivers to scan for all those radio waves and infrared light beams. If the receiver picks up a frequency or infrared burst that looks like something law enforcement uses, then it alerts the driver – or in some newer cases, uploads the location onto a digital map for cross-checking purposes. A radar detector is simply an advanced radar receiver turned toward the opposite purpose. If you’d like to see how this process works in video format, there’s a good Techquickie video about the basics for all the visual learners out there.
There’s a problem with this radar detection approach, however: It becomes a war of technology. Law enforcement officers switch to different frequencies to throw off detectors, and detectors add more frequencies to their searching technology, and on it goes…until radar detectors are searching for several frequencies and infrared bursts all at once, which can lead to a lot of false positives. As a result, new detectors come with algorithms that examine data from the radar waves detected and try to separate fake from real. This is why digital maps are handy – if many detectors pick up the signals in the same area, it’s probably real.
On the topic of legality, if you were curious: As long as radar detectors don’t interfere with speed tests (like jamming signals, for example), they are legal to use in every state…except for Virginia. Why is Virginia different? Well, there are some questions even science can’t answer.