The humble radar detector has been the source of frustration, misinformation, and controversy for as long as it’s been around. Who knew a little box that makes beepy noises could divide the automotive enthusiast community so deeply.

Fortunately, there are a lot of options available out there, all equipped with different features. There really is a radar detector for everyone. For those who want an overwhelmingly average detector there are Whistlers and Beltronics. For those who pretend that they actually use whiz-bang technology features, there are Escorts. For those who think the original Game Boy was the best Game Boy, there’s the Valentine One. And for people who want a radar detector that does nothing at all, there are Cobras.

Personally, I love them – I’ve been happily using a Valentine One Radar Locator for years. I enjoy radar detectors because I’m both a driving enthusiast, and an electrical engineer (that obviously loves to nerd out on this kind of stuff).

A common point of misunderstanding I’ve found is that so many people think that a radar detector will protect them from being pulled over. A radar detector doesn’t protect you from anything; it’s merely a tool that requires a well-informed operator to extract any value from it. That said, I don’t think everyone needs to be an engineer to appreciate a radar detector and understand the basics of how it works.

Note – Radar detectors are illegal to use or possess in some locations. In the United States, legality varies by state. Check the laws in your location before buying or operating a radar detector. The Wikipedia page on radar detectors provides a good summary of country and state restrictions.

First – a Little About How Radar Works

Radar emits electromagnetic waves from a source (e.g. a police car or radar gun) towards a target (e.g. your car). These waves bounce off of the target and return to the source. If your car is moving, the amount of time it takes for each reflected wave to return to the source decreases or increases depending on if you’re moving towards or away from the source (called the Doppler effect). This information is then recorded and used to calculate the speed of the target. In police radar, these waves are emitted billions of times per second and travel at the speed of light, so it doesn’t take long at all for the radar system to report your speed.

Just like how your radio tunes to different radio stations at different frequencies, there are different frequency ranges of radar as well. Since it’s a little clunky to refer to these ranges by their actual frequencies (“I’m scanning for radar signals in the 27 GHz to 40 GHz range!” Try saying that as fast as you can), they’re each given a letter designation to make it simpler.

Police Radar

The main frequency ranges used by police radar are called X-band, K-band, and Ka-band. Not all radar detectors scan for all three of these – make sure yours does.

X-band was used by some of the oldest radar systems, and is very rarely used anymore. K-band was quite ubiquitous and used for a long time. Nowadays, K-band is typically only used by older equipment, radar guns, and for smaller-scale enforcement (think: small towns). Ka-band is the new gold standard, and is where most police radar systems now operate.

Since radar operates by emitting waves, those waves spread out like an arc with greater distance to cover wider areas. That means that radar isn’t necessarily the smartest way of detecting speed. The radar system will report what the speed of a car is, but if there are other cars nearby it isn’t always clear which car it’s reporting about. In those cases, a police officer also has to determine which car is the target visually or through other means. If you have a radar detector it will alert you when this is happening, and it might give you enough time to slow down. Further, it can alert you well before a police officer is actually measuring your speed – if it’s sensitive enough, it can detect the weak radar signals from deflections and the scattering of the waves off of other targets, far in front of or behind you.

However, having a radar detector doesn’t give you a free pass to drive as fast as possible. First of all, driving as fast as you want on public roads is generally reckless and stupid. Also, police can still use their eyes – if a car is travelling 15 times faster than the rest of traffic, it’ll be quite clear which car’s speed their radar is reporting. Even if they don’t have their radar on, there’s still a whole host of other citations a police officer would love to give you just based on their observation of your driving (reckless driving and reckless endangerment, just to name a couple).

There are also other defenses that police radar systems have for fighting radar detectors.

Instant-On Radar

Police don’t use radar guns all that much anymore; instead, most frequently there are radar systems mounted on the front and rear of a police car that scan speeds of cars traveling in front of and behind the police car. This means that the officer can use those systems to scan your speeds while their car is moving. If those radar systems were on at all times, a good radar detector could be able to detect the police car from miles away. To get around this, police radar systems use a feature known as instant-on radar (also called RF-hold). This gives the officer the ability to turn their radar system on or off with the flick of a switch.

If you’re coming around a bend, and all of a sudden you are surprised to see a police car coming towards you, it’s probably not your radar detector’s fault. Most likely, the police officer didn’t have their radar system on specifically for that reason – so people with radar detectors won’t see them coming. If there’s no one else on the road with you, as soon as the police officer turns on their radar to check your speed it’s already too late.

This is one reason that it drives me absolutely nuts when I hear people say things like, “My cop detector doesn’t work,” or, “My radar detector doesn’t detect cops.” Your radar detector wasn’t built to detect cops; it was built to detect radar. No radar signal, no alert.

POP Radar

Additionally, police can use POP radar, which is a radar mode that emits very short bursts of radar that give enough information to report a vehicle’s speed, but don’t last long enough to trigger a radar detector. As Car and Driver notes, this isn’t usually used for writing tickets, but indicates to an officer to switch to a normal radar pulse to verify the speed. Plus, POP is only used in select handful of states anyways.

Radar Detector Detectors

As noted before, it is illegal to possess or use a radar detector in some locations. To combat the illegal use of radar detectors, speed enforcers began using radar guns that can pick up on slight radio frequency oscillations that emit from a radar detector. This informs them that a radar detector is being used, for which they can pursue the vehicle, confiscate the radar detector, and issue a ticket. However, to combat radar detector detectors, radar detector manufacturers began working to eliminate any radio frequency emissions from their detectors. Thus, radar detectors that are not detectable by radar detector detectors were born. Good grief, this is turning into a tongue-twister.

New Kid on the Block: LIDAR (Laser)

As radar detectors became more popular, speed enforcers looked to new technologies for more ways to stay ahead. One of the biggest game-changers in the new millennium was the adoption of LIDAR technology for measuring speed. LIDAR can be quite complicated; to summarize, it basically works the same way as radar, but rather than emitting an electromagnetic wave it emits laser light. The consequence is that instead of emitting in a wide arc, the light is emitted with the focus of, well, a laser.

Although laser is fast and incredibly accurate, it does require that a police officer use a laser gun to get your speed, and so they can’t be moving. The laser guns even have an optical sight on them for pinpoint accuracy in their epic game of laser tag.

Just like the different bands of radar, not all radar detectors also detect laser. Any radar detector that isn’t built to detect the three radar bands and laser is probably not worth buying.

However, just because your detector can pickup laser doesn’t mean you’re off the hook. Since laser is light, it works off of line-of-sight. Consequently, so does your laser detector. A police officer with a laser gun has to have a direct shot at your car, and they usually aim for the center of mass (license plate, headlights, front bumper, etc). The laser gun’s beam is so focused that if the gun is aimed at your car’s center of mass, there’s a decent chance that a laser detector sitting on your windshield is too far away to detect it. Even if your detector does pick it up, your detector’s alarm only signifies that the police officer already got you. There is absolutely no warning time – the best you can hope for is about one second.

Fortunately, there is still some hope. Laser can only be used for distances of about 1000 feet, and is highly sensitive to disturbances from rain, snow and fog. Additionally, the laser gun will only work if you’re traveling directly towards or away from it. Therefore you know the police officer will probably be sitting in the median, on an overpass, or on an entrance or exit ramp.

Shopping for a Radar Detector: What to Look for

There are a lot of different radar detectors out there with different capabilities and features, and some are more important than others. However, a good rule of thumb is that you get what you pay for. I’ll try and highlight the features that I view as most important.

As mentioned, make sure the detector is capable of detecting X, K, Ka, and laser. Also, make sure the detector has both front and rear antennas and laser sensors so you can detect both in front of and behind your car. Believe it or not, a lot of detectors only have a single, front-facing antenna.

With respect to features, directional arrows such as those on the Valentine One and Escort Max 360 alert you to not only what band of radar you’re being hit by, but also which direction it’s coming from. This is very helpful information when you suddenly get a hit of radar from seemingly nowhere. Additionally, radar detectors that indicate signal strength can act as a proxy for distance to the source.

When choosing between brands, look for any tests that have been done to compare detector sensitivities and ranges. The Car and Driver test linked above was helpful for me when I chose the Valentine One.

But What About False Alarms?

Ah, yes, how could I forget? The great false alarm controversy of the modern era has positioned itself to completely shatter all support for radar detectors amongst enthusiasts. As you start using radar detectors you will quickly find that just because your radar detector is making noise, it doesn’t necessarily mean there’s a police car nearby (again, it’s a radar detector not a cop detector). You will primarily find this when you receive alerts for X-band and K-band.

False alarms have been a problem with radar detectors for a long time – things like automatic door openers for stores and other radar-based equipment are notorious for regularly lighting up radar detectors and fooling operators. However, according to https://towingless.com, as modern cars have gotten more intelligent, the problem has only gotten worse. Blind spot monitoring systems, adaptive cruise control, and collision-avoidance systems on most models rely on K-band radar to see other cars.

Also, Chevy Trailblazers, GMC Envoys and Buick Rainiers from the mid 2000’s had taillights that would often trigger a laser detector. I’ve even noticed newer Volvos tend to trigger laser as well.

With all of these false alarms coming through, some feel that radar detectors are completely pointless because you can’t trust them. I disagree with that notion – radar detectors are every bit as important as they always have been, but being well informed on their functionality is significantly more important.

You should never disregard an alert until you have verified the source of the radar. Also, you should always remain aware of the severity of the various frequency bands. For example, X-band is so infrequently used that it’s very rare that you would ever want to pay attention to an alert. If you’re in a major metropolitan area, it’s also unlikely that you would pay much attention to K-band, either. However, Ka-band is almost always coming from police radar, and a laser alert is far too critical to disregard.

However, if nuisance beeping is simply too much for you to handle, there are still other options. To get ahead of the false alarm issue some radar detector manufacturers have built their detectors to filter out any signals it judges to be false alarms. Others have included GPS with their detectors to automatically learn where false alarms always occur (e.g. when you drive through the parking lot at the mall) and eventually silence their alerts. I’m sure in the coming years there will be even more digital signal processing incorporated in radar detectors to further combat false alarms.

I think the value of those features is a matter of preference. Personally, I’m inclined to agree with the self-appointed “Valentine’s Law”: the only thing worse than detecting a false signal is failing to detect a real radar signal. That’s yet another reason why I got a Valentine One – I’d rather receive the raw information and do the filtering myself.

The Conclusion

Hopefully by reading this you now feel equipped with better information for choosing your own radar detector and for using it smarter. Regardless, make sure you always drive safe and never drive in a way that puts anyone’s life in danger. Radar detectors are powerful tools that, in knowledgeable hands, can keep you one step ahead on the road.