EmailRadar threats 101
Before you purchase a radar detector, it's important to understand the different kinds of radar used by the police. Police radar guns work by emitting a microwave pulse to measure the speed of a moving vehicle; radar detectors work by sending out a signal that mixes with this pulse to produce a lower, more easily detected frequency.
X-band radar (10.5 to 10.55 GHz) used to be the most popular gun used, but it is now almost totally obsolete. X-band is also the frequency that causes the most false alarms. That's because many supermarket automatic doors, garage-door openers and motion detectors run on the same frequency. More expensive radar detectors have a city mode that lets you downgrade or disable a detector's sensitivity to X-band, thereby cutting down on the number of false alarms from sources other than law enforcement.
Right now, the majority of radar guns operate on the K-band (24.05 to 24.25 GHz) or Ka-band (33.4 to 36 GHz) frequency. Ka-band guns are the most common: "41 states are now standardized on this band by state contract," SpeedZones.com says. K-band and Ka-band guns are especially tricky because they can be turned on instantly. If an officer chooses your car, it's almost impossible to be warned ahead of time. However, some detectors can provide a warning if a radar gun is targeting vehicles ahead of yours, giving you enough time to slow down.
Law enforcement has found a new way to stack the deck with POP modes on Ka-band and a few K-band radar guns. POP modes allow officers to send out signals in bursts too short to be picked up by many radar detectors. The catch is that speeders caught using POP modes can't be ticketed because the law requires a radar gun to lock onto a vehicle. However, if law enforcement detects a speeding vehicle using POP mode, he or she can then flip the gun into constant-on mode and get a lock on a vehicle.
Ka-band POP poses no problem for any radar detector in the latest test at Speed Measurement Laboratories, with every unit detecting Ka-band POP almost every time. However, in a previous year, none of the units tested could detect K-band POP at all. Still, the testers say POP isn't widely used anyway: "Your chances of encountering POP mode are the same as you traveling to the moon on a bungee cord."
The laser gun is becoming increasingly popular. Police particularly like to use them on crowded roads because laser light beams are so tight, they can easily pick a speeding car out of a crowd. Another positive for police is that, generally speaking, laser guns give off little advance warning -- unlike radar, which puts out a relatively broad signal that can be detected miles away. That means that once a laser detector sounds its alert, it's usually too late, as the laser that it is detecting is often aimed squarely at you. Laser guns do have some downsides for police, however: Since the laser must reflect back to the gun off a flat surface, the police have to get a good aim, usually at your front or back license plate or headlights. In addition, laser guns have to be used from a stationary position -- giving you some opportunity to visually spot the speed trap.
Most radar detectors can also detect laser guns, but experts say a laser detector alone is of limited use. Instead, they recommend coupling the detector with a laser jammer (which, unlike radar jammers, remain legal in most states) or another countermeasure such as an anti-reflective coating on your headlights or license plates.
Finally, some police departments use a device known as a radar-detector detector (RDD) to alert them to vehicles equipped with radar detectors. For passenger cars, using a radar detector is legal everywhere in the U.S. except Virginia, Washington, D.C. and on military bases. However, they are illegal in big commercial trucks and in much of Canada. Most RDDs can detect most radar detectors, though some detectors are better at covering up their telltale signal leakages than others. In Speed Measurement Laboratories' latest tests, two models were invisible to RDDs: the top-rated Beltronics STi Driver (*Est. $500), the Cobra XRS 9960G and the Cobra XRS R10G (*Est. $300).
It's also important to realize that no radar detector will report every single radar encounter. There are too many variables, such as terrain, angle of the gun to the car, interference from other traffic, etc. While certain models do better than others, no radar detector will spot 100 percent of radar threats 100 percent of the time.
Choosing the right radar detector
Here's what experts say to consider when you're shopping for a radar detector:
- The further away the device is able to detect radar guns and laser, the easier it will be for you to slow down in time to avoid a ticket. In tests, most major-brand radar detectors have no problem detecting all radar bands from up to two miles away under ideal conditions (a flat, straight road in the middle of the desert -- you'll rarely get that range in normal terrain and traffic). However, pricier models usually show a stronger signal from far away. Laser is a different story: Experts say that laser guns' narrow signals are harder to detect, so you won't get much warning at all no matter which unit you buy.
- Radar detectors should filter out noise and trigger signals only from actual radar guns. All of the ConsumerSearch Best Reviewed models offer city/highway mode, which varies sensitivity to limit urban false alarms from grocery-store doors, motion detectors and the like. Many radar detectors now allow you to disable X-band alerts. X-band radar guns are now nearly obsolete in most areas, and conflicts on the X-band frequency often trigger false alarms.
- A detector should provide easy-to-understand audio and visual warnings. It should also have a dark mode for discreet nighttime use.
- An automatic or manual mute silences audio alarms if you're in an area with lots of interference.
- A cordless radar detector can be an attractive option if you need your lighter/outlet for other uses. However, running on battery power diminishes performance, and reviewers do not usually recommend these models.
- Remote detectors have antennas that mount behind the grill, with controls under the dashboard for discretion and protection against thieves. They're pricier than one-piece models and may require professional installation, but they are less prone to theft.