Radar Detector FAQ and Troubleshooting


This is not the car you're looking for......
Corgi Lovers
Advanced User
Lifetime Premium Member
Mar 20, 2018
Reaction score
Outer Rim - Hiding from 35.5 I/O
  • Thread starter
  • Staff
  • #1
Q: Why didn't my detector go off when I spotted a police vehicle?

A: It’s very likely that the officer was not using radar.
Radar detectors operate by scanning for the presence of radar waves within the specific permitted frequency ranges used for speed enforcement. The presence of a police vehicle is not a guarantee that there will be any radar to detect. This could be for any number of reasons:

Not all police vehicles are equipped with radar units.

The radar equipment could simply be turned off as the officer may only be driving to the office, doing paperwork or waiting for a call and may not be doing speed enforcement with a radar system. Many officers will park their vehicles out in the open while doing these things simply for the deterrent effect.

Police use alternate methods besides radar for speed enforcement like visual estimation, LIDAR (laser), pacing and VASCAR which can all acquire your speed without setting off your radar detector. If LIDAR is being used, though most radar detectors advertise Laser detection, it is important to understand that laser speed enforcement is very difficult to detect and getting any advanced warning is unlikely in most situations. Laser is a very narrow beam that is directly targeted at an individual vehicle and therefore very difficult to pick up until it is aimed directly at your detector. For this reason, radar detectors are not recommended as your sole method for LIDAR protection.

The LEO might be waiting until they have visually observed that a vehicle is likely to be speeding and then turn on the radar unit suddenly to get the target vehicles exact speed (known as “instant on” or “I/O”). If you didn’t appear to be going fast enough the officer might not activate the radar unit at all and instead wait for a juicier target.

Credis: @thebravo @Vortex

Q: Why am I getting what seem to be very short detections? Is something wrong with my detector?

A: Although it could be a problem with your detector, it’s more likely that the terrain, vegetation or angle of the signal is the culprit. The officer may also be using methods designed to foil detectors.
To answer this question more in-depth, a little must be understood about how radar waves behave and travel. Radar waves are emitted from an antenna and much like sound waves are emitted from a loudspeaker, the radar waves travel outward in a fairly broad conical shape that gets wider as its distance from the source increases. Radar waves can reflect off objects, be absorbed by objects and be blocked by objects. The objects between you and the radar source can have a very large impact on the distance the radar waves travel and consequently, how far away your radar detector can pick them up.

Terrain elements like elevation, curves, vegetation and buildings, as well as other vehicles, all impact the radar waves as they travel. Hills, curves, and vegetation all tend to reduce the range of your radar detections by blocking the wave’s direct path from the radar source to the radar detector or absorbing the radar wave’s energy. Other vehicles and buildings can have multiple effects depending on where the radar source is in relation to the receiver. In some cases a vehicle or building could be between your detector and the radar signal and partially block it, shortening your range, in other cases the radar wave could reflect off a vehicle or building and actually increase your range. As you move along, objects in between the source – which may be moving as well – and your detector are constantly changing, absorbing, blocking and reflecting the radar waves which can lead to intermittent acquisition and loss of signal, or very short fast ramp ups.

Another probable reason for a short detection is the direction of from which the radar antenna is directed towards your vehicle. In a situation where the officer is targeting traffic coming from the opposite direction of your travel, the signal that your radar detector will pick up is going to actually be the reflected signal off of objects ahead of you. This will result in shorter detection's as you aren't getting direct signal, but rather a weaker reflected signal. Fortunately, in a case like this the officer isn't going to be able to measure your speed until you are in front of his radar antenna so the short alert doesn't put you at as much risk. Officers could also be positioned in such a way that their radar antenna is perpendicular to your direction of travel, this often results in very short alerts as the radar waves are traveling perpendicular to your direction of travel and are not as likely to reflect back towards your radar detector. Again, since you are not in line with the radar antenna the officer cannot acquire your speed via radar in this manner.

Other factors such as the radar frequency being used and the power output of the radar gun can also impact detection range. Radar guns operating at higher frequencies tend to be harder to detect as the high frequency waves don't propagate as well over distance, and are more readily absorbed by terrain elements. Think about high and low frequency sound as an example, you hear the low booming of distant thunder first as the low frequency waves travel further and are not easily absorbed or blocked by the terrain. This same phenomenon applies to radar. Radar guns with a lower power output design emit waves have less amplitude and therefore fade out to nothing in a shorter distance. You won’t get as much range on their detection, but fortunately the range at which the radar gun can acquire your speed will also be shorter.

Another possibility that may cause a short alert distance would be the use of “instant on” or “I/O” by the operator of the radar unit. This is a method used with which a radar unit is turned off or not transmitting any radar waves until the officer spots a vehicle that appears to be speeding at which point the radar unit is suddenly turned on and allowed to transmit. As no radar waves are being emitted until that critical moment, your radar detector will go from silent to a full-strength alert very quickly. While it may initially appear to be a very short detection, in reality there was nothing to detect until the officer turn the radar transmitter on.

One final consideration is the sensitivity of the receiver, your radar detector. The more sensitive the detector is the more range you are likely to get. Since there are so many things that can reduce range, more sensitivity and a high quality detector can help you get the maximum range possible. There are times and conditions where even the most sensitive detectors cannot overcome the challenges of terrain, direction of radar antenna relative to your direction of travel, objects in the path and frequency and power output of the radar antenna. With each detection there are many factors that are constantly changing while your vehicle is in motion that have impacts to the range, and ramp-up of the alerts. A good sensitive detector gives you your best chance at a long range alert but even for the times where the terrain limits the range significantly, this sensitivity can still give you some additional reaction time over a less sensitive detector that might have alerted too late to save you.

Consider all the factors above to judge whether your alert distance on a particular detection was reasonable. It helps to have a dash cam to review the factors after the fact.

Credis: @thebravo @Vortex

Q: Why does my detector alert when there are no police around?

A: Given that you are sure you didn’t miss seeing a hidden police officer, a false alert can be caused by quite a variety of things. It could be another vehicle near you with on-board monitoring systems or stationary sources like door openers at the corner drug store.
Since Radar detectors operate by scanning for the presence of radar waves within certain frequency ranges, they will detect anything with a strong enough signal that’s within those ranges. This isn’t limited to police radar. A lot of blind spot monitoring systems or BSMs on modern vehicles operate in the same frequency range as police radar. These are usually K band alerts. Traffic sensors along the highway that monitor the flow of traffic can also set off your detector, usually on K band as well. Automatic door openers such as those found at your local stores frequently cause detectors to alert on K band or X band. Your detector may pick up the harmonic frequencies from other radar detectors or even from satellite dishes! The last two alerts mentioned are usually on Ka band which is normally dedicated to police radar, making them all the more fun. We call these false alerts, or just “falses”.

Falses can drive you nuts, desensitize you to alerts, or even worse, stop you from using your detector all together. With those issues in mind, and although your detector may see every signal that’s strong enough within the range it’s programmed for, modern detectors try to filter out these falses so they don’t become an issue. Unfortunately, when these signals act a lot like police radar, it can get a little complicated to do so and some detectors are better at it than others.

So filtering these falses is good but excessive filtering can cause problems too, such as not alerting to real police radar or being slow to alert while the detector decides if the alert is legitimate. The radar detector manufacturers have to find a happy medium with their filtering and it’s not easy.

Because of the problems inherent with false alerts, quality filtering should be a major consideration in deciding when to replace an older detector or which new detector to purchase. A sensitive detector is very important as well, but the more sensitive a detector, the harder the filtering has to work. The detectors that can combine both, good sensitivity and good filtering are in high demand.

If your detector is also capable of detecting laser, it can sometimes false alert to that as well. It could false to the taillights on certain models of cars, near airports or military bases, from your cellular phone or from other vehicle’s adaptive cruise controls among other things. Laser falses are generally pretty rare compared to radar falses but they certainly can happen too.

Credits: @OBeerWANKenobi @Vortex

Q: Wait! I’m still pretty sure something is wrong with my detector!

A: If none of the above helped you to answer your question, please start a forum thread and copy/paste in the template below along with your edits. This will assist forum members in helping you.
Detector Make and Model

Overwrite this text with make and model of your detector.

Purchase date

Overwrite this text with your purchase date which is useful in determining warranty status.

Purchased from

Overwrite this text with the vendor you purchased from. This is useful to determine who to contact and what their return policy may be.

Do you have something to test with?

Overwrite this text with your answer and a brief description of what you are using to test your detector.

If your problem can’t be solved here, would you be willing to ship your detector to a forum member for testing?

Overwrite this text with your answer.

Describe the problem.

Overwrite this text with your description.

Current Settings

Overwrite this text with the description of any settings that may influence results such as filters, segmentation or narrow vs. wide.

What have you done to try to correct the problem?

Overwrite this text with your description.

How can the problem be reproduced?

Overwrite this text with your description.

Last Updated 10/23/18


Learning to Drive
General User
Mar 26, 2017
Reaction score
Regarding the question of Q: Why am I getting what seem to be very short detections? Is something wrong with my detector?
instant-on, and if I understand correctly, Kpop. What is the actual length of time you need to be tracked for their radar result to be admissable?
Also does it apply to laser?


Learning to Drive
General User
Jul 24, 2018
Reaction score
Used to get plenty of Ka band alerts from MA S.P...now, very few. Anyone know if they're using something different? Just drove the length of the Mass Pike both ways, and didn't get any alerts! This worries me. I'm using Escort Max and 9500ix in my cars.

Discord Server

Latest threads

Forum statistics

Latest member
Andrew Greer