RL100 Radar Detector

Portable, All-Band Radar and Laser Detection with GPS Technology

The K40 RL100 offers the ultimate portable protection from every kind of police radar and laser, meaning you drive ticket-free. Guaranteed. Fully customizable for every vehicle and driving environment.

  • Features
  • Specifications
  • Guarantees
  • FAQ's
  • Reviews & Testimonials
  • 12 Customizable Settings - No two drivers, vehicles, or driving environments are the same. The K40 RL100 is completely customizable to the way you drive.

  • GPS-based "Mark to Alert" - Mark points of interest that you deem worthy of an alert. This feature gives you the ability to "Mark and Unmark" any location. Build your own database of locations. No annual subscriptions, no internet databases, and no weekly downloading or updating from a home computer or laptop.

  • K40's exclusive Quiet Ride - Allows you to set a minimum MPH detection speed that eliminates all audible alerts until the vehicle exceeds your selected speed. Ideal for long road trips or when you only want to be alerted to radar/laser if you exceed a certain speed.

  • K40's Speed Monitor (programmable feature) - Gives the driver a constant audible alert whenever a preselected speed is exceeded, as well as a visual alert telling you to "slow down." Great for young or new drivers. Speed Monitor will override Quiet Ride.

  • Fully Programmable Radar/Laser Alert Options - Enables you to eliminate audible and visual alerts to specific radar bands or laser. This programmable feature is particularly useful if your vehicle has radar-based safety accessories, or when travelling in congested urban areas where non-police radar signals may be prevalent.

  • Accessories Included - Everything you need to install the RL100 is included: Fully-adjustable windshield mounting bracket with suction cups, a standard coiled power cord with 12V outlet adapter, and a straight power cord for a custom hard-wired installation.

  • Voice or Tone with Digital Display - Unique audible and visual warnings alert you to the specific police radar band targeting your vehicle as well as provide a "Geiger" audio alert that accelerates as you near the threat.

  • Vibrant LCD Digital Display - Great looking and easy to read, day or night. Easily adjust the brightness to suit your driving environment. Default display shows your filter setting, your compass direction, and your speed reading.
Product subject to one or more of the following U.S. Patents:
  • 7,298,248 B2
  • 5,001,777
  • RE39,038
  • RE40,653
  • RE41,905
  • Other patents pending.

Detects every FCC-approved police radar frequency and radar gun:
Operating Frequencies

10.500 - 10.550 GHz (X band)

24.050 - 25.250 GHz (K band)

33.400 - 36.000 GHz (Ka band)

830 - 945 nanometers (Laser)

GHz = gigahertz

Power Requirements

11.0 - 16.0 Volts DC negative ground

170 mA typical standby


4.625 in. L x 2.625 in. W x 1.1250 in. H


6.0 oz.

Temperature Range

5° F to + 150° Fahrenheit

Three Filter Settings:
Level/Mode Sensitivity Recommended Use
1. Highway
(factory default
Detects all types of FCC-approved police radar or laser signals at full sensitivity. For highway travel or in any area in which you are
unfamiliar with the types of radar used.
2. City The X-Band sensitivity is reduced. This is because it is the most common source of non-police radar
signals. K, Ka, and Laser will remain at full sensivity.
When traveling in an urban area with minimal non-police radar signals.
3. Filter Eliminates X-Band detection completely. Reduces
K and Ka-Band sensitivity. Laser detection will remain at full sensitivity.
When traveling in a congested traffic area with a high concentration of non-police radar signals.

Programmable Features:
  • Voice Type - Male / Female
  • Audible Voice - Voice On / Voice Off
  • Test - Test On (Full) / Test Off (abbreviated start-up sequence)
  • Speed Displayed - Speed On / Speed Off - for MPH on screen
  • Compass Heading - On / Off - directional heading on screen
  • POP Radar Band - On / Off - turning POP on will greatly increase alerts to all radar emissions
  • Quiet RideTM - Set minimum detection speed from 20mph - 65mph
  • X-Band - On / Off
  • K-Band - On / Off
  • Ka-Band - On / Off
  • Laser - On / Off
  • Factory Reset

Radar Receiver Type - DSP Datadyne Technologies

GPS Receiver Type - SiRFstar III

Display Type - Full LCD Text Display

Signal Strength Indicators - Audible Geiger and numeric signal strength indications

RDD Guard


K40's Exclusive RL100 Radar Detector Guarantees: If you get a speeding ticket, we’ll pay for it.*

K40 was the first radar detector manufacturer in the world to offer a speeding ticket guarantee. Thirty years later, we are still the only company with the confidence to back all of our products with this guarantee: all radar speeding tickets covered in full, no questions asked, for one full year from the date of purchase.*

K40 guarantees your satisfaction, 100%

K40 continues to offer the best guarantees in the industry as it has since 1981. It’s a confidence that comes from three decades of designing the very best automotive radar and laser protection systems in the world.

Along with the industry’s only comprehensive speeding ticket guarantee, your RL100 guarantee also includes:

  • 100% Performance Guarantee – If your RL100 does not outperform any other radar detector you’ve owned, return it within 30 days for a full product credit.
  • 100% One-Year Quality Guarantee – K40 will repair or replace any defective RL100 for one full year from date of purchase.

Register to Ensure You’re Covered

To ensure you’re covered by all K40 guarantees, register your product today.

*Speeding ticket guarantee not valid for tickets written in school or construction zones, or incurred with a DUI or DWI violation. All tickets covered for first year of product ownership. Speeding ticket guarantee extension available. Call 800.323.5608

Frequently Asked Questions regarding Police Radar

Q. How much warning time does a K40 radar detector provide?

A. Trying to estimate warning time in an actual mile or feet measurement is impossible because true warning time is influenced by many outside variables that have nothing to do with the radar detector itself. For example, the strength of the radar signal being transmitted, the direction the gun is pointed, the length of time it is transmitting, the positioning of the patrol car, and the influence of other objects around you may all affect how your radar detector receives a signal.

For these reasons, don't expect your detector to achieve the same warning distance every time you encounter police radar. Just expect it to do what you bought it for, giving you enough time to slow down and save yourself from receiving a speeding ticket.

Q. What's the difference between sensitivity and selectivity?

A. Sensitivity refers to a radar detector's ability to pick up police signals at the greatest distance. Selectivity refers to the detector's ability to filter out signals that are not true police signals, yet operate on the same frequencies as police radar (i.e. security alarms, garage doors, automatic doors, etc.).

The filtration software built into K40 radar receivers features very unique microelectronic processors that minimize distractions that come from non-police radar transmitters. This helps give you the time you need to react to real potential threats without the constant "falsing" that makes other detectors difficult to use in today's challenging driving environments.


Q. Sometimes I pass a parked police car, or one traveling in the other direction, but my detector doesn't alarm. Why is that?

A. Radar detectors are essentially superheterodyne radio receivers. Like any radio, they're passive devices that listen for microwave signals. The main difference is that they are specially-tuned to detect microwave frequencies transmitted by police radar and laser guns.

If a police car is not equipped with a radar or laser gun, a radar detector cannot possibly locate it. Also, if no signal is transmitted when you pass the police car, there won't be any signals for your detector to receive.

Police may also use a sinister technique called "Instant-On" or "RF Hold." During this type of encounter, an officer will wait until a targeted vehicle is within range to send a quick burst of radar to clock the vehicle's speed. K40 radar detectors are sensitive enough to detect these brief, weak signals, but you have to pay attention and react quickly.


Q.  I drove past a speed box and it displayed my speed. How and why?

A. Speed signs - or speed reading boxes - are radar-based. Radar detectors are not radar jammers. Jamming radar is a federal offense and is prohibited by federal law nationwide. These information-only speed readers, if working properly, should always detect and display your speed.


Q.  I drove past a speed box and my radar detector didn't go off.  Why?

A. Speed signs - or speed reading boxes - are not used to issue traffic tickets or citations. As a result, these portable systems are not calibrated regularly and can "drift" away from the FCC-authorized frequencies. Because of this, when passing one of these signs that say "Your Speed Is...," you may or may not receive an alert. These devices are primarily placed in residential areas as a reminder to obey the speed limit.

Q. What is “POP” Mode?

A. POP Mode, when turned on, enables the detection of a special band of radar known as “POP.” This is a very short transmission signal that allows the user of a radar gun to capture a quick reading of a vehicle’s speed prior to setting the gun to another band. K40 recommends that you keep the POP Radar Mode turned off for two reasons: 1) POP radar does not transmit long enough to gather information needed to issue a speeding ticket, and 2) keeping POP Mode “on” is known to cause far more false alerts than actual alerts.

Q. Do you “jam” radar?

A. No, we do not. The sale and use of radar jammers has been banned by the Federal Communications Commission (FCC) since 1997. The fines for each violation can reach up to $11,000.

Q. Can a tinted windshield negatively affect the performance of my radar detector?

A. Today, many high-end car manufacturers, such as Mercedes-Benz and BMW, are incorporating special tints into their windshields to protect the interior look and comfort of their cars. Unfortunately, this creates a very real problem for people who own portable radar detectors.

Putting tint of any kind on your windshield that contains metal film is essentially like putting a blanket over your radar detector. While radar microwave signals can still travel through fiberglass, plastic, and glass, they cannot penetrate metal. Some tints are worse than others, but if it contains metal of any kind, it will reduce the performance of any portable radar detector mounted inside the car.

Q. I've heard that you pay speeding tickets... Is that for real?

A. We have absolute confidence in the performance of our products, and you should never get a speeding ticket when they are operating and used properly. In the rare event that you receive a speeding ticket in the first 12 months of ownership, we'll pay any and all fines (excludes tickets issued in school zones, construction zones, and/or when DUI or DWI is involved). No questions asked.


Even though the best method of avoiding speeding tickets is to simply not speed, for most car guys this is not an option. “Lead footers” (or speeders) range from the “chronically late” and “always in a rush” crowd, to those like me who love driving as fast as possible.(read more...)

K40 RL100

K40 RL100 - Radar Detector Reviewed - Simple, Easy and Effective

(Click here to read review)

I recently installed your RL100 in my vehicle and I have been nothing but completely impressed with it. I recently moved from Iowa to Indiana and this saved me many, many times. The range on the system blew me away. I was able to know about speed traps in plenty of time before I came upon them so there was plenty of time to reduce my speed. The GPS in the system is great. It helped me know that I was indeed going the way I needed to when the road signs were unclear. I think one of my favorite features is the "Mark" feature. I have used it a few times since I have arrived here. It is great to know that I am coming up on an area that I have noticed a lot of police activity. I have also "Marked" a couple of areas where kids play so I know to be extra cautious.
All in all this is the finest dash mounted Radar/Laser detector I have ever had the pleasure of using. The LCD display along with audible tones give me all the info I need to know that I need to be alert for what is coming ahead.

--Brad Marvin

"This is my second K40 radar detector.  The first one I purchased in 2001 saved me from a ticket the very first day.  I thought this one was defective because it alerted me 4 miles before I saw a state patrol.  This convinced me how well this product works!  It has saved me countless tickets since then.  Thanks for making a superior product.

--Patrick Dowling
Douglas, Georgia

Speed Zones Test
Speed Measurement Laboratories - Long Range Test 2013

“I have to commend your engineers on an outstanding job of designing the RL100.  Regardless of the sensitivity setting, when it alerts me, I know without a doubt that the above mentioned are in the area.  This from a driver with 43 years of driving experience going all the way back to the FUZZBUSTER days.

Thank you K40 and Audiodriven"

--John Gately

Oak Forest, IL


“The range on my K40 radar detector system is way better than any radar detector I have ever owned. I was sold on the no ticket guarantee. The K40 has also provided 75% less falsing when driving in and around the DFW area. I don’t know it’s there unless I need it.”

  Terry Lynn G., Dallas, TX


"After using my new RL100 for three weeks I have to tell you this unit is amazing! After trying 6 different units over the years, I finally have one that works the way I want it to. The Quiet Ride feature is fantastic. I can set my minimum speed and let it go. If I don't hear it, I don't have to worry about it. I love the fact that when it does go off it tells you what band and the strength. The GPS also allows the unit to double as a heads up display so your speed is never more than a quick glance away. The RL100 is the best radar detector I have ever used. Period."

-- Michael R., Elgin, IL