Radar Detector Laws, Functioning and Tech History


Continuing our car radar detector series, we thought it best to go over radar detector laws and how radar detectors works. Both topics give use a better understanding of why the question stands “are radar detectors illegal” and we touch on “what states are radar detectors illegal”

Radar detectors are electronic devices that drivers use to detect whether law enforcements aka police

are monitoring their speed using radar guns.

Drivers mostly buy radar detectors to assist them reduce their driving speed before speeding or getting ticketed for the speeding.

Simple and plain.

Radar detectors can only discover Doppler radar based devices and they won’t discover any other radar device including those using Piezo Sensors, ANPR and VASCAR technology.

LIDAR devices will require a different form of sensor even though most modern detectors consist of LIDAR sensors.

Many of the modern detectors radar detectors will recognize signals across several wavelength bands which include X, K, and Ka. And in Europe KU band is also common.

What Makes a Radar Detector Devices Tick

One of the many technologies which law enforcement agencies utilize in measuring the speed of any moving vehicle is Doppler radar which beams the wavelength at the vehicle. It then inters the vehicle’s speed.

To achieve this it measures the Doppler effect-moderated change in the vehicle’s reflected wave’s frequency.

A radar gun is easily held on the hand, mounted on fixed objects like traffic signals or fixed on a vehicle.
Most radar detectors use superheterodyne receiver to detect electromagnetic emissions from radar guns and produce an alarm to notify the driver once they have recognized a transmission.


They can raise false alarms due to the many devices like automatic door openers…

For Example: Those used in supermarkets

…and adaptive automotive cruise controls which operate in the same electromagnetic spectrum with radar guns.

In the recent years:

Radar detectors have also included GPS technology.

GPS technology enables the users to manually store the common locations where the police or other law enforcing agencies often monitor traffic.


The radar detector produces an alarm any time the vehicle approaches the locations like the information thats stored in the Waze app.

The driver achieves this easily by pressing a button and moreover it doesn’t require any entering of coordinates.

The detectors in addition, allows the user to manually store coordinates of the frequent false alarms and any time they are in the location the GPS will ignore the signals.

There are GPS detectors that will download speed monitoring camera’s GPS co-ordinates and that of redlight from the internet. The GPS coordinates are contained in the TRINITY database.

Interstate travelers may receive alarms any time they approach a location with a speed monitoring camera.

The Counter Technology: Tech That Makes Your Detector Better

For several decades, detectors and radar guns for evolved alternately to counter each other’s technology in the form of civilian electronic warfare.

For example, as new frequencies are brought in, radar detectors remain blind to them until such a time their technology is also updated.

In a similar manner, the strength and the length of time of each transmission has been lowered to reduce detection possibilities.

This in turn has lead to the introduction of more sophisticated software and sensitive receivers to counter the technology.


Radar detectors also combine some other technologies like the GPS-based technology featuring point of interest database of well known speed trapping locations in a single device with an aim of raising success levels.

Breaking it Down To A Science: How Radar Detectors Work

So far in our series we’ve been highlighting to best car radar detector devices. Here is an overall breakdown of those devices.

Superheterodyne receivers in radar detectors feature local oscillators which slightly rotate making it possible to build a radar detector-detector.

This form of detectors recognize emission or the radar frequency of the targeted radar plus around 10MHz. VG-2 interceptors were the first such devices to be developed for the purpose. But ever since, the Specter III has eclipsed it.

The electronic warfare has always cut on both sides.

Since the detector-detectors use the same superheterodyne receiver, many of the early stealth radar detectors consisted of a radar detector-detector-detector circuits which can shut down the primary radar receiver any time it senses a detector-detector signal and therefore prevented being detected by such equipments.

The technique borrows from the ELINT surveillance countermeasures.

Around the 1990s, BEL-Troncis Inc. in Ontorio Canada, where metal detectors are illegal realized that local the detectors oscillator frequency can be altered to exceed the range of VG-2 interceptors.

This resulted to radar manufacturers changing frequency of their local oscillators. And today almost every radar detector available in the market is immune to VG-2 interceptors.

A New Generation of Speed Detectors: LIDAR detection

The newer radar detection devices utilize pulsed laser light commonly called the LIDAR (Light Detection and Ranging), instead of radio waves.

Any radar detector that can detect radio transmissions cannot detect infrared light that LIDAR guns emit and therefore the need of LIDAR detector is useful in such situations.


LIDAR detectors are not as effective as the radar detectors because their beam output is highly focused.

Radar radio waves can extend to 85 feet equivalent to 26 meters, across at 1000 feet equivalent to 3000 meters, from the source LIDAR’s light beams only diffuse to about 5 feet equivalent to 1.8 meters.

You May Be Interested In: The Best Radar Detector Under $200

In addition, police officers targeting a car will mostly target the center mass or the vehicle’s headlight and since the radar detectors are usually mounted on the vehicles windscreen, they may fail to alert at all.

Furthermore, with such focused beams, a police officer using LIDAR gun may target a single car in a closer proximity to the others at a range of 3000 feet – 910 meters.

As a result, some manufacturers now produce LIDAR jammers.

Unlike radar detectors, FCC does not control the use of LIDAR’s frequencies and their use. The jammers confuse the police LIDAR into showing no speed on their display. Mostly, the LIDAR is usually successful and therefore most LIDAR manufacturers produce LIDAR guns consisting of Jam codes which indicate when they are being jammed. The LIDAR guns will work on some LIDAR jammers and not on others.

See: Expert Law Forum- LIDAR Ticket Defense Forum

Despite this, they police can easily tell when they are jammed as they won’t get any reading on their LIDAR.

Most Jammer equipped motorists try to counter the technique by returning their speed to legal limits before turning the jammer off or “kill the equipment” known as the “jam to kill” or “JTK.”


Officers can tell that this is happening by just watching their LIDAR equipment unable to lock properly in a speed and the indication of the targeted vehicle sudden deceleration. They then pull the offending vehicle over and check for the LIDAR jammers on the vehicle’s front.

Under such circumstances, the police can hit the motorist with an obstruction of justice charge if found. There are some states with laws concerned with police radar or LIDAR jamming.

In the states penalties are usually severe.

Despite the invention of LIDAR speed detection, the radar remains more prevalent due to its lower price relative to the LIDAR equipments and radar equipment in the service. Moreover, for an officer to use the LIDAR, they must be stationery. And they can’t be moving at all regarding to the need of a precise aim.

Radar Detector Laws: Are Radar Detectors Illegal In the US?

The legality of radar detectors depend on the state. All states will not treat the devices in a similar manner and this is why there is much confusion existing.

As a rule of thumb:

A radar detector is typically lawful on private vehicles according to the Communication Act of 1934. According to the act, owning radar equipment is legal and it is unlawful for authorities to destroy or seize the devices without arresting the driver for any other crime or as a part of search warrant because the radar detector is your personal property.

See: FindLaw- Are Radar Detectors Legal?

However, even though it is lawful to own a radar detector, it may be illegal to use them. Two areas specifically that have laws prohibiting radar detectors usage while driving are Virginia and the Washington DC.

Any driver caught using a radar device in these areas will be subject to ticketing. Radar guns will easily detect whether a driver is using a radar detector including when using a detector with advanced technology which mask their usage. Therefore the police can easily get you.

Detectors Usage Inside Military Bases

While using and having radar and using radar equipments remains lawful for private drivers, their use in military bases is another matter to consider. It is typically unlawful to enter in a military base with a radar detector mounted on your car.

Of course, because most military bases require all drivers to pass through a checkpoint there is higher chances of fining, ticketing or arrest. The security officer simply asks the driver to remove the radar detector and keep it away while in a military property.

What about in Commercial Vehicles Using Radar Detectors?

Private drivers can use radar detectors in any place. But this is quite a different matter for the commercial drivers.

According to the federal laws, any commercial vehicle above 10,000 pounds is prohibited from using a radar detector while moving.

Furthermore, several states have laws which prohibit commercial vehicles from using the detectors. These states include Illinois, New Jersey and New York.

Therefore, a professional driver should highly avoid their use altogether to avoid license suspension or ticketing.

Windshield Mounting Laws

The other issue that confuses most people is where to mount the radar detectors. While owning a radar detector and using it in Minnesota and California is legal, mounting one on your vehicle will definitely result to your ticketing.


The two states have laws against mounting anything to your vehicles windscreen that might obstruct your vision. To be clear, these aren’t 100% radar detector laws, its just simply where you place your radar detector that can be an issue.

While there are other devices mounted on a windscreen in the states without concern, law enforcers tend to be sensitive on their presence due to the nature of work they do and they will most likely ticket you if they find one.

There are other states with laws touching on visual obstruction.

But the laws are strictly constructed such that the obstruction have to pose a hazard like something directly inline with the driver’s sight, the front windscreen tinting or vision field permanent reduction with permanent fixed visors.

If a driver is intending to use a radar detector, and mostly when traveling cross country, perhaps they should mount on the dash or to sun visor.

Radar Scrambler Laws

To be more specific on radar detector laws:

While radar detectors are typically legal across the US – except in military bases and for the commercial vehicles, radar jammers are illegal under the federal laws on the fact that their use is very serious.

Their use can cause a felony charge a jail time or a hefty charge.

On the other hand

The federal laws have not prohibited radar detectors. Radar jammers exist in grey area since they have experienced legal issues with FCC.

In addition to impairing police equipments, they can also impair ground control for air traffic.

However, laser jammers cause fewer problems since they hardly emit stray light beams. Nevertheless, several states have banned them and many law enforcement agencies frown on their use.

You May Be Interested In: The Best Radar Detector Under $100

Some states where laser jammers are unlawful include California, Illinois, Colorado, Minnesota, Oklahoma, Nebraska, Tennessee, South California, Nebraska, Virginia, Utah, Texas, South Carolina and Washington DC.

Here are a few specific state laws in regards to Radar detector Laws

Are radar detectors illegal in New York?

In New York, you can use a radar detector on a private vehicle but not on a commercial vehicle. The state has passed laws that prohibit their use on any commercial vehicle weighing above 10,000 pounds. Most people have used them for a very long time to escape fines and ticketing associated with speeding on passenger vehicles.

Are radar detectors illegal in Indiana?

In this state, you can use a radar detector in your vehicle. However, the state prohibits mounting of anything on the windscreen which can interfere with the driver’s line of vision.

Enforcement agencies are also more sensitive on radar detectors affixed to the windscreen. If you want to use them in this state, you should highly avoid fixing them on the windscreen.

Possibly, you can mount them on the dash or any other part.

Are radar detectors illegal in Oklahoma?

In this state, radar detectors are lawful but you are prohibited from using them on any commercial vehicle. You can only use them on private passenger vehicles.

You will notice a lot of states laws will say “Radar detectors are permitted for passenger vehicles but prohibited for use by commercial vehicles”

Coming to A Halt

In most states in the US, police officers will try to identify any driver traveling in excess of the set speed limits. They will then confirm that speed using speed measuring devices – laser or radar.

A radar detector will be helpful if there is a blanket radar set up ahead or if the officer fails to hold a button on the side of his radar in between targets.

The button stops the SMD from emitting radar waves and this way, there will be nothing for the radar detector to detect.

Hopefully we answered all your question in regards to radar detector laws in the US, How radar detectors work and most, importantly if radar detectors illegal. 

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