Radar Detectors

[TIZAO]

split from this thread by jay@af.

Ok since we are talking about speed I have a question about radar detecters. If I am going like 90 down the freeway, will a detecter really help me from getting pulled over? Or will it be too late by the time my detector sees the radar. What about the kind that jams police radar? Will that work if I am heading 90mph? Thanks guys I need to know!:smoka: :licker:

[Nemisis626]

Ok here we go Radar Detectors. the ones u can get in ur car detect up to 3 different types (Frequencies) of radar signal, and if its set up right, it can detect the radar traps emmissions before u get into the accurate range of the trap which can be up to 1/2 mile or so from it upto about 1 mile on the freeway( maybe further i havent fitted 1 for a while cos it is illegal to "use" 1 in the UK.) But if its set up that sensitive allsorts of stuff can set it off. Radar Jammers are 1: illegal to use for civilians 2: rather large (mostly) 3: make u appear to be doing like 200mph+ on the police detectors The only way to beat a detector is drive a F117 Stealth fighter :help::rocket: And some cops are using laser detectors now and u cant beat them (yet ) Hope this helps ya:sun:

[TIZAO]

THanks Nemis. Hm...I am still debating rather to get one or not. It sounds like the jaming one is bad because they would pull you over any ways is that true? I sure would if I saw someone going 200mph ha hahah. So if I am driving out in the country and have the detector set at highest setting, then I should be ok. HOw bout on the freeway? I understand the whole shoping mart door thing so I wouldnt need highest setting in the city, I dont speed in the city. I just need somthing for the country area, and for the free ways. THanks, hope you can still help me a little more. SO should I invest or not?!:alien: :licker: :smoka:

[gang$tarr]

yeah radar detectors are illegal in north america too.... illegal to use that is

but they're not as good an investment as they used to be since police are using the laser detectors now

but they aren't very big, and if you get a cordless one you can quickly sneek it under your seat if you get pulled over

[TIZAO]

Yea I think they are illigle here too, but so are many of the mods me and my friends have.....SO are you saying that its not a good investment. I am thinking of buying one off of e-bay.:alien: :smoka:

[moe182]

Originally posted by gang$tarr
yeah radar detectors are illegal in north america too.... illegal to use that is

They're not illegal everywhere.....its legal in Alberta, and a whole bunch of the states. It just depends where you are.

[Chris]

They are illegal in Ontario, but in almost all of the states they are legal. Try and find a Valentian 1.

[gang$tarr]

no they're illegal to use everywhere... they're just not illegal to sell
you can buy one but if you get caught using it you get in trouble..... i know it's stupid

[Chris]

I'm pretty sure that in some states it is legal to use, but jammers are illegal.

[TIZAO]

Hey DOnt forget my question.!:smoka:

[Chris]

Valentine 1's are the best. They are also the most expensive, but they are the best. I think they work well, detecting stuff pretty far in advance. It would probably be enough at 130mph, maybe, and plenty for slower speeds. Unless they are using laser, which sucks.

[gang$tarr]

i think they're switching over to laser, so radar isn't gunna be the best investment

[JD@af]

The Valentine 1 was the best. I can't remember the model, but I think that Escort has come out with a new detector that has ousted the V1 as the best radar on the market. The V1 still sits pretty in the #2 spot and remains an outstanding detector, but there is a superior unit available now.

Oh, and gang$tarr, the V1 and other top drawer "radar" detectors are equipped to detect laser as well.

[Nxtyoung]

Just cought this conversation. My opinion is just get a cheep one. if you find one for a hundred bucks it will just as good as a 3 hundred one. But like other people have said that the police are manly using laser. they just tucked in a small hole and as soon as some one comes by they clock them. Some Cops still us X ban, or the constent streem, which is what radar ditectors are good for. and the thing about the jammers is that in order to work for laser, the laser has to hit practicly on top of the jammer. When i say practicly i mean with in 4 to 5 inches. If you cant afford a hundred bucks just go between 5 and 10 miles an hour over if you need the speed and try to avoid the 130 mph joy rides.

[kris]

Ok, I am a little behind on this topic. But it is something I have looked into.

With the Lidar detectors on the market, you can detect lidar pointed at your car, but lidar measures your speed so fast you don't have time to react. What can you do?

A detector will save you sometimes If they target a car ahead of you, and you are ideally situated to detect the lidar, your detector might go off.

Stealth in combination with a Lidar detector will save you at long range. If they are targeting cars at 1000 feet, and your car has reduced reflectivity, they don't get a speed reading until you come into range. Your detector goes off and you have time to slow down. At short range, if they point the gun at your license plate and you have a stealth plate cover, your detector goes off, and you have time to slow before they retarget another part of your car.
Table of Contents

Lidar Gun Description

Police lidar is 904 nanometers, 5 nanosecond pulses of 25 Watt instantaneous power delivered into a 4 milliradian cone angle at 1 KHz repetition rate. The long wavelength and low average power aids eye safety. The divergence angle on transmit allows the units to be used without a tripod. The time of flight of the pulses are multiplied by speed of light and the resulting distances are plotted as a function of time. A least square fit is used -the slope gives the car speed, and the variance gives a validity test.

Lidar power estimates

You need to know this power if you want to build a jammer.
The lidar beam width at 250 meters is about 1 meter^2. The license plate (Colorado) has about .001 meter^2 of retroreflective paint. - 30 dB loss. They are illuminating the retroreflective paint with 25 milliWatts

The return beam (from the retroreflective paint) is also about 1 meter^2 and the receiving aperture is about .001 meter^2 - 30 dB loss.

The return (Colorado) is thus 25 microWatts instantaneous power. The effective measurement bandwidth is 30 GHz. Other states have stronger returns, with Georgia 14 times as strong.

Lidar Range

Lidar range goes as the fourth root of target crossection. This is a very weak function, and so the range for your state probably falls between these extremes of measurment range to the best and worst liscense plates measured.

Georgia license plate, by itself = 2577 ft.
Colorado license plate, by itself = 1339 ft.
With no plate- detection range of a Mazda RX7 with headlights retracted is around 800 ft.
No plate, and the lights covered - detection range < 500 ft.

The Uniden detector ad (Aug 95 Road&Track p31) claims that:
Uniden detector is good to about 8000 feet. Lidar guns are effective to about 2000 feet. Average operating range of police lidar is about 800 feet. In AUTOtronics, March 99 that typical radar ambushes are 600-800 feet because the police must identify the car and make a visual estimate of speed as well. This argument may not apply to lidar with its narrower beam, since the beam itself identifies the car.

Stealth

Stealth is not invisibility, it is just reduction of the range. This may help in combination with a detector, if the police target cars at the far half of their range as defined by the reflectivity of the average car. You get the warning before they get the speed measurement. Without stealth, in most circumstances, lidar detectors only go off when you have been targeted, and you don't have the time to slow down. With some range reduction due to stealth, they might target you before you come into range. They are trained to point at your license plate. If you have a stealth plate cover, your detector goes off, and you have time to slow before they retarget another part of your car.

A. Lidar targets on your car. (what is most important)
To find out what is most important on your car, stand with the light source behind you (park in the sun at dawn or dusk), and look at the region of the car right next to the shadow of your ear. You are looking at light reflected back towards the source. Alternately, you can at night use a flashlight held against your ear and pointed at the car. Stand back by at least 30 feet to see light returned at an angle close to straight back at the source. Another technique is to park your car on a dark street, stand >30 feet away and take a flash photo. Most car parts have similar properties in the visible and near IR. Some special materials absorb in the near IR and transmit in the visible and hence this test using visible light is not indicative that a special police-lidar countermeasure is working.

The license plate is the strongest target on the front of the car. License plates have retroreflective material that returns light in a 4 milliradian cone angle (Colorado plate measurement). Different States have a very large difference in the lidar return from the plates. Colorado is one of the lowest, using retroreflective paint on only the letters and a thin border. Most large states have better retroreflective material covering a larger area of the plate.

The strongest reflection of the rear of the car is an array of little corner cubes in the red tail light cover. All cars have a hexagonal array in the plastic tail light covers. These are just like a bicycle reflectors. You can distinguish these retroreflectors from the tail light lens by the array pattern. The tail light lenses are in a rectangular array, and this corner cube array is in a hexagonal pattern. The second strongest target on the rear is the rear liscense plate.

There is also a corner cube array on the side-front turn signal indicators. These do not present much of a target unless the police target you from the side in which case the cosine factor in speed measurement will give them too low a speed to worry about.

Next in strength are head lights, brake lights, turn signal indicators, and fog lights. Of these, headlights are highest, followed by turn signals and fog lights. The retroreflection mechanism is interesting. Light enters one-half of the light and is returned from the other half. I suspect that the light enters one half, hits the back reflector, is focused near the filament, expands to the other side back reflector, and is recollimated returning towards the original source. This phenomena happens over a moderately narrow range of angles directly in front of the car.

Grills, forward facing chrome, and any rounded specular material are the next strongest targets. Look for a bright glint from any rounded surface which always presents one small region facing the source. Flat regions are almost always pointed away from the source and hence do not contribute to the return.

B. Stealth Techniques. (what to do about these Lidar targets)
The license plate is the most important on the front of the car, unless you are blessed with a plate without retroreflectors (The only example I know of this is the old California yellow on blue plates) In some states you can legally remove the front plate. In some states it may be sufficient to paint over the retroreflective paint with glossy house paint to match the color. Check your local laws first. Many states use 3M retroreflective material, which would be difficult to paint over inconspicuously. For these states it is preferable to use a lidar crossection reducing license plate cover. One such cover , is reviewed at the end of this document.

The array of corner cubes in the tail light cover. These are on all cars, and are probably required by law. If you paint them black, a car driving by would not see your car on the side of the road as easily. The only thing I can figure is to get one of the liscense plate covers that block IR, and cut out a piece and glue it over the corner-cube array. (expect new products for this application to come out soon)

Head lamps, turn signal lamps, and fog lights. Get retractable headlights or glue a section of IR absorbing liscense plate cover over your headlights. Remove the fog lights, glue liscense plate cover over your turn signal indicators. The "smoke" headlight covers that are on the market do a fine job of reducing retroreflection from headlights. The down side to these things is that they really aren't legal in most states.

The most extreme stealth includes taking care of all other possible glints. Get a flat black car bra, paint over flat surfaces with glossy paint, paint over rounded surfaces with flat paint. These returns are small compared to the Plates, cornercube array, and lamps.

Lidar (and radar) range goes as the fourth root of return signal power. By eliminating the single strongest return, the best you can hope for is to reduce the range by about a factor of 2 to 4, from reducing your crossection by a factor of 16 to 256. This is because even if you reduce the strongest return by a larger factor than 256, you probably have something else which returns the lidar signal by at least 1/256 as much as this strongest factor. When you eliminate the strong return you still have the other source of returns. To get a range reduction of more than a factor of 4, you probably have to apply stealth measures to multiple reflectors on your car. If you get the license plate, the corner-cube array (back of car only) and the lamps I think you'll get your visibility under the average range at which police target cars.

Jamming Police Lidar

There have been reviews of radar and lidar jammers in which tested products that use these jammer techniques and found they didn't work.

Is Jamming feasible? The two techniques outlined here do not appear to be viable on technical grounds. Assumptions about these techniques are built into the descriptions below, and a more $ophisticated jammer might work.

Is it legal? Jamming lidar is not illegal under FCC rules since they don't regulate this part of the spectrum, but most jurisdictions have a law which makes it illegal to "interfere with the duties of a police officer." I am not a lawyer and the above should not be considered legal advice.

There are two kinds of jamming proposed and on the market -

pulsed LEDs and CW Headlights.

My calculations indicate that neither of these work without combining them with stealth measures. These calculations are specific to the range of 250 meters.

CW Jamming sources.

Headlights aimed into .5 by .2 radian distribute their power over 0.1 steradians, at 250 meters range, this illuminates 6000 square meters or 10^(-6) of the police receiving aperture. 200 Watt lights put 200 microWatts into the lidar gun. Presumably the lidar gun has a narrow band filter passing about 10 nanometer of the spectrum, reducing this CW jammer by a factor of about 40, meaning that the light is now 5 microWatts. The detector is AC coupled so we calculate the shot noise due to this background ShotNoise = SQRT[RecievedPower * PhotonEnergy * MeasurementBandwidth] Sqrt[5. Micro Watt PlanckConstant SpeedOfLight/(900 Nano Meter)*30 Giga Hertz] = 0.200 microWatt equivalent optical power. This is small compared to the 25 microWatts return from a license plate. The Car and Driver article indicates that this jamming technique works, contrary to this calculation, and to Craig Peterson's article.

Pulsed Jamming sources

LEDs:
At a 250 meter range, LEDs broadcast into .005 steradians (.5 radian horizontal times .01 radian vertical) would have to be 500 times brighter than the 25 milliWatts they hit you with to beat the retroreflective paint which broadcasts into only 10^(-5) = ( 4 milliradian times 4 milliradian) return.

This is 12 Watts, well beyond the power of an LED. At shorter range, the problem of jamming is worse. The police lidar power grows as 1/(Range^4) power as the range decreases, and your jammer power grows only as 1/(Range^2). The reason jamming is not feasible is that you have to broadcast into all directions, reducing the power aimed at the lidar gun.

Laser diodes:

The strongest laser diode you can buy is the one they put in the lidar gun (see product data sheet below). Unless you actively steer this jamming signal towards the police lidar gun, it will only be an effective jammer at ranges farther than about 200 meters for a jamming signal broadcast into .005 steradians.

Fighting Tickets

What's "judicial notice" mean? When something has been given judicial notice, it means that the theory of operation has been proven to the court and expert testimony to prove that is no longer needed. Radar is one such example. Aircraft speed traps are another.

Laser, however, has not been proven to the courts, so the prosecution will have to fly in expert testimony to prop up their case and new toy) to prove that their latest gadgetry actually works as advertised.

Laser -cannot- be used while the cop car is rolling. The vibrations would scatter the beam everywhere. I've only been ambushed by a laser trap once, and the setup had one officer doing the laser, another next to him radioing the to the chase vehicles, and 4 or 5 chasers. So, this is hardly a valuable use of scarce police resources!

In cases of aircraft tickets, if someone contests one, both the arresting officer and airplane spotter (or pilot, if the same) have to be hauled into court to say that yes, that driver was the one we stopped. Theoretically the same should happen with laser traps, but don't count on it until someone says something. ("Shhh. It's our secret. Don't let the public know" kind of stuff) One of our members in Texas has been fighting a laser ticket for 2 years now. He's only asked for one or two continuances (extensions) the rest of the time has been the prosecutions fault. Still no outcome. This works to his advantage. Since laser isn't on judicial notice there, they had to fly in experts.

[Also from [email protected], some info on lidar in New Jersey, and who is paying for lidar guns]

State Police based in Morris County have begun using 23 of the $3,800 LTI 20-20 Marksman laser guns. Newspaper accounts say that the new units will be distributed to other parts of the state when a municipal judge convicts a driver of speeding with a laser (i.e., no judicial notice yet). The initial group of units was purchased with a grant from the National Highway Traffic Safety Administration. New Jersey is the 15th state to adopt lasers.