Radar Detectors

[lanceh007]

I'm thinking about getting a radar detector, but I'm having trouble choosing which one to get. I'm not going to spend much more than $150 so that kinda limits few things. I found the cobra's for a pretty good price, but other places on the net say they aren't very good. One page reccomended the BEL 880 but I don't know anything about it. What would you reccomend getting?

[NSX-R-SSJ20K]

some cops told me and some people i know that Radar detectors are useless

because A) if it goes off you can see them and they can see you

B) something else that i forgot

but C) i think this is bullshit

D) Radar jammers are much better send out that fake Speed bitch

[Neutrino]

Originally posted by NSX-R-SSJ20K

D) Radar jammers are much better send out that fake Speed bitch

Are jammers legal and are you sure they are effective?

[RiceRocket]

i heard that jammers are illegal in some states, but ok in others.

i had a radar detector and my bro had one too, they are totally useless... when the cops actually laser you out, you're already too close to even slow down and they're already right behind you flashing their lights.

it's a waste of money... if you're going to speed, speed wisely and allocate a few hundrend bucks for your next ticket... put it in your budget.

[BigBlock454]

yeah I heard about these radar jammers, and also laser deflectors or whatever, anybody know anything about them, how much they cost and how exactly they work, cuz I was thinking I should get one in the future especially if I get myself a nice speedy car...

[S Brake]

I drove to washington recently with a bunch of friends and our detector saved us a bunch of times, except when the pic was hiding behind an overpass and about 25 feet away from the actual road. there was no way to even see the pig. but when it went off my friend slowed down and pulled to the right lane. the first thing the cop said was where is the detector. we had already unplugged it and thrown it in the back. but if they are legal why do cops care so much.

if money wasn't an issue i'd get the valentine one. they are extremely good but expensive.

[Blackbird01]

Radar Jammers do not work.
I've seen tests performed on several "radar jammer" models.

The best radar detector out is Valentine 1.
I have it. It's save my ass countless times.
And works FLAWLESSLY. It's spotted cops from over 1/2 mile away for me. Only downside is, it's $300.

[RiceRocket]

If you get caught with a radar detector in your car, doesn't matter how legal it would be... it would still look obvious that you are a speed freak. The cop would mark it on your ticket and when you go to court, the odds are the judge would be more against you... so make sure to unplug that thang when you get pulled over...

get very dark tint so while they are walking towards you they won't see you unplugging the thing... he he he

[Neutrino]

Originally posted by snowboarder
I drove to washington recently with a bunch of friends and our detector saved us a bunch of times, except when the pic was hiding behind an overpass and about 25 feet away from the actual road. there was no way to even see the pig. but when it went off my friend slowed down and pulled to the right lane. the first thing the cop said was where is the detector. we had already unplugged it and thrown it in the back. but if they are legal why do cops care so much.

if money wasn't an issue i'd get the valentine one. they are extremely good but expensive.

This is kind of funny if the radar detector is so legal why did you trew it in the back? Feling guilty?
Actually I would do the same thing.

[Neutrino]

Originally posted by Blackbird01
Radar Jammers do not work.
I've seen tests performed on several "radar jammer" models.

The best radar detector out is Valentine 1.
I have it. It's save my ass countless times.
And works FLAWLESSLY. It's spotted cops from over 1/2 mile away for me. Only downside is, it's $300.

But how good are they about fake alerts. I used to own a bell and the fake alerts were driving me nuts.

[Polygon]

Jammers are a hoax they don't work for crap. Do you understand how much equipment it would take to jam a radar or laser signal?

Most of the time the radar detectors are unreliable though the Valentines are the only I would.

[NSX-R-SSJ20K]

Originally posted by Neutrino


Are jammers legal and are you sure they are effective?

jammers are illegal in most places around the world

dunno how they gonna find out you got one unless you do 100 in a 40 and it comes up as 35 or somethihng

[lanceh007]

Well, I don't have $300 to get a valentine 1, but it looks like the Bel is a pretty good deal for the money (or anything less than $150). Even though it does have false alerts, it's better than none at all. If I were to get a ticket, my insurance would go up like crazy, and that won't do. What would you guys reccomend? I'm getting a new engine in my car in a week, and I'll be wanting to test it out, so a ticket is unnactable, and my dad would never let me get near the car again if I got a ticket. THanks for the help.

[kris]

Here is what I posted in the last topic regarding radar detectors:



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.



Original thread can be found here:

http://www.automotiveforums.com/vbul...&threadid=8869

[NSX-R-SSJ20K]

i found a place that sold jammers it was in sweden it was like the eqivalent of Radio Shack only you had to pay 1.50 for a freakin catalog that looked like a leaflet

yea anyway i wonder if they still sell em ...


who makes jammers i dunno that one