Good radar questions

[MOUNTAINWOLF]

1. If you are driving and see an oncoming patrol car, do you slow down even if your radar does not go off, or just keep cruising ?

2. Can a cop with radar tell if you have a radar detector without stopping you? In other words does his radar detect the dectector ?

3. If you are in a group of cars or just driving alongside another car going fast and a cop approaches with radar on, how can he tell which car he is detecting the speed of ?

 

[Tiepilot]

1. Slow down if you are speeding.

2. No, there is no such device.

3. The radar emits a Doppler tone, the higher the pitch the faster the speed of the target. Radar can not pick out a single vehicle that is in a group. The Officer must visually identify the vehicle speeding and estimate it’s speed. The radar has to contact the speeder and several things must happen in order for you to single out who is speeding.

1. The radars ground speed must match the patrol vehicles speedometer (within reason).

2. The target speed indicator must coincide with the Officers visual estimate of the speeding vehicle.

3. The Doppler sound must coincide with the target speed and be steady.

This is how you can pick a speeder out of a crowd, but it only works sometimes as the reflective capacitance of the surrounding vehicles affects the beam.

Only laser can positively and easily pick a speeding car out of a crowd.

 

[monnieh]

Is there any good radar absorbant material available for comuser use?

I know RAM was very expensive when the materials first came out.

 

[phiebert]

Go find a wrecker that had an old Stealth bomber, peel off the nose cone and apply it to your grill. That should help.

PS, my Valentine picks up other people's cheap detectors. That is if I pass a guy that has an old detector my detector often goes off. The old/cheap ones must be very leaky and produce their own radar (not intentionally). So theoretically a cop could also detect a detector if it was a crappy one. But from what I've experienced, it's their eyes that detect your detector on your windshield!

Has anyone ever had any success with radar jammers? I suppose they would work if they just flood out radar in all frequencies but can they send out laser beams accurately enough to confuse that signal too?

By the way, my Valentine picked up a cop coming home from our Autocross event this last weekend from nearly 3 miles away. Lots of time to fine tune my speed!

 

[Viperfreak2]

Of course there's such a thing as a radar detector finder! Virginia and Canada have been using them for years.

 

[joe117]

In the lab, I adjusted the local oscillator of a radar detector so it would detect the local oscillators of other radars. So I know it can be done.

A good way to reduce your radar cross section is to cover your headlights with a very light shade of window tint plastic.

There isn't any radar absorbing material that is practical for a car.

Tiepilot, what do you mean by this?
"but it only works sometimes as the reflective capacitance of the surrounding vehicles affects the beam."

 

[SylvanSRT]

i believe the detector-detector is called the VG-1 and it picks up on stray waves(dont know the kind or freq.) and these set off this device. i dont know how many states have anti detector laws but my guess is these would be the only ones using VG-1 devices. the valentine V1 does not emit these waves and should be invisavble to VG-1

 

[GR8_ASP]

1. If you are driving and see an oncoming patrol car, do you slow down even if your radar does not go off, or just keep cruising ?

2. Can a cop with radar tell if you have a radar detector without stopping you? In other words does his radar detect the dectector ?

3. If you are in a group of cars or just driving alongside another car going fast and a cop approaches with radar on, how can he tell which car he is detecting the speed of ?

1. Yes, slow down. The police can ticket you for observed speeding, even without radar. I think just about any of them can tell when you are going more than 10 over. And to continue to do so in front of them is just plain asking for it.

2. Yes, but most states do not attempt to do it. I know WV and Canada do.

3. Radar cannot select which vehicle. It is noprmally in the mode where it selects the highest speed from a fairly wide approach angle. The officer must identify which vehicle is the one, and often is mistaken. The old adage about only the larger vehicle is seen is no longer true. Modern radars identify a relatively small target with larger targets nearby without a problem.

Note also that radars work on a doppler or frequency shift of a pattern of radio waves directed out of and received by the radar unit. Most radar detectors work by creating a similar wave and measure for changes in the wave magnitude. That is how they are detected in that they are emitters as well as receivers. The Valentine, and other expensive detectors, emit very little and thus are nearly undetectable.

 

[ceieio]

Mountainwolf - you have a PM.

 

[RonC]

Note also that radars work on a doppler or frequency shift of a pattern of radio waves directed out of and received by the radar unit. Most radar detectors work by creating a similar wave and measure for changes in the wave magnitude. That is how they are detected in that they are emitters as well as receivers. The Valentine, and other expensive detectors, emit very little and thus are nearly undetectable.

Uh, don't think so. Radar detectors do NOT emit radar signals of any kind on purpose. Any leakage is unintentional and due to the fact that any high frequency signal propagating on a wire, printed circuit board or what have you can and will radiate into space. Sheilding the oscilators and other components help to alleviate this problem but cannot eliminate it completely. The reason that "radar detector detectors" do not work on newer detector models is because the companies got wise and changed the primary oscilator frequencies, making a specific radar detector detector temporarally obsolete (plus better sheilding).

Radar detectors are receivers + microcontroller + programming, that is it.

Ron

 

[joe117]

RonC is right, any signal from a radar detector is an unwanted by product.
The receiver used in radar detectors needs to produce a local oscillator signal. It uses this signal to mix with the incoming, reflected signal in order to produce the intermediate frequency that it uses to filter out unwanted signals.

In states where detectors are illegal, the cops might look for your LO signal. A good detector will have a reduced LO leakage.

Military aircraft go through quite a bit of testing in order to make sure there are no stray signals coming from electronic equipment on board.

This testing is called "tempest" testing.

During WW2 there were a few cases of the German night fighters using stray signals to find bombers in the dark.

 

[GR8_ASP]

Thanks RonC. What you said is what I was trying to say. That is there is aoscillator, or wave generator, in the detector and that it is leakage that is emitted. I did not mean that intentionally emit external to the unit. Sorry for the confusion.

 

[Tiepilot]

Tiepilot, what do you mean by this?
"but it only works sometimes as the reflective capacitance of the surrounding vehicles affects the beam."

Hi Joe,
I was a traffic cop for many years and I used many different laser and radar units. I was able to select speeders out of packs of cars easily and what I found to be true was that if there were larger vehicles with the pack they would reflect more of my beam. I would have a high doppler tone and get a target speed of the larger vehicle. The tightest band width radar I used was "Ka" and it still suffered from the reflective capacitance of larger vehicles. Most often you could get a positive lock and coupled with the other factors that you must verify it always resulted in good cases. The biggest factor is the officer and his experience.
The unit of choice was laser as it suffered none of the problems that radar encountered. The cars that were the hardest to lock on with laser were the newer stlye Trans Am's as they were rounded really well. I never shot a Viper though, everything else was a duck shoot.

The best way to defeat laser is to hide your headlights, put those ANGLED tag, headlight, taillight and fog light covers on your car. The beam requires arrow straight contact with the vehicle to strike and return back to the unit.

I'd be glad to be a sounding board for any questions you guys might have and give you a cops perspective as I did the job for 12 years. So, the theory and the what not you guys have I can answer with real life experience.

 

[joe117]

I see what you are saying TP. My question was about "reflective capacitance". Without putting words in your mouth, I think you just mean large reflection. In the trade, the size of the reflector is called the "radar cross section". The term capacitance has an electronic meaning but it doesn't have anything to do with radar.

And when you say Ka has the tightest band width I think you mean beam width.
The X band and Ka guns both have about the same size antenna in the gun. The Ka is 2 times the frequency of X band. That means that the wave length of Ka is half that of X. If the antennas are about the same size, then the shorter wavelength will cause the antenna to have higher gain. That simply means that it will have a narrower beam width. This will make it cover a smaller area when you point it, just like a narrow beam of light compared to a wider beam.

My front license plate has reflective white paint on it. I always wondered if I could get away with repainting it with regular white. It would still reflect laser but not as well. Who would know?

 

[monnieh]

I'd be glad to be a sounding board for any questions you guys might have and give you a cops perspective as I did the job for 12 years. So, the theory and the what not you guys have I can answer with real life experience.

Oh, brother, I have a bevy I can throw at you.

1) Do bra's help defeat radar/lidar?
2) What's the most effective way to defeat lidar from your personal experiance?
3) Is using tractor trailers and other big vechicles truely effective? (seems to work for me)
4) Do he bear trackers work?

I have alot more. I must tell you I find my local traffics cops nothing more than unlawful tax collectors and a menance to commuters. They have never once done anything positive for me.

 

[RonC]

Tiepilot, what do you mean by this?
"but it only works sometimes as the reflective capacitance of the surrounding vehicles affects the beam."

Hi Joe,
I was a traffic cop for many years and I used many different laser and radar units. I was able to select speeders out of packs of cars easily and what I found to be true was that if there were larger vehicles with the pack they would reflect more of my beam. I would have a high doppler tone and get a target speed of the larger vehicle. The tightest band width radar I used was "Ka" and it still suffered from the reflective capacitance of larger vehicles. Most often you could get a positive lock and coupled with the other factors that you must verify it always resulted in good cases. The biggest factor is the officer and his experience.
The unit of choice was laser as it suffered none of the problems that radar encountered. The cars that were the hardest to lock on with laser were the newer stlye Trans Am's as they were rounded really well. I never shot a Viper though, everything else was a duck shoot.

The best way to defeat laser is to hide your headlights, put those ANGLED tag, headlight, taillight and fog light covers on your car. The beam requires arrow straight contact with the vehicle to strike and return back to the unit.

I'd be glad to be a sounding board for any questions you guys might have and give you a cops perspective as I did the job for 12 years. So, the theory and the what not you guys have I can answer with real life experience.

With all due respect TP, except for laser, there is no way you can verify which vehicle you are reading. Since you have no visual way to know (ie. no CRT) you cannot guarantee which car is on your readout. Condidering the scattering that occurs, reflections etc. the only time you can be sure is if it is the only car on the road. Now I am not saying that radar cannot be accurate (although that is an entirely different conversation and that too is debatable) but if you have more than one reflective target, your guess is as good as mine as to who it was that you just got that velocity reading from. So in effect you were always guessing.

Ron

 

[joe117]

You didn't ask me but I can tell you about #1.
A bra won't do anything for radar.

The laser will reflect best from a retro reflector. A retro reflector is a thing designed to reflect light right back to where it came from, like a street sign or reflective safety tape.
Your headlight, taillight, reflectors are retro reflectors.
The next best thing to reflect laser is a flat white painted surface.

The worst reflector is a smooth, curved, black surface.
A smooth, curved, dark surface will absorb quite a bit of the laser energy. The energy that is reflected will not be returned to the lidar.



So, my answer is that a bra will probably not help you and very well might hurt you.

 

[joe117]

If you have a radar antenna that is 6" in diameter and your frequency is 24GHz, that's Ka band, your -3dB beamwidth will not be better than 6 degrees.

This calculation gives an answer that is the best theory predicts. In the real world, the beam will probably be wider than 6 degrees.

If the antenna is smaller than 6" in diameter the beam will be wider.

So, how wide a spot is 6 degrees? Well, for comparison, the sun or moon in the sky are 1/2 degree wide. So it would be 12 sun widths.

Someone who remembers their trig functions could tell us what the base of the triangle would be. Figure the cop is, say 1000 ft from you and the apex of the triangle would be 6 degrees. The base would be the field that the radar would see. The angular resolution.

 

[monnieh]

thanks Joe, thats good info. I don't have a front lic but the headlights and my silver stripes are good reflectors.

I guess I could put some kind of light tint film over the headlights (very poor solution) but don't know what to do about the stripes.

The highway unlawful tax collectors on my commute all use lidar for the most part. Wonder if the bear tracker would pick them up.

I have already had 3 scares where I was going with the flow of traffic, spotted the HUTC slowed and watch him put his bike in gear an pull out. 1st got the 350Z coming up next to me, second got a modified miata coming up next to me, and third was using a 18 wheeler for cover. I wonder how many people have gotten tickets zooming up to race me when they did not see the HUTC?

 

[joe117]

A quick trig review shows the beamwidth at 1000ft is 104 feet. Any cars within 104 feet of one another, will be in the radar beam.

 

[MOUNTAINWOLF]

ceieio, check PM.

 

[Tiepilot]

HI Joe,
My bad,I meant capacity (objects ability to absorb) as in if you were in your Viper driving beside a tractor trailer the radar would not see your car because of the reflective capacity of the tractor. I've seen cars go flying by a big truck and all the radar could get was the speed of the truck, and a high doppler tone of the speeding car. That situation demands no action be taken by an officer.


Hi Ron,
Your not correct assuming I guessed which car was speeding. There are factors involved that make the id of the speeder rather easy. The most important thing is visually tracking the violator and estimating his speed. So, if a pack of cars is coming toward you and doing 45mph and the speeder is doing 60mph or better you can see him passing cars. The radar will see the speeder by doing two things, a clear doppler tone and a target speed.

Depending on whether you are operating stationary radar of moving radar you have to confirm your ground speed with your speedometer and the radar ground speed. When these factors agree you have your speeder. No guess work.

Now what happens sometimes is that other cars will reflect your beam and display that cars low speed while you hear a high doppler tone which indicates you are also contacting the speeder. In this case you take no action, action is only taken when you have a positive target speed coupled with a doppler tone and it matches your visual estimate of the cars speed.

Radar is by no means selective it bounces off of everything it hits and the operators experience is what makes the tool work.

Monnieh,

1) Do bra's help defeat radar/lidar?
I found that bra's will not reflect the laser beam back well enough for the unit to get a reading. I used to aim at headlights, foglights and any flat frontal surface I could see. Radar is a tough one as you have to have a way to absorb it or most of it so that enough of the beam can't make it back to the unit.


2) What's the most effective way to defeat lidar from your personal experiance?
Those angled stealth covers deflect the beam at an angle and not directly back to the laser unit.


3) Is using tractor trailers and other big vechicles truely effective? (seems to work for me)
Yes, they eat up the radar beam because of their size


4) Do he bear trackers work?
Dunno what that is.

 

[MOUNTAINWOLF]

Thanks for the good replies. Tiepilot, travelling on the interstate quite often, I have been involved in (as I'm sure most others have) sort of a "fast" caravan of vehicles. That being when you find yourself going above the speed limit along with a few other vehicles, no verbal agreement or anything, just that you all know that you feel safe travelling at a certain speed and you all stay close together. Eg: Say I am travelling I-575 with three other vehicles of roughly the same size ( eg. all SUV's), two in the left lane & two in the right forming sort of a square, and we are doing 90 mph in a 65 zone. From what I understand, an oncoming officer shooting radar would not be able to actually tell which vehicle his signal was coming from (no visual help because all are travelling the same speed). Could he legally turn around and pull any one of the vehicles ? I have heard that an officer will then pull one of the front vehicles to make an example, but is that legal ? What would you do as that officer; let the caravan go, or pull one and write the ticket ?

 

[Big Medicine]

4) Do he bear trackers work?

Yes, they do. Mine has worked several times in instances where the HP was over the hill, around a curve, & VERY selectively targeting vehicles with instant Ka band. So selectively in one case, my detector never went off till he gunned the guy flying up behind me. He actually passed me over, prolly cause I wasn't speeding. You see, his radio was on & everytime dispatch keyed their mich, his secondary transponder went off, alerting me to his presence from a couple miles away. I adjusted my speed & cruised past. The guy behind me wasn't so lucky.

I was skeptical at first, but after having been saved by one on the road, verifiable, I can tell you without question that they work in INDIANA.

 

[Roadkill]

Thanks for the good replies. Tiepilot, travelling on the interstate quite often, I have been involved in (as I'm sure most others have) sort of a "fast" caravan of vehicles. That being when you find yourself going above the speed limit along with a few other vehicles, no verbal agreement or anything, just that you all know that you feel safe travelling at a certain speed and you all stay close together. Eg: Say I am travelling I-575 with three other vehicles of roughly the same size ( eg. all SUV's), two in the left lane & two in the right forming sort of a square, and we are doing 90 mph in a 65 zone. From what I understand, an oncoming officer shooting radar would not be able to actually tell which vehicle his signal was coming from (no visual help because all are travelling the same speed). Could he legally turn around and pull any one of the vehicles ? I have heard that an officer will then pull one of the front vehicles to make an example, but is that legal ? What would you do as that officer; let the caravan go, or pull one and write the ticket ?

I've seen em pull over the entire pack here in California.. 7 cars at once.. pulled up and pointed them all over to the side.. pack attitude can just get everyone a nice speeding ticket, so i wouldn't rely on it.

 

[BruceW]

What is the model number for the bear tracker? I did a search at the Uniden site and couldn't find it nor could I find a link to an older thread where I thought I saw it listed.
TIA
Bruce

 

[Roadkill]

Bruce,
Check this thread.. there are a few links to beartracker pages..
http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=genvipdis&Number=261107&page=0&view=collapsed&sb=5&o=&fpart=1

 

[Daffy Duck Viper]

BearTracker BCT7 Police Locator...

Scannerpro.com: $164.99
http://www.scannerpro.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=AW&Product_Code=BCT7&Category_Code=

Dmart2000.com: $165.88
http://www.dmart2000.com/bcunbear80pr.html

SamsDiscountStore.com: $175.00
http://www.samsdiscountstore.com/beartracker.html

Globalmart.com: $199.95 - normally: $320.95. You save: $121.00...oh boy!!!
http://www.globalmart.com/page/b/bct7.htm


Ammtech.com: $199.99
[url="http://www.ammtech.com/bct7.htm"]http://www.ammtech.com/bct7.htm

In addition to the BCT7 unit, there is a BCT-12 unit, but it does not sound near as good.
http://www.radartest.com/article.asp?articleID=8000

Uniden.com (information)
http://www.uniden.com/product.cfm?product=BCT7[/url]

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[joe117]

The protection you might get from being near a big rig, isn't based on the tractor trailer absorbing the radar signal.
It's the strong reflection from the big rig that captures the AGC, automatic gain control, of the radar.
When there is a very strong reflected signal, the radar automatically turns down it's sensitivity. The reduction of sensitivity keeps the radar from seeing the smaller target.

 

[Blue Pilot]

Here is another question for you radar guru's out there. I was once told by a cannon baller that they install aircraft transponders on their cars. This person stated that the transponder, when close to a police radar unit, sends out such a strong return signal that it will fry a police radar unit when close. For those of you that do not know what a transponder is, it is a device used on airplanes that responds and sends a signal back to the tracking ground station. Sometimes these radar antenna's are over 100 miles away that the transponder is 'talking' to and therefore sends out a very strong signal.
Is there any truth to this persons claim?
(I also know this is illegal!)