Radar Gun Fundamentals

On Fri, 27 Oct 2006 13:45:43 +1000, Clifford Heath Gave us:

Wrong. Nice try though. In auto radars, it is where the radar acquires the fastest article in its field of view, but the cop incorrectly chooses the wrong vehicle as being the vehicle that was traveling at the clocked speed. It is the very reason that radars are successfully fought in the courts of many states. Cop pops a radar scan down twenty cars on a highway, but picks you as the one that was pegging the radar gun. Lots of room for human error there.

Looking down a road on an angle changes the operation of the device not one iota. It takes a reading in its FOV rather quickly, and it does it well, regardless of whether you are approaching it, receeding from it, or crossing its field.

Does the radar automatically correct for the angle?

I would expect that a LIDAR gun uses something similar to a direct-sequence spread spectrum pulse of LED flashes that it correlates to back on the receiving side. That would make it rather difficult to jam!

Anyone know for certain?

JoeBloe is ignorant ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

One of the car magazines did some real world testing and the best "jammer" was a set of very hot driving lights. It drives the preamp into saturation. Once the car gets close enough the gun can more selectvely choose a spot to look at and it gets a reading.

Legally the cop is supposed to identify a suspected speeder and then use the guin to verify his suspicion. We know that is not really the way it works, particularly with a radar trap. A guy with a good radar detector can easily "frame" an innocent driver by slowing down at the right time and making the guy going the legal speed look like the bad guy.

Of course not. It doesn't know what the angle is! It can only measure direct closure (or its opposite) between the gun and the target. So, unless you are directly in front of, or behind the target, you get a certain amount of error. However, that error is in the targets favor, so it doesn't help you in court! And a laser can still get the wrong vehicle, it depends on how good the aim of the user is...

Charlie

Yeah, that's understandable. I'd think the guns would have an overload detector (just as some contemporary radar guns have jammer detectors), although perhaps with a *pulsed* set of ultra-bright lights you could avoid the overload detector triggering (since presumably it needs some filtering to prevent falsing when, e.g., the cop swing the gun around and it briefly stares into a headlight or the sun or whatever).

True enough, I suppose... although it's at least a little harder than a cop simply claiming outright you were speeding and the court taking his word alone?

What part of the body is the petar(d)? And have you ever been hoisted by yours? That must really hurt. =:-O

Thanks, Rich

Cheers! Rich

There are a couple of spots in Whittier where you're on the honor system - they have those "your speed is" displays (solar-powered) in a couple of school zones, or where the limit changes from 45 to 30 or so.

Very fascinating displays - they're those little mechanical flipper pixels (a little flapper, black on one side and yellow on the other), with an interesting twist - if the number is over, say, 35 (or whatever it's set at), the yellow pixels flash orange.

Cheers! Rich

A petard is a portable bomb with a "slow" fuse attached, used in the case cited by Shakespeare to blow a hole in a fortification. Typically an engineer would dig a tunnel under a wall, place his petard, and light it, and then try to get away before the explosion. Sometimes the wall came down, sometimes the engineer went up.

You've got to read the classics more Rich. I believe a petard is either a type of morter/cannon or similar to a satchel charge. (gee, maybe I should read the classics more myself and find out) M Walter

Interesting anecdote I read. Someone circa 1940 built just such a device. It was for an electronic exposition. The engineer's were worried some Scotish officer would show up in kilts.

M Walter

I knew that, you dingleberry. That's why I thought I was qualified to make what I thought was a joke.

Here's one for ya:

Why did the dyslexic cross the road?

Cheers! Rich

"Joel Kolstad" wrote in news: snipped-for-privacy@corp.supernews.com:

AFAIK,laser speed guns send out a 904nm laser(not LED) pulse train of about

500pps,a PW of ~30ns,and measure consecutive pulse returns to determine distance travelled in the time between pulses,IOW,a repetitive rangefinding then calculating speed for that time interval.Got that from a laser industry magazine article many years ago. Today's laser guns probably have some sort of "jam" detection,perhaps by audio like the radar runs.

--
Jim Yanik
jyanik
at
kua.net

You are taking his word alone no matter what. The gun does not take a picture or anything. It is only his word about what it read and which car he was pointing at. They don't let you get out of your car and go look at the radar.

The problem is "so what" the fcc does not regulate IR transmissions.

On Fri, 27 Oct 2006 13:56:20 +1000, Clifford Heath Gave us:

They do once they pass through the optics, you retarded f*ck. Any laser bench setup (which these are even at the micro-size level they are at) has optics.

When such light hits the target, very specific reflection are noted. The range finders use a serial pulse to determine distance, and do so quite accurately. The speed determining circuitry in the police variant of that same range finder is not plagued by ANY error producing problems. They are dead accurate, and do not need any calibration on a per use basis as radars do. They get calibrated at the factory, and periodic verifications of that calibration are made in service.

Radars require calibration before each shift that intends to use them. Said calibration is done with an audible tuning fork device.

You're an idiot. No one is arguing basic laser optics here, dumbfuck.

There is no IR beam. They are aimed optically by the user.

A single beam is used, and it is in the visible spectrum.

Go teach some elementary school kids your basic crap. You aren't enlightening anyone here, and we don't need your primer.

That's funny.

The EARLY lasers that were pointed at the moon were indeed miles wide by the time they got there. Much less so now with the better lasers that we have for that purpose.

You're fundamentally full of shit.

You're an idiot.

No, it is nearly impossible, actually.

Wrong. They pulse a data stream. They capture the stream on return. If a "bad" stream is encountered, the test runs again. It doesn't make a determination with errant data, it runs the routine again, until it gets verifiable data.

You're an idiot. The pulse train sent by the laser in the gun is the pulse train it detects coming back. It ignores all your "false fool it" baby bullshit, and any other crap you make up. It has nothing to do with directionality of the receiver. The field of view of the receiver is very narrow in fact. Less than one degree.

On Fri, 27 Oct 2006 00:28:22 -0400, snipped-for-privacy@aol.com Gave us:

Perhaps you should f*ck off.

This has nothing to do with fire control, you retarded twit.

It has to do with a group of cars, and the human error of a cop choosing a car that was not the fastest car in the pack.

Funny that you have even proven yourself to be stupid.

You're an idiot. The difference is negligible and the industry has done nothing to deal with it since it is negligible. Radar guns are VERY accurate. The problem is when there are several cars in a pack of moving cars. The radar only details the top speed in the test window, it does not determine the culprit. Laser guns ONLY give the speed of the target vehicle they are applied to.

THAT is the difference.

Bullshit. They detect perpendicular crossing traffic speed as well as ANY angle of incidence to the target FOV as well as any directly on axis targets. Pretty much blows your bullshit, ass zit from sittin' on it too much made up theory right out of the water.

Again, you're an idiot. The speed of the EM pulse is far faster than the targets they are capturing reflected data from The difference is less then a single MPH throughout the spectrum of variance you piss and moan and make shit up about.

Total proof that you are a big f****ng dope. Radar guns work just fine on perpendicular crossing traffic.

Nope. The gun shoots at a field or window of sensitivity. Any moving object in that window get pegged multiple times, and its speed is determined no matter where it resides in the field of sensitivity, nor what direction it is traveling in said field. With the laser, a specific car is targeted, and it is that car's speed that gets reported, period. No matter where the car gets "shot" at or from.

Also a non issue. Radar guns can work effectively out past a half mile range, and none are used at those lengths so you are again lost.

You're a total dweeb. You went through your entire life making crap up.

Just so you know... you have been doing a poor job of it.

You're an idiot. Radars work. Lasers work. One is 100% accurate, the other is 100% accurate but doesn't define the target in multiple, group element settings. That is its only flaw.

I have a bridge in Brooklyn I can sell you.

Dude, you have been reading too much bullshit, and then you make up your own to add.

When do you get the autoclave?

Dude. You're full of shit, and you need help spelling.