Everything I've read states that they don't work.

One site claimed that previous models worked, but that the guns (especially radar ) are getting software updates that allow them to deal with the jamming signals. That would mean that EVEN if they do work, you'll be in an arms race that you probably can't win.

If you really want the answer to the Xenon spectrum question, try CAndlepower forums. Those guys will KNOW this off the top of the heads. If you don't believe me, take a look at some of their forum discussions. They have way too much free time and engineering experience on their hands.

http://www.candlepowerforums.com//ubbthrea...hreads.php?Cat=
There's great info there about high end flashlights, and since the Xenons and HID lamps are (to them) just flashlights with a really big carrying device attached, I know that they've discussed these issues to death and back already.

 

MacGyver,

You're not accounting for the fact that the beam is only nicely collimated on the way to the car, and not on the return.

Have a friend hold a laser pointer beam on your license plate, and walk around the car. Can you see the red dot from the entire hemisphere in front of the plate? If so, it means once the return of the projection on your car is, as you put it, "spraying/flooding" the entire area in front of your car, at all angles, in three dimensions.

Add to that the fact that the nicely collimated beam is 3ft in diameter by the time it gets to your car 1000ft away from the lidar gun (rather than the nice dot you get from the laser pointer at short range) and has to travel all the way back to the gun, giving an in-car light source a 4x power advantage.

The only surface that would send back a nice beam to the officer is a perfect mirror, but would also be error-prone as the beam would have to hit the mirror at exactly 90degrees on every axis, if the receiver is in the same spot as the emitter gun. The officer by the side of the road would get nothing back unless he puts himself directly in the path of your car (or stands in the correct place on a curve).

It would be interesting to use a video camera (CCDs are sensitive to IR light from remote controls and lidar) to check which of the in-car laser emitters are strongest and to plot out the coverage pattern. You should easily be able to trigger the countermeasure system with any remote control in the house.

I believe lidar devices will eventually modulate the pulses chromatically or by varying the pulse length in a certain sequence in order to distinguish their own returns, but for now I have very little doubt a well-deisgned $200-300 IR LED-based pulser would work.

-- Alex.

[QUOTE]Originally posted by MacGyver
[B]Randy, Use of the same (or similar) laser diodes is an option we considered, but the expense is significant, as you suggested.

 

Wow, this is an old one...

Yes, and no. While I can't give specific power figures once it hits the car and bounces back, I would bet good money the return figure is significantly higher than anything broadcast at a wide angle from the car itself. Not much use in arguing this point, though, until someone CAN give us some useful figures.

True, the return happens in a hemisphere spreading the energy over a large region, but a significantly larger portion of the return will be along the angle of incidence/reflection. Think of it this way...have some one stand in 5 feet in front of you and yell. Now have them face away from you and do the same thing. When they're facing you the yell seems louder, even though BOTH are spreading their vocal energy over an ever increasing sphere.

I'm not sure how you came across the 4x advantage (maybe you were just using it as an example value), but as I stated in the first paragraph, I would bet good money the return seen by the LIDAR gun is significantly large than anything being squeezed out by the car units.

Saying the officer will get nothing back should be obviously wrong to anyone who has ever received a ticket from LIDAR. Our cars are again obviously not perfect mirrors, yet the return beam is strong enough for them to take accurate measurements of our speed. A signal is returned at angles other than 90 degrees because almost every surface out there (certainly anything on the front of our cars) has texture to it (even with 10 coats of Zaino...STEVE! ), and texture means lots of surface with angles.

Unfortunately a CCD camera would probably not give us the info we need. It certainly won't be able to tell us how strong each unit is since we have no way of measuring the signal strength. We can't say one has a stronger signal merely because the spot is brighter...that could merely mean the signal is more focused. Once the CCD has autoleveled itself to the bright spot in the canter, it won't be sensitive enough to show much outside of that point, so seeing the pattern in 2D or 3D will be impossible. Also, some systems won't trigger unless it sees the right frequency of chirp come across, so a TV remote may not trigger it (I don't have a clue one way or the other on this one, we'd have to do trial and error).

I also believe LIDAR guns will become more advanced as people find way to TRULY beat them. I also believe some of us could make an LED-based defeater, but I'm not so sure I would agree with your price point. It's going to take a lot more energy than a standard IR LED, so the price will start to rise. I'm thinking something along the lines of $500 (cost, not sale) to get a workable solution.

-- Alex.

[/B][/QUOTE]

 

The area where the reflection is strongest depends on the properties of the material and angle of incidence of the beam, and will not necessarily be "towards the source". The larger the angle and the more mirror-like the surface, the more of the beam will go to the opposite side of the road from where the cop is standing, assuming the surface is perpendicular to the axis of travel (as is the front of your car as a whole).

Quote:

I'm not sure how you came across the 4x advantage (maybe you were just using it as an example value), but as I stated in the first paragraph, I would bet good money the return seen by the LIDAR gun is significantly large than anything being squeezed out by the car units.

The 4x advantage comes from the halving of the distance traveled.

[B][QUOTE]
Saying the officer will get nothing back should be obviously wrong to anyone who has ever received a ticket from LIDAR.

 

Wow, this again? I haven't stopped by here in a while and look what has resurfaced...

Mail me the check!

Just to enter a dose of reality over theory in this discussion, I have had my Lidatek successfully jam an officer in the act. (Posted the whole interaction back in July, the 5th was it?)

He was baffled, asked if I had a jammer 'cause his unit "beeped back at him", then said, "This is your lucky day" as he handed my license back to me.

Since the Lidatek uses the same diode as LIDAR guns and has actually worked in (literally) real-world circumstances...need I say more?

Enjoy,

Randy

PS: At $50 per contested ticket, even here in CT w/highest ticket rates nationwide, a $300+ Lidatek would require 7 jams to pay for itself. I enjoy it's entertainment value as well, but financially it's cheaper to simply show in court for the discount rate.