Ghost Laser Warnings - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Rail26 · 04-03-2007, 03:49 PM

Question for all the tekkies out there: I am starting to get a lot of false Laser warnings on my Passport X50. I understand that a lot of new cars these days have active cruise control that follows the car in front of you by using a laser...would this laser happen to be on the same wavelength as the laser detector? What say you?

Side note: All I wanted was sharks with frickin' laser beams on their foreheads.

Cloudsurfer · 04-03-2007, 04:42 PM

I've also noticed that some of the new SUV's brake lights (the newer neon on LED variety) seem to be at the right height to set off my V1 in close traffic.

Patrick

SigmaPi · 04-03-2007, 07:08 PM

Most police LIDAR's work around 900nm range or the just inside the Infra Red spectrum. The are also pulsed lasers as opposed to continuous wave. There may be some other wavelengths used but they are not very far from the 900 nanometer wavelength. Typical beam divergence is .3 meters for every 100m distance or 3 feet per 1000 foot distance. This is a very common wavelength and is used in such applications as medical or dental laser as well as TV remotes. But basically, if you can see the light it's not IR. Taillights and headlights are visible so not in the IR spectrum.

Jeph · 04-03-2007, 08:38 PM

Mine goes off occasionally on a certain stretch of highway (114 here in Dallas) just outside of the airport. I wonder if there's anything at all there that could cause it to go off. Does yours go off where ever, or generally a consistent region/area?

My X50 has never balked at tail lights... and if it did, I'd get a different detector.

There's nothing scarier than that laser warning BLASTING out loud. Ug, I wet my pants JUST a little every time it happens.

I need new seats.

SigmaPi · 04-03-2007, 10:36 PM

Rail,

After a tad bit more research, your assessment might be correct. Vehicles with "Dynamic Laser Cruise Control" might be your problem. I was unable to find exact specs for any of them but clues in my search have led me to believe they use the exact or similar wavelengths as police laser's. If I could get some more specs, I could calculate the divergence for you. If you take the assumptions from my previous post and extrapolate the distances, you could be receiving interference from some cars using DLCC If for example, you are 5000 feet away from an oncoming vehicle and within 15 feet of its centerline you could receive interference. There are quite a few cars with it now, wiki has a list.

I too am in the military and started my officer career as the Airborne Laser Safety officer as well as the targets dude. I was up the road from you at Kirtland AFB and was down at WSMR on a monthly basis. Have fun in El Paso, I got to leave there a long time ago. Actually I lived in Clint between Fabens and El Paso.

Rail26 · 04-04-2007, 02:58 AM

SigmaPi,

Wow, I am glad you had a job with lasers otherwise I was seriously starting to wonder why you knew so much about frickin' laser beams.

Glad you were paroled from this area...I am not a fan of Hell Paso or Fabens for the matter. Thanks for the info...it just seems the frequency of laser warnings have increased and I wondered why.

Jeph, the laser warning sucks...it is full blast immediately...scares the crap out of me also!

z12358 · 04-04-2007, 04:42 AM

Quote:

Originally Posted by SigmaPi

Taillights and headlights are visible so not in the IR spectrum.

Sigma, I'm not familiar with LED tailights but couldn't they be radiating energy in the LIDAR (IR) spectrum, as well?
Z.

Allen K. Littlefield · 04-04-2007, 05:22 AM

[QUOTE=Jeph]Mine goes off occasionally on a certain stretch of highway (114 here in Dallas) just outside of the airport. I wonder if there's anything at all there that could cause it to go off. Does yours go off where ever, or generally a consistent region/area?

Jeph, my laser detector goes off while passing Stewart International Airport while traveling in either direction on rte. 17 here in the Mid Hudson Valley. Something in the airport sets these things off but I haven't a clue what it is. Any more info. from you flyboys??

986geezer

MitchB · 04-04-2007, 07:28 AM

I have had a few false laser alerts near airports as well - maybe some other new technology? I have had them near PHL, ABE and EWR. Other than those false alerts the alarm has only gone off twice for me - so these at least remind me that the function is (somewhat) functional.

BTW - if you can't get the sharks with laser beams at least go for the ill-tempered sea bass.

MNBoxster · 04-04-2007, 08:56 AM

Hi,

There are a number of NAV aids, Meteorological Instruments and such, especially at large airports, which can/will interfere with a Detector. The most likely is the Ground Radar which is used.

I've also heard that several municipalities have installed unmanned transmitters at known speeding locations to purposely trip/negate a Detector in an effort to slow the Traffic...

Happy Motoring!... Jim'99

SigmaPi · 04-04-2007, 10:04 AM

Quote:

Originally Posted by z12358

Sigma, I'm not familiar with LED tailights but couldn't they be radiating energy in the LIDAR (IR) spectrum, as well?
Z.

I guess anything is possible. Typical specs for LED modules in brake lights are around 640 nanometers. Relative intensity peaks at that wavelength but a typical brakelight projects it's light over a range i.e. 620 to 670 nanometers. With that being said, it may produce some IR light. The IR spectrum is huge and starts at about 750 nm all the way out to 1mm. Some laser detector's may have an IR detection range that is from 750 to 905. I don't think this is probable though. Two issues are at hand, cost and appearance of crappy quality. If a detector company chose to employ a photodiode that detected over that wide a range it would be costly. A photodiode that has the ability to view wavelengths over that much range are expensive. I am not sure why a company would want to do this because it would obviously induce more false positives, therefore giving the user the impression it sucks. I am assuming BEL, Cobra etc all use a very specific photodiode with a range from 850 to 910nm. It's cheaper and is made to look for the only wavelength police LIDAR guns utilize today. Long story short, I don't think LED taillights would do it, but I have been wrong before. Something more plausible is the detector may be picking up natural IR light.

I talk to much

shaman1204 · 04-04-2007, 07:27 PM

I was on the highway and my radar detector was going off non stop. Looked up the road, behind me, nothing. Then noticed the Caddy in front of me I was following had the reverse sensors on the bumper, as soon as I passed him, nothing. Not saying this could be the culprit, but you never know.

Uncle Bob · 04-06-2007, 10:10 AM

Quote:

Originally Posted by Rail26

the laser warning sucks...it is full blast immediately...scares the crap out of me also!

No kidding! I loose a couple of seconds off my life each time.

Thanks for all the info, guys, it explains allot. I was ready to send mine in for a $75 repair!!

Rodger · 04-06-2007, 01:24 PM

I got stuck behind a semi truck with LED brake lights between Boise, ID and Salt Lake City, UT for nearly an hour. Every five minutes my Passport Turbo would flip out from a "laser" warning. I finally turned it off.

My V1 has been better at not freaking out from "lasers", but not totally foolproof.

Fire the "laser"!

Switz · 04-06-2007, 02:05 PM

I am quite sure that Infiniti SUVs use laser for their cruise control systems, everytime that I get a Laser warning with my V1 there is an Infiniti SUV lurking.