Hey I was wondering...
What is the area covered by a LI jammer head at 1000ft?
I know the diode is polarized, and I am trying to picture the coverage in my head.
Thanks,
-Oyu
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Hey I was wondering...
What is the area covered by a LI jammer head at 1000ft?
I know the diode is polarized, and I am trying to picture the coverage in my head.
Thanks,
-Oyu
This is a good question, and relates to one I've wondered about -- mounting non-recessed so as to have good reception of an over-pass or off-angle type shot... but the dispersion of the responding signal is still straight down the road to whatever dimensions it has... I'm not totally understanding how the counter-measure works in those kinds of Lidar shots.
Cal
I wonder the same things..
someone help us!
Oh hey Cal, nice car/laser combo. Did you ever post your install pics? I'd really like to see. I think I'm gonna get a 550i and I need ideas. =)
Ty
-Oyu
EDIT:
Nevermind... Found it! :D http://www.kodakgallery.com/gallery/..._photos_button
Assuming an Osram SPL PL90_3 (75 Watt) pulse laser is used without lens:Quote:
Originally Posted by Oyusan
Horizontal around 2x 20deg : (sin(20) * 1000ft) * 2 = 700ft
Vertical around 2x 7deg : (sin(7) * 1000ft) * 2 = 250ft
So this laser would project an oval of around 700x250ft @ 1000ft distance
At the edges the intensity of the laserlight is around 20% of the intensity in the center.
By using a lens in front of the laser, you can change this pattern of course.
Thank you, this answers my question. I wonder how the LI lense focuses them.. like if they make the beam smaller but more powerful for an area.
Yes I did: http://www.radardetector.net/forums/...-bmw-550i.htmlQuote:
Originally Posted by Oyusan
Bump
Any comment on the LI's signal beam dimensions related to hitting a Lidar gun on an overpass or serious off-angle? How does that work, anyway, since we work so hard to get the alignment level and down the road?
Keep in mind that the gun has to look into the beam's source for reflections so it is more than the beam size being projected that comes into play.
OK... but I still am not "seeing" how the emanation from the jammer diodes hit the off-angle gun to jam, IF it has a similarly tight dispersion dimension. Maybe it doesn't, I'm not sure but someone here surely knows how this works.
It has to do more than just hit it to jam it. Sunlight "hits" my eyes all day long, but it doesn't blind me until I look straight into it.
Right... here's a simplified version of the question I'm puzzled with - we strive very hard to get the LI's (for example) aligned exactly perpendicular to the horizon, shooting right down the road, not to the side, up, or down. And, we strive to have them exposed for receiving Lidar signals from above or from the side for so-called off-angle shots. But if the jamming beam is relatively columnated (low dispersion), then how do they hit those off-angle Lidars in response to their ping? And, if on the other hand they are highly dispersed responses to hit off-angles, then why do we work so hard to get exact perpendicular alignment?
I'm sure there is a clear answer, I just haven't read it anywhere here.
Thanks in advance,
Cal
The total beam divergence for the Osram SPL PL90_3 that the LI (and probably other diode jammers) uses is 11 (+/- 5.5) degrees vertical and 25 (+/- 12.5) degrees horizontal.
http://catalog.osram-os.com/catalogu...00a3dd000100b6
Is this what you are looking for? I found this on a BMW forum.
That is the easy part to answer. It's because you never know what your next encounter will be. If you start off with neutral alignment, then you are equally protected in all directions. If you start off with them favouring one angle, then every other angle will always be underserved.Quote:
Originally Posted by calpalmer
That link isn't working for me... but these angles are helpful, much larger than I somehow had imagined. Thus it explains the main question, how can it respond and jam a serious off-angle hit. It also makes me realize that while alignment is very important for the reason SS states in his response, general jamming performance for much of the threat isn't highly compromised with SLIGHTLY misaligned heads. 25 degrees horizontal is a pretty wide sweep!Quote:
Originally Posted by category4
Thanks for the information,
Cal
Try this:Quote:
Originally Posted by calpalmerThat link isn't working for me... but these angles are helpful, much larger than I somehow had imagined. Thus it explains the main question, how can it respond and jam a serious off-angle hit. It also makes me realize that while alignment is very important for the reason SS states in his response, general jamming performance for much of the threat isn't highly compromised with SLIGHTLY misaligned heads. 25 degrees horizontal is a pretty wide sweep!Quote:
Originally Posted by category4
Thanks for the information,
Cal
http://catalog.osram-os.com/catalogu...00a3dd000100b6
But install is everything, 1 degree may not be much, but 5 is trouble!!
That worked. Thanks!
Using Fulcrum's numbers of 750' wide by 250' high at 1000' distance and the heads level, the beam would be 125' high above the road (with 1/2 the beam hitting the road), 67' high at 500' and 33' high at 250' feet.
I don't see a typical overpass being much higher than that (clear a 13' semi + 4' to spare + 3' thick girders and a 3' guard rail = 23' high.
Hmm...thinking about 1/2 the beam shining on the roadway makes me wonder if heads should be angled up just a smidgen.
It's made us all think that. This is not groundbreaking thinking. But you never know where that next shot is coming from. If you try to plan for just one kind of shot, you're going to fail epically at all others.
But if you want to be the first to risk it, be my guest.
You're right and I installed my two jammerheads on the front of the car exactly like that. Tilted up just a little bit. (a few deg). This helps for overpass situations and (for me more important) under strong breaking. Why would you jamm the road?Quote:
Originally Posted by Swamp
I did the same for the horizontal direction. (My left jammer points just a little bit to the left, and the right one to the right)
I'm using LI's
That spec sheet talks about a 75 watt sensor so that would be 300 total watts of laser output (75w x 4 sensors - 2 front 2 rear).*CPU like the one used for LI states - max current is*700mA which only equates to 9.6 total watts.
Something is not adding up right or that sensor is not what is being used in any laser jammers.
You guys worried about nose dipping are thinking back-arsewards. You won't jam on your brakes until at least three seconds after the shot. That means, your nose won't dip down to put your heads into position until well after the officer has your speed. The jammer starts jamming at the same time the shot is taken, not when you jam on your brakes. Where your heads are when you are shot is MUCH more important than where they are after you brake.
This is some very, very good advise! Thanks for sharing this info SS. :thumb2:Quote:
Originally Posted by Stealth Stalker
I can only agree on one point (more or less) with you, and that is the fact that it is important where the heads point when you are being shot.Quote:
Originally Posted by Stealth Stalker
But.....
- I tilt up the heads just a little, so the heads are pointing in the right direction when being shot anyhow, so the jammer will be fully effective right from the start.
- Do you really need 3 secs before you start breaking??? I think that around 1 sec. is a lot more realistic. (3 seconds @ 160 kmh is 133meters/400ft... I wouldn't dare drive that fast if I were that slow.....)
- During real-life lasergun encounters with cops I had here (In The Netherlands) It always took them a lot longer then 1 sec. to get a valid speed reading. (I know under ideal circumstances the guns can do a lot better)
Do all your shots come from overpasses? :confused:Quote:
Originally Posted by fulcrum
Studies say you are wrong. In real life, when you are driving relaxed and unprepared for the hit, it'll take you at least two seconds to recognise what is going on and even think about moving your foot to the brake, and that's a best-case scenario. More often, the average person takes twice that long to hit the brakes, even when prepared. A lot of people totally freeze up when the alarm goes off because they are so startled. Many are confused, or don't even recognise the alert because of their stereo playing. Unless you are der Übermensch, I doubt that you significantly beat the averages.Quote:
- Do you really need 3 secs before you start breaking??? I think that around 1 sec. is a lot more realistic.
You have zero way of knowing how long it took them.Quote:
- During real-life lasergun encounters with cops I had here (In The Netherlands) It always took them a lot longer then 1 sec. to get a valid speed reading.
Shots from overpasses are not very common here, best guess about 1-2% of all encounters.
Again - pointing the jammers a few degrees up, doesn't negatively influence normal performance. As far as I was able to test. (LI on LTI LR, Jenoptic, PL III and Laser Atlanta)
I can only speak for myself, but around 1 sec is a realistic number for me. When I'm over the PSL more then 39kmh (on highways) I'm not exactly cruising on autopilot. (or cruise control if you wish) You can train and improve yourself on these things. (Und ich bin sicher kein Uebermensch!)
The government here always uses 1-1.5 seconds reaction time in their road safety propaganda. (Subject: tail-gating and speeding)
I know exactly how long the gun is pointed at my car. I use a (self build) detector that sounds a short audio beep for every laserpulse received on its pin-diode. It is a great tool, totally independent of the jammer. It also stores the pulses in flash for later evaluation.
If the cop keeps pointing the gun at my car after I killed the jammer, I can be (almost 100%) sure that the jammer did its work. Or use the option of a U-Turn which is a valid strategie for some encounters. (It once saved my license)
I thought the whole ideal behind using the LI was you did not have to Jam on your brakes. The LI's highly effective capability allows one to decelerate normally or maybe moderate braking and then turn it off.
For me, slamming on the brakes will in many cases potentially cause an accident in that I can out decelerate most vehicles out there. That's the last thing I want is to have someone hit me from behind.
I like the idea of this gizmo.Quote:
Originally Posted by fulcrum
Exactly!Quote:
Originally Posted by WaltBurkett
This is what LI and maybe other jammer have to analyze and collect new data from new guns...Quote:
Originally Posted by CarrotsI like the idea of this gizmo.Quote:
Originally Posted by fulcrum
Man, I hope this question hasn't already been answered a hundred times.
What is the function of the raised area on the end of the heads? I am guessing the receptors are directly behind the bump (raised area). I positioned the bumps outboard, near the headlights based on the above premise.
BTW I built the LED circuit that is on another thread. It's mounted directly forward of the steering wheel, just barely visible over the hub of the steering wheel. I can;'t test it as I don't have a laser divice that will activate the LI heads. I tried several laser devices that I have. That's a good sign.
I didn't run into any lasers wielding gendarmes since I removed the ZR4 and installed the LI dual a couple of weeks ago.
Oh, well.
JL
Those are the receiver bubbles where the two receiver diodes are located. Simply put, the bubbles function much like that of the canopy of a fighter jet, allowing the pilot to see better with his peripheral vision to spot threats.Quote:
Originally Posted by Jerry Lee
Cliff
power declared is "optical" and NOT RMS power, so 75W of RMS is not only not possible thru LI power supply wires but also insaine amount of power for optical devices... Look it this way.. LIDAR operates houres nad houres from batery or?? :-)
So there is different types of power and they all use W as measurment, in this case 75W is optical power declarared by LD manufacturer.
Regarding the indicator of "when are you targeted" or "hit" just look at the power switch LED.. it will flash EXACTLY as LIDAR operator squezes the trigger.. :-)
BTW... tnx for a great forum! :-)
So this is what i get from this thread:
1- Basally beam dimensions expand as they get farther away (1000ft):
Horizontal around 2x 20deg : (sin(20) * 1000ft) * 2 = 700ft
Vertical around 2x 7deg : (sin(7) * 1000ft) * 2 = 250ft
So this laser would project an oval of around 700x250ft @ 1000ft distance
At the edges the intensity of the laser light is around 20% of the intensity in the center.
2- A gun has to look into the beam's source for reflections so it is more than the beam size being projected that comes into play, its the quality of the guns projection back too.
3- Though Jammer placement should be as level and striate as possible slightly off wont make much difference. If you start off with neutral alignment, then you are equally protected in all directions. If you start off with them favoring one angle, then the opposite angle will always be underserved.
This answers some of my questions about my placement and strengths and weakness. Great info.:)
I must just indicate that there is a LOT more then Light (IR) to think about when jamming... I agree that carier (IR beam from LIDAR) is esential, but dont forget that LIDAR needs a predefined number of impulses to aquire a speed.. so dont forget impulses in those scenarios...