I have been looking at install options for a LI system. One option I've considered is under a ledge that is formed by the top surface of an air intake. Most recommend that the sensors need to be flush with the front edge of the ledge or protrusion and this would work. However, if I could set the sensor back just an inch or two, it would be almost invisible to a person standing near the car (ie a LEO).
So then what's wrong with the reasoning in this thread copied from e90post.com (can't post a direct link as I'm new but you can google a phrase from it)?
My simple calcs (and bear with me as the last science class I took was high school physics so I wouldnt be surprised if there were some obvious mistake here):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. At those angle, power output is half the peak. At twice that angle, the output is virtually zero:
Therefore, if your jammer heads (or input and output diode locations) have +/- 11 degrees clearance vertically, and +/- 25 horizontally, there is no point in wanting extra clearance.
- Say you want to mount the sensor set back slightly under a ledge as described above
- The height of a LI jammer sensor unit is 0.56" per their website. Thus assume the center of the diode is 0.28" from either the top or bottom of the sensor.
- Now imagine a right triangle formed by an imaginary line from the diode to the mounting ledge and perpendicular to the ledge (one leg), the outer edge of the spreading laser beam (hypotenuse) and the line defining the setback from the front edge of the ledge (other leg)
- If the maximum clearance angle needed is +/- 11 degrees, then the angles of the right triangle would be: 11 degrees / 79 degrees
- We also have a known side length which is for the first leg (between the diode and the ledge / mounting surface or the height of the sensor = 0.28")
Based on an online triangle calculators (why didn't they have these when I was in school), the diode in the sensor could be recessed about 1.44" back front the protruding edge of the ledge before diode output was impacted. At this setback, a person of average height would need to be standing 11+ feet away to see any part of the sensor and much further back to see the centerline of it.
What's wrong with this thinking?