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Thread: Radar guns

  1. #1

    Default Radar guns

    I've read on stickies and many different websites how radar works but I am still a bit confused. Let's say a cop is on the side of the highway with his gun on and there are 3 cars that are about 2 miles away all speeding at 90 mph. Does the cop actually have to directly see the car and then aim specifically at one to get a result? Or do the radar waves just flow out and hit the cars even though he can't see them? If so, then it would probably hit all 3 cars so do 3 speeds show up on the radar gun? i know that with lidar guns the cop has to directly aim at one specific car but apparently with radar guns you don't need good aim? Thanks.

  2. #2
    Old Timer
    Join Date
    Jun 2005
    New Hampshire


    Most radar guns report the speed of the strongest signal return. The closer a car is to the gun, the stronger the signal is. Also, larger vehicles cause stronger returns. Which means, if there is a Geo Metro in one lane traveling 75 mph and a tractor trailer in the other lane traveling 65 mph, the radar will most likely pick up the tractor trailer's speed.

    Some of the newer digital Ka guns can also report the fastest vehicle in addition to the strongest return. So using the Geo Metro and tractor trailer example above, the gun would show two speeds: the 65 mph of the tractor trailer, and the 75 mph of the fastest vehicle (the Metro).

    In heavier traffic, officers have to use their eyes and heads to determine which vehicles are speeding based on the radar readings and visually sighting the vehicle.
    If I'm passing you on the right, YOU are in the wrong lane!

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  3. #3


    but does the cop have to see you to get a reading?

  4. #4
    Power User
    Join Date
    Aug 2005
    South Florida


    Quote Originally Posted by onelove4uk
    but does the cop have to see you to get a reading?
    Legally yes. If your asking can the radar get a cars speed at greeat distance that the officer can not see the car way up ahead, the answer is no, radar will not return at that great distance. The distance at which the radar can get is still pretty far, generally speaking, a good RD will have farther range than a radar gun becuase a RD is not dependent upon returning radar energy... just dependent on one way travel, the radar gun is dependent upon that radar energy to return.

    The general rule of thumb is if the officer can visually spot you no matter how far away, then he can get you on radar. Now legaly he has to be able to visually identify you make/modle of car etc. but in the real world an officer can cheat.

    So if you can see the officer (line of sight) then he sure can see you and get you on radar. :wink:



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