Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!uw-beaver!milton!sumax!thebes!ole!ssave
From: ssave@ole.UUCP (Shailendra Save)
Newsgroups: sci.electronics
Subject: Re: POLICE hand-held RADAR units
Message-ID: <1810@ole.UUCP>
Date: 13 Feb 91 01:09:19 GMT
References: <1991Feb12.035201.16098@nntp-server.caltech.edu>
Organization: Seattle Silicon Corp., Bellevue, WA.
Lines: 46

From article <1991Feb12.035201.16098@nntp-server.caltech.edu>, by fjs@nntp-server.caltech.edu (Fernando J. Selman):
> 
> Yes, I did get a ticket. It was a 71 on 55 mph freeway. Because that
> extra 1 mph is so painfull I would like to know how reliable it is.
> Somewhere in the ticket it is written "Speeding. K-15". So I assume
> it was a K-band gunn. Because these devices actually compare the speed
> of the car with the speed of light, it would imply an accuracy of
> 1 part in a billion to be able to measure that extra 1 mph. Because
  
First off, they don't use the speed of light to compare with the
speed to the car.  If anything, they use their own speed for
calculations.
There are usually two types of radars, one which
uses a doppler effect to get your speed, and the other uses phase
shift amplitude modulation. Both are pretty accurate.

> of temperature, and humidity effects I would doubt such a reading (it
> was made in Honolulu). Anyone with advice? References? Should I contend
> this ticket? Thanks,
  
  The other thing to remember is that usually they do not give away 
  tickets unless you are grossly over the speed limit. Which is upto 
  5mph above at which point they just give you a warning. 

  The radar beams are quite wide. They return the speed of the largest
  object they bounch the waves off. So, if there was a truck
  travelling at 70 in front of you, and you were travelling at 55, but
  in the fast lane, they are more liable to pull you over instead.

  If you want to get away with the least trouble and the least fine,
  always agree with the cop. Tell him that you didn't realise that you
  were going that fast. Ask him if he was sure. Then tell him that you
  will be more careful in the future. In that order.

  If it is your first ticket, you can get it out of your moving
  violation record by attending a 3 hour class about safe driving. 

  If it is your second or third, forget it.

  If you have a radar detector in plain view of the cop, expect the
  worst.

					Shailendra

   
> 			- Fernando