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==Phrack Inc.==
Volume Four, Issue Thirty-Eight, File 6 of 15
_____ BEATING THE RADAR RAP _____
/ / \ / / \
( 5/5 ) Part 2 of 2 : "The Technical Side" ( 5/5 )
\_/___/ \_/___/
by Dispater
______________________________________________________________________________
| |
| Introduction | Welcome to the second installment in this series where we
|______________| will briefly explore some of the technical sides to the
operations, error analysis of the police traffic RADAR
unit, the basics of how this technology was developed, then how it was
implemented, a list of common RADAR errors, and finally the technical analysis
of various types of traffic RADAR by National Highway Safety Administration.
RADAR stands for Radio Detecting And Ranging. A traffic speed RADAR works
under the principle of physicals called the "Doppler effect." This theory
means that when a signal is reflected off of an object moving toward you, the
signal will be at a higher frequency when it is closer to you than when the
object is farther away or at the initial position. So the "Doppler effect" is
THE basis for the use of the traffic speed RADAR.
Right now in the United States, there are three bands that are allocated by the
Federal Communications Commission (FCC) for "field disturbance sensors." These
three bands have non-technical names, and all operate in the GigaHertz range
(GigaHertz is a measure of frequency, i.e. 1 GHz = 1 billion cycles per
second). The following is a list of the RADAR bands (as a point of reference
FM radio modulates at 0.088 GHz to 0.108 GHz).
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
BAND : FREQUENCY NOTE ABOUT SPECIFIC BAND
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
X-Band : 10.525 GHz This is the frequency in which most RADAR units operate.
K-Band : 24.150 GHz K-Band was developed to give a longer range of the beam.
Ka-Band : 26.450 GHz This bandwidth is primarily for use with RADAR units
that are used for "photo-speed traps."
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
"So if RADAR is so unreliable," you ask, "why don't we have planes crashing on
a daily basis?" In the first place, TRAFFIC RADAR operates on a COMPLETELY
different basis than, say, the type of RADAR that tracks weather or airplanes.
The technology of traffic RADAR can in no way be compared to the accuracy of
other types of RADAR. Traffic RADAR does NOT "sweep" like a regular RADAR.
"Sweeping" means that the RADAR is picking up every single return signal it
gets and plots them proportionally on a two-dimensional cathode ray tube. On
the other hand, traffic RADAR uses a stationary beam. Also, traffic RADAR does
not use a modulated beam like regular RADAR; it uses a constant beam. ***This
is an important distinction because this means that if there are multiple
images, the constant RADAR beam cannot distinguish between them!***
Furthermore, traffic RADAR is limited to things such as size. It must be able
to fit inside a patrol car and it is also subject to cost. That means a
municipality usually picks up the lowest bid it can get from various
manufacturers.
______________________________________________________________________________
| |
| Implementation of Traffic RADAR | It is important to note at this time that
|_________________________________| while government standards for accuracy
for military and commercial airline RADAR
exist, traffic RADAR is NOT subject to ANY government standards whatsoever. An
attempt was made to do this by the police and two government agencies, but were
refused any type of compliance with traffic speed RADAR manufacturers and the
Reagan administration.
In the late 1970s, there was wide-spread publicity of about RADAR errors,
including the well known tree clocked at 86-MPH in Florida. So, in 1979 the
National Highway Safety Administration (NHSA) assigned to the National Bureau
of Standards the task of testing all brands of traffic RADAR in use at that
time for the purpose of discovering the source of these errors and proposing
federal standards to eliminate them. In January of 1981, the proposed
standards were published in the Federal Register. However, the Reagan
administration took no action on the proposal (the last part of this file
contains the profile from this report of various RADAR units).
After THREE years of government inaction on the problem, the International
Association of the Chief of Police (IACP) provided non-government standards by
which all traffic RADAR units could be tested to assure accuracy: Volume I of
the standards was published in April, 1984 and Volume II in June, of 1984.
In June of 1986, the traffic RADAR manufacturers announced the formation of
their own trade association, saying that they would not submit traffic RADAR
units for IACP testing! Instead, they said they would use their own standards.
So far, NO ONE has any idea of what these standards are; not the police, not
the government and, most importantly, not the public! Basically, there are no
performance requirements or standards for traffic RADAR and the claims of
86-MPH trees and 28-MPH houses cannot be refuted.
______________________________________________________________________________
| |
| Common Traffic Radar Errors | Below is a list of common errors and how they
|_____________________________| occur. This is the part of the article that
must be used in conjunction with the previous
file in this series. You must attempt, while pleading your case, to tie in
some of the following errors to the situation you found yourself in when you
got your speeding ticket. See Phrack #37 file #5 for details.
"The Look-Past Error" Even when the RADAR operator aims his gun properly, the
RADAR is subject to this type of error. This is caused by the RADAR reflecting
off of a larger surface area in the background rather than the smaller
reflective surface in the foreground. Evidence of this the Look-Past Error was
printed in the October 1979 issue of "Car and Driver." The author measured the
effectiveness of KR11 RADAR system against various vehicles. The author showed
that the typical sedan did not show up on the RADAR until it was less that 1200
feet away, however, a Ford 9000 semi tractor trailer could be picked up at 7600
feet.
"The Road Sign Error" Due to the reflectability of microwaves, road signs,
buildings, billboards, large trees, and other stationary objects are a source
of errors.
"Radio Interference Error" According to the Texas Department of Public
Safety, "UHF frequencies broadcast today can force RADAR to read various
numbers when transmitted within the area." This type of interference could
come from the radio within the patrol car, citizens band radio, or television
stations.
"Fan Interference Error" When the antenna is mounted inside the patrol car,
"RADAR will have the tendency to read the pulse of the fan motor (air
conditioner, heater, defroster)." This is a statement provided by the Texas
Department of Public Safety who conducted a study of RADAR guns in 1987. The
Texas Department of Public Safety offered no safeguard for this error.
"Beam Reflection Error" Since microwaves are so readily reflected, the Texas
Department of Public Safety cautioned mounting the antenna within the patrol
car. One instructor said, "It is possible that a reflective path can be set up
through the rear view mirror that will produce RADAR readings on the vehicles
behind the patrol car when the RADAR is aimed forward. And those vehicles can
be either coming or going since traffic RADAR cannot distinguish between the
direction."
"Double Bounce Error" Again, since microwaves are easily reflected, the
operator must be aware of a "bad bounce" and an ordinary reflection. And, as
stated before, since large objects are more efficient than smaller ones,
microwaves are attracted to them more. So, in effect, you could have an
initial RADAR bounce off of the target vehicle, then from the target vehicle to
a house or a truck going the opposite direction, and finally back to the patrol
car. This error will mathematically get larger the slower the target vehicle
is moving.
"The Cosine Error" This is a mathematical error that takes place when the
RADAR gun attempts to calculate the trigonomic equation that is programmed into
it. The RADAR gun measures the angle at which the target enters a point and
then exits a point (i.e. 25 degrees). The cosine of 25 is .9063. The RADAR
gun was designed to calculate the speed of the patrol car by multiplying the
speed of the patrol car (i.e. 50 mph) and the cosine of the angle (.9063) and
it gets the false speed of the patrol vehicle as 45mph. Therefore, when you
subtract the patrol speed from the target speed (i.e. 50, the same as the
patrol car) you get the false sense that the target vehicle is traveling 5mph
faster than the patrol car.
______________________________________________________________________________
| |
| Technical Analysis Report | Below is a copy of the report mentioned above
|___________________________| was conducted by the NHSA. But first I will
explain what some of the criteria were under the
testing conditions. It is also important to note that ALL RADAR units were
subject to "panning error" except the CMI Speedgun-6 and Speedgun-8 models.
Panning error occurs when the RADAR antenna is aimed at it's own display
console. Unintentional errors of this sort can be eliminated when police
officers are given adequate training.
TEST UNIT : Model and manufacturer of the police speed RADAR
unit in question.
BAND : The short hand used for determining the broadcast
frequency of the RADAR unit. X-Band is 8.2-12.4 GHz.
K-Band is 18.0-26.5 GHz.
BEAM WIDTH : The number that is 1/2 of the actual beam width.
In other words, if a RADAR manufacturer says the beam
width is 24 degrees, the actual beam width is
48 degrees. Very deceptive, eh?
SHADOWING ERROR : This occurs in moving mode only. It is the result
of the RADAR mistaking another vehicle for it's
ground reference and adding speed to the target
reading.
POWER SURGE : This occurs when the RADAR unit is first turned on.
This also occurs when the "kill switch" is used to
defeat RADAR detectors. Lag time for kill in the
moving mode ranges from 1.5-5 seconds.
EXTERNAL INTERFERENCE : The NBS test only used CB radio and police-band radio
for "external interference." There are many other
kinds of outside electromagnetic interference that
may effect police RADAR.
INTERNAL INTERFERENCE : Internal interference "may be caused by ANY
electrical component or accessory in the vehicle,
especially when the patrol car's primary power source
is used to operate the RADAR.
[It should be noted that TWO of MPH's K-55 RADAR units were tested. This
demonstrates that each RADAR unit can contain its own quirks regardless of the
fact that it can be from the same model from the same manufacturer.]
_______________________________________________________________________________
NATIONAL BUREAU OF STANDARDS SUMMARY ON TRAFFIC RADAR
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Kustom Signals MR-9 K 13.3 Minor
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Switch-ON gave CB radio caused false CB radio caused
stray reading of 7mph readings of up to 25' erroneous readings
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
MPH Industries K-55 X 20.4 Added 12mph to target in one
(first of two units) test
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
No valid reading for CB radio caused false CB radio many
2.4 sec in moving mode readings of up to 20' erroneous readings
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
MPH Industries K-55 X 24.6 Increased target speed 12-15mph
(second of two units) about 20% of the time
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
2 sec delay in moving mode, CB radio caused false CB radio cause many
2.5 sec in stationary mode alarms up to 175' away erroneous readings
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Decatur MV-715 X 17.5 Added 8-23mph to target in
repeated testing
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
No valid reading for Not effected by external Extreme interference
2+ seconds in moving mode CB radio from heater fan,
ignition, & CB radio
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
CMI Speedgun-6 X 18.8 Very severe, added 12-20 mph
to target
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
7 sec delay in moving mode, Not effected by external CB radio and police
2 sec delay in stationary CB radio radio boosts
readings 20mph
_____________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
CMI Speedgun-8 X 18.6 target traveling 41mph shown as
74mph; target 30mph shown as
41mph
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
2 sec delay in moving mode, Not effected by external No adverse effect
1.2 sec delay in stationary CB radio noted
_______________________________________________________________________________
TEST UNIT BAND BEAM WIDTH SHADOWING ERROR
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Kustom Signals MR-7 X 14.3 No effects noted
POWER SURGE EXTERNAL INTERF. INTERNAL INTERF.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
25.4 sec delay in moving mode, Not effected by external Police band radio
0.6 sec delay in stationary CB radio caused intermittent
increases of 10mph
______________________________________________________________________________
| |
| In Closing... | I hope you have learned a little about how police speed
|_______________| RADAR operates, the errors that they frequently incur, and
possibly a way to avoid the highway robbery that occurs
each time Officer Friendly decides to make a little extra dough for his "job
security."
Also, if you are interested in obtaining cheap traffic RADAR equipment to play
with, you can write to: AIS SATELLITE INC., 106 N. Seventh Street, Perkasie,
PA 18944. You can also call them for a catalog at (215)453-1400 or place
orders at (800)AIS-2001.
______________________________________________________________________________
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