Table of Contents
Advertisement
• A valid target motor vehicle speed in the operational range will
always override the source of interference and will be confrmed
by the audio component (See paragraphs 7 2 2 through 7 2 8 )
• The Doppler tone will lack the pitch and clarity component
• Speeds are irregular
• Speeds appear to track with the engine speeds
7.2.1 Angular Interference (Cosine Efect)
The cosine efect causes the system to display a speed which is
lower than the actual vehicle speed This condition occurs when
the target vehicle's path is not parallel to the antenna, including
conditions such as the vehicle traveling on a curve or hill
As the angle between the beam of the antenna and the target
vehicle increases, the displayed speed decreases Ideally, an angle
of zero (0) degrees is preferable, because the displayed speed is the
actual target vehicle speed However, in all uses of police radar, the
radar device is always at a slight angle to the target vehicle to avoid
collisions
Radar
An angle between the antenna and the target vehicle causes the cosine efect
26
Velocity
Vector
Angle
Figure 7.2.1a
25/Aug/2010
The following table shows the efect that an increasing angle has
on a displayed speed
Horizontal Angle Degrees
0°
1°
3°
5° 10° 15° 20° 30°
Actual
Speed
Displayed speed:
50 km/h
50 49 49 49 49
65 km/h
65 64 64 64 64
80 km/h
80 79 79 79 79
90 km/h
90 89 89 89 88
100 km/h
100 99 99 99 98
110 km/h
110 109 109 109 108
Table 7.2.1b
Actual and displayed speeds at diferent antenna-to-target angles
Small angles (less than 10°) have little efect on accuracy As the
angle increases, the displayed speed decreases At 90°, the target
speed is 0—grossly incorrect Cosine Efect will always result in a
target speed being displayed that is less than the actual speed of
the moving motor vehicle, which will always be advantageous to
the motorist
7.2.2 Fan Interference
Fan interference is the most common form of interference that you
are likely to experience It is caused when the radar measures the
speed of the vehicle blower fan Changing the fan speed causes a
proportional change in the display speed
7.2.3 Electromagnetic Interference (EMI)
Operating electric motors may produce EMI With the DSP
algorithms the GHD and Scout has eliminated this
7.2.4 Feedback Interference
When the radar beam is directed at computer screens, streetlights,
and other electronic devices, it can display spurious speeds To
correct the interference, relocate the radar gun antenna
25/Aug/2010
45° 60° 90°
48
46
43
35
25
0
62
61
56
45
32
0
77
74
69
56
40
0
86
84
77
63
45
0
96
93
86
70
50
0
106
103
95
77
55
0
27
- Quick Links:
- 1 Menu
Hide quick links:
Advertisement
Table of Contents
