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target motor vehicle’s path is not parallel to the antenna, including
conditions such as the motor vehicle traveling on a curve or a hill .
As the angle between the beam of the antenna and the target
motor vehicle increases, the displayed speed decreases . Ideally,
an angle of zero (0) degrees is preferable, because the displayed
speed is the actual target motor vehicle speed . However, in all uses
of police radar, the radar device is always at a slight angle to the
target motor vehicle to avoid collisions .
Velocity
Vector
Angle
Radar
Figure 6.2.1a
An angle between the antenna and the
target vehicle causes the cosine effect .
The following table shows the effect that an increasing angle has
on a displayed speed .
Horizontal Angle Degrees
Actual
Speed
0° 1° 3° 5° 10° 15° 20° 30° 45° 60° 90°
Displayed speed:
50 km/h
50 49 49 49 49
48
46
43
35 25
0
65 km/h
65 64 64 64 64
62
61
56
45 32
0
80 km/h
80 79 79 79 79
77
74
69
56 40
0
90 km/h
90 89 89 89 88
86
84
77
63 45
0
100 km/h
100 99 99 99 98
96
93
86
70 50
0
110 km/h
110 109 109 109 108 106
103
95
77 55
0
Table 6.2.1b
Actual and displayed speeds at different antenna-to-target angles .
Small angles (less than 10°) have little effect on accuracy . As
the angle increases, the displayed speed decreases . At 90°, the
displayed target speed is 0 km/h .
6.2.2 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 motor vehicle blower fan . Changing the fan speed
causes a proportional change in the display speed .
6.2.3 Batching
With the DSP algorithms the Genesis II Select Directional uses
batching will not occur .
6.2.4 Electromagnetic Interference (EMI)
Operating electric motors may produce EMI . With the DSP
algorithms the Genesis II Select Directional has eliminated this .
