SI-3
™
User’s Manual
17
As the angle between the beam of the antenna and the target
increases, the displayed speed decreases. Ideally, an angle of zero
(0) degrees is preferable, because the displayed speed is the actual
target speed. However, in all uses of police radar, the radar device is
always at a slight angle to the target vehicle to avoid collisions.
Velocity
Vector
Angle
Radar
Figure 5.2.1
An angle between the antenna and the
target causes the cosine eect
The following table shows the eect 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:
30 mph 30 29 29 29 29 28 28 26 21 15 0
40 mph 40 39 39 39 39 38 37 34 28 20 0
50 mph 50 49 49 49 49 48 46 43 35 25 0
60 mph 60 59 59 59 59 57 56 51 31 30 0
70 mph 70 69 69 69 68 67 65 60 49 35 0
80 mph 80 79 79 79 78 77 75 69 57 40 0
Table 5.2.1
Actual and displayed speeds at antenna-to-target angles
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