Motorola Radius CM200 Manuale di installazione - Pagina 31

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Noise Reduction Techniques

10.2.3 Ignition Coil Interference

This type of interference is characterized by a popping sound which is most noticeable when the

engine is running slowly. To suppress the noise, connect a 0.1 µF coaxial capacitor (Motorola Part No.

0882571B02) from the battery side of the ignition coil to vehicle ground (see Figure Figure 10-1). This

keeps the distributor noise from being conducted through the battery lead into the electrical system of

the vehicle. Note that some electronic ignition systems do not route the battery lead to the ignition

coil; proper operation of the ignition system can be impaired if the "input" terminal is bypassed.

Step 3.

Connect wire lead to capacitor

using lockwasher and nut.

Step 1.

Mount Capacitor

(0.1 F Coaxial Type)

to vehicle chassis

using lockwasher

and self-tapping screw.

Step 2.

Disconnect wire (dashed)

from battery post and

connect to capacitor using

lockwasher and nut.

This type of interference is characterized by popping sounds which are present at all engine speeds.

It is caused by sparking between the rotor and the distributor cap inserts as the rotor turns. To

suppress this noise, use resistance ignition wire to connect the ignition coil to the distributor cap.

The radio set power cable can pick up noise generated in the vehicle. This can be minimized by

connecting the power cable directly to the battery instead of the fuse block. The battery acts like a

large capacitor (about one Farad for a 50 amp/hour battery), which bypasses induced noise. The

battery ground lead should be securely bonded to the vehicle frame. Undesirable parallel ground

currents can be minimized by using the vehicle frame as a common ground point. If ignition switch

control of the radio is desired, the radio power leads may be connected to the battery through a relay

which is controlled by the ignition switch.

Figure 10-1. Ignition Coil Noise Suppression

Step 4.

Connect capacitor

lead to battery post.

From distributor

Distributor Post

Battery Post

FL0830264-O