Motorola GM Series User Manual

Noise Reduction Techniques 2-9
4.2.4 Distributor Interference
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.
4.2.5 Battery Connections
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.
4.3 Alternator/Generator Whine
This type of interference is characterized by a high-pitched whine which varies with engine speed. A
0.5 µF coaxial capacitor (Motorola Part No. 0882571B01) can be used to bypass the whine. For
generators, the capacitors is connected in the armature lead. Never use a capacitor in the field lead.
Use the field suppressor assembly supplied in the TLN6252_ Noise Reduction Kit. For alternators,
the capacitor is connected in the lead to the battery post (see Figure 2-6 Generator Whine
Suppression and Figure 2-7 Alternator Whine Suppression).
Figure 2-5 Ignition Coil Noise Suppression
Step 3.
Connect wire lead to capacitor
using lockwasher and nut.
Step 1.
Mount Capacitor
(0.1µF 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.
Step 4.
Connect capacitor
lead to battery post.
From distributor
Distributor Post
Battery Post
FL0830264-O

Motorola GM Series Specifications

General

Brand	Motorola
Model	GM Series
Category	Radio
Language	English