Motorola Gm300 Installation Manual

Noise Reduction Techniques2-7
3.2 Sources of Noise
Some interference is due to geographic location. This interference does not need to be eliminated
since it is possible for the vehicle to be moved away from the interfering noise source. Noise from
power lines, fluorescent lights, and other vehicles (emitting high levels of radiated noise) are
examples of noise which depends upon location. Make certain that you are not attempting to
suppress noise in a vehicle while it is in a noisy location. If you...

2-8REDUCING NOISE INTERFERENCE
4.2 Ignition System Interference
4.2.1 Engine Maintenance and Tune-Up
The most important step in reducing ignition noise is insuring that the engine is in proper tune. Pay
particular attention to the following points if the noise interference from the ignition system is severe:
1.Be sure the spark plugs distributor points, and condenser are in good condition.
2.Be sure ignition timing is properly adjusted.
3.Be sure the distributor cap and rotor are in good condition. They...

Noise Reduction Techniques2-9
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...

2-10REDUCING NOISE INTERFERENCE
Figure 2-6Generator Whine Suppression
Figure 2-7Alternator Whine Suppression
Step 1.
Mount Capacitor
(0.5µF Coaxial Type)
under generator ground screw.Step 3.
Connect wire lead to capacitor
using lockwasher and nut.
Step 4.
Connect capacitor
lead to armature post.
Caution:
Do not connect
capacitor to field teminal.
Step 2.
Disconnect wire (dashed)
from armature post and 
connect to capacitor using
lockwasher and nut.
FL0830310-O
Step 1.
Mount Capacitor to
(0.5µF Coaxial...

Noise Reduction Techniques2-11
4.4 Voltage Regulator Noise
This type of interference is characterized by erratic popping noises which change only slightly with
changes in engine speed. The noise is generated by arcing in the vibrating breaker contacts of the
voltage regulator. It can be suppressed by connecting a 0.5 µF coaxial capacitor (Motorola Part No.
0882571B01) in the battery and armature leads of the voltage regulator (see Figure 2-8 Voltage
Regulator Noise Suppression).
4.5 Hood and Trunk Lid...

2-12REDUCING NOISE INTERFERENCE
4.6 Other Electrical Noises
Other elements of the electrical system which can generate noise are listed below. These can be
suppressed by connecting a 0.5 µF bypass capacitor between the noise source and ground.
1.Ammeter-to-battery lead
2.Gauges (oil, fuel, temperature)
3.Ignition Switch
4.Lamp bulbs (headlamps, tail lamps, dome lamps, etc.)
5.Accessory wiring (electrical fuel pump, electric windshield wipers, heater fan motor, window
openers, etc.)
4.7 Wheel Static
Road...