Motorola GM1200E, Руководство по установке

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Noise Reduction Techniques
Reducing Noise Interference in Mobile Two-Way Radio Installations 2-7
5.0 Noise Reduction Techniques
5.1 General
There are three basic ways to suppress noise. The first is the addition of resistance in circuits
subject to ringing. This method is used for the ignition coil HV cable, spark plug wires, and spark
plugs. The second is to filter noise from low voltage wiring using coaxial bypass capacitors. The third
is to control static charge build-up using wipers for movable parts such as automobile hoods and
trunk lids, or flexible bonding leads for fixed members. Static in wheels may also be controlled using
collector rings. Applications of each of these techniques are discussed below.
The vehicle manufacturer’s service manual also may provide noise suppression information which is
valuable in any 1st attempt at noise suppression.
5.2 Ignition System Interference
5.2.1 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 should be replaced at least
every 30,000 miles.
4. Be sure that spark plug wires make good, solid contact at each end and are routed as far as
possible from low voltage leads.
5. Many late-model automobiles are equipped with a shield over the distributor points. Check to
see that this shield is properly positioned and securely attached.
5.2.2 Available Noise Reduction Kits
Motorola offers two noise reduction kits; Model TLN8845A for alternator-equipped vehicles and
Model TLN6252A for generator-equipped vehicles. These kits are for suppression of noise in the
primary and secondary of the ignition coil and for bleeding of static charges on the hood. The
TLN6252A also is used to suppress noise from the generator and voltage regulator. Figures 2-3 and
2-4 show the contents of the kits and their usage.
Motorola also offers wheel static collectors (Motorola Part No. 1K534254-regular type and
1K563173-small type. Use of these items are described in section 5.8.
Most auto parts dealers can supply 0.05
µ
F bypass capacitors (condensers), resistive ignition wires,
and resistor spark plugs. The type of spark suppression used in noise reduction should always be in
accordance with the recommendations of the vehicle manufacturer, that is, if spark plugs are to be
replaced with built-in suppressor types, they should be in the proper heat ranges and thread sizes
for the particular engine. In each ignition system, there is a maximum amount of resistance that may
be connected between the distributor and a spark plug. If resistance-type ignition wire is used, the
length of each wire must be limited so that its resistance does not exceed the allowable maximum.