Motorola Radius CM200 Instrukcja instalacji - Strona 30

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Chapter 10

Noise Reduction Techniques

10.1

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 may also provide noise suppression information which is

valuable in any first attempt at noise suppression.

10.2

The most important step in reducing ignition noise is ensuring 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.

Motorola offers one noise reduction kit: Model TLN5277 for alternator-equipped vehicles. This kit is for

suppression of noise in the primary and secondary of the ignition coil and for bleeding of static

charges on the hood. The TLN5277 also is used to suppress noise from the generator and voltage

regulator. Figure 9-1, on page 20 illustrates the kit's usage.

Most auto parts dealers can supply 0.05 µF 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.