Motorola Radius CM200 Installation Manual - Page 28

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Chapter 9

Detection of Noise Sources

9.1

Detection of offending noise sources is the heart of noise suppression because, after the noise

source is identified, the solution becomes obvious. A logical step-by-step procedure is basic to

effective noise suppression.

Use your available equipment to best advantage. A pick-up loop, about one inch in diameter, can be

connected to a portable CB radio or a mobile radio being operated at a frequency similar to the

installed radio frequency but from an isolated supply voltage. The pick-up loop can be moved

throughout the vehicle with the radio used as a radiated noise detector. Be sure the pick-up loop has

sufficient insulation to prevent the input of the radio from coming into direct contact with high voltage

points in the vehicle ignition system.

A non-polarized bypass capacitor, which has alligator clips firmly attached, can be used on a trial-

and-error basis to locate wiring which needs additional filtering. Keep capacitor lead lengths short for

best suppression. Ceramic disc capacitors are not as suitable or effective as automotive coaxial

capacitors. (See Figure 9-1for part numbers.)

Ignition

Switch

Battery

Notes:

1. Noise reduction can only be achieved if components are grounded properly.

2. Items not supplied in kit. See auto parts dealer.

Figure 9-1. RLN5277 Noise Reduction Kit for Alternator-Equipped Vehicles

Ignition

Coil

Breaker

Points

Resistive Wire

Distributor

(Note 2)

Resistor

Spark Plugs

(Note 2)

FL0830262-O