Motorola GM Series, Руководство по установке

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2-2 REDUCING NOISE INTERFERENCE
When a spark discharge or arc takes place through air, energy is radiated at frequencies from a few
kilohertz to hundreds of megahertz. This spurious radiation may have some energy radiated at a
frequency near or even identical to the desired radio signal. The standard receiver may be unable to
distinguish between the two signals (desired and noise). Therefore they both enter the receiver,
resulting in degradation of the desired signal.
It is impractical to prevent all arcing in the standard vehicle electrical system. In an 8-cylinder engine
running at 2,000 RPM, arcing occurs across the spark plugs at a rate of 8,000 sparks per minute or
133 sparks per second. Electrical motors and generators also produce arcs.
1.3 Conducted Noise
Conducted noise enters the radio through the points where the radio is attached to the vehicle’s
electrical system such as battery cables, ignition switch, chassis ground etc. It can be generated by
electrical transients, electrical motors, poor grounding points, or inadequate electrical system
filtering (from alternators, generators, voltage regulators, or weak batteries). Conducted noise can
degrade both transmit and receive performance of a mobile radio.
Figure 2-1 Noise Sources
Spark Plugs
Idle Stop
Solenoid
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Spark Plug
Wires
Alternator or
Generator
Voltage
Regulator
Distributor Ignition
Coil
Wheel Static
Electric Fuel Pump
Antenna Ground
or Location
Radiated Noise Pick-up
Inadequate Terminal
or Fuse Block Filtering Windshield Wiper Motor
Heater Air Conditioner Blower
Electric Windows Motors
Hood Static
Power Seat Motor
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