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Two Types of Signals
There are two basic types of radio signals... AM or
Amplitude Modulation, in which the transmitted sound
causes the amplitude, or height, of the radio waves to
vary... and FM or Frequency Modulation, in which the
frequency of the wave is varied to carry the sound.
Electrical Disturbances
Radio waves may pick up electrical disturbances during
transmission. They mainly affect the wave amplitude,
and thus remain a part of the AM reception. They
interfere very little with the frequency variations that
carry the FM signal.
AM Reception
AM sound is based on wave amplitude, so AM reception
can be disrupted by such things as lightning, power lines
and neon signs.
FM Reception
Because FM transmission is based on frequency varia-
tions, interference that consists of amplitude variations
can be filtered out, leaving the reception relatively clear,
which is the major feature of FM radio.
NOTE: On vehicles so equipped the radio, steering
wheel radio controls and 6 disc CD/DVD changer if
equipped, will remain active for up to 45 seconds after
the ignition switch has been turned off. Opening a
vehicle front door will cancel this feature.
170 UNDERSTANDING YOUR INSTRUMENT PANEL