2008 Dodge Avenger Owner's Manual - Page 193

UNDERSTANDING YOUR INSTRUMENT PANEL 191 RADIO GENERAL INFORMATION RADIO BROADCAST SIGNALS The radio will provide excellent reception under most operating conditions. Like any system, however, automotive radios have performance limitations, due to mobile operation and natural phenomena, which might lead you to believe your sound system is malfunctioning. To help you understand and save you concern about these "apparent" malfunctions, you must understand a point or two about the transmission and reception of radio signals. 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. 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. 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 variations, interference that consists of amplitude variations can be filtered out, leaving the reception relatively clear, which is the major feature of FM radio. 4