Volvo Trucks North America, Inc. Date Group No. Page
Service Bulletin 4.2004 392 08 3(47)
Radio Signals
The radio signal is sent from a broadcast station and this
signal is then received by an antenna. The strength of the
signal depends on the following:
•
The power output (wattage) of the broadcasting station.
•
The location of the receiver relative to the broadcast
tower.
•
Obstacles between the tower and the receiver.
•
Atmospheric conditions.
•
What band (AM or FM) the station is broadcasting.
•
Type of antenna and the grounding bases.
In North America, commercial radio signals are legislated
into two bands:
•
AM 530-1710 kHz (in 10 kHz steps)
•
FM 87.9-107.9 MHz (in 200 kHz steps)
Each frequency range uses a different modulation
method. Since a radio wave is really just electromagnetic
energy, it must be controlled in a certain way to carry
information. The process of adding the information to the
radio signals is called modulation.
There are two modulation techniques used in radio
broadcasts:
•
AM = Amplitude Modulation
•
FM = Frequency Modulation
The characteristics of the signal depend on both
the frequency and the modulation. It is important to
understand these characteristics to properly verify a
complaint.
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