Volvo Trucks North America, Inc. Date Group No. Page
Service Bulletin 4.2004 392 08 41(47)
Antenna
The antenna collects radio frequency signals.
Electromagnetic energy (radio waves) from a broadcast
antenna induces a very small AC voltage in the receiving
antenna. The small AC voltage is then brought to the
radio receiver for processing and conversion to acoustical
energy. For best performance, the receiving antenna
would be sized to receive the wavelength being broadcast.
This is impractical as vehicle radio systems tune in a wide
range of frequencies with wavelengths between roughly
3 meters (FM) and 566 meters (AM) (10 ft. and 1856
ft.). A vehicle antenna is a compromise of utility over
performance with the receiver carrying the additional
burden.
The vehicle antenna system consists of not only the mast
but also the ground plane. The ground plane is more
important than the antennae itself. However, a ground
plane cannot exist without an antenna. The ground plane
is a maintained area of “0 Voltage” potential across the
entire vehicle chassis, with all points electrically tied
together at the negative side of the battery. The antenna
cable shield must be properly grounded at the antenna
base. Without proper grounding the signal can be weak
or even eliminated. Improper grounding can also make
the antenna susceptible to noise.
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