Kia Optima Manual page 224

How vehicle audio works
FM reception
AM and FM radio signals are broad-
cast from transmitter towers located
around your city. They are intercept-
ed by the radio antenna on your vehi-
cle. This signal is then processed by
the radio and sent to your vehicle
speakers.
However, in some cases the signal
coming to your vehicle may not be
strong and clear.
This can be due to factors, such as
the distance from the radio station,
closeness of other strong radio sta-
tions or the presence of buildings,
bridges or other large obstructions in
the area.
AM reception
AM broadcasts can be received at
JBM001
greater distances than FM broad-
casts. This is because AM radio
waves are transmitted at low fre-
quencies. These long distance,low
frequency radio waves can follow the
curvature of the earth rather than
travelling straight. In addition, they
curve around obstructions resulting
in better signal coverage.
Features of your vehicle
FM radio station
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FM broadcasts are transmitted at
high frequencies and do not bend to
follow the earth's surface. Because
of this, FM broadcasts generally
begin to fade within short distances
from the station. Also, FM signals are
easily affected by buildings, moun-
tains, and obstructions. This can lead
to undesirable or unpleasant listen-
ing conditions which might lead you
to believe a problem exists with your
radio. The following conditions are
normal and do not indicate radio
trouble:
JBM003
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