lock VOLVO S90 1998 Repair Manual

1998 Volvo S90

Sending signals

The FM waves do not follow
the earth's surface nor do they
bounce off the atmosphere. For
this reason their range is
limited. The AM waves follow
the earth's surface and reflect
against the atmosphere, giving
them a wide range.
Weak reception (fading)

Because of the limited range of
the FM senders and the fact that
these waves are very reflective,
this problem usually occurs
with FM reception. If the sender
is blocked by buildings or
mountains, static can result.

Static

The reason why FM but not AM
is audible is covered parking
areas, under bridges, etc, is that
FM signals reflect against solid
objects such as buildings.
Because these waves are very
reflective, static can result. This
static is the result of the reflected
signal and the direct signal
reaching your antenna at slightly
different times causing a
cancellation of all signals. This
problem occurs largely in built-
up areas. Your car is equipped
with a dual antenna system
which helps alleviate this
problem.
Audio systems, general information (cont.) pg. 163

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