Shadow Effect - Saab 2006 9-5 Owner's Manual

110 Saab 9-5 Audio System

Shadow effect

Because FM radio waves travel in straight
lines from the transmitter, a shadow effect
can occur when tall buildings or hills
obstruct the propagation path from the
transmitter to the car.
Cross modulation
If the radio is tuned to a weak transmitter in
the vicinity of a stronger one, the car's
antennas will receive signals from both.
Such interference is apparent when the
unwanted broadcast can be heard faintly in
the background.
FM
Radio waves, FM/AM
FM radio waves radiate in straight lines from
the transmitter. Because such waves do not
follow the curvature of the Earth, their
strength becomes weaker the further they
travel. That is why a large number of trans-
mitters is needed to provide good reception.
AM waves, on the other hand, are reflected
off the ionosphere, thus greatly extending
their range.
AM