Saab 2000 9-5 2.3 Turbo Ecopower Owner's Manual page 97

Sources of FM interference
Interference to FM reception can be caused
by the electrical systems in other vehicles,
particularly if the signal from the transmitter
is weak.
Cross-modulation
When the radio is tuned to a weak transmit-
ter 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.
Saab 9-5 Audio System
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.
AM waves, on the other hand, are reflected
off the ionosphere, thus greatly extending
their range.
97
AM