2001 Saab 9-3 Owner's Manual - Page 112

112 Saab 9-3 Audio System FM AM IB979 IB980 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. Car phones can also produce interference. To maintain good radio reception do not tint the rear windshield, particularly with film containing small metal flakes. Cross-modulation When 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. 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 transmitters are needed to provide good reception. AM waves, on the other hand, are reflected off the ionosphere, thus greatly extending their range. IB388