Signals from an FM transmitter are high frequency and similar to beams of light because they do not bend around corners, but they do reflect. Since FM signals can be reflected by obstructions, it is possible to receive both the direct signal and the reflected signal at the same time. This causes a slight delay in reception and may be heard as a broken sound or a distortion.
Signals become weak in valleys between mountains, tall buildings, and other obstacles. When the vehicle passes through such an area, the reception conditions may change suddenly, resulting in annoying noise.
As signals become weak, noise may appear more in stereo reception. Compared to stereo reception, noise in monaural reception is relatively less apparent.
Utilizing the characteristic of monaural reception that noise is relatively less apparent than stereo reception, the audio system automatically changes the reception from stereo to monaural and lessens annoying noise when signals become weak or a multipath phenomenon occurs.
When signals become weak or a multipath phenomenon occurs, the audio system restrains the volume level in the high frequency band and lessens the annoying noise.
The separation and high tone controls influence sound quality, Therefore they are specifically tuned to the individual model. (Comparison of characteristic must be done on the same models)
Signals tend to reach longer distances at night. This is particularly true for AM signals where foreign broadcasts or noise may cause inadvertent operation. Though the audio system restrains the sensitivity of the SEEK and SCAN functions at night, the audio system may select other than desired broadcasting stations other than those desired when signals are considerably strong. This function is linked to the parking light. When the parking light or the headlights are turned on, SEEK and SCAN may not function for weak signals.
