In contrast to a home radio, a car radio is constantly subjected to changing reception conditions. At one point reception is excellent, however, already after travelling a short distance reception can be very poor.Reception can be best checked by driving in a circle.In this way, the rear window antenna is pointed in all directions.
An antenna each for the AM (amplitude modulation) and FM (frequency modulation) band is integrated in the rear window.The received signal is amplified by the antenna amplifier and is transferred via a high frequency line (HF line) directly into the radio.
In the antenna diversity option, one antenna is connected for the AM band and three separate antennas for the FM range.In the diversity amplifier, the three received FM signals are switched through to the radio cyclically via the HF line.The radio sends a feedback signal relating to the quality of the received antenna signal (the intermediate frequency signal) to the antenna diversity system.The antenna diversity system decides which of the three antennas has the best reception quality at present and switches this antenna through to the radio until the next measuring cycle is carried out.In the case of interference in the intermediate frequency signal, the antenna (FM1) arranged vertically in the rear window is used.
Due to different connector assignments than for stereo, the tweeter is not operated by means of the diplexer integrated in the front of the loudspeaker but rather it is activated as all loudspeakers directly from the active amplifier.