Function

Bottom left rear window antenna amplifier (A2/24), function
The radio signals (FM2, 3) are received by the rear window antennas and transferred to the two FM signal inputs on the bottom left rear window antenna amplifier (A2/24). The FM1 and AM signals arrive already preamplified by the top left rear window antenna amplifier (A2/8).
All signals are amplified and relayed to the radio tuner over a common coaxial output.

Power supply
The bottom left rear window antenna amplifier (A2/24) is activated by the COMAND operating, display and control module (A40/3) or by the radio (A2) via a switching lead. It then supplies the following components with power:
- top left rear window antenna amplifier (A2/8)
- top right rear window antenna amplifier (A2/9, optional)
- bottom right rear window antenna amplifier (A2/25, optional)

Antenna diversity, function
The purpose of the diversity processor integrated into the A2/24 amplifier is to switch between the three rear window FM antennas depending on the reception in order to achieve the best possible reception:
- Initially, the radio (A2) or the COMAND operating, display and control module (A40/3) receives the signals from the FM antenna momentarily active over the bottom left rear window antenna amplifier (A2/24).
- The radio tuner generates the IF (intermediate frequency) reference signal from the FM signals received and transmits it back to the A2/24 amplifier via a separate lead.
- The diversity processor checks after demodulation whether the IF signal is free of interference. If interference is present, it automatically switches over to the next of the three FM antennas in the rear window.
- The switchover speed depends on the frequency with which interference occurs. This prevents continuous switchover between the antennas in the event of extremely poor FM reception, which could cause interference itself.