Roof antenna module, component description - GF82.62-P-3127GZ

MODEL 164 with CODE (551) Anti-theft alarm system (ATA [EDW]) except CODE (494) USA version except CODE (498) Japan version up to Model Year 2008

Fig 1: Identifying Roof Antenna Module

Courtesy of MERCEDES-BENZ USA

The roof antenna module is installed in the rear area beneath the headliner.

There are two variants, GPS without Keyless Go and GPS with Keyless Go (code 889).

Fig 2: Identifying Roof Antenna Module Component

Courtesy of MERCEDES-BENZ USA

Antenna amplifier

The antenna amplifier in the roof antenna module is configured depending on the national version. It receives:

AM, FM
Radio remote control central locking (FZV)
Keyless Go (KG)

The antenna amplifier in the roof antenna module is supplemented by the FM rear window antenna amplifier (A2/19), a dual FM amplifier for the FM2 antenna and the FM3 antenna. The amplifier is directly connected to the antenna amplifier in the roof antenna module via a coaxial cable.

AM/FM/RRCL [FZV] antenna

The FM/AM/RRCL antenna is designed as a wire antenna in the roof antenna module and is connected directly to the antenna amplifier.

AM reception:
Filters and amplifies AM frequencies for radio reception. (Long, medium and short wave).
FM reception:
Filters and amplifies FM frequencies for radio reception.
RRCL reception:
The RRCL signals are demodulated and transferred directly to the rear SAM control unit (N10/8).
KG reception:
The KG signal (authorization signal) is transferred directly to the Keyless Go control unit (N69/5).

Additional tasks of roof antenna module

As well as providing antenna signals for the COMAND operating, display and control unit (A40/3), the radio and navigation unit (A2/56), the radio (A2), the radio remote central locking and the Keyless Go, code 889, the roof antenna module provides additional antenna signals for communication and telematics.

These are:

The telephone antenna signal for telephony (Preinstallation for telephone "Handy", UPCI system, code 386, Telephone "Handy", UPCI system (code 388) and
the GPS antenna signal for navigation (MB Audio 50 APS radio, code 525 and COMAND APS (with navigation) code 527)

Antenna diversity feature (FM)

The diversity feature serves for reduction of reception interference. The diversity feature integrated into the roof antenna module serves for switching over between the FM antennas (FM1 to FM3) in order to allow the best possible reception.

Initially, the COMAND operating, display and control unit or the radio and navigation unit or the radio receives the signal of the active antenna from the roof antenna module. These then generate the IF [ZF] reference signal from the incoming FM signal. The reference signal is transmitted to the roof antenna module via a separate line.

The diversity feature checks whether the IF signal is free of interference after demodulation. If interference is present, the system automatically switches over to the next of the three FM antennas.

The switchover speed depends on the frequency at which interference occurs. This prevents continuous switching between the antennas in areas where FM reception is very poor which in turn would result in interference.

Demodulation

Demodulation of the RRCL [FZV] signal takes place in the antenna amplifier of the roof antenna module. During demodulation, the useful signal is generated from the HF signal received. The wanted signal is transferred to the rear SAM control unit via a separate line.