TV Reception

TV Reception

To ensure TV reception, even under changing reception conditions, two aerials are used to receive the TV signals. In Drive variant with rear-compartment monitor, the digital video module has a third aerial to ensure reception while the vehicle is being driven.

Brief description of components

Rear-window aerials
The rear window incorporates an aerial on both the left and right sides. An assignment of "aerial left / aerial right" to "aerial 1 / aerial 2" is not possible at the control-unit input.

Aerial amplifiers
To amplify the received TV signals, separate amplifiers are installed for the aerials. The amplifiers are supplied with power by the video module via the HF line.

Video module
The amplified HF signals are applied at separate inputs to the video module. The signals are conditioned according to their subsequent use in the video module. The video module monitors current, voltage and field strength of the aerials connected to an input.

Main functions

Aerial recognition
The analog video module recognizes aerial 1 and aerial 2 with the aid of the diversity function. However, because the aerial connectors are not coded, it is not possible to recognize which is the left or right aerial.
The digital video module recognizes aerials 1, aerial 2 and on the Drive variant aerial 3. The numbering of the aerials runs from the centre of the module consecutively towards the outside - aerial 1, aerial 2 and on the Drive variant aerial 3.
For fault localization, a signal path must be checked in accordance with the connection scheme. For this purposes, a channel with TV signal must be adjusted before the check.

Service notes for the analog video module
The right amplifier operates perfectly with a power consumption of 60 mA. The field strength can be read out as a current value.

Display Evaluation
0 ... 80 No reception or poor reception
120 ... 250 Good reception

If the field strength is significantly lower than before once the aerial has been disconnected, this aerial path is O.K.

Service notes for the video module with digital reception
The video module for digital reception provides the possibility to read out the aerial currents of each individual aerial as a value. There is the same possibility for the field strength.

Display of field strength Evaluation
0 ... 20 no reception ... poor reception
25 ... 99 colour recognisable ... very good reception

Display of aerial current Evaluation
30 - 80 mA Within the tolerance