To ensure TV reception, even under changing reception conditions, two aerials are used to receive the TV signals.
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. The aerial pointing to the base plate (control unit) is aerial 1.
To amplify the received TV signals, separate amplifiers are installed for the left and right aerials. The amplifiers are supplied with power by the video module via the HF line.
The power supply to the amplifiers for radio reception by the aerial tuner is not affected by this.
The HF signals amplified in the two amplifiers 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 aerial connected to an input.
The video module recognises 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 recognise which is the left or right aerial.
For fault localisation, a signal path must be checked in accordance with the schematic. For this purposes, a channel with TV signal must be adjusted before the check.
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.