To ensure TV reception, even under changing reception conditions, two antennas are used to receive the TV signals.
The rear window incorporates an antenna on both the left and right sides. An assignment of ”antenna left / antenna right” to ”antenna 1 / antenna 2” is not possible at the control-module input. The antenna pointing to the base plate (control module) is antenna 1.
To amplify the received TV signals, separate antenna amplifiers are installed for the left and right antennas. 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 antenna 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 antenna connected to an input.
The video module recognizes antenna 1 and antenna 2 with the aid of the diversity function. However, because the antenna connectors are not coded, it is not possible to recognize which is the left or right antenna.
For fault localization, 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 antenna has been disconnected, this antenna path is O.K.