Antenna amplifier with antenna diversity
The antenna amplifiers are located in the antenna diversity. The amplifiers are designed separately for AM and FM. The antenna diversity is installed on the inside of the luggage compartment lid, above the rear window.
| Index | Explanation |
|---|---|
| 1 | VICS antenna (Japan version) |
| 2 | Power supply and FBD receiver |
| 3 | Mounting bolt with earth connection |
| 4 | Rear-window antenna (FM2, FM3, TV3) |
| 5 | Antennas in the rear spoiler (AM, FM1) |
The antenna amplifiers receive a DC power supply from terminal RAD_ON when the radio is switched on. The radio tuner is connected across a coaxial line with the antenna diversity.
The "antenna diversity" function is used to select one of the FM antennas for reception. If the antenna signal of this antenna deteriorates, there is an automatic switch to the next antenna.
The order of the antenna diversity for FM is specified as:
FM1 -> FM2 -> FM1 -> FM3
Thereafter, there is a switch back to the FM1 antenna. The position of this antenna in the rear spoiler means that the FM antenna has the best reception properties. The specified order for switching over ensures that the FM antenna with the best reception properties is active most frequently.
Antenna diversity selects the next FM antenna if the following criteria occur:
- The signal level rapidly drops.
- At the same time, high frequencies (noises) interfere with the signal.
The automatic interference suppression prevents any audible interruption as the antennas are switched. Antenna diversity evaluates the signal quality and switches to the antenna with the best reception. A DC voltage (Us) is used to switch between AM antenna signal, antenna diversity and diagnosis mode. The DC voltage (Us) is generated by the radio and is evaluated in the antenna diversity.
- At Us = 0 Volt, the AM/FM antenna is selected (or the self-diagnosis has a negative result).
- Antenna diversity is active when Us =2.5 Volts.
- When Us =5 Volts, the diagnosis mode is active.
A number of signals are simultaneously connected on the coaxial cable. Reciprocal interference is not possible due to the difference frequencies.
Among others, the following signals can be applied simultaneously:
- HF signal (e.g. 88-108 MHz) from antenna diversity to the radio
- DC voltage Us from the radio to antenna diversity