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I have installed an aftermarket radio. The radio signal is poor and through investigation I have found a antenna amplifier module inline with the external antenna. This module is powered. It would make sense this module would be intended to be active only when listening to the radio. Therefore it would seem logical there is some type of control wire that would be connected to the HU. I have googled and found various pictures of this module. There appears to be 3 wires on it. It would make sense if 2 wires were + and - voltage, and the 3rd wire could be a + control wire from the head unit to activate it.
First, would somebody confirm my investigations of this module on my 2008 C300 (W204). And if this all makes sense, does anyone have the wire color for that 3rd wire (control wire) that would be in the dash (if it exists). I would like to avoid digging through the headliner and toning out the wire if possible.
I wonder which external antenna are you referring to and which "in-line amplifier" did you actually find. Can you post the MB part number for that amplifier.
Which head unit did your car have before you abandoned the original radio?
The antenna is the shark fin antenna on the C300 W204. The inline amp is mounted very close to it, under the headliner.
the OEM number ANTENNA AMPLIFIER AMP MODULE 204820438.
The radio was:
08 MERCEDES C300 AUDIO EQUIPMENT W/O COMMAND,ID 2048700794 249574
I think you're referring to the GPS antenna. Look at your front windshield and see if you can detect a very fine wire in the glass which in essence is an FM dipole.
I have been able to find through this forum, and general searches of google, a resolution for the issue. The W204 Chassis for 2008 has an inline RF Amplifier for its AM/FM Antenna. That RF Amp is powered by 12 volts that is sent through the antenna coax that attaches to the radio. The command system injected this straight out the radio. When installing an aftermarket radio, this feature (voltage) does not exist. So I purchased a Metra 40-EU56 for this vehicle off Ebay. This adapter allows you connect the motorola style connector on your radio to the Fakra style on the coax of the W204 lead to the external signal amplifier and antenna. There is a power lead that comes off this adapter (blue) that connects to 12 volts or the antenna wire of the aftermarket radio. (mine is Kenwood) The (car end) coax to connect is the larger of the 2 that appear in the dash with all the other wiring. This larger size coax connects to the RF amp in the headliner and a short trip thereafter to the antenna. When power to this amplifier is applied, the signal level increases significantly.
The 40-EU56 I purchased went from a motorola connector to two Fakra leads. Both those leads are identical in their function and pass the same signal along and out. I only had the need to use one, I heat shrunk the other and left it off to the side.
This vehicle came with an antenna that was with a satellite antenna, and without. Both AM/FM and the Satellite antenna are located in or around the shark fin Antenna.
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