Does anyone know what is the voltage of the build-in radio antenna ampilifer that located on the rear glass? Is it 12V or lower?

I install an aftermarket head unit on my 04 STi and has no AM radio reception and very weak FM reception. The local dealership cannot find out how much the voltage for the radio antenna ampilifer. Can someone please help me out.

Also, if the headunit does not have a wire to provide the power to the radio ampilifer, how and where can I put out the power supply for the radio ampilifer?

Thank you

 

Thanks, Mulder