Rear bumper antenna vs power antenna
 

I have a 95 S class with rear bumper FM antenna(prewired for cell phone by the manufacturer),the power antenna is only for cell phone use,and innoperable with the radio.My problem is that the factory set up is poor,reception is miserable with the small amplifier connected next to the bumper.I wonder if there is any way I can move the antenna cable to the power antenna and get it working properly,to power up when the radio is on,so,I get better radio reception.I tried switching the factory amplifier for fm antenna,with no results,the set up is just poorly designed,so,what would it take to get the power antenna to be controlled by the head unit and not the cell phone that is not even in the car anymore...