Radio signal problems

I have a P38 4.0SE and have been having trouble with the signal on the radio since i have had it. It had the factory fitted stereo in when i bought it and i now have an Alpine head Unit so i can connect my ipod.
However i still experience the same poor signal on the radio, i asked the fitters of the stereo if there is anything i can do and they said but a bee sting aerial on the car. No thanks dont wanna look a chav.
They said the arial is in the rear side window on the drivers side
Is this correct?
Does anyone have any ideas how i can improve the signal and overcome this knightmare i am having. any gadgets i can put in line or whatever???
Carl

The aerial is in the rear side window like you've been told, it is connected to an amplifier to boost the signal, this amp is fitted behind the rear trim near the aerial, it could be that the amp is knackered or there is no power to it, check for power to the amp, if you've got power then possibly the amp is shot, also check the aerial lead for damage/corrosion/poor connections, especially the connection to the window itself, check continuity of the window to make sure there is no breaks in the wire in the glass.