rapat

My 2007 R350 FM reception is getting weaker and weaker. At first only the weaker stations would fade out when I left town, but now I can no longer get ANY stations in the more remote parts in Arizona. The radio is the 6 cd oem model. In the past I used to receive the same stations with clarity. I can't determine if I have an antenna amplifier that is fading out ( I think I have one), antenna, or it is the radio itself. The antenna is the original and seems to be by appearance in good condition. Any insight would be appreciated.