AM Radio Reception inside a steel building. 

I installed an Alpine radio into a 1968 Mustang and the AM radio reception is being blocked while inside of the steel building during the vehicle build. It is also affecting the HD radio signal and is reducing it's signal strength. I turned the radio on and since I had shortened the antenna coax, I was worried about a connection issue but by touching the antenna, the radio sounds changed and this means I have a good connection between the antenna mast and the radio. If I had touched the radio mast with no audio change, then this would lead me to believe I had an antenna to radio connection issue but this is not the case. It's just the shielding from the steel building.