Use an outdoor FM antenna and feed the signal to the radio with 75 ohm co-axial cable. If the FM source is weak or overlapped by a strong station, then you may need a better radio. AM signal can travel several thousand miles, depending on the original signal level and atmospheric condition.
You could mount a small outdoor FM antenna on the ceiling and aim it for optimal signal strength. Unfortunately, if the building in encased with steel support, then you may need to move it outdoor.