The range for most AM stations is greater than for FM, especially at night. The longer range can cause station frequencies to interfere with each other. Static can occur on AM stations caused by things like storms and power lines. Try reducing the treble to reduce this noise.
FM stereo will give the best sound, but FM signals will reach only about 10 to 40 miles (16 to 65 km). Tall buildings or hills can interfere with FM signals, causing the sound to fade in and out.
XM™ Satellite Radio Service gives digital radio reception from coast to coast. Just as with FM, tall buildings or hills can interfere with satellite radio signals, causing the sound to fade in and out. The radio may display NO SIGNAL to indicate interference.