That would be because fm stations transmit stereo. If you want the simulated dolby sound, then you need to pudhthe function button on the surround system to select that instead of having it set to digital input for dolby 5.1 sound that the television stations transmit. If you don't have the user manual...you should be able to get it online. John
2012 F350 6.7 L dually, 2013 3800RE with 6 pt leveling, Sumitomo 17.5" load range h tires, Samsung 18 cu ft residential fridge, 8k Morryde I.S. with disc brakes. Full timing since 2012.