We did this for TV in 2009 switching from analog to digital transmission. Problem was that people had to then purchase a new digital receiver and digital antenna in order to get over the air broadcasts - many stayed with cable TV for that reason alone.
As part of our a/v setup at home, we have a digital tuner/antenna and can pick up 7 stations broadcasting over the air (free) ... there are more channels than that, but only 7 air in English, the rest are in Spanish.
FM has largely replaced AM in this country, although there are still a significant number of AM stations, particularly in very remote areas.
Our PBS station (KUAT) has multiple broadcast frequencies to allow listeners from locations in the outlying regions to enjoy classical music.
