FM uses 10 times the bandwidth and conveys more audio frequency range within it's signal than an AM one. FM has the benefit that building antenna gain is relat

FM uses 10 times the bandwidth and conveys more audio frequency range within it's signal than an AM one. FM has the benefit that building antenna gain is relatively easy so the Total Power Output of FM transmitters is often lower than for AM transmitters. You can generally expect to get 100kW Effective Radiated Power with only 20kW of input. AM uses a significantly lower frequency and ground wave propagation is much more likely which gives AM the benefit of being able to reach "over the horizon" where FM simply cannot.