 All powers are specified as effective radiated power (ERP), which takes into account the magnifying effect (gain) of multiple antenna elements.The U.S. is divided into Zone I (roughly the northeastern quarter of the U.S. mainland, excluding the far northern areas), Zone I-A (California south of 40 degrees latitude, U.S. Virgin Islands, Puerto Rico), and Zone II (all other locations).The highest-power stations are class C in zone II, and class B in the others.