47 CFR § 73.506 - Classes of noncommercial educational FM stations and channels.
(1) A Class D educational station is one operating with no more than 10 watts transmitter power output.
(2) A Class D educational (secondary) station is one operating with no more than 10 watts transmitter power output in accordance with the terms of § 73.512 or which has elected to follow these requirements before they become applicable under the terms of § 73.512.
(3) Noncommercial educational FM (NCE-FM) stations with more than 10 watts transmitter power output are classified as Class A, B1, B, C3, C2, C1, or C depending on the station's effective radiated power and antenna height above average terrain, and on the zone in which the station's transmitter is located, on the same basis as set forth in §§ 73.210 and 73.211 for commercial stations.
(b) Any noncommercial educational station except Class D may be assigned to any of the channels listed in § 73.501. Class D noncommercial educational FM stations applied for or authorized prior to June 1, 1980, may continue to operate on their authorized channels subject to the provisions of § 73.512.