47 CFR § 73.210 - Station classes.
(a) The rules applicable to a particular station, including minimum and maximum facilities requirements, are determined by its class. Possible class designations depend upon the zone in which the station's transmitter is located, or proposed to be located. The zones are defined in § 73.205. Allotted station classes are indicated in the Table of Allotments, § 73.202. Class A, B1 and B stations may be authorized in Zones I and I-A. Class A, C3, C2, C1, C0 and C stations may be authorized in Zone II.
(b) The power and antenna height requirements for each class are set forth in § 73.211. If a station has an ERP and an antenna HAAT such that it cannot be classified using the maximum limits and minimum requirements in § 73.211, its class shall be determined using the following procedure:
(1) Determine the reference distance of the station using the procedure in paragraph (b)(1)(i) of § 73.211. If this distance is less than or equal to 28 km, the station is Class A; otherwise,
(2) For a station in Zone I or Zone I-A, except for Puerto Rico and the Virgin Islands:
(i) If this distance is greater than 28 km and less than or equal to 39 km, the station is Class B1.
(ii) If this distance is greater than 39 km and less than or equal to 52 km, the station is Class B.
(3) For a station in Zone II:
(i) If this distance is greater than 28 km and less than or equal to 39 km, the station is Class C3.
(ii) If this distance is greater than 39 km and less than or equal to 52 km, the station is Class C2.
(iii) If this distance is greater than 52 km and less than or equal to 72 km, the station is Class C1.
(iv) If this distance is greater than 72 km and less than or equal to 83 km, the station is Class C0.
(v) If this distance is greater than 83 km and less than or equal to 92 km, the station is Class C.
(4) For a station in Puerto Rico or the Virgin Islands:
(i) If this distance is less than or equal to 42 km, the station is Class A.
(ii) If this distance is greater than 42 km and less than or equal to 46 km, the station is Class B1.
(iii) If this distance is greater then 46 km and less than or equal to 78 km, the station is Class B.