47 CFR § 73.211 - Power and antenna height requirements.
(a) Minimum requirements.
(1) Except as provided in paragraphs (a)(3) and (b)(2) of this section, FM stations must operate with a minimum effective radiated power (ERP) as follows:
(i) The minimum ERP for Class A stations is 0.1 kW.
(ii) The ERP for Class B1 stations must exceed 6 kW.
(iii) The ERP for Class B stations must exceed 25 kW.
(iv) The ERP for Class C3 stations must exceed 6 kW.
(v) The ERP for Class C2 stations must exceed 25 kW.
(vi) The ERP for Class C1 stations must exceed 50 kW.
(vii) The minimum ERP for Class C and C0 stations is 100 kW.
(2) Class C0 stations must have an antenna height above average terrain (HAAT) of at least 300 meters (984 feet). Class C stations must have an antenna height above average terrain (HAAT) of at least 451 meters (1480 feet).
(3) Stations of any class except Class A may have an ERP less than that specified in paragraph (a)(1) of this section, provided that the reference distance, determined in accordance with paragraph (b)(1)(i) of this section, exceeds the distance to the class contour for the next lower class. Class A stations may have an ERP less than 100 watts provided that the reference distance, determined in accordance with paragraph (b)(1)(i) of this section, equals or exceeds 6 kilometers.
(b) Maximum limits.
(1) Except for stations located in Puerto Rico or the Virgin Islands, the maximum ERP in any direction, reference HAAT, and distance to the class contour for each FM station class are listed below:
| Station class | Maximum ERP | Reference HAAT in meters (ft.) | Class contour distance in kilometers |
|---|---|---|---|
| A | 6 kW (7.8 dBk) | 100 (328) | 28 |
| B1 | 25 kW (14.0 dBk) | 100 (328) | 39 |
| B | 50 kW (17.0 dBk) | 150 (492) | 52 |
| C3 | 25 kW (14.0 dBk) | 100 (328) | 39 |
| C2 | 50 kW (17.0 dBk) | 150 (492) | 52 |
| C1 | 100 kW (20.0 dBk) | 299 (981) | 72 |
| C0 | 100 kW (20.0 dBk) | 450 (1476) | 83 |
| C | 100 kW (20.0 dBk) | 600 (1968) | 92 |
(i) The reference distance of a station is obtained by finding the predicted distance to the 1mV/m contour using Figure 1 of § 73.333 and then rounding to the nearest kilometer. Antenna HAAT is determined using the procedure in § 73.313. If the HAAT so determined is less than 30 meters (100 feet), a HAAT of 30 meters must be used when finding the predicted distance to the 1 mV/m contour.
(ii) If a station's ERP is equal to the maximum for its class, its antenna HAAT must not exceed the reference HAAT, regardless of the reference distance. For example, a Class A station operating with 6 kW ERP may have an antenna HAAT of 100 meters, but not 101 meters, even though the reference distance is 28 km in both cases.
(iii) Except as provided in paragraph (b)(3) of this section, no station will be authorized in Zone I or I-A with an ERP equal to 50 kW and a HAAT exceeding 150 meters. No station will be authorized in Zone II with an ERP equal to 100 kW and a HAAT exceeding 600 meters.
(2) If a station has an antenna HAAT greater than the reference HAAT for its class, its ERP must be lower than the class maximum such that the reference distance does not exceed the class contour distance. If the antenna HAAT is so great that the station's ERP must be lower than the minimum ERP for its class (specified in paragraphs (a)(1) and (a)(3) of this section), that lower ERP will become the minimum for that station.
(3) For stations located in Puerto Rico or the Virgin Islands, the maximum ERP in any direction, reference HAAT, and distance to the class contour for each FM station class are listed below:
| Station class | Maximum ERP | Reference HAAT in meters (ft.) | Class contour distance in kilometers |
|---|---|---|---|
| A | 6kW (7.8 dBk) | 240 (787) | 42 |
| B1 | 25kW (14.0 dBk) | 150 (492) | 46 |
| B | 50kW (17.0 dBk) | 472 (1549) | 78 |
(c) Existing stations. Stations authorized prior to March 1, 1984 that do not conform to the requirements of this section may continue to operate as authorized. Stations operating with facilities in excess of those specified in paragraph (b) of this section may not increase their effective radiated powers or extend their 1 mV/m field strength contour beyond the location permitted by their present authorizations. The provisions of this section will not apply to applications to increase facilities for those stations operating with less than the minimum power specified in paragraph (a) of this section.
(d) Existing Class C stations below minimum antenna HAAT. Class C stations authorized prior to January 19, 2001 that do not meet the minimum antenna HAAT specified in paragraph (a)(2) of this section for Class C stations may continue to operate as authorized subject to the reclassification procedures set forth in Note 4 to § 73.3573.