List of North American Broadcast Station Classes - FM

FM

Class / ERP / HAAT / Typical range

• C: 100 kW, 300 m to 600 m, 91.8 km
• C0: 100 kW, 300 m to 450 m, 83.4 km
• C1: up to 100 kW, under 300 m, 72.3 km
• C2: up to 50 kW, up to 150 m, 52.2 km
• C3: up to 25 kW, up to 100 m, 39.1 km
• B: up to 50 kW, up to 150 m, 65.1 km
• B1: up to 25 kW, up to 100 m, 44.7 km
• A: 100 W to 6 kW, up to 100 m, 28.3 km
  • AA (Mexico): up to 3 kW, the former limit for A
• D: up to 250 W ERP, except U.S. non-translators to 10 W TPO
  • L1 (U.S., also LP100): 50 W to 100 W ERP, up to 30 m, 5.6 km
  • L2 (U.S., also LP10): 1W to 10 W ERP, up to 30 m, 3.2 km]
  • LP (Canada): 10-50W ERP
  • VLP (Canada): up to 10W ERP
• Unlicensed: 250µV/m at 3m in U.S., 100µV/m at 30m in Canada

Notes:

• Canada protects all radio stations out to a signal strength of 0.5mV/m (54dBu), whereas only commercial B stations in the U.S. are. Commercial B1 in the U.S. is 0.7mV/m (57dBu), and all other stations are 1.0mV/m (60dBu). Noncommercial-band stations (88.1 to 91.9) are not afforded this protection, and are treated as C3 and C2 even when they are B1 or B. C3 and C2 may also be reported internationally as B1 and B, respectively.
• Class C0 is for former C stations, demoted at request of another station which needs the downgrade to accommodate its own facilities.
• In practice, many stations are above the maximum HAAT for a particular class, and correspondingly must downgrade their power to remain below the reference distance. Conversely, they may not increase power if they are below maximum HAAT.
• All class D (including L1 and L2 LPFM and translator) stations are secondary in the U.S., and can be bumped or forced off-air completely, even if they are not just a repeater and are the only station a licensee has.
• The United States is divided into separate regions that have different restrictions for FM stations. Zone I (much of the U.S. Northeast and Midwest) and I-A (most of California, plus Puerto Rico) is limited to classes B and B1, while Zone II (everything else) has only the C classes. All areas have the same classes for A and D.
• Power and height restrictions were put in place in 1962. A number of previously-existing stations were grandfathered in, such as KVYB in Santa Barbara, California and WMC-FM in Memphis, Tennessee.