This is the list of broadcast station classes. Domestic classes are listed as subitems under international ones. Effective radiated power (ERP) and height above average terrain (HAAT) are listed unless otherwise noted.

North America

The United States, Canada, and Mexico.

AM

• A: clear channels, 10kW to 100kW
• B: 250W to 50kW (to 10kW on 1610 to 1710kHz)
  • D: daytime 250W to 50kW, nighttime under 250W or off-air, field strength up to 140mV/m² at 1km, no new stations except downgraded B
• C: 250W to 1kW (also grandfathered 100W)
• TIS: travellers' information stations up to 10W transmitter output power
• LPAM: 50mW, no license needed (US only?)

Notes

In the Western Hemisphere, medium wave AM broadcasts are on channels spaced 10 kHz apart from 530 kHz to 1710 kHz with certain classes restricted to subsets of the available frequencies.

Class A stations can be found only on the frequencies of 540 kHz, 640 to 780 kHz, 800 to 900 kHz, 940 kHz, 1000 to 1140 kHz, 1160 to 1220 kHz, and 1500 to 1580 kHz.

Class B and D stations can be found on any frequencies from 540 kHz to 1700 kHz except where frequencies have been reserved for Class C stations.

Class C stations can be found in the lower 48 US states on the frequencies of 1230 kHz, 1240 kHz, 1340 kHz, 1400 kHz, 1450 kHz, and 1490 kHz. Other countries may use other frequencies for their Class C stations.

TIS stations can be found on any frequency from 530 kHz to 1700kHz in the US, but may only carry non-commercial messages without music.

Low Powered AM stations located on a college campus are allowed to be more powerful, so long as their signal strength does not exceed roughly 14 to 45 µV/m² (depending on frequency) at a distance of 30 m from campus.

AM classes were previously assigned Roman numerals from I to IV in the US, with subclasses indicated by a letter suffix. Current class A is equivalent to the old class I; class B is the old classes II and III, with class D being the II-D, II-S, and III-S subclasses; and class C is the old class IV.

See also: North American Radio Broadcasting Agreement (NARBA)

FM

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

Notes

• Canada protects all radio stations out to a signal strength of 0.5mV/m², whereas only commercial B stations in the U.S. are. Commercial B1 in the U.S. is 0.7mV/m², and all other stations are 1.0mV/m².
• 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 and may not increase power if they are above maximum HAAT.
• All class D (including L1 and L2 LPFM) 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 class B, while Zone II (everything else) can reach class C.
• Power and height restrictions were put in place in 1962. A number of previously-existing stations were grandfathered in, such as KRUZ in Santa Barbara, California and WMC-FM in Memphis, Tennessee.

TV

• full-service stations:
  • VHF low (2-6): 100kW video, 10kW audio; 20kW digital
  • VHF high (7-13): 316kW video, 31.6kW audio; 63.2kW digital
  • UHF all (14-69): 10MW video, 1000kW audio; 2MW digital
• class A stations (U.S.):
  • VHF all (2-13): 3kW video, 300W audio
  • UHF all (14-69): 150kW video, 15kW audio
• LPTV (secondary):

Translators, boosters, and other LPTV stations are secondary, unless they have upgraded to class A. Class A is still considered LPTV with respect to stations Canada and Mexico.

External links

• http://www.fcc.gov/mb/audio/amclasses.html
• http://www.fcc.gov/mb/audio/fmclasses.html