List of North American broadcast station classes

AM

Station class descriptions

• A — clear-channel stations — 10 kW to 50 kW, 24 hours.
• *Class A stations are only protected within a radius of the transmitter site.
• *The old Class I was divided into three: Class I-A, I-B, and I-N. NARBA distinguished between Class I-A, which were true clear-channel stations that did not share their channel with another Class I station, and Class I-B, in which a station operated with 50 kW at night but shared its channel with at least one other I-B station, requiring directional operation. This distinction was superseded by the Regional Agreement for the Medium Frequency Broadcasting Service in Region 2, which instituted the current class system.
• *The former Class I-As are omnidirectional, with the exception of 870 WWL New Orleans and 1030 WBZ Boston, which use directional antennas to put a better signal over their largest population areas.
• *Most former Class I-Bs are directional at night, although a few are also directional during days.
• *Former Class I-N stations exist only in Alaska, where they are too remote to interfere with other clear-channel stations in the contiguous 48 states. They are only held to Class B efficiency standards.
• *No new Class A stations are licensed in the conterminous United States, although the FCC states it may be possible to license additional Class A stations in Alaska.
• B — regional stations — 250 W to 50 kW, 24 hours.
• *Stations on the AM expanded band, 1610 kHz to 1700 kHz, are limited to 10 kW days and 1 kW nights, non-directionally.
• *Several expanded band stations operate DA-N or even DA-2 with up to 10 kW during all hours, after providing proof that such operations will not cause co- or adjacent-channel interference.
• *If under 250 W at night, the antenna must be efficient enough to radiate more than 140.82 mV/m at 1 km.
• C — local unlimited-time stations — 250 W to 1 kW, 24 hours.
• *Class C stations that were licensed at 100 W are grandfathered.
• *Rare Class Cs operate with directional arrays, such as KYPA and KHCB.
• D — current and former daytimers — Daytime 250 W to 50 kW, nighttime under 250 W, or off-air.
• *Field strength is limited to 140 mV/m at 1 km.
• *No new class D stations are licensed, with the exception of Class B stations that are downgrading their nighttime operations to Class D. The station's daytime operation is then also reclassified as Class D.
• *If a Class D station is on the air at night, it is not protected from any co-channel interference.
• TIS/'HAR — travelers' information stations / highway advisory radio stations — Up to 10 W transmitter output power. Stations within US national parks are licensed by NTIA and not the FCC.
• Unlicensed broadcasting — — 100 mW DC input to final amplifier with a maximum length radiator, no license needed, may be measured at edge of campus for school stations and neighborhood broadcasters.

• In the Western Hemisphere's, medium wave AM broadcasts are on channels spaced 10 kHz apart from 530 kHz to 1700 kHz, with certain classes restricted to subsets of the available frequencies.
• With few exceptions, Class A stations can be found only on the frequencies of 540 kHz, 640 to 780 kHz, 800 to 900 kHz, 940 kHz, 990 to 1140 kHz, 1160 to 1220 kHz, and 1500 to 1580 kHz. The exceptions are cited in relevant international treaties.
• While US and Canadian Class A stations are authorized to operate at a maximum of 50,000 watts both day and night, certain existing Mexican Class A stations, and certain new Cuban Class A stations are authorized to operate at a higher power. Certain Mexican Class A stations are authorized to operate at less than 50,000 watts at night, if grandfathered, but may operate at up to 100,000 watts during the day.
• 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.
• American territories in ITU region 3 with AM broadcasting stations use the 9 kHz spacing customary to the rest of the world. All stations are class B or lower.
• Canada also defines Class CC and LP.
• TIS stations can be found on any frequency from 530 kHz to 1700 kHz in the US, but may only carry non-commercial messages without music. There is a network of TISs on 1710 in New Jersey.
• Low-power AM stations located on a school campus are allowed to be more powerful, so long as their signal strength does not exceed roughly 14 to 45 μV/m at a distance of 30 meters from campus.

  Former system

AM station classes and clear channels listed by frequency