Broadcast Frequency Bands
AM radio is broadcast on several frequency bands. The allocation of these bands is governed by the ITU's Radio Regulations and, on the national level, by each country's telecommunications administration (the FCC in the U.S., for example) subject to international agreements. The frequency ranges given here are those that are allocated to stations. Because of the bandwidth taken up by the sidebands, the range allocated for the band as a whole is usually about 5 kHz wider on either side.
- Long wave is 153–279 kHz, with 9 kHz channel spacing generally used. Long wave is only used for radio broadcasting in ITU region 1 (Europe, Africa, and parts of Asia), and is not allocated elsewhere. In the United States, Canada, Bermuda, and U.S. territories, this band is mainly reserved for aeronautics navigational aids, though a small section of the band could theoretically be used for microbroadcasting under the United States Part 15 rules. Due to the propagation characteristics of long wave signals, the frequencies are used most effectively in latitudes north of 50°.
- Medium wave is 531–1,611kHz in ITU regions 1 and 3, with 9 kHz spacing, and 540–1610 kHz in ITU region 2 (the Americas), with 10 kHz spacing. ITU region 2 also authorizes the Extended AM broadcast band between 1610 and 1710 kHz. Medium wave is by far the most heavily used band for commercial broadcasting. This is the "AM radio" that most people are familiar with.
- Short wave is approximately 2.3–26.1 MHz, divided into 14 broadcast bands. Shortwave broadcasts generally use a narrow 5 kHz channel spacing. Short wave is used by audio services intended to be heard at great distances from the transmitting station. The long range of short wave broadcasts comes at the expense of lower audio fidelity. The mode of propagation for short wave is different (see high frequency). AM is used mostly by broadcast services – other shortwave users may use a modified version of AM such as SSB or an AM-compatible version of SSB such as SSB with carrier reinserted.
Frequencies between the broadcast bands are used for other forms of radio communication, and are not broadcast services intended for reception by the general public.
Read more about this topic: AM Broadcasting
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