Editing AM broadcasting (section)

===Broadcast band frequencies===
AM broadcasts are used on several frequency bands. The allocation of these bands is governed by the [[International Telecommunication Union|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 [[sideband]]s, the range allocated for the band as a whole is usually about 5&nbsp;kHz wider on either side.

{{anchor|AM_longwave_band}}

====Longwave broadcasting====
''[[Longwave]]'' (also known as [[Low frequency]] (LF)) (148.5&nbsp;[[Kilohertz|kHz]] – 283.5&nbsp;kHz) Broadcasting stations in this band are assigned transmitting frequencies in the range 153&nbsp;kHz – 279&nbsp;kHz, and generally maintain 9&nbsp;kHz spacing. 
Longwave assignments for broadcasting only exist in [[ITU region|ITU Region&nbsp;1]] (Europe, Africa, and northern and central Asia) and are not allocated elsewhere. Individual stations have coverage measured in the hundreds of kilometers; however, there is only a very limited number of available broadcasting slots.

Most of the earliest broadcasting experiments took place on [[longwave]] frequencies; however, complaints about interference from existing services, particularly the military, led to most broadcasting moving to higher frequencies.

====Medium-wave broadcasting{{anchor|commercial_AM_bands}}====
''[[Medium wave]]'' (also known as [[Medium frequency]] (MF)), is by far the most commonly used AM broadcasting band. In ITU Regions&nbsp;1 and 3, transmitting frequencies run from 531&nbsp;kHz – 1602&nbsp;kHz, with 9&nbsp;kHz spacing (526.5&nbsp;kHz – 1606.5&nbsp;kHz), and in ITU Region&nbsp;2 (the Americas), transmitting frequencies are 530&nbsp;kHz – 1700&nbsp;kHz, using 10&nbsp;kHz spacing (525&nbsp;kHz – 1705&nbsp;kHz), including the ITU [[AM expanded band|Extended AM broadcast band]], authorized in Region&nbsp;2, between 1605&nbsp;kHz and 1705&nbsp;kHz, previously used for police radio.<ref>{{cite report |title=Federal Communications Commission rules |at=47 CFR §2.106}}</ref>

====Shortwave broadcasting====
''[[Shortwave]]'' (also known as [[High frequency]] (HF)) transmissions range from approximately 2.3 to 26.1&nbsp;MHz, divided into 14&nbsp;broadcast bands. Shortwave broadcasts generally use a narrow 5&nbsp;kHz channel spacing. Shortwave is used by audio services intended to be heard at great distances from the transmitting station. The long range of shortwave broadcasts comes at the expense of lower [[High fidelity|audio fidelity]].

Most broadcast services use AM transmissions, although some use a modified version of AM such as [[Single-sideband modulation]] (SSB) or an AM-compatible version of SSB such as "SSB with carrier reinserted".

====VHF AM broadcasting====
Beginning in the mid-1930s, the United States evaluated options for the establishment of broadcasting stations using much higher transmitting frequencies. In October&nbsp;1937, the FCC announced a second band of AM stations, consisting of 75&nbsp;channels spanning from 41.02 to 43.98&nbsp;MHz, which were informally called ''[[Apex (radio band)|Apex]]''.

The 40&nbsp;kHz spacing between adjacent frequencies was four times that of the 10&nbsp;kHz spacing used on the standard AM broadcast band, which reduced adjacent-frequency interference, and provided more bandwidth for high-fidelity programming. However, this band was eliminated effective 1&nbsp;January 1941, after the FCC determined that establishing a band of FM stations was preferable.<ref>[http://www.theradiohistorian.org/Apex/Apex1.htm "America's Apex Broadcasting Stations of the 1930s"] by John Schneider, ''Monitoring Times Magazine'', December 2010. (theradiohistorian.com)</ref>