The 80 meter or 3.5 MHz band is a span of radio frequencies allocated for amateur use, from 3.5–4.0 MHz in North and South America (IARU and ITU Region 2); generally 3.5–3.8 MHz in Europe, Africa, and northern Asia (Region 1); and 3.5–3.9 MHz in south and east Asia and the eastern Pacific (Region 3).[a] The upper portion of the band, which is usually used for phone (voice), is sometimes referred to as 75 meters; however, in Europe, "75 m" is used to name an overlapping shortwave broadcast band between 3.9–4.0 MHz used by a number of national radio services.
Because high absorption in the ionosphere's Sun-activated D layer persists until nightfall, 80 meters is usually only good for local communications during the day, and hardly ever good for communications over intercontinental distances during daylight hours. But it is the most popular band for regional communications networks from the late afternoon through the night time hours.[according to whom?] At night, 80 m is usually reliable for short- to medium-distance contacts, with average distances ranging from local contacts within 200 miles / 300 km out to a distance of 1,000 miles / 1,600 km or more at night – even worldwide – depending on atmospheric and ionospheric conditions.
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