The 40-meter or 7-MHz band is an amateur radio frequency band, spanning 7000 to 7300 kilohertz (7200 kHz in ITU Region 1), allocated to radio amateurs in all countries worldwide. The 40-meter band was made available to amateurs in the United States by the Third National Radio Conference on October 10, 1924. The band was allocated on a worldwide basis by the International Radiotelegraph Conference in Washington, D.C., on October 4, 1927.
40 meters is considered one of the most reliable all-season DX bands, most useful for inter-continental communication for one or two hours before sunset, during the night and for one or two hours after sunrise. It is extremely useful for short to medium distance contacts from local contacts out to a range of 500–1500 km or more, depending on conditions, during the day. In higher latitudes, daytime intercontinental communication is also possible during the short days of winter, for example a good path often opens between Japan and northern Europe in the hours leading up to European midday from late November through late January, with a long path opening to the west coast of the United States and Canada after midday.
For many years the portion of the band from 7100–7300 kilohertz has been allocated to short wave broadcasters outside the Americas and not available to radio amateurs outside ITU Region 2. At the World Radio Conference WRC-03 in 2003 it was agreed that the broadcast stations would move out of the section 7100–7200 kilohertz on 29 March 2009 and that portion would become a worldwide exclusive amateur allocation afterwards. Discussions on releasing the remaining 100 kHz of the band to amateurs at a later date will continue in future conferences.
Due to the 24-hour nature of the band, the wide variety of ranges that can be spanned with it, and its shared nature, it tends to be extremely crowded, and interference from other amateurs and broadcasters can be a serious limiting factor. In addition, amateurs in east and southeast Asia have suffered severe interference from illegal users in recent years.
Radio propagation characteristics
This band supports both long distance (DX) communications between late afternoon and a few hours after sunrise, and short distance NVIS contacts during most daylight hours.
With its unique combination of intra- and intercontinental communications possibilities, 40 meters is considered a key band in building a winning HF contesting score during any part of the sunspot cycle.
GW1NGL NA7KR Kevin Roberts Ham Radio
Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information