|
The 6-meter band is a portion of the very high frequency (VHF) radio spectrum allocated to amateur radio use. Although located in the lower portion of the VHF band, it nonetheless occasionally displays propagation mechanisms characteristic of the high frequency (HF) bands. This normally occurs close to sunspot maximum, when solar activity increases ionization levels in the upper atmosphere. During the last sunspot peak of 2005, worldwide 6-meter propagation occurred making 6-meter communications as good as or in some instances and locations, better than HF frequencies. The prevalence of HF characteristics on this VHF band has inspired amateur operators to dub it the "magic band". In the northern hemisphere, activity peaks from May through early August, when regular sporadic E propagation enables long-distance contacts spanning up to for single-hop propagation. Multiple-hop sporadic E propagation allows intercontinental communications at distances of up to . In the southern hemisphere, sporadic E propagation is most common from November through early February. == History == On October 10, 1924, the 5-meter band (56 64 MHz) was first made available to amateurs in the United States by the Third National Radio Conference. On October 4, 1927, the band was allocated on a worldwide basis by the International Radiotelegraph Conference in Washington, D.C. 56 60 MHz was allocated for amateur and experimental use. There was no change to this allocation at the 1932 International Radiotelegraph Conference in Madrid. At the 1938 International Radiocommunication Conference in Cairo, television broadcasting was given priority in a portion of the 5 and 6 meter band in Europe. Television and low power stations, meaning those with less than 1 kW power, were allocated 56 58.5 MHz and amateurs, experimenters and low power stations were allocated 58.5 60 MHz in the European region. The conference maintained the 56 60 MHz allocation for other regions and allowed administrations in Europe latitude to allow amateurs to continue to use 56 58.5 MHz. Starting in 1938, the FCC created 6 MHz wide television channel allocations working around the 5-meter amateur band with channel 2 occupying 50 56 MHz. In 1940, television channel 2 was reallocated to 60 MHz and TV channel 1 was moved to 50 56 MHz maintaining a gap for the 5-meter amateur band. When the US entered World War II transmissions by amateur radio stations were suspended for the duration of the war. After the war, the 5-meter band was briefly reopened to amateurs from 56 60 MHz until March 1, 1946. At that time the FCC moved television channel 2 down to 54 60 MHz and reallocated channel 1 down to 44 50 MHz opening a gap that would become the Amateur radio 6-meter band in the United States.〔(【引用サイトリンク】title= Whatever Happened to Channel 1? )〕 FCC Order 130-C went into effect at 3 am Eastern Standard Time on March 1, 1946 and created the 6-meter band allocation for the amateur service as 50 54 MHz. Emission types A1, A2, A3 and A4 were allowed for the entire band and special emission for Frequency modulation telephony was allowed from 52.5 54 MHz. At the 1947 International Radio Conference in Atlantic City, New Jersey, the amateur service was allocated 50 54 MHz in ITU Region 2 and 3. Broadcasting was allocated from 41 68 MHz in ITU Region 1, but allowed exclusive amateur use of the 6-meter band (50 54 MHz) in a portion of southern Africa. Amateurs in the United Kingdom remained in the 5-meter band (58.5 60 MHz) for a period of time following World War II, but lost the band to UK analogue television channel 4. They gained a 4-meter band in 1956 and eventually gained the 6-meter band from 50 52 MHz, when it was decided to terminate analogue television broadcasts on channel 2. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「6-meter band」の詳細全文を読む スポンサード リンク
|