|
Just above the mediumwave broadcast band, 160 meters refers to the band of radio frequencies between 1800 to 2000 kHz, which is the lowest radio frequency band allocated for use by amateur radio in most countries. Older amateur operators often refer to 160 meters as the Top Band. It is also sometimes referred to as the "Gentleman's Band" in contrast to the often-freewheeling 80- and 20-meter band activity. ==History== The 160 meter band is the oldest amateur band and was the staple of reliable communication in the earliest days of amateur radio, when almost all communications were over relatively short distances. The band was allocated on a worldwide basis by the International Radiotelegraph Conference in Washington, D.C., on October 4, 1927. The allocation was 1715–2000 kHz. The International Radio Conference of Atlantic City reduced the allocation to 1800–2000 kHz under the provision that amateurs must not interfere with LORAN operation. As the high frequency bands were developed in mid-1920s — along with their smaller, more convenient antennas — 160 meters fell into a period of relative nonuse. Although there has always been activity on the band, fewer and fewer hams are willing (or able, due to lack of sufficient real estate) to put up the antennas necessary to take advantage of the band's unique properties. For most amateurs, the HF bands are much easier to use and HF antennas need a lot less real estate. After World War II, the 160 meter band was apparently not coming back. A large part of the U.S. 160 meter band was allocated on a primary basis to the LORAN radio-navigation system that began operating in and around the 160 meter band in 1942. Amateurs were relegated to secondary, non-interfering status, with severe regional power limitations and restricted day/night operations on just a few narrow segments of the band. Many older hams recall, with no great fondness, the ear-shattering buzz-saw racket of high power LORAN stations that began in 1942 until LORAN-A was phased out in North America on December 31, 1980, and most of the world by 1985. LORAN-A was still operating in China and Japan in 1995. Great ingenuity was used to eliminate the pulse noise of the powerful LORAN-A transmitters through such famous circuitry as the "Select-O-Ject" of the late 1950s. The technology was adapted to modern noise blanking circuits used in current amateur receivers and transceivers. Despite many obstacles and threats from commercial and military spectrum users, the efforts of a small number of determined 160 meter operators enabled the band to survive. In the UK it was the primary band for mobile operation for many years. The band experienced a rebirth with the demise of LORAN-A in the United States in December, 1980 and the removal of power restrictions below 1900 kHz soon thereafter. Power restrictions above 1900 kHz were removed in March 1984. 160 meters was then no longer regarded as the "orphan" band as it had been for more than half a century. 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「160-meter band」の詳細全文を読む スポンサード リンク
|