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Apex was an experimental radio broadcasting system introduced in the United States in 1934 that used high frequencies between roughly 25 and 42 MHz and wideband AM modulation (as opposed to traditional AM broadcasting's narrowband modulation) to achieve high fidelity sound with less static and distortion than medium wave AM stations in the so-called standard broadcast band (then, 545-1505 kHz) experience. They were called "apex", "skyscraper" or "pinnacle" stations because of the height of the broadcast antennas used. The Federal Communications Commission thought initially that very high frequency (VHF) radio waves would have a small, discrete range, and would allow two or more stations to broadcast on duplicate frequencies without interfering with each other. But later it was realized that during peaks in the 11-year sunspot cycle even VHF radio waves could reflect from the ionosphere, and Apex station signals could sometimes be heard on the other side of the planet. In October 1937, the FCC made public its allocation plan for VHF radio broadcasting: 75 channels with 40 kHz separation on 41.02 to 43.98 MHz for Apex stations and 16 channels in 30-40 MHz for relay stations.〔"Short-Wave Range Put in Radio Rule", ''The New York Times'', Oct. 19, 1937, p. 11.〕 Twenty-five of the 75 channels were reallocated for educational use in 1938. Until the late 1930s, commercially made radio receivers did not operate within that band of frequencies, so early listeners to Apex stations used self-built receivers, or built converters for existing models. Most Apex stations operated under experimental licenses, and were affiliated with and subsidized by commercially licensed stations. In 1934, Buffalo, New York's W8XH, WBEN's ultra short wave station, became the first 5-meter station to air a regular schedule. It is a direct predecessor of current Buffalo FM adult contemporary station WTSS.〔(Buffalo Broadcast Pioneers ) timeline〕 In 1936, Milwaukee's W9XAZ (a service of The Milwaukee Journal's WTMJ (AM), which eventually became current day FM station WKTI-FM at 94.5) became the first Apex station to originate its own programming on a regular basis.〔"(Apex Station On Its Own )", ''Broadcasting'', Jan. 1, 1937. "(Milwaukee Station Using Apex Band Tells of Results )", ''Broadcasting'', May 15, 1937.〕 By 1939, Apex stations were operating in 34 cities in 22 states. Apex radio broadcasting's goal of high fidelity sound was later realized by frequency modulation (FM), which operated at 42–50 MHz (later 88–106 MHz, 88–108 MHz later still, and currently 87.8–108 MHz), immediately above the Apex band of frequencies. The FCC in 1939 began encouraging Apex stations broadcasting in AM to consider the change to the technically superior FM system. The former Apex band is, as of 2012, allocated to land mobile communications. ==References== 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「Apex (radio band)」の詳細全文を読む スポンサード リンク
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