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Dynamic carrier control (DCC) is a method of reducing power consumption in radio transmitters during periods of low audio activity or silence. It is a type of Modulation-Dependent Carrier Level control, or MDCL. All modern high-power (>50 kW) shortwave radio transmitters incorporate DCC of some kind, as well as some mediumwave (MW) transmitters. DCC causes the carrier wave level to be automatically reduced when the audio is very weak or no audio is present. During periods of silence (no audio), the carrier power is reduced by 50%, so the 250 kW transmitter is putting out a carrier of 125 kW during audio pauses. This carrier power reduction saves electricity. == History == This amplitude modulation (and vestigial SSB modulation) energy-saving mode was devised in the late 1930s. DCC was not implemented in transmitter designs until the 1980s, because of some of the complexities of the control circuit. * DCC's development is linked to NATO nations trying to save energy as a result of the ripple effects of OPEC related oil supply crises. * DCC is still an option on all shortwave transmitters sold on the open market today, since it is almost universally mandated by the purchasers of shortwave transmitters. * Eastern European manufacturers of shortwave transmitters tended not to adopt DCC because Russia in particular had no energy crises, due to its abundant supply of oil. 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「Dynamic carrier control」の詳細全文を読む スポンサード リンク
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