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RG-59/U is a specific type of coaxial cable, often used for low-power video and RF signal connections. The cable has a characteristic impedance of 75 ohms, and a capacitance of around 20pF/ft (60pF/m).〔http://objects.eanixter.com/PD361313.PDF〕 The 75 ohm impedance matches a dipole antenna in free space. ''RG'' (for ''radio guide'') was originally a unit indicator for bulk radio frequency (RF) cable in the U.S. military's Joint Electronics Type Designation System. The suffix ''/U'' means ''for general utility use''. The number ''59'' was assigned sequentially. The ''RG'' unit indicator is no longer part of the JETDS system (MIL-STD-196E) and cable sold today under the RG-59 label does not necessarily meet military specifications. RG-59 is often used at baseband video frequencies, such as composite video. It may also be used for broadcast frequencies, but its high-frequency losses are too high to allow its use over long distances; in these applications, RG-6 or RG-11 is used instead. In cases where the transmission distance is too long for these media, such options as UTP (unshielded twisted pair) or fiber optic can be used. RG-59 coaxial cable is commonly packed with consumer equipment, such as VCRs or digital cable/satellite receivers. Manufacturers tend to include only RG-59 cables because it costs less than RG-6 does. However, given the short lengths provided (usually ), this is generally sufficient for its typical use. RG-59 is frequently used to synchronize two digital audio devices, such as ADAT optical devices. This is called word clock. The higher breakdown voltage of RG-59 allows for higher voltage use in scientific experiments. ==See also== * BNC connector * Coaxial cable * RG-58 — A similar cable but with an impedance of 50 or 52 ohms 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「RG-59」の詳細全文を読む スポンサード リンク
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