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SMA (''SubMiniature version A'') connectors are semi-precision coaxial RF connectors developed in the 1960s as a minimal connector interface for coaxial cable with a screw type coupling mechanism. The connector has a 50 Ω impedance. SMA is designed for use from DC to 18 GHz, but is most commonly encountered with WiFi antenna systems and USB Software Defined Radio dongles. SMA connectors can be visually confused with the standard household 75 ohm Type F Coax Connector (Diameters: Male 7⁄16" (11 mm) circular or hex; Female 3⁄8" (9.5 mm) external threads), as there is only about a 2mm difference overall in the specifications. Type F can only be mated with SMA if there is an adapter (possibly coupled with a Gender Changer). ==Connector design== The SMA connector employs a 1/4"-36 thread. The male is equipped with a 0.312 Inch (5/16 Inch) hex nut. This is not to be confused with a hex nut that accommodates a screw/bolt with 5/16" nominal outer diameter. This would result in an SMA connector that has larger minimum cross section dimensions than 5/16". Instead, the dimensions of the SMA connector are such that the width across the flats is 5/16". This is the same as the #6 SAE hex nut. Thus, the SMA connector requires a 5/16" wrench to fit across the flats. A 5/16" hex nut would require a 1/2" wrench to fit across the flats. In SMA connectors, the terms "male" and "female" refer exclusively to the male center pin and its female sleeve counterpart rather than to the threads that are used to hold the connection in place. The male connector has inside threads while the female connector has outside threads. The SMA connector uses a polytetrafluoroethylene (PTFE) dielectric which will contact along the mating plane. Variability in the construction and the mating of the connectors limit the repeatability of the connector impedance. For that reason and the fact they are just rated for a limited number of connection cycles, an SMA connector is not usually a good choice for metrological applications. SMA connectors are rated for up to 500 mating cycles,〔http://www.amphenolrf.com/products/CatalogPages/SMA.pdf〕 but to achieve this it is necessary to properly torque the connector when making the connection. A 5/16 inch torque wrench is required for this, set to 3–5 in·lbf (0.3 to 0.6 N·m) for brass, and 7–10 in·lbf (0.8 to 1.1 N·m) for stainless steel connectors. Flats are sometimes also provided on the cable side of the connector assembly so that a second wrench can be used to prevent it from rotating and damaging the joint to the cable. It is also advisable to inspect and clean out loose debris from the internal surfaces with compressed air or a gas duster can before mating. 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「SMA connector」の詳細全文を読む スポンサード リンク
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