SMA connector
SMA connectors are miniature coaxial 50 Ω connectors good to about 20 GHz.
The male connectors have a protruding center pin and ground shroud that screws on. The female is threaded on the outside. (Note that in the "Reverse Polarity" or "RP-SMA" connectors found in WLAN equipment, the pin is swapped to the shell with the exterior thread.)
SMA are somewhat similar to UHF connectors, but much smaller - initial Tektronix literature(Note1) calls them "3 mm connectors" - and with much tighter tolerances and better controlled impedance. SMA connnectors are used on the S-50, S-51, S-52, 7T11, S-4, S-6 and many later GHz-class instruments.
For yet higher frequencies, connectors similar to and partially compatible with SMA are used, such as the 3.5 mm connectors and 2.92 mm connectors found e.g. on some SD-xx series sampling heads.
(1) See Service Scope No. 52, Oct 1968 p.16, Something New in Oscilloscope Connectors
Pictures
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SMA Male
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SMA Female
