SubMiniature Version A Connector

What Does SubMiniature Version A Connector Mean?

An SubMiniature version A (SMA) connector is a coaxial cable connector developed in the 1960s as a semi-precision minimal connector interface with a screw-type coupling mechanism for coaxial cables. This connector features only 50 ohms of impedance and a 1/4-inch-36-thread-type coupling mechanism. It offers excellent performance from 0 to 18 GHz and is usually used as an RF connector for antennas.

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Techopedia Explains SubMiniature Version A Connector

The SMA connector is considered a semi-precision, sub-miniature and high-frequency connector that is rated to deliver reliable broadband performance from DC to 18 GHz, with a constant impedance of 50 ohms and low reflection. The main features of this connector are its high mechanical strength and high durability, as evidenced by its robust-looking metal construction.

The male connector is the one with the center pin and inside threads of size 1/4-inch-36, whereas the female connector is the sleeve counterpart that features an outside thread and is used to hold the connection in place. The latter is often placed on and attached to a stable device, whereas the former is located on the detachable wire attachment.

A newer reverse-polarity SMA specification (RP-SMA or RSMA) reverses the polarity of the genders so that the female connector now has the center pin and the male connector has the center receptacle, but the threads and other features remain the same. This was apparently done on purpose by the FCC to prevent home users from damaging sensitive RF equipment when screwing on the antenna.

Some mechanical features of the SMA connector include:

  • It uses a 1/4-inch-36-thread-type coupling mechanism.
  • The male connector is equipped with a 5/16-inch hex nut to allow torque by a 1/2-inch wrench.
  • The female connector has a 4.32-mm-long thread for coupling.
  • It has a silicon rubber O-ring, which separates the main body and coupling nut for dust resistance.
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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.