![]() ![]() These are similar to the SMA connector, but with the geometries incompatibly scaled, and a metric thread to prevent accidental intermating. The precision versions use an air dielectric with appropriately scaled center conductors.īeyond 46 GHz, the 2.4 mm, 1.85 mm (also known as V type) and 1.0 mm (also known as W type) connectors exist. These connectors keep the same outside thread as the SMA, so they can potentially be cross-mated, but the precision connector can be easily damaged when mating with low-grade SMA connectors. These include the 3.5 mm connector, rated to 34 GHz, and the 2.92 mm (also known as 2.9 mm, K type, or SMK), good up to 46 GHz. For performance above this, other SMA-like connectors are used. The SMA connector is typically rated for mode-free operation from DC to 18 GHz, though some proprietary versions are rated to 26.5 GHz. The air-dielectric is clearly visible in the 3.5 mm and 2.92 mm versions Top: male versions, bottom: female versions. ![]() Picture of SMA (left), 3.5 mm (center) and 2.92 mm (right) coaxial connectors. Type F cannot be mated with SMA connectors without the use of an adapter. SMA connectors must not be confused with the standard household 75-ohm type F coax connector (diameters: male 7⁄ 16 inch (11 mm) circular or hex female 3⁄ 8 inch (9.5 mm) external threads), as there is only about a 2 mm difference overall in the specifications. 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. 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. A 5⁄ 16 inch torque wrench is required for this, set to 3–5 in SMA connectors are rated for up to 500 mating cycles, but to achieve this it is necessary to properly torque the connector when making the connection. For that reason and that they are just rated for a limited number of connection cycles, an SMA connector is not usually a good choice for metrological applications. Variability in the construction and the mating of the connectors limits the repeatability of the connector impedance. ![]() The SMA connector uses a polytetrafluoroethylene (PTFE) dielectric that contacts along the mating plane. There are also reverse-polarity ("RP") SMA connectors in which the pin and sleeve are swapped so that the "male" RP-SMA has a center sleeve surrounded by an inside-threaded barrel, and the "female" RP-SMA has a center pin and an outside-threaded barrel. As with most other connectors, the gender assignment corresponds to the innermost electrical component. The centre pin is the same diameter as the centre of RG402 Coax so that connections can be made with no discontinuity, forming the pin from the coax itself. The male is equipped with a hex nut measuring 5⁄ 16 inch (0.3125 inch / 7.9 mm) across opposite flats, thus taking the same wrench as a #6 SAE hex nut.Ī standard-polarity SMA male connector has a 0.9mm diameter center pin surrounded by barrel with inside threads, and the standard SMA female connector has a center sleeve surrounded by a barrel with outside threads. The SMA connector employs a 1⁄ 4 inch diameter, 36-thread-per-inch threaded barrel. ![]() The interface dimensions for SMA connectors are listed in MIL-STD-348. It is also commonly used in radio astronomy, particularly at higher frequencies (5 GHz+). The SMA connector is most commonly used in microwave systems, hand-held radio and mobile telephone antennas and, more recently, with WiFi antenna systems and USB software-defined radio dongles. There are also mechanically compatible connectors such as the K-connector which operate up to 40 GHz. SMA was originally designed for use from DC (0 Hz) to 12 GHz, however this has been extended over time and variants are available to 18 GHz and 26.5 GHz. 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. Standard male SMA connector: male body (inside threads) with male inner pin ![]()
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