SMA Characteristics and Key Points

• SMA is often confused with RP-SMA (Reverse-Polarity SMA). SMA is more typically used in cellular wireless, GPS, and HAM radio applications, while RP-SMA is more commonly used with Wi-Fi, Bluetooth, ZigBee, and LoRaWAN (in the United States).
• SMA female connector is also called "jack" and SMA-male is also called "plug."
• SMA is a round screw-type connector, with medium-sized, threaded coupling connectors that are rated for frequencies from the lowest (DC) up to 18GHz.
• SMA gender is counter-intuitive: The bender is based on the orientation of the pin and socket (on the interior of the threaded section of the body): Male has a pin and female has a socket.

SMA-Connector Materials Composition

• Connector Body:
  • SMA connectors that are on antenna cables have a gold-plated brass body (in almost all cases), because this is the best alloy for the connector-body, if intended for indoor use.
  • SMA adapters that are expected to be exposed to water or weather have a nickel-plated brass body for protection from rust and corrosion.
  • SMA connectors for cables and antennas, if they will have weather exposure, can be made with a nickel-plated brass body for corrosion protection.
• Center Contact: Beryllium Copper, Gold Plated
• Crimp Ferrule: Nickel Plated Copper
• Insulators: PTFE

SMA male and female diameter

• SMA female outside diameter is 5/16" (7.9375mm): Accommodates a hex nut (bulkhead nut) with 5/16" nominal outer diameter
• SMA male inside diameter is 5/16" (7.9375mm) (the inside diameter where the threads are).

Panel cutout for SMA bulkhead jacks

• Anti-rotation “D-hole” (best practice): Ø 6.5 mm (0.256 in) with a flat that leaves 6.0 mm (0.236 in) across the flat. Prevents the connector from spinning while tightening.  Data Alliance's default SMA connectors versions have the anti-rotation D-hole.
  

• Round hole (common, works with star washer): Ø 6.5 mm (0.256 in). This fits the ¼-36 UNS threaded barrel typically used on SMA bulkheads.
  

Other fit notes you’ll likely need

• Thread & nut: SMA bulkhead uses ¼-36 UNS threads; typical panel nut across-flats ≈ 8.0 mm (5/16 in). Leave clearance if a socket is used.

• Panel thickness: varies by the “short” vs “long” bulkhead style. As an example, one front-mount SMA jack shows max panel thickness ≈ 2.2 mm (0.087 in); long-thread versions allow more. Check your specific part’s drawing.

• Torque on panel nut: datasheets range from ~5 in-lb (0.57 N·m) for standard bulkheads to 12–15 in-lb for heavier/hermetic feed-through styles. Use the part’s spec and material (plastic vs metal panel) to set final torque.

Exceptions to watch for

Not all “SMA bulkhead” parts use the small 6.5 mm hole. Hermetic feed-through adapters (female-to-female) and some ruggedized variants can require much larger holes (e.g., Ø 0.500 in)—always confirm against the exact drawing.

Quick install tips

1. Prefer the D-hole when you can; it prevents rotation during assembly and service.

2. If using a round hole, include the supplied star/lock washer and don’t exceed the connector’s torque spec.

3. For sealed front-mount parts (IP67/68), mind the O-ring land and panel finish per the drawing. (Dimensions are usually on the same sheet as the D-hole callouts.)

If you share the exact SKU(s) you’re using, I can pull the customer drawings and give you a one-page cutout sheet (DXF + PDF) with hole, flat, and keep-out dimensions for your panel fab.

FOOTNOTES:

1. We offer an SMA wrench to assist in installing antennas, SMA cables and adapters with SMA or RP-SMA connector(s).