SMA vs BNC vs RP-SMA: RF Connector Differences Explained
Time:2026-06-26
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These three look similar at a glance — they‘re all threaded RF connectors — but they‘re not interchangeable, and getting the polarity wrong is the classic trap. The one-liner: SMA and RP-SMA are the same size but with the centre pin on opposite sides, and BNC is a bigger, quick-connect cousin used for test gear and video.
SMA. SMA (SubMiniature version A) is the standard threaded RF connector for antennas and RF modules. The male has a centre pin, the female has a socket, and the thread is on the outside of one side. It‘s rated to 18GHz or higher, handles up to a few watts, and it‘s what you‘ll find on Wi-Fi and cellular modules, GPS, and RF test equipment. It‘s small, precise and, because of the thread, it stays connected through vibration — which is why antennas use it instead of a press-fit.
RP-SMA. RP-SMA is the reverse-polarity version, and it exists mostly because of a regulatory rule for consumer Wi-Fi equipment. The centre pin is flipped: the side that looks like a male has a socket, and the side that looks like a female has a pin. It‘s the same thread and the same size, so an RP-SMA and an SMA will physically screw together — but the centre pins won‘t connect, and you‘ll get no signal. If you‘re buying an antenna for a Wi-Fi router or module, check whether it‘s RP-SMA or SMA before you order, because the two are frequently confused.
BNC. BNC is a bayonet connector — you push and twist a quarter turn instead of screwing — and it‘s bigger than SMA. It‘s rated up to about 4GHz, which is plenty for the test equipment, CCTV cameras and older video gear where it‘s used. The bayonet is the point: it connects and disconnects in a second, which is exactly what you want on a scope probe you‘re plugging and unplugging all day. It‘s also common on RF test leads and some broadcast gear.
Picking one. If it‘s an antenna on a module, the datasheet usually tells you straight out whether it wants SMA or RP-SMA — match it, don‘t improvise. If it‘s test equipment, BNC is the safe default. And when you‘re sourcing, watch the impedance: these come in 50 ohm and 75 ohm versions, and mixing them on video or RF lines costs you signal. We stock SMA, RP-SMA and BNC connectors and cable assemblies in 50 and 75 ohm, plus adapters between them. Send us the module or antenna you‘re mating to and we‘ll get the polarity right the first time. If you‘re interested, please contact us right away.
Frequently Asked Questions
Can I connect SMA to RP-SMA?
Not directly. RP-SMA has reversed polarity, so the centre pin and socket are swapped. You need an adapter.
Is BNC the same as SMA?
No. BNC is a bayonet quick-lock rated to about 4GHz; SMA is threaded and goes to 18GHz or higher.
Which one do I need for Wi-Fi antennas?
Most Wi-Fi gear uses RP-SMA, so verify polarity before ordering. We stock SMA, RP-SMA and BNC connectors and assemblies.
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