RF Connector Types (SMA, RP-SMA, BNC, N)
RF connectors are designed to join cable and antenna without breaking impedance continuity. SMA is threaded and small, RP-SMA is a reverse-polarity variant of it, BNC has a bayonet lock and fits quickly, and the N type is larger and suited to outdoor installations. Mismatched types may look mechanically similar but do not provide electrical continuity.
Connector choice concerns three criteria at the same time: impedance continuity, mechanical strength and sealing.
- SMA / RP-SMA: in RP-SMA the male-female arrangement of the inner conductor is reversed. They look the same, they screw together and it looks as if a connection has been made, but the inner conductor does not make contact.
- BNC: fits with a quarter turn, practical where it is frequently disconnected and reconnected; it is more prone than a threaded type to loosening in a vibrating environment.
- N type: larger, mechanically robust and, with its gasketed versions, suited to outdoor mounting.
The most frequent problems in industrial installation are the connector not being tightened enough, being left without a gasket outdoors and taking in water, and oxidising over time. All of these degrade return loss and reduce range. In AXI's IP67 sets the antenna is supplied together with cable glands; sealing the transition point with the gland is also the most practical way of protecting the connector from moisture.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety