What is the difference between SMA and RP-SMA?

02.10.2019

The terms SMA, RP-SMA and the corresponding sockets and antennas, which are referred to as male and female, can easily cause confusion. To ensure that the screw always fits the nut, we have taken a closer look at the various connection options for WLAN and GPS antennas.

What is SMA?

The abbreviation SMA stands for "SubMiniature Version A" and refers to a coaxial connector for high-frequency applications, which was developed in 1960. As this connector is screwed , it is mechanically very robust and also offers good electrical shielding.

It is used in microwave (to connect the high-frequency cables that transmit microwaves), portable radios and cell phone antennas. In our mini PCs, SMA is used for connecting WLAN or GPS antennas. An SMA connector is used in frequency ranges from 1 GHz to 18/26.5 GHz. From 27 GHz, more modern connectors, so-called "Super SMA", are used. SSMA (Small SMA) was developed for use in space and can be used up to 40 GHz.

What does an SMA plug look like?

The SMA connector consists of a plug and a socket. The connector is the SMA antenna connection, which consists of a union nut with an internal thread and a metal pin as the inner conductor. In this case, this is the so-called "male" connection. The corresponding "female" SMA socket is located on the housing of the PC, with an external thread and a metal tube into which the pin of the plug fits.

What is RP-SMA?

RP-SMA stands for "Reverse Polarity" (sometimes just referred to as Reverse-SMA or "R-SMA" for short). It was developed to prevent unauthorized connection of an external antenna to increase the range. The gender of an RP-SMA connector has been swapped, so to speak. The RP-SMA male is also the connector with the union nut, but it has the metal tube as the inner conductor. The RP-SMA female connector has an external thread and a pin on the inside.

When plugged in, the two are indistinguishable and the signal quality is also the same. An RP-SMA plug fits mechanically into an SMA socket, but not electronically. Such a connection is therefore not functional. If the socket and plug do not match, adapters can provide a simple solution to equip these mini PCs with antennas.

More spo-comm knowledge