Question: What is the Difference Between SMA and Reverse Polarity SMA Connectors?

Tech Support: Reverse Polarity Connectors

(Image Comparing Standard and Reverse Polarity SMA)

Question: What’s the difference between a regular SMA Connector and a Reverse Polarity SMA Connector?

In the late 1990’s, at the dawn of the WiFi technology boom that has inevitably changed the way we communicate, the Federal Communications Commission was greatly concerned. Soon, wireless routers and access points would be entering the market and blasting the airwaves with short-distance transmissions that had never previously entered our airspace. While these devices were designed to have a limited range, generally enough to cover a typical residence or office, the FCC knew that it was only a matter of time before users would attempt to boost the device’s range with amplifiers and/or external antennas, which could potentially wreak havoc on the WiFi band. The FCC’s solution was a stop-gap measure known as Reverse Polarity Connectors.

For decades, SMA and TNC connectors have been used successfully for high-frequency applications, such as cell-phone networks. The problem was that SMA’s and TNC’s were readily available on the market in the form of coaxial cable assemblies and antennas. To prevent users from equipping their wireless routers with such accessories, the FCC mandated the WiFi manufacturers utilize a new type of connector on the back of their devices — The Reverse Polarity Connector. For a couple of years, this strategy worked, but eventually Reverse Polarity versions of SMA and TNC connectors, known as RP-SMA and RP-TNC respectively, became just as readily available as their regular counterparts.

So how do you tell which one is which? A second look at the image above will help you. An SMA Male Connector is shown on the left. Notice that there is a pin sticking out of the center of the connector. A Reverse Polarity SMA (RP-SMA) Connector is displayed on the right. Notice that instead of a center pin, there is a center socket. It is the swapping out of a center pin for a center socket that makes the connector a Reverse Polarity SMA (RP-SMA). Note that both of the above connectors are considered male connectors. Male SMA and Male RP-SMA connectors both feature their threads on the inside of the connector shell, i.e. they twist onto a female SMA or RP-SMA connector that feature their threads on the outside of the shell.

You can never mix and match SMA and RP-SMA connectors because the pins and sockets will never actually make contact and allow the signal to pass thru. At Amphenol Cables on Demand (http://www.CablesOnDemand.com), we will soon be offering a complete selection of Reverse Polarity SMA (RP-SMA) and Reverse Polarity TNC (RP-TNC) Coaxial Cable Assemblies for use with your WiFi equipment. Not sure which type you need? If the RP-SMA does not look familiar, below is a comparison of a TNC and Reverse Polarity TNC (RP-TNC) connector for your reference: