When looking for SMA you may find SMA and RP-SMA connectors. What is the difference in these two?
Reverse polarity SMA (RP-SMA or RSMA) is designed to be incompatible with standard SMA connectors to comply with U.S. FCC regulations which seek to prevent consumers from attaching non-standard aerials to wireless devices.
The male RP-SMA connector has the same external housing as a standard male SMA connector except the center male pin is replaced by a receptacle. The female RP-SMA connector has the same housing as a standard female SMA connector however the pin found on a male SMA connector is on the female RP-SMA connector.
Here are some picture examples to help show the difference.
In this first picture the plugs are on the left and the jacks are on the right. The pair of SMA are shown on the bottom the RP-SMA pair is on the upper half of the photo.
This second picture shows the RP-SMA pair on the left and the SMA pair on the right.
Here are the different types you can click on to bring you to a list of each catagory if you would like further examples.