Connectors 101: RP-SMA vs. SMA
What is the difference between RP-SMA and SMA connectors, and why are they both necessary?
SMA connectors were introduced in the 1960s as a name change to the BRM connector developed by James Cheal in 1958, and are commonly used in radio and communication equipment. They follow connector gender standards, with the female having a center hole, and male having a center pin.
Contrary to popular opinion, RP-SMA (which stands for reverse polarity SMA), was not developed to make consumers go crazy. WiFi equipment manufacturers needed to develop equipment with connectors that would not breach FCC EIRP restrictions. RP-SMA was developed as a solution.
RP-SMA looks nearly identical to SMA but the pin and hole are inversed. Therefore RP-SMA male have a center hole, while RP-SMA female have a center pin.
For most Rokland WiFi and Helium hardware, the connectors will be RP-SMA so that manufacturers will be in compliance with the FCC EIRP rules. Other radio equipment we sell, such as our LILYGO hardware for Meshtastic, uses SMA connectors. At time of this article publication, we don't sell coaxial cables with SMA connectors. This is because the bulk of our business is RP-SMA related. But you can use any of our RP-SMA cables with SMA devices with this barrel converter.
The converter is a must-have for anyone in radio, especially hardware devs, as sooner or later you will find yourself holding an SMA female device and an RP-SMA antenna or cable.