![]() Both male and female connectors use polytetrafluoroethylene (PTFE) dielectric. SMA connectors have an impedance of 50 Ohms used from DC to 18GHz. Connectors are made out of stainless steel or brass, coated with nickel or gold around the contacts. This coupling is fairly secure and has an outstanding mechanical durability. The male connector has a hex nut that fits securely around the female barrel for a tight coupling. The female connector has a threaded barrel with a density of 36 threads per inch. The SMA connector (Sub-Miniature Version A) is a semi-precision RF coaxial connector with a screwing coupling feature. ![]() This reversing is done on some equipment where there is a danger that the user might damage the connectors wile coupling due to their position or repeated mating. Standard SMA and RP-SMA connectors are not compatible. Similarly, the female has a central pin rather than a receptacle. R everse Polarity SMA (RP-SMA): The male has a central pin where the SMA-male has a receptacle. ![]() The female has a central receptacle and an outer casing with external threads. Standard SMA: The male has a central pin and a hex nut barrel with internal threading.Reverse Polarity SMA (RP-SMA) connectors: Standard brass connectors are also relatively inexpensive. Pretty simple, right?! Just make sure to match the antenna frequency with the your board.Īnd just in case if you happen to find the old and new mixing, we sell a SMA male to RP-SMA male and a RP-SMA female to RP-SMA male connector that will most combinations of antenna and connector to be mated.SMA connectors are favored for their screw coupling mechanism which is reliable and vibration resistant. If you have a RP-SMA board or module, you need a RP-SMA antenna and so forth for SMA. ![]() Really, you can ignore the gender descriptor. If the board does not have a u.FL connector to attach an external antenna, SparkFun RF boards and antennas will use a combination of the old (SMA) and new (RP-SMA):Ĭellular and GPS (900/1700/1800MHz and 1.57542GHz respectively) generally use the old convention: SMA male for the antennas and SMA female for the modules.Īnything 2.4GHz (Bluetooth, ZigBee, WiFi, and Nordic) generally use the new convention: RP-SMA male on the antennas and RP-SMA female on the modules. The next two photos are considered reversed polarized (RP-SMA). The RP (reverse polarity) is named after its “thread gender” and has an opposite-gender pin. The only thing that changed with the Part 15 compliance was the center pin, thus reversing the polarity of the connection and forming a “new” standard the reversed polarized SMA (RP-SMA). All of our boards are either SMA female or RP-SMA male. All of our antennas are either SMA male or RP-SMA female. There is one consistency however all antennas, cables or anything was being attached to a potential stationary object used an outer nut or inner thread design and all stationary devices used the outer thread design. If all antennas are female, there is no way to damage the center connector. The FCC gender change was instituted to prevent home users from damaging RF equipment (think home WiFi) when screwing on an antenna. Really annoying for those of us who need to mate an antenna to an RF device. All this means is that all the SMA RF connectors are changing gender (center pin). The above two connectors were designed to be used together, but there was a problem with this configuration and the FCC started moving towards Part 15 compliance. The original SMA design called for two compliant connectors: But from what I have found there was an original “old” design for SMA connectors. There are 4 different types of SMA connectors using a combination of gender, which refers to the center pin and polarity, which refers to….uh, this is where it gets confusing. Therefore, we need different antennas to match the specific gender or polarity of the RF connections. However, some of these boards use different genders and polarities of the SMA connector. SparkFun uses SMA-type connectors on a few boards that need a 50 Ohm impedance connection to an external antenna ( GPS, Bluetooth, cellular, Nordic, and XBee).
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