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Explain Reverse Polarity “RP” Connectors

Why are some of your connectors RP (reverse polarity)? What is the difference between RP and a standard connector?  Identifying RP connector gender is very confusing!

BACKGROUND:
The reverse polarity (RP) connector specification is mandated by FCC Part 15 for ISM equipment which includes WiFi equipment. The FCC specifies that these connectors must be reverse polarity which means that the pins/contacts are switched between genders so that adapters will not mate with standard coaxial connectors.

Properly identifying a connector involves first determining the GENDER and then determining the POLARITY.  The two are independent of each other.

STEP 1: DETERMINING RF CONNECTOR GENDER:
Contrary to most people’s instinct, the polarity of connectors is determined by the *BODY* of the connector, not the center jack or plug.  When determining gender, ignore the center jack or plug and instead look at the body of the connector.

  • All threaded RF Connectors with the THREADS ON THE INSIDE of the body are MALE connectors regardless of polarity.
  • All threaded RF Connectors with the THREADS ON THE OUTSIDE of the body are FEMALE connectors regardless of polarity.

STEP 2: DETERMINING CONTACTOR GENDER AND POLARITY:
Now that you have identified the gender of the body using the above rule, you need to identify the gender of the contactor to determine if the connector is standard or reverse polarity.  Focus on just the contactor in this step.  Regardless of the gender of the body, if the contactor is a plug (a pin), it is a MALE.  If the contactor is a jack (a hole) then it is a FEMALE.  Now compare this to the gender of the body.  If the gender of the body and contactor are the same, it is a standard polarity connector. If the gender of the body and contactor are opposite, it is a reverse polarity connector with the GENDER of the BODY.  Here are the four possible outcomes:

  • A MALE connector body with a MALE PLUG is a MALE standard polarity connector
  • A MALE connector body with a FEMALE JACK is a MALE reverse polarity connector
  • A FEMALE connector body with a FEMALE JACK is a FEMALE standard polarity connector
  • A FEMALE connector body with MALE PLUG is a FEMALE reverse polarity connector

Example of the difference using an SMA connector:

sma male SMA Male

  • BODY GENDER: Male – Threads are Inside
  • CONTACTOR GENDER: Male Plug (pin)
  • POLARITY: MALE Standard polarity – Body and Contactor Gender Match
RPSMA Male RP-SMA Male

  • BODY GENDER: Male – Threads are Inside
  • CONTACTOR GENDER: Female Jack (hole)
  • POLARITY: MALE Reverse polarity – Body and Contactor Gender are Opposite
SMAF SMA Female

  • BODY GENDER: Female – Threads are Outside
  • CONTACTOR GENDER: Female Jack (hole)
  • POLARITY: FEMALE Standard polarity – Body and Contactor Gender Match
RPSMAF RP-SMA Female

  • BODY GENDER: Female – Threads are Outside
  • CONTACTOR GENDER: Male Plug (pin)
  • POLARITY: FEMALE Reverse polarity – Body and Contactor Gender are Opposite

Other Notes:

There is no difference between the standard and RP type connectors as far as RF performance is concerned.

If you are developing a product for the ISM band, you should be using reverse polarity connectors for any user accessible external connectors on your device. This is according to FCC rules for Part 15 devices.

If no gender is specified, it is always assumed to be a Male connector. Example: “RP-SMA” indicates an RP-SMA Male connector

A Male connector is also known as a “Plug”
A Female connector is also known as a “Jack”

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