Yeah, it is a reverse polarity TNC plug. Unfortunately, the FCC mandated that all 802.11 transmitting devices had to be limited in coverage, which usually meant an internal antenna, or a compliant OEM external antenna. But thankfully, there is this newfangled thing called the internet, which has all kinds of goodies, like RP to "normal polarity" adapters, cables, etc! Legally, an owner of an 802.11 transmitting device CANNOT change the antenna to something other than the useless piece of crap provided by the manufacturer, but "hey" who HASN'T done that!