Want to build my own WiFi antea, don't know what coector I need.

I have a TP-LINK TLGWN722N WiFi USB adapter. The adapter has a coector on it so you can attach different exteal anteas to it. The manufacturer's website states the coector is RP-SMA. However, I think the coector is very small; it's 3/16 inches in diameter. I would assume the coector is female since it's reverse polarity and has a pin in the middle of the coector. Would just buying a cable that's RP-SMA male allow me to coect to it? Every coax cable I've found in my attic seems to be twice the diameter of the coector on the WiFi USB. I have a RG58 cable and the coectors on either end are twice the size of the coector on the USB. I thought that RG58 was made for RF (WiFi) purposes. I'd appreciate any insight on this.

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