One option is to buy a ready made BNC pigtail cable that is long enough and fix a socket on the board to match.

Alternatively as I do solder a RG174 type cable direct to PCB and then to your rear connector.

Do not extend the original wire.. I recommend everyone to replace it with a cable.

Raj

At 04/10/2020, you wrote:
>I'm trying to put my uBITX into one of the water resistant plastic "ammo cans" from Harbor Freight. So far it's going fine, but I'd like to put the antenna hookup further back than the cable will stretch. How can I run it back further without it picking up interference? If I use some thin coax, will that work? What sort of connector should I use on the main board?