All mini-pci wireless cards will have one (or two) connectors for an external antenna. They are really, really tiny connectors that are circular with a dot (wire) in the middle.
The connector type on the card will be a U.FL connector, also [less commonly] known as I-PEX. Most wifi antenna's will have a RP-SMA or TNC connector. Therefor, you will need three things:
- Mini-pci wireless card
- u.fl to RP-SMA adapter pigtail (or u.fl to TNC adapter pigtail)
- Wifi Antenna with either RP-SMA or TNC connector
Unfortunatly, the adapter pigtails are more then what you would expect to pay for them. They run about $10-13, plus shipping. There's lots of places online to find them, just search for "u.fl pigtail adapter"
There are lots of mini-pci wireless cards, so shop around to find one with the networking type (a, b, n, or combo of these) and output transmit/receiver power that you want. Higher output power means you'll have a better chance of a stable connector over a farther distance.
If you really need some examples, let me know.. but there's are LOTS out there -- especially if you look around at laptop supply places.