Connecting an antenna to a Wi-Fi card (or USB Wi-Fi device) requires a way to connect an external antenna to the card. If there is any kind of external connection at all for an antenna on the card, you can probably find a way to connect almost any antenna, although it may require a special adapter, sometimes called a radio pigtail. You can find lists of pigtails to fit most Wi-Fi cards (and buy them) at www.wifi-plus.shoppingcartsplus.com/page/page/557856.htm, or www.hyperlinktech.com/web/cable_radio_pigtails_list.php, or www.jefatech.com/category/cable_assemblies/.
Some cards come with sockets that will fit most antennas without any special adapter. For example, Figure 17.5 shows the D-Link DWL-520 card installed with the antenna that ships with the unit.
To install a more powerful antenna than the one that ships with this model, unscrew the original antenna so that you see the antenna socket, shown in Figure 17.6.
With the antenna unscrewed, you can use the socket to connect many antennas with the connectors that ship with the antenna.