The short answer is to put a SMA connector on it. From an RF standpoint, many of the USB WIFI adapters have pretty decent chipsets that are used to make up for their small antennas and limited board availability. In the case of the DLink DWL-122 (yes, I mis-spelled it on the board), the choice is a small f-strip antenna. The feed port can be identified by the tapered, triangle-looking trace, so that is where the SMA center feed will go. The other pad is for the return and will be connected to the outside of the SMA connector. Now that the USB device has a standard RF port on it, it’s quite easy to experiment with some personal antenna designs. The performance is not optimal since the tapered feed pad along with the SMA connector will create an impedance discontinuity, but it is quite easy to get better performance with simple designs. Below are comparisons of the signal strength with the f-strip and the whip antenna from the Fonera.