You will need a spare USB cord and your Fonera's power supply. Cut whatever length of cable you want off of the Fonera power supply. This will determine the overall length of the cord. Then, cut about 2-3" off of the male end of your spare USB cable.

Strip about 1" off of the USB cable. You will see a number of wires, the only ones we're interested in are the red and black wires so cut off all the rest. The red wire will connect to the positive wire of the Fonera AC adapter and the black will go to the negative.

On the AC adapter that came with my Fonera 2200, the dotted lines indicated the negative wire and the writing indicated positive.

To figure out which is positive and negative, plug the AC adapter into the wall and use a multimeter to test both wires. If you get a negative reading, then you have the wires switched around (the positive lead is on the negative wire and the negative lead is on the positive wire).

Solder the connections, do not cheap out and just electrical tape them together. The USB wires are very tiny and electrical tape just won't hold it in place.