I use a modification of this plan for a wifi antenna and it works great.

Instead of a coffee can, I used a heavy steel pasta strainer.

I soldered the nail in the center hole with copper wire wrapped around the nail.

I connected the wire from the old antenna to the copper wire and the ground to the outside handle of the strainer.

Attached to the computer I was able to pick up 9 more wifi signals than the original antenna. Even my friends network 4 blocks away