I swear I was fixing to go to buy a $30 antenna from the store for my wireless router, when I suddenly snapped out of my dull torpor. Checked for diy on the 'net first! And then I found your site. I tried the parabolic reflector template on my little D-link 802.11g wireless router, and it worked like a charm. Since there were no detailed instructions for someone who has no clue, thought I should send them:
I basically added +3dB of signal in the far corner of the house! Awesome! Thanks for the tip.
It should take less than 30 minutes to make your own parabolic reflector that will dramatically increase the range (in a single direction) of a wireless access point with an external antenna.
Draw a parabola, using pencil and string is an animated tutorial showing you how to create your own template. Be sure that the focal point is ~ 2.267 inches from the surface of the parabola. Now cover your manila folder or thin cardboard with the foil, and bend into the parabola that you just drew. Put the wireless antenna at the focal point and point it towards the access point.
The Parabola Calculator freeware program was designed design solar collector projects, but it works just as well calculating the focal length and (x, y) coordinates for a parabola of any diameter and depth.