Summary

This is a slotted waveguide antenna for the tp-link WR703N wifi travel router. It fits over the box, so no modifications to the router are needed. It changes the radiation pattern to a pie-segment shape: horizontally it is about 120degrees wide, vertically it is much narrower.
The dimensions are limited by the lasercutter I used, an antenna with more slots would give a better gain.
I have not tested this antenna yet...

Instructions

Cut out the drawings from 3mm plywood, I used birch ply, but any wood that cuts good on the laser is fine, 1/8" should work as well.
Assemble the box without the front panel. I had to use an extra offset (in the drawing) to compensate for the laser kerf thickness. It was designed to be a tight press fit, but If you wish to use glue that is fine too (probably better if you wish to use it outdoors).
With the backside assembled, spray glue on the inside. Cover the inside with aluminium foil, making sure not to puncture the foil in the corners. Fold the foil over the side and cut it off any excess.
Cover the front panel backside with foil too, take care to cut away the foil from the slots as those are very important for the function of the antenna.
Next glue or tape the tp-link box on its spot at the bottom. Its edge should just align with the edge of the bottom panel.
Lastly , put the front panel in to close the box. The more electrical contact you have with the back, the better.

sorry, the TV interface seems to be broken again. I cannot upload a flickr image:
here is one: http://www.flickr.com/photos/protospace/8527427267/in/photostream
edit: no, it is the design that is broken: ther eis a textbox, but with it being white on white, is is functionally unfindable. -1 for vocking design.

here is the link that I used to calculate dimensions: http://www.protospace.nl/fabmoments/wr703n-slotted-waveguide

here is the thing on our site, in dutch, with some more pictures: http://www.protospace.nl/fabmoments/wr703n-slotted-waveguide

Slotted waveguide for TP-link WR703N