Originally Posted by Penforhire
I've read several on-line plans for directional antennas, mostly a shaped framework holding aluminum foil (I recall one was a modified Pringles can).
AFAIK that's just for the receiver end. Either the tablet itself would need to be manufactured with an external antenna connector (not happening), or you would need to substitute an external USB WiFi receiver for the one inside the tablet (maybe possible).
I don't think you will get as spectacular improvement with a transmitter-side antenna improvement as you can on the receiver side. On the transmitter side, I would instead probably go for buying some sort of repeater, such as Harry suggests in number five. But if just a modest boost would be good enough for Villordsutch, I would try this:
Boost Your WiFi Antenna for Less Than a Dollar
The reason I didn't try the Pringles idea for my parents (see #2) was appearance and aiming. Most pictures of homebuilt directional antennas I see on the net include a camera tripod for aiming, which wouldn't have enhanced their bedroom. It was worth $20 for the gadget I bought just to have the easy-to-aim-and-forget plastic hinge design.