Most often you don't want or need to increase your transmission power. What you are looking for is a better signal to noise ratio (often written as SNR, S/N). And a directional antenna will receive less noise from directions it's not pointed at.
To stay within the valid "effective" output power of your regulatory domain, you can lower the transmission power of the transmitter. Or you can spend your excess gain by adding a little of high-quality cabling that puts your antenna at a better suited location (but more often it will be easier to just move the whole WLAN router/card/dongle).
To stay within the valid "effective" output power of your regulatory domain, you can lower the transmission power of the transmitter. Or you can spend your excess gain by adding a little of high-quality cabling that puts your antenna at a better suited location (but more often it will be easier to just move the whole WLAN router/card/dongle).
A "pringles-like" design made out of stainless steel toilet-brush holders that includes experimental and simulation results (in German): http://www.heise.de/netze/artikel/print/100565