I'm having some issues with the signal dropping from my wireless router. It seems to drop from very good to low to non-existant in the upstairs rooms. Router is downstairs and is beside a window and outside wall – I've read that this is probably the worst place for a router but it's not really practical to have it anywhere else. I could possibly run a phone extension into the understairs cupboard which is the only room with no external walls.

But I'm thinking a signal booster may be an easier option. Any recomendations?

I built a cantenna recently as I needed a bit more range on a wireless connection.

I followed these instructions:
http://www.turnpoint.net/wireless/cantennahowto.html

and built this:

I went from 8 access points using the built in antenna to 100 odd in kismet with some antenna moving – bear in mind its pretty directional.

I must add I am doing nothing illegal and not connecting to any network that does not belong to me or that I have permission to access.

Have you checked the channel your wireless is on?

Download netstumbler to see other SSID's around your area, when I had your problem I found that 3 other houses nearby were on the same channel as mine. Changed my channel and not one drop since

HTH