totally amateur question: How to attach an antenna to my laptop?

Hi,

I have a thinkpad T40 running OpenBSD and live in a small, nice city close to Barcelona whose city hall offers free wifi Internet to everybody.

Unfortunately they do not have a good coverage and where my building is, I don't get any signal. The card is identified by OpenBSD as ath0, which means it's Atheros.

Now, I am thinking of building an external wifi antenna but I don't have the slightest idea of how to do it. I don't have the time (unfortunately! it looks fun!) of building the antenna by myself, like here

Antenna on the Cheap (er, Chip)

so that I'd buy one. The problem is... which one? I have seen a lot of them in ebay but I'm not sure they are for the laptop and not just for the router, to enhance its signal.

This guy seems to have managed to do exactly what I would like

PORTATIL IBM CON ANTENA WIFI 9 DBI EXTERNA Y 2 BATERIA en venta en eBay.es (finaliza el 27-ene-08 14:55:38 H.Esp)

So, my question is

1) which kind of antenna do I need? I think I will need to increase the coverage radius to up to 1-2 km

2) how do I attach the antenna to the thinkpad?

3) will it be compatible with the card?

4) will the OS automatically "see" a broader range? I mean, is it something mechanical or will I have to play around with the driver?

thanks in advance!

Pau

1. You cannot (legally) have an omni-directional antenna that does 1-2km. I don't feel like doing the math right now but that would be a REALLY, REALLY powerful antenna. You can however make/buy a directional antenna that will go that far.

Please see this informative, yet horribly designed, animation on how wireless networks work.

2. The example ebay listing given is obviously a hack job. There are wires that run into the LCD panel area to connect to antennas there from the wireless card in the bottom of the laptop. I am the maker just drilled a hole, put a connected in and re-routed one of the wires. It's a nice mod, good luck.

3. Just buy (or make) the appropriate length cable to go from the wireless card to the spot on the back of the laptop. Be sure to make sure you get the proper connectors (i.e. buy the antenna first).

4. It's pure mechanics, or rather antennas.

9dbi is a decent gain, but if your house is not even getting the slightest hint of a signal at all, you may just be SOL.

See http://www.usbwifi.orcon.net.nz/ for some nice and cheap directional antenna ideas.

-MLFnet