Slashdot Mirror
Portable Wi-Fi Antenna for Centrino Laptops?
Quinthar asks: "For years I've been reading of amazing extensions to wifi-range, but they always seem to include external hardware rather than what's built into regular laptops. As wifi makes it almost everywhere, is there anything I can use to eek out extra coverage in the coffeeshops? I've read of USB antennae -- are these snakeoil? If not USB, how else can I plug a real antenna into a simple Centrino chipset without the hassle of an external card? My dream would be a tiny parabolic dish with a tripod that folds up neatly. Does such a thing exist? Can I hold a Pringles can up to the right spot and expect results? Basically, what are my options, and which do you recommend?"
Yes, actually. I built one, and it works quite well. I have only bothered getting signals from a mile or so, but it should work up to two or even three.
Wonder what the public key field is for?
reflectors don't work unless their diameter is at least on the order of the wavelength you're trying to reflect. for 802.11b/g that's about 12cm - way bigger than most people would like to carry around.
A better alternative is the modern waveguide cantenna design - far more compact than the original Yagi pringles can designs.
Antennas generally achieve more gain by giving up coverage. Most stock 802.11 antennas are designed to radiate more or less spherically. Otherwise, you'd have to keep your laptop in a specific orientation to get a signal. Imagine the tech support... "Turn your laptop 20 degrees to the right. Anything now? Hmm. Try propping a book under the left side."
Cantennas get great range because they are highly directional. If I twist my Pringles can more than about ten degrees, the signal drops off to nil. And since 802.11 is a two-way protocol, there needs to be an eqivalent antenna on the far end. Your Yagi won't do you no good if the Omni at the far end can't even reach halfway back to you.
If all you want to do is listen, or send a signal from your house to your barn, cantennas are a good choice. But for a coffee shop?? Probably not. Just buy a laptop with a large antenna. Newer Thinkpads and Powerbooks generally have large built-in antennas.
Despite all this... Does anybody know of a reasonably priced USB wifi device that will accept a pigtail and a homemade antenna? I'd like to attach a large omni to my PCI-less and PCMCIA-less in-car computer.