On Sun, Nov 13, 2005 at 03:18:16PM +0000, Stroller wrote: > On Nov 13, 2005, at 5:51 am, Willie Wong wrote: > > > >If you have line-of-sight, you might be able to make do with a > >pair of directional antennae set up in the right way, and you might > >need a way of increasing the power output of the antennae. Any such > >modifications, however, is surely ILLEGAL in most civilized > >municipalities. > > > >The long-range wireless guys who have been doing stuff like this all > >have ham licenses, and are allowed quite a bit more power from their > >devices then us lowly consumers.... > > I think you're mistaken here. 802.11 is on an unregulated part of the > frequency spectrum, so ham radio operators have no more rights when > operating in it than the rest of us.
My bad. Somehow I thought 802.11 is regulated, which, of course, on hindsight, is completely stupid. Barring that, there are still transmission power limits by local governments. > > 802.11 is perfectly achievable over distances of a kilometer, providing > line of sight is available, and legally. The requirement is not to emit > more than a certain signal strength (about 18dB or 20dB, I think) but Hum, you are probably more knowledgeable then I am, but I am sure there are both absolute power limits AND power density limits imposed by most governments? http://www.oreilly.com/catalog/802dot11/chapter/ch15.html of course, one presumably won't go hacking the transmitter to output more power than was set at the factory, which is probably close to the legal limit anyway. So one does need to only worry about power density. > signal strength is a product of transmitter power and amplification > caused by the aerial. A very directional aerial amplifies the signal > lots, but if you combine this with a low-power transmitter then you can > still creep in under the legal signal strength. If, you are in Europe, for example, to get reliable 1km coverage from the 66mW legal limit on the transmitting device, some simple math (or a quick search on the internet-what I did) says you need a 10-12dB gain from your antenna. You probably need a good Yagi or Parabolic for your antenna to get the required gain. And I would _hate_ to be the one having to set up the line-of-sight link between two parabolic antennae.... W -- (aikamuotojen k?ytt? aikamatkustuksessa) "You can arrive (mayan arivan on-when) for any sitting you like without prior (late fore-when) reservation because you can book retrospectively, as it were when you return to your own time. (you can have on-book haventa forewhen presooning returningwenta retrohome.) " Sortir en Pantoufles: up 1 day, 11:03 -- gentoo-user@gentoo.org mailing list
