>From a simple perspective.. I can see packets from sites at Stanford at my home in the Berkeley hills.. quite a long path!
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Tim Pozar Sent: Tuesday, December 10, 2002 12:00 PM To: Robert R. Ballecer, SJ Cc: [EMAIL PROTECTED] Subject: Re: [BAWUG] Cross-Bay link On Sat, Dec 07, 2002 at 06:30:56PM -0800, Robert R. Ballecer, SJ wrote: > Has anybody had experience with shooting 802.11b across the bay? I ask > because my organization has properties Fremont, Berkeley, San Jose, Santa > Clara (University), Los Gatos, Los Altos and San Francisco. Each location > is high enough to be able to "see" at least two of the other sites through a > telescope. There are not many practical uses for the link at the moment > (each site already has broadband access) but it might be a nice project for > my free time. > > I was thinking about getting a few of those Senao 200mw cards and use them > in conjunction with some homebrew antennas. Anybody have the equations I > need to figure out how the distance will affect S/N? What says the FCC about > 200mw cards? We tried one 20 mile link with 250mW amplifiers from Sign Hill in South San Francisco to a house in Hayward. The antennas were 24dBi dishes. We were able to get both ends to associate and get some data back and forth, but not consistently. You can see the path profile at: http://www.lns.com/projects/sunsetwireless/paths/Matt2SignHill.pdf Some of the problems we ran into was antenna alignment. 802.11 radios do not update C/N data fast enough and the data tends to bounce around. We decided that in order to line up paths you really need to use different transmission gear for antenna alignment such as a carrier wave at the frequency you want and a spectrum analyzer. This also helps as you really have a hard time tracking SS signals on a spectrum analyzer. Of course there are a number of things you need to look at before you get to this point. Looking through a telescope will pass some some tests but you need to look at other things like "refraction" and "fresnel zones" to insure that the data will get from one transmitter to the other. I think there has been some discussion on the list before in "engineering" paths. If not, I can put together one. Tim -- Snail: Tim Pozar / LNS / 1978 45th Ave / San Francisco CA 94116 / USA POTS: +1 415 665 3790 Radio: KC6GNJ / KAE6247 "A mass in movement resists change of direction. So does the world oppose a new idea. It takes time to make up the minds to its value and importance. Ignorance, prejudice and inertia of the old retard its early progress. It is discredited by insincere exponents and selfish exploiters. It is attacked and condemned by its enemies. Eventually, though, all barriers are thrown down, and it spreads like fire. This will also prove true of the wireless art." - Nikola Tesla in 1908 -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
