Victoria to Port Angeles Wireless Link
On February 29, 2004, PersonalTelco's AaronBaer held an Antenna Workshop where we assembled biquad antennas based on the design by Trevor Marshall. When joined to a PrimeStar dish, the combined units should produce a gain of 30db. A similar design in Western Australia near Perth, resulted in a 30 mile range over the ocean.
The goal is to create hardware for an international link, from Canada to the United States over the Strait of Juan de Fuca, the major shipping channel that divides the two countries.
The city of Port Angeles, Washington is some 30 miles from Victoria British Columbia. On July 10th a "free" 802.11a link will be attempted between these two cities.
Here's The Terraserver for maps and Acme Mapper for photos.
Trevor Marshall's biquad design (see here for detailed construction info), feeding a Primestar satellite dish has established has established a solid 30 mile capability with 10-15 dB (SNR) link from Rottnest Island off the West Australian coast, to a number of APs on the escarpment east of Perth; a distance of 48 km (30 miles).
Technical Approaches
Trevor Marshall, Perth's Community LAN site, E-3, and Everett Wireless have been building homebuilt waveguides.
Here's a +22 dB design made from aluminum foil and styrofoam.
Tests with Long-Distance Waveguides look good but a PrimeStar dish will provide more gain, as it's much more directional. Slotted waveguides are definitely not suited to point-to-point links, as they are omni-directional, while a PrimeStar dish is very directional.
The 5.8 GHz Option
The 5 GHz band has about 8 dB more loss than 2.4 GHz at long range. With 6 db loss, range is halved. So 5.8GHz will need more than twice the gain.
Atheros Xtended range chips claims receive sensitivities up to -105dBm. That's more than 10-20 dB better than other 802.11 chips. Atheros claims XR will triple the range for their dual-band, AR 5004. The Atheros 5004x brings "Xtended Range" to the 5.8 GHz band.
Netgear's WGT624 uses Super G technology. 
D-Link's DI-624 Wireless Router, their DWL-G810 "G" bridge and Netgear's WGT634U Wireless Media Router use them. Right now they're "G" only. But a dual-band 802.11a/g wireless router that doubles as a bridge might provide increased range and sensitivity at 5 GHz.
The AR5004X 802.11a/g chip set with XR, can reach distances of over 700 meters, but the XR technology is a two-way technique that must also be implemented in an access point.
You might feed a couple Proxim MP.11a bridges ($600) into a 500mw, 5.8 GHz amp ($675), with a 28 dBi 5.8 GHz flat panel ($535) on each side. [http://www.ydi.com/calculation/som.php YDI's Operating Margin Calculator can help you estimate operating range.
The tiny Asus Access Point can also be used as a bridge. A long distance link might simply use a +23db, 5.8 GHz flat panel, with an Atheros Xtrended Range bridge plugged in. Could 100 mile WiFi Video be possible?
References