There are several ways to set up long-range Wi-Fi, all of which essentially involve a pair of directional antennae. The antennae can simply be wireless router antennae placed near the foci of anything roughly paraboloidal in shape, e.g. a metallic bowl, a can, or a satellite disk.
Depending on distance, standard wireless cards rigged to a can may suffice. For long distances, you'll need to position an antenna in a satellite dish with some precision.
Try getting in touch with ham radio enthusiasts. There are several forums that can probably help you; read about these guys, who set up a 304 km link.
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