Project Byzantium: Zero To Ad-Hoc Mesh Network In 60 Seconds (Video)
Project Byzantium calls itself Ad-hoc wireless mesh networking for the zombie apocalypse. It's also potentially useful for less-thrilling emergencies, such as floods, earthquakes, and political uprisings (or getting everyone at the office their /. fix when the network goes down). The latest version debuted at the HOPE (Hackers on Planet Earth) conference in July, 2012. You can download your very own copy of Byzantium any time you like. Hopefully you will then burn a dozen or so CDs (it's compact enough that it doesn't need a DVD) for friends and neighbors, so that if you suddenly see zombies approaching and your regular ISP has already been overrun and isn't working, you can set up a wireless mesh network and coordinate your anti-zombie efforts. And you won't even need to use the command line. (slides and audio of their presentation)
Put the antenna higher up or use a directional one. Absorption by the environment is usually even worse than inverse square losses.
With clear line of sight and no Fresnel zone obstruction, a quarter mile should be completely possible. Look up the distance record, it's remarkable.
In regular ad-hoc, you can see the people around you, but not reach their neighbours (there is no routing by default). Byzantium uses babeld, which is a routing layer over an "ad hoc" mode. The mesh network automatically recalculates routes, depending on their signal and link saturation. If you're into networking, it's really trivial to setup and lots of fun (especially with ipv6, although ipv4 works too of course).