A pair of motorola WR850G routers, and DD-WRT firmware, using "client
bridge" on your side.
Look on ebay, there's a fellow selling them with the fimware already on for
$40
They use a single RPSMA connector.

Then pop over to here: http://www.wlanparts.com/product/1CO-24002
Apparently I got the last one for now, but they have others, and they have
RPSMA connectors for LMR-400, but you will need the right crimp tool.
LMR400 is a low loss, high frequency, semi-rigid cable.

Without a line of sight it's dicey, and very little wifi stuff is low power,
but you may be able to do a bounce off something like a building, water
tower, billboard, etc that you both can see.

Southern Ca foxhunters know all about the "Baldy Bounce", reflecting signals
at 144 MHz off Mt Baldy.
Been there, done that, literally. :)
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