[Hidden-tech] extended range wifi needed

[Dan Nachbar]

I have an "off the grid" wifi application (it's for
realtime data collection) where conventional wifi
doesn't have quite enough range.  

I need about 700 feet, outdoors, generally unobstructed,
and line of sight. There are four data collection locations.
Each data location needs to connect to a central location.
All of the data locations are within about 180
degrees of azimuth with respect to the central location.
I don't have the option of putting repeaters between the
central location and the data points.

I've tried several amps and antennae from several different
web stores but they don't seem to do much better than
the little "rubber duck" antennae on the usual boxes.

In contrast, I've had good luck with some 1-watt mesh-y
units (i.e. Ayrston's Ayrmesh boxes -
http://www.ayrstone.com/products.html )
But these units always need to "contact the mother ship"
at boot-time.  So "off the grid" doesn't work.

Anybody have a good source for higher powered wifi units?
I'd like to get away from Ayrmesh if general. They are
pricey and I hate having to rely on their website in order
to boot.

Alternatively, it is possible that I'm botching the set-up
of the amps/antennae that I already have.  Is there a good
resource (website?, book?, person?) on the process and pitfalls
of this sort of thing somewhere?

Thanks in advance,
Dan Nachbar