One on-line coax-loss calculator indicates about 144 dB of loss in
RG-59, at 2.4 GHz over an 800-foot span.

Added to the antenna losses at both ends, and I have real doubts as to
whether a usable signal will result. It *might* work if the 802.11
radios were plugged directly into the coax, with no antennas involved,
but that does not sound feasible.


If you get a pair of preamp/power amp modules, like these:
http://cgi.ebay.com/2-4GHz-802-11b-1-Watt-WiFi-amplifier-signal-booster_W0QQitemZ5845608031QQcmdZViewItem?hash=ite m5845608031&_trksid=p3286.c50.m20.l1116
and use them at both ends of that long run of coax, it might work. But
at $186 times 2, that's rather expensive for something that's not
guaranteed. At least, with the amps feeding directly into the coax, you
probably would have a minimum of interference from other wifi users and
microwave ovens.