There are various ways to do this.
What version of the linksys do you have? You might be able to install
replacement firmware on it and use it as a wireless ethernet bridge in
the distant house.
Or maybe better this way:
Put your chosen antenna on the Westel AP (if it takes external
antenna) and then buy a wireless ethernet bridge for the other end and
put an antenna on it.
Recommended bridge: Buffalo WLITX4G54HP
These antennas will need to be mounted to get line of sight between
them. The ones you mentioned seem about right for the distance, (I
have the same antenna) but to be more certain and understand the
setup, you go do some link calculations:
http://www.zytrax.com/tech/wireless/calc.htm#system
Be sure to use low loss cable (LMR400 is best for over 10') or else
put the bridge in a weatherproof box with the antenna. At your chosen
site:
http://jefatech.com/product/ll400
Finally, if you don't need wireless at the remote cabin, fine, connect
directly to the bridge. If you do, then run an ethernet cable from
the bridge to your linksys and place it inside for good coverage of
the cabin.
Assuming that your existing router/modem takes external antennas, then
you need one new device (bridge), two antennas, two cables. Lightning
protectors and grounding too. Possible weatherproof box instead of
one antenna cable.
Most longer cables will be N female to N- male to fit your antenna.
At the router end, it's best to use a short pigtail to adapt it to
your router which will be either RP-TNC or RP-SMA. You can buy the
long cable with the correct connector, but LMR400 is thick cable and
can break off your connector on the router. Thus the thinner pigtail
as an adapter.
Steve
Steve