I think this is similar to what Gary Tennesen was suggesting; you might 
experiment with homemade parabolic reflector to see if you can increase the 
signal to noise ratio enough to make a difference.  It does sound like you 
have a fairly directional set-up.

See this page as an example: 
http://www.freeantennas.com/projects/template2/index.html

(If you go up to the main page, http://www.freeantennas.com/ , you see links 
to some other templates, as well.)

John Sproule

-------- Original Message Below -------

Date:    Fri, 11 Mar 2011 15:01:37 -0500
From:    Tom Waddell <[log in to unmask]>
Subject: Extending wireless range

I have a computer in my workshop, about 50 feet in a straight line from the 
home desktop router. In a straight line the signal would have to pass 
through a house wall, a mudroom wall and a garage wall, all insulated but 
none with foil backed insulation. The signal strength is always "very low" 
and often drops out completely. How can I improve the signal so I can listen 
to on line content while I work?

         PCBUILD maintains hundreds of useful files for download
                     visit our download web page at
                  http://freepctech.com/downloads.shtml