Just use an insulator at the point where the antenna leaves the house, and 
separate the wire from the fence, especially if the fence is metal.  Plant a 
mast at the end of the antenna and anchor the end of the antenna to that. 
You can strap the mast to the fence post.  If you are worried about rf burns 
from touching the wire, use insulated stranded wire.  coax will work just 
fine to.  Longwires really like resonnent counter poizes to work well and 
keep the rf away from the shack.