Don't forget that many homes today use foil-backed insulation. The foil is ... obviously ... conductive. I use two 1/4 x 20 threaded brass rods with cone insulators on both the inside and outside of the wall. I made larger holes and removed the foil around both holes before installing the feed-throughs. 73! Ken Kopp - K0PP k0pp at arrl.net or k0pp at ixpres.com