Use the tower as a quarterwave vertical fed at the base on 80m and connect an 160m quarterwave inverted L at the same feedpoint and run the wire up alongside the structure to the top and let the rest slope to any convenient high point. This way you have two antennas who won't "see" each other and can be fed with one feedline preferably matched with an L-network. 73 Gert, PA3AAV.