Hi Joe, One method I have used (with EZNEC+ v.4.0) is to assume the ground is flat, and tilt the tower(s) by the same angle as the slope of the field. This appears to work for 3 in-line elements, at least forward and reverse directions in the direction of the slope. You then have to correct the take-off angle by the same amount, of course. Bert, VE3QAA