How does the radiation pattern of a horizontally-polarized antenna mounted above a long slope compare with the same antenna mounted above flat ground?

When an antenna is mounted over sloping ground, the slope itself acts as the effective ground reflection plane. Because the ground falls away from the antenna in the downhill direction, the resulting radiation lobe is angled lower relative to the true flat horizon. This means the effective takeoff angle of the signal decreases in the downhill direction, which significantly enhances long-distance (DX) communication in that specific direction. Conversely, the takeoff angle increases in the uphill direction, making DX communication poorer that way. Distractors often suggest the beamwidth changes or the angle increases downhill. Remember that the signal tends to follow the slope of the land; pointing downhill effectively lowers the launch angle toward the horizon.