*You can see this by considering an instance when the current in the vertical portion of the antenna is flowing in the downward direction. Think of the two horizontal sections as having been created by splitting the original horizontal section of wire in half lengthwise. Since the two horizontal sections are part of the same quarter-wave monopole as the vertical section, the current in both of them must be flowing into the three-way junction at the top of the vertical section. For the current in both horizontal sections to be flowing into the junction, the current in the left-hand section must flow to the right, and the current in the right-hand section to the left. These two segments of wire constitute a two-element horizontally polarized array, and at any point in space directly above the antenna (or nearly so), the fields from the two wires cancel because they are of opposite polarity.