The ornamental design for a hornantenna, as shown and described.
FIG. 1 is a perspective view showing the top, front, and right sides of a
horn antenna, embodying my new design, the dotted line depiction of a
support mast being shown for illustrative purposes only and forming no
part of the claimed design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof the left side being a
mirror image of the right side as shown;
FIG. 4 is a top plan view thereof, the bottom side being a mirror image of
the top side as shown; and,