The bottom half of each
antenna consists of 9 quarter-wavelength wires that connect to the
center of
the tower and slope downwards to the ground at a 45 degree angle.

Sure, thats a "1/2 wave" antenna, but I would always consider that
a ground plane, rather than 1/2 wave vertical. It's got sloping
radials.
Same thing I used to run on 40m. I always called it a 1/4 wave ground
plane... MK