Erm the active element and the back reflector are shorted through the middle core screw thing... I havent run the numbers on the disc sizes but if it was done correctly it would just be like a fairly normal wide band yagi antenna
There would be a massive improvment in performance if the active element (second disc from the back to which the cores of the wires are connected) was isolated electrically from the middle screw axel mount thingy.
This looks like a lot of effort though; a cantenna is easier to build and will likely work much better