Hinged base plate
The antenna was first assembled according to the revised instructions provided by DX Engineering. I had first prepared the mounting base by removing the 30/15 meter vertical from the two mounting plates (see separate gallery for photos of that antenna). The black plate is a 3.5 inch aluminum rack panel cut to a length of 15 inches. A stainless steel hinge affixes it to the bottom plate. The top has two holes that mate with two #10 bolts mounted in holes in the top plate. I measured everything very carefully and it all lined up. Only the insulated base mounting bracket is mounted to the black plate; the assembled antenna is then slipped over the aluminum tube at the top.