Re: Tunable HF antenna
My opinon is that it will not work.
Are you sure that the center piece is a monopole antenna, and not a coaxial line running up to the top. If you ran coax up to the top, and then ran one wire back to ground from the center conductor, and the other wire from the shield at the top, and then to the ground plane, you would have a (junky) dipole that would receive on both horizontal and vertical polarization. You could use the lumped elements at the end to make it resonate.