"folded unipole", which was extensively studied by John H. Mullaney in the mid-20th century. When the combination is a "unipole", the cage wires are usually called a "skirt". The cage wires are always fed at the ring connecting the cage's lower edge, with the other electrical side of the feedpoint always being the ground system, regardless of whether or not the tower itself is grounded. Example At 1,000 kHz the wavelength is 300 m. Therefore, the minimum wave height of the cage antenna is a bit less than 75 m for the cage, plus about 2 metres to raise the lower end of the cage out of reach from the ground (depending on the details of the antenna feed, the lower end of the cage can carry a very high RF voltage). Radio frequency antenna types Antennas (radio)