Where is the wave length computed from with this antenna? Lets say if I wanted to lengthen or shorten elements where is the ground plane measured from? The bottom of the magnet? The botom of the chrome cone? the bottom of the center element connection? What about the coils, what is the value of the coils? I've been toying all day long and would appreciate any suggestions. I'm mostly trying to fine tune into VHF airband 118-137. If you had the materials what length would be ideal for VHF airband?