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Roy, W7EL addressed several provocative questions to Cecil. Anyone can
comment, so I will. Roy wrote: "And where those coulombs are going that go into one end of the inductor and don`t come out the other." Coulombs travel back and forth in an inductor and may go actually nowhere. Their movement in an unshielded inductance may result in radiation and certainly produces some heat. The purpose of a loading coil in a short loaded vertical antenna is often to add to the existing degrees of antenna length to reach a resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band DXing", and included on Yuri`s web pages. Fig 9-22 is illustrative. First, a full-size 90-degree vertical is shown. Current is maximum at the base and zero at the top. This is also true for what Kraus calls a "normal-mode helical antenna". A normal-mode helical antenna has its principal radiation at right-angles to the axis of the helix. The normal-mode helix is fed from a generator with two terminals. One terminal feeds the base end of the helix directly. The other generator terminal feeds the ground end of a capacitance between the ground, various turns, and the tip end of the helix. The impedance is only a few ohms at the ground end of the helix and perhaps several thousand ohms at the tip end of the helix. This means a lot more amps at the ground end of the helix than at the tip end, though the power flow through the generator`s terminals is the same in either terminal. Best regards, Richard Harrison, KB5WZI |
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