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Old November 3rd 03, 02:49 PM
Richard Harrison
 
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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