On Sun, 6 Jul 2008 20:28:49 -0700, Alfred Lorona wrote:
>One way to eliminate it is to use a quarter wavelength long feedline with a
>good earth ground at the station end. The impedance at the ground end is
>ideally 0 ohms and the far end of the feedline shield looks like, ideally,
>an open circuit. The Rf current does not flow into an infinate impedance of
>millions of ohms! Worse case scenario is a feedline one half wavelength
>long. The impedance of the shield to the Rf at the dipole center is now zero
>ohms. The RF will love that!
>It is extremely difficult to avoid a common mode current unless the antenna
>is perfectly symmetrical in every respect to it's surroundings; situation
>hardly every achieved in a practical installation.
You're right on target about antennas being unbalanced by their surroundings,
but you're in the dark ages with respect to solutions to this problem. See
The chokes described in my "cookbook" will virtually kill common mode current.
And these are multi-band solutions! You do NOT need to go to the trouble of a
Jim Brown K9YC
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