[TenTec] OT SWR VS Power Loss

[Jim Brown K9YC]

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. 

Al,

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 
http://audiosystemsgroup.com/RFI-Ham.pdf  and 
http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf

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 
resonant line. 

73,

Jim Brown K9YC