On Tue, 21 Apr 2009 00:14:50 -0500, chas wrote:
>WHERE are the facts about ladderline??
Ladderline does not radiate differential mode current (the power it
carries from the transmitter to the antenna). Ladderline DOES
radiate COMMON MODE current. So does coax.
Common mode current is the result of imperfect balance at either end
of the feedline. Nearly all practical ham antennas are unbalanced by
their surroundings. Common mode current causes radiation, and
antenna imbalance causes common mode receive current.
An important difference between coax and ladder line is that coax
can be CHOKED to kill common mode current, but ladder line cannot.
To understand why, study
http://audiosystemsgroup.com/RFI-Ham.pdf
and also the Power Point on Coaxial Chokes at
http://audiosystemsgroup.com/publish
73,
Jim Brown K9YC
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