In a message dated 96-10-17 13:10:38 EDT, you write:
>This is another case of worshipping the "SWR god". Match the antenna, NOT
>the coax. If you want to really raise the resistance of the inv L, make
>it a folded inverted L. That will give you a step up from about 37 ohms
>resistance to about 148 ohms. ( and about a 1.4 SWR using a 4 to 1 balun )
>( or about 1.28:1 if you use a 1/4 electrical wave of 72 ohm coax from
>the antenna to your 50 ohm line.
>
>Using that same principal, and assumming we have a vertical height of
>about 65 feet, why not make the entire antenna vertical using a folded
>tripole? At about 18 ohms to start with, we increase the RESISTANCE of
>the antenna to 162 ohms, with 0 reactance, ( better know as resonance )
>giving us a match of about 1.4:1 with either a balun or a quarter wave..
The net result is the ground current and losses are exactly the same either
way, folding the element does not change the radiation resistance or current
or loss of the ground system.
You merely change the feedpoint resistance by connecting the feedline across
PART of the current flowing at the base. The sum of current, and the loss,
remains almost exactly the same.
The same thing with lengthening the flat top of an L. Unless you want
horizontal polarization, maximum FS occurs with maximum current integrated
over the entire length of the vertical structure. Current moved into the flat
top represents higher radiation resistance, but unfortunately the radiation
is straight up. The effect is one of robbing current from the vertical
section of the antenna, and it (unless the ground system is *very* poor )
will decrease vertical radiation. A non-radiating hat is a different story.
73 Tom
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