w8ji at contesting.com
Fri Nov 11 15:41:54 EST 2005
> But I've read the results of modeling from others
here on TT. Their models show minimal current flowing in
the tower below the connection point for the shield and
nearly equal currents flowing in the slant wire. (Check Tom
N4KG's posting that I've cited several times recently:
I don't know how or why anyone can assume a slopper worked
against a tower at one installation would work the same as a
slopper worked against some other tower.
First, guaranteed, the current leaving one coax terminal
into a load ALWAYS equals the current at the other terminal
of the coax. The only exception is when the coax is acting
like an antenna and radiating. The current, once it gets in
the tower away from the feed connection point, can increase
or decrease. It also splits or divides between the tower
above and the tower below. The division and the amount of
current going each and every place depends on what is above
or below that point.
The tower is indeed the other "dipole" leg of the system.
This is why the N4KG feed system and quarter wave sloppers,
or any antenna that works against a random tower, are so
unpredictable performance. It's pure random luck how well or
how poorly these random systems work. As a general rule they
never radiate better than a proper shunt fed tower or
Marconi of similar height....and they certainly can be and
often are significantly worse.
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