[TowerTalk] Unequal Radial Currents
Richard (Rick) Karlquist
richard at karlquist.com
Sat Aug 29 22:16:28 EDT 2020
On 8/29/2020 5:44 PM, Dennis W0JX via TowerTalk wrote:
> Unequal currents in 1/4 wave radials is to be expected primarily due to three factors: 1.) varying quality of the ground under each radial; 2.) the effect of close by objects such as buildings and other towers; and 3.) the variation in the length of the radial wires depending on type of wire, insulation, and construction methods. Effect on the actual radiation pattern depends, of course, on the severity of the current variation and the number of radials utilized.
> Dick Weber, K5IU, wrote a very informative article in the late 90's which was published in Communications Quarterly. He argued that 1/4 wave long radials were the poorest length on could use. He strongly recommended radial lengths of either 60-70 degrees (shortened) or 120 degrees long. These radials are tied together at a common point and fed either through a coil or a capacitor.
> W5UN had a very successful 4 square for 160 meters which used four, 96 foot long radials fed through a common coil. The radials were about 15 feet off the ground.
> Here at W0JX, I have four, 48 foot radials on my elevated 80 meter ground plane. The four radials come to a common point below the radiator and are tied to the coax shield through an inductor of approximately 3.3 uh. A big advantage of this arrangement is that I can resonate the antenna system by moving the tap on the radial loading coil. After many years of using full-sized radials, my on the air results tell me that the shortened radials are working better than the full size radials did.
> 73 Dennis W0JXMilan OH
>
I'm not following the logic here. If various radials have
unequal impedances, I don't see now tying them in parallel
though a coil or capacitor with magically make them have
equal currents. Did Dick actually compare the currents in
the various configurations as built? All I see are anecdotes,
not AB comparisons or measurements.
Now if someone told me to use shortened or lengthened radials
and put individual coils or capacitors in series with each radial, then
I might believe the currents would be forced into equality.
Are you sure you got the story straight about Dick's article?
(I don't have access to it).
73
Rick N6RK
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