[TowerTalk] Radial Connection to tower

[Richard (Rick) Karlquist]

You can estimate 20 nH per inch for these hook up
wires. On 80 meters, think of that as as about
a half ohm of inductive reactance per inch,
or 6 ohms of inductive reactance per foot.
Thinking of it that way, you can see why a single
10 inch wire in series with your ground connection
isn't a great idea. You might try modeling it
and see if it rises to the "noticable" level.

I have a 230 foot diameter ground screen with
wires spaced 3 feet apart in each direction.
When I first completed this, I placed a 40
meter vertical at the center junction, such
that there were four wires emanating from the
shield of the coax connector. These 4 wires
run 3 feet until they reached the next junction,
etc. The driving impedance of this was
70 ohms, despite being over a gigantic ground
screen. After adding 30 foot radials to tie it into
the ground screen 30 feet away from the vertical,
the impedance steadily decreased with the
number of radials until it reached the
theoretical value of 36 ohms. This is the
kind of weird stuff that happens if you deviate
from the classical radial paradigm.

Rick N6RK


On 12/13/2015 2:28 AM, Stan Stockton wrote:
> Rick,
>
> I noticed this response and have a question.
>
> Background:
>
> I have an 80m 4 Square insulated 25G verticals and another tower that is grounded that I shunt feed for 160m.  In all cases the radials are soldered to a wire that goes around the concrete bases of the towers.  Then there is a wire or two from the ring to a plate that that has a female UHF connector on each of the 4 Square towers or to a tower leg on the one that is shunt fed.  Those wires are probably 12-18 inches long and maybe #10 or so.
>
> Question:
>
> Based on your measurements, do you think I can make a noticeable improvement by doing something different?
>
> Thanks... Stan, K5GO
>
>> On Dec 12, 2015, at 10:26 AM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
>>
>> I have played around with this problem and made some actual
>> measurements.  My conclusion was you need a considerable number
>> of radials between the ring and the tower; at least 12 and
>> preferrably 20 or 30, especially on 40 meters.  A mesh is a
>> lot of trouble and would need to be fairly closely spaced
>> to be effective.
>
>