Topband: Current Distribution on Buried Radials Used WithVertical Monopoles

[K1FZ-Bruce]

On Sun, 8 Mar 2015 20:44:36 -0400, Guy Olinger K2AV 
<k2av.guy at gmail.com> wrote:
On Sun, Mar 8, 2015 at 5:57 PM, Eduardo Araujo via Topband <
> topband at contesting.com> wrote:
> >
> > When I read that they have measured the current in one radial and
> > multiplied it by the number of radials, I wonder why even though I used
> > simple instruments, got some different result......my method, my instrument
> > or both perhaps??
> >
>
> The Brown, Lewis and Epstein study (BL&E) was most likely done over very
> uniform, and over pretty good dirt for RF. I would trust your measurements
> as far more typical of ham circumstances. 
   
> The answer was that those figures were wildly variable, even in different
> spots in the same back yard. Sometimes there were large variations between
> one placement and another with same center and at right angles. 
 
> This is in contrast to many of our ham situations with no reason to expect
> uniformity of ground composition across a radial field. 
>
> From various clues in my case, including excavations to flatten out US 64
> Hwy when they four-laned it some years ago, the ground beneath contains red
> or grey clay hard pan, a varying depth layer of carbon/charcoal from an
> ancient forest fire, several varying layers of sand in areas draining to
 
That part of the property
> was a great site for the necessary septic field, further ruining any chance
> for uniformity at RF. 
  >
> 73, Guy K2AV
 
Agree with your posting Guy. My first 100 foot vertical was to become a 
two band 4 square. I initially laid out 16 equal radials. Measuring 
the currents with a MFJ 854 current meter, found variances in the
wires, near & equal distance from the tower base. 

I also found evidence of ancient forest fire. Five feet down against 
the ledge of the hill top found burnt sticks still identifiable as 
semi-round sticks (pieces of branches). Lack of oxygen, and water under 
the clay possibly slowed decay. 

Aware of the different top end impedance, small diameter vs fat 
diameter tower. The large diameter tower, has lower top tower impedance, that results 
in lower Q, lower voltage, and wider low VSWR frequency width. 
 Also many low-banders shunt feed their towers with caged wires to get a "fat" 
diameter to lower the impedance, and wider band width. 

Later in time. the ground radials for the 4 square,  a "fat" radial 
scheme was carried out. The radial field was not equal lengths of wire, 
but to form of a square  to the four square antenna. 
The goal was, in the space  available, reduce voltage at the far ends 
to keep voltage to earth leakage to a minimum.   (Yes, know that the 
current is divided by the number of radials.) Looking to close the 
"fat" diameter ground system, ran a  perimeter wire around the 
ends, and at the shortest radial wire.points. Resulting a loose fitting wire mat. 

The 4 square is not still standing, but two of the 100 foot towers are used working against the ground system on 
160 and 80 meters

73
Bruce-K1FZ
www.qsl.net/k1fz/beverage_antenna.html