[TowerTalk] Radials Questions - 270 or 360 degrees.

[Red]

 Hi, Bill and TTs;

EZNEC modeling indicates a very slight assymetry and reduction of gain 
resulting from omitting 90 degrees segment of the radials.  Both figures 
are within the inaccuracies associated with errors and assumptions in 
the modeling.

The assymetry, 1.1 dB, can be reduced to 0.2 dB by removing the opposing 
90 degrees of radials, at the cost of about 0.5 dB of maximum gain.

The performance will benefit some from using more radials, even if, in 
the interest of limiting the amount of wire used, some are shorter than 
60 feet.  However, variables associated with modeling errors, 
assumptions of ground characteristics, terrain features, wires and pipes 
in the structure, etc. are generally greater than the calculated 
differences in performance.  Put down as many radials as you can and 
don't worry much about the 90 degree gap.  If you can fill the gap 
without introducing excess interference or complexity, do it.

73 es HOPE CU ON THE AIR de WOØW

Bill Coleman wrote:

>
> I am shunt feeding my 15m high tower on 80m. I recently added more 60 
> foot ground-mouted radials to go from 13 to 24 total radials. Because 
> the tower is situated at the corner of my house, the radial field only 
> completes 270 degrees of the circle.
>
> I've been impressed with the improvement in this antenna by doubling 
> the radials. The lack of radials in 90 degrees of the circle has me 
> wondering if there isn't a way I could improve this further.
>
> Question 1: How does the missing 90 degrees of radials affect the 
> pattern of the antenna? The missing segment goes from roughly NW to NE 
> -- some important directions from this location.
>
> In thinking about the problem of running radials in this segment, it 
> occurs to me that I do have some limited room to sneak a ground wire 
> into the basement and run some radials there. This boils down to two 
> options:
>
> A) have a 3 foot wire from the tower base enter the basement at the 
> floor, then fan out to 3-6  radials varying from 15 to 45 feet. These 
> would be either 14 gauge copper wire, or more likely copper foil tape 
> (which would stick to the floor and I can walk over it without tripping).
>
> B) have a 3 foot wire from the tower base enter the basement at the 
> floor, then rise 9 feet vertically to the ceiling, then fan out to 3-6 
> radials varying from 15 to 45 feet, run across the ceiling.
>
> Question 2: In looking at option B, is the vertical segment going to 
> have an adverse effect on the pattern in the NW to NE direction? Is 
> the vertical segment going to change the phase of the currents and 
> ultimately destroy any gains by adding the radials?
>
> Question 3: Is there any coupling or danger associated with having 
> these radials inside the house? Is there a potential for high voltages 
> to appear, or to have the elements radiating RF inside the structure? 
> Is this different from option A or B?
>
> Question 4: Of the three options (A, B or do nothing) which offers the 
> best possibility of improving the antenna efficiency or evening out 
> the radiated pattern of the vertical? What would you recommend and why?
>
>
> I'd appreciate any suggestions.
>
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Quote: "Not within a thousand years will man ever fly!"
>             -- Wilbur Wright, 1901
>
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>
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