Re: [TowerTalk] Radials Questions - 270 or 360 degrees.

[Bill Coleman <aa4lr@arrl.net>]

On Jan 5, 2005, at 11:50 AM, Red wrote:

> 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.

Is 1.1 dB considered very slight?

> 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.

This doesn't seem like a good idea, then. The net change would be to 
increase the gain in the assymmetric direction by 0.3 dB, at the cost 
of 0.5 dB elsewhere in the circle....

> 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.

Well, that about answers my first question -- how about the other three 
questions?

> 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?

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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