[HCARC] Radials - The Math

Thu Oct 11 12:57:19 EDT 2012

Notice that if A=B then N= 50. -AC4CA

Here's the dope on the radials for a vertical etc ..

Let A be the lowest frequency you want to operate (mHz)
Let B the the highest frequency you want to operate (mHz)

We take the max length of the radial to be 0.2 wavelength at A
and the spacing between the wire ends to be 0.025 wavelengths
at B.

We now have the following variables ...
A = lowest frequency system will operate (mHz)
B = highest frequency system will operate (mHz)
L = radial length (fee)
S = spacing between ends of radials
C = circumference of radial system
N = number of wires in radial system
T = total length of wire required.

Given A adn B ... the rest follow (with L and S set according
to the rules above)

L = 0.2(984/A) = 196.8/A ... feet

S = 0.025(984/B) = 24.6/B ... feet

C = 2(pi)L = (62.8)(196.8)/A = 1235.9/A ... feet

N = C/S = (1235.9/A)/(24.6/B) = 50.24(B/A) ... number of radials

T = NL = 50.24(B/A)(196.8/A) = 9887.2(B/(A*A)) ... feet

If A = B   then N = 50 radials ...

If A = 3.5  and B = 28   then
         L = 56.2 feet
         S = 10.5"
         C = 353.1 feet
         N = 401.9
         T = 22587.9 feet

so the calculations are definately CONSERVATIVE!

Change the ASSUMPTIONS on L and S as you see fit ....

-----Original Message-----
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Subject: HCARC Digest, Vol 18, Issue 10

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Today's Topics:

   1. Re:  Vertical Antenna Radial System (galeheise at windstream.net)

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Message: 1
Date: Thu, 11 Oct 2012 07:22:33 -0500
From: <galeheise at windstream.net>
Subject: Re: [HCARC] Vertical Antenna Radial System
To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>,
	<hcarc at mailman.qth.net>
Message-ID: <84172791F21A42F79CA8BF5BD93E7C79 at GalePC>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=original

Gary-

  If you're a member of ARRL you can find an article on vertical antenna
ground radials via the "QST Print Archives" @ arrl.org.

  When you get to the section requesting search information, input:

Month: June
Year: 1985
Keyword: Radial

  It should provide you with a PDF file Titled "Radial Systems for
Ground-Mounted Vertical Antennas".  There are charts presented that you can
view for input to determine your level of diminishing returns.  The charts
relate to soil categories - poor, good and very good.  The article contains
tables providing definitions for these three soil categories as well.

Gale
KM4DR

-----Original Message-----
From: Gary and Arlene Johnson
Sent: Wednesday, October 10, 2012 4:09 PM
To: hcarc at mailman.qth.net
Subject: [HCARC] Vertical Antenna Radial System

Almost everything I read about putting radials down for a vertical antenna
has a radically different answer.  In many cases they preface their
recommendations with "it depends on how conductive your ground is".  Since I
am on typical to better than typical Hill Country rocky ledge soil, what
kind of radial system will I need.  When I say my land is better than the
average Hill Country soil I mean that compared to the Hunt Ingram area with
its almost all rock, and compared to the soil around the area North of
Tierra Linda which is almost all rock, I have some good soil and some rocky
areas.  I do have to garden in raised beds and I do drill holes with my Big 
Hammer drill for T-post installation.   I surely do not have as good a soil 
as the alluvial plains along the river.  My questions are: 1) what should
the center plate should be made from - copper, brass, aluminum, stainless
steel???  Would a ring of soft copper A/C freon line work vs a plate??  2)
what metal should the rad ials be made from copper, aluminum and what
gauge??  (3) how to attach - nuts and bolts, silver soldered, regular
electrical soldered and last 4) how many radials??  I have heard anything
from 4-120 recommended.  DX engineering says 60 for the Hustler 5-btv
antenna I picked up from Gale H. 
yesterday, but that number matches the number of holes and bolts on the
$150.00 radial plate system they sell - i.e. they probably have some bias. 
One thing I have heard is "the more the better", but that probably has a
level of diminishing returns.

73's

Gary J
N5"BAA"
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