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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The concentric radial approach I mentioned I thought was discussed
within the 564 page book: Radio Antenna Engineering, by LaPorte. This is
a classic and good addition to anyone’s antenna library –
particularly considering the price – free.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Go to <a href="http://www.lulu.com/">www.lulu.com</a> and
type “Antenna Engineering” into the search box. It’s
the first book returned in the search. You can download all 33Meg for
free.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Meanwhile, I can’t find the particular radial approach
I was thinking of in the book, although many different radial schemes are
discussed.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Concentric system:</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The problem with radials that simple radiate out from a
central point is that they do not cover each square meter of ground equally
well. They are spaced far apart at the ends and tightly bunched at the
center. To get a “really good” radial system it is sometimes
recommended that 120 radials be used or the ends be no more than 0.02
wavelength apart – broadcasters frequently use 120. For the first
few feet from the tower its nothing but solid copper and most of this is
wasted. The alternative is as follows:</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Suppose you want a 64 radial system of 100 foot
radials. Place a concentric circular loop wire 33 feet out from the
center and another 66 feet out from the tower. Connect 16 radials from
the center to the fist ring wire, 32 radial wires from the first ring wire to
the second, and 64 wires outward from the outer ring wire to 100 feet. In
all cases the wires should be equally spaced around in azimuth angle.
This system will use around 55% as much copper as 64 full sized radials (I forget
the exact ratio) and yield the same performance. Soldering all the wires
to the ring loops however, is a lot of extra work. If its going to be in
or on the ground for a long time then regular solder should not be used either –
it should be silver solder.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>73</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hal</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>N4GG</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
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