Use tapered wire.
----- Original Message -----
From: Hal Kennedy
To: secc at contesting.com
Sent: Friday, August 24, 2007 3:48 PM
Subject: **Possible_Spam** [SECC] Reference for radial discussion
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.
Go to www.lulu.com and type "Antenna Engineering" into the search box. It's
the first book returned in the search. You can download all 33Meg for free.
Meanwhile, I can't find the particular radial approach I was thinking of in
the book, although many different radial schemes are discussed.
Concentric system:
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:
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.
73
Hal
N4GG
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