On Sat, 8 Mar 2008 16:53:30 +0200, Marinus Willemstijn wrote:
>Can the tower grounding system be put BELOW the tower BEFORE the
>concrete is poured?
Yes, BUT: grounding electrodes need to be in moist (wet) earth to be
effective. Your tower base, being concrete, will reduce that moisture.
AND -- concrete that is conductive functions as a grounding electrode to the
extent that it is a conductor with a large surface area in contact with earth.
This concrete should not REPLACE other grounding electrodes, but it will, by
its nature, reduce the impedance to earth.
>2) What is the best configuration for this grounding - 4 rods with a
>star configuration where one rod is put in the one corner with straps to
>each of the rods in the other corners? Or just link the 4 rods up in a
Lightning, by its nature, produces an RF current, with the peak of the energy
in a broad spectrum between about 300 kHz and 3 MHz. This means that
INDUCTANCE dominates the impedance of the ground system. Ground rods that are
close together will have mutual inductance to each other, so will partially
cancel each other out. Thus, the common advice that you want to begin with
ground rods around the power and additional rods at some distance from the
AND: Any radials that you may have will provide capacitive coupling to the
earth, and they should also be bonded to the ground electrode system. Remember
that it is important that all grounds be bonded together by a path having the
lowest practical inductance. This minimizes the potential between them in the
case of a strike, and also reduces the total impedance to earth. As with any
earth connection, more is better as long as all the electrodes are bonded
Jim Brown K9YC
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