Jim,
Not enough information from you to determine an answer. Is the tower a
vertical antenna? Or does it support wire horizontal antennas, or
beams, or loops, or ?
Local noise is often picked up from local sources like power wiring in
the building or near field of your antenna. Vertical antennas may pick
up more than horizontal, depending on the nearness of noise sources and
type. A balanced antenna, beam, dipole, or loop, may be less
susceptible than others.
Radials mostly have an RF function to complete a quarter wave vertical
antenna. They cannot magically reduce all sources of your local noise,
as it may be picked up inside the shack or house. In earth conductors
attached to the tower base, can act to spread strike currents from
lightning to the tower, and lessen possible transmission of such current
into the shack via the control cables and transmission lines, but there
is no guarantees with lightning. They probably will not affect your
noise, unless the tower was in in touch with the ground to start with.
You need to do some noise sniffing and find the directions and sources
of noise to your installation. There have been broadband detectors and
antennas described from time to time in QST for doing this, and in the
Handbooks. Techniques as used in the Radio Direction Finding sport
competitions can be used, especially at vhf and uhf for power line
source noise.
ARRL has had RFI booklets that can also help you determine the problem
you have and possible solutions.
-Stuart Rohre
K5KVH
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