Model GRK-88
Ground Radial Kit For The DX-88 Antenna
INSTRUCTION MANUAL
GENERAL INFORMATION
This radial kit consists of 4 sets of 4 radial wire
assemblies (16 total). Each radial is made from
7/23 copperweld and is 14 feet (4.3 m) in
length. A bracket and U-bolt is supplied for
attachment of the radials at ground level. This
permits the radial wires to lie at ground level
so that you may mow the grass over the radials,
and not trip over them. Two pigtail wires are
supplied to attach the bracket to the base
assembly of the OMNI DX-88 vertical antenna.
This ensures a higher conductive path from the
antenna base to the radial assembly.
This kit also contains a DC shorting coil which
can also be used to obtain a better match on the
80 meter band.
When the DX-88 is installed on the ground, a
radial system is normally required. The mini-
mum recommended radial system consists of
16 radials, each 14 feet (4.3 m) long. See
Figure 1.
Since the radials of a ground-mounted vertical
are actually on, if not in, the ground, they are
coupled by capacitance or conduction to the
ground, and thus resonance effects are not im-
portant. Basically, the function of ground
radials is to provide a low-loss return path for
ground currents. Longer radials and more
radials will reduce the ground losses and
effectively increase the gain of the antenna.
See the article entitled "Radial Systems for
Ground-Mounted Vertical Antennas" by Brian
Edward, pages 28-30, QST magazine, June,
INSTALLATION
The OMNI DX-88 vertical, when mounted on
the ground, should be mounted in the clear, at
least 20 feet from buildings, metal fences,
metal masts or flag poles and other metallic
WARNING
Installation of this product near power
lines is dangerous! For your safety,
follow the installation directions.
Do not install this antenna near any power line.
Not only is it dangerous to put up and take
down, the power lines could cause excessive
noise to be received by the radio connected to
The radial length of 14 feet (4.3 m) is ap-
proximately 0.1 wavelength a 7 MHz. With
poor earth conditions (dry, rocky soil), the gain
of this vertical antenna system will be
approximately 3 dB below the gain from a
perfect earth or 120 radials. With good earth
conditions (agricultural land, low hills), the
gain of this vertical antenna system will be
approximately 2 dB below the gain from a
perfect earth or 120 radials.
SHORTING/MATCHING COIL
This coil may be added to the DX-88 as shown
in Figure 2. It will provide a DC ground for the
antenna, which may help to reduce
reci
itation static.
The coil may be adjusted by altering the
number of turns or the length of the coil. This
will allow you to obtain a nearly perfect 1:1
match on the 80 meter band.
