Butternut GRK User manual
831 North Central Avenue Wood Dale Illinois 60191-1219 Telephone 630.238.1183 Facsimile 630.238.1186 http://www.bencher.com
VI00404Z 082699-1-
Instructions
Model GRK
NOTE: Please read all instructions thoroughly before proceeding
to installation and assembly. During assembly and installation
take extreme care to avoid contacting power lines with any part
of the antenna or other conductors.
INSTALLATION CONSIDERATIONS
Ideally the antenna should be installed 30 ft (9.1 m) from any structure as shown
in figure 2. In most cases this will not be practical and an alternative method such
as the one shown in figure 3 may be used.
WARNING: Do not install the antenna in any place where any
part of it can come into contact with power lines in the event
of structural failure, in the course of normal flexing after
installation or during installation.
WARNING: In no case should the antenna be installed in any
place where structural failure of any part of the antenna or its
supporting system can endanger persons or property.
CAUTION! A grounded antenna will be at D.C. ground
potential! To avoid the danger of shock connect all station
equipment to a good earth ground. It is also recommended
that all station equipment be disconnected from the power
mains before connecting the feed line to the antenna. Please
consult the A.R.R.L. Handbook or other reference manuals for
additional safety procedures when working with electrical
equipment.
Tube w/insulator (A) should be protected against corrosion if it is to be placed in
concrete, damp acidic or alkaline soil. Asphalt roofing compound, polyurethane
varnish or other sealant that protects against moisture may be used.
Concrete may be used in areas of high winds for greater strength, in which case
the post may be twisted slightly during setting for easy removal later.
-2-
Figure 1
Figure 2
ASSEMBLY
1. Plant tube w/insulator (A) (packaged with antenna) in a hole approximately 21
in (53.3 cm) deep so that the upper end of the fiberglass insulator is
approximately 7 in (17.8 cm) above ground level. Pack earth tightly around
tube w/insulator (A) so that it remains vertical.
NOTE: Hammering tube w/insulator (A) into the earth may cause
the insulator to splinter. If the post must be hammered into the earth,
protect the end of the insulator with a block of wood.
2. Assemble and install antenna per instructions.
3. Insert a copper ground rod 6 to 12 in (15.2 to
30.5 cm) from tube w/insulator (A). The
ground rod should be at least 48 in (1.2 m) in
length.
4. Attach radials onto the screw protruding from
tube w/insulator (A) along with coil (Q) base
matching, braid side of the feed line and
bonding wire from the ground rod as shown in
figure 1. Secure with the supplied flat washers and hex nuts.
NOTE: Coil (Q) base matching
is not used when the TBR-
160-S Top Band Resonator
160 meter Kit is installed.
5. Fan out radials as shown in
figures 2 or 3. Make sure that
the radials are as equally spaced
as possible.
Ideally, radials should be equally
spaced as in figure 2 but in most
cases they will need to be bent
around structures and other
obstacles as in figure 3. Make sure
that you make your bends no sharper
than 90° and as gradual as possible.
6. Slit the earth 1 to 2 in (2.5 to 5.1
cm) with a square shovel or
-3-
Figure 3
ASSEMBLY
similar tool along the path of a radial.
7. Leaving a little slack at the base of the antenna, carefully press the radial into
the slit. Make sure not to cut the radial.
Radials may left on top of the ground however they should be buried for the sake
of pedestrians and lawnmowers.
8. Repeat steps 5 and 7 for the remaining eleven radials.
9. Tune antenna per instructions.
THEORY OF OPERATION
A vertical antenna in its simplest form, is
electrically equivalent to one-half of a
dipole antenna. The earth below the
antenna takes the place of the missing half
of the dipole.
Capacitance between the vertical radiator
and the ground causes return currents to
flow along the earths surface back to the
transmitter. If they have to come back
along the untreated lossy earth they get
back to the source greatly attenuated.
This return loss is like a resistor in series
with the antenna radiation resistance and
will therefore affect the feed point
impedance.
If ground conductivity is excellent, a ground
rod may provide a sufficiently good
connection for resonant and low SWR
operation on the bands for which the
antenna is designed.
In almost every case the efficiency of a
vertical antenna will be greater when radials are used to improve ground
conductivity.
Butternut Manufacturing Co.
831 North Central Avenue
Wood Dale Illinois 60191-1219
Telephone 630.238.1183
Facsimile 630.238.1186
http://www.bencher.com
THEORY OF OPERATION
Since it’s not practical to copper-plate the back yard, the best approach is run out
a number of radials. Because most ground losses occurs within a 1/48from the
antenna, the GRK Ground Radial Kit provides a good ground plane for 160 thru 6
meter operation without using much real estate. If the ground is extremely lossy,
as in the desert, additional longer radials may need to be added.
Parts List
Part No Description Qty
VS00405Z Ground Radial Wire 12
VJ00078Z #8 x 1 Screw 1
VJ00083Z #8 Washer 5
VJ00081Z #8 Hex Nut 2
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