MFJ Enterprises MFJ-1796 User manual

ME
Vertical Antenna
Model MFYJ-1796
INSTRUCTION &
ASSEMBLY MANUAL
WARNING:
You can be killed tf the
antenna, feedline, or the
equipment used to install
the antenna accidentally
contacts utility lines.
Never install an
antenna near utility lines.
READ ALL INSTRUCTIONS BEFORE OPERATING EQUIPMENT.
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: [phone] Fax: [phone]
VERSION 3
COPYRIGHT © 1993 MFJ ENTERPRISES, INC.

S
40 Meter
Capacitance Spokes (6)
& Loading Coil
20 Meter (6)
15 Meter (4)
10 Meter (4)
6 Meter Center
Stub Elements Conductor pniorar
Shield Stub Elements
ean
_W
Balun
with Drip Loop
Note: This drawing is not to scale
MFJ-1796
: Vertical Antenna
Always
Follow
Assembly
Instructions!!
~~Coax Connector Assembly

MEF J-1796 Vertical Antenna
Instruction Manual
Table Of Contents:
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Choosing a Location for the Antenma..............0..cccccccccessccecsceeeesscecerseeresseeens 3
Permanent Installation..........0:..c..cc00:e0001. saeastuseneneemarunmunusen cunt eRae. 3
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MEJ-1796: Parts List). 202.2. e.gsyce 020508 2s RSE Sed ae ra eeeassi ances 4
Safety Precautions: «.créc.ccc.ccicssecscaceecd sons se reabaarenemecumannaserentsEethacas bee 5
Assembly and Installation Procedure .............c.cccccccssesscesceesseeeseseecesenssesseesees 5
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‘Tuning the Antenna ss ssshot ris, ener radheest perpen eommmanne tu esa eae naccacatet 12
Tuning the Low Frequency Bands............ csnasssacousniwaciusruansinoumneuruarmusres 13
Tuning the High Frequency Bands (VHBP)..............0:cc:ccccccccesseesseeseeeesessveeees 14
Grounding Considerations. .........6.........++: emcenungeneenondboonenenemanrenmmemcacranacersien 15
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MFJ-1796
Vertical
Antenna
Instructions
MFJ-1796 Vertical Antenna
INTRODUCTION
The
basic
40
meter
quarter
wave
vertical
antenna
is
33'
tall
and
requires
a
reasonably
good
ground
or
counterpoise
system
to
function
properly.
The
usual
way
to
eliminate
the
requirement
for
a
complicated
and
space
consuming
ground
system
is
to
center
feed
a
1/2
wave
(in
this
example
a
66'
tall)
antenna.
ME]J
solved
these
problems
by
combining
efficient
end
loading
with
a
balanced
center
feedpoint
design.
The
result
is
a
physically
small
vertical
antenna
that
gives
good
performance
and
does
not
require
any
type
of
RF
ground
system.
The
reduction
in
size
is
accomplished
by
adding
separate
loading
coils
and
capacitance
hats
at
each
end
of
the
antenna
for
the
HF
bands.
The
efficient
end
loading
coils
are
wound
on
fiberglass
forms.
The
high
quality
materials
and
construction
of
the
HF
loading
system
allows
a
maximum
power
rating
of
1500
watts
on
40,
20,
15
and
10
meters.
The
six
and
two
meter
bands
are
covered
with
the
addition
of
four
quarter
wave
decoupling
stubs
on
the
side
of
the
main
elements.
The
power
rating
of
this
antenna
varies
from
band
to
band.
The
PEP
ratings
are
primarily
determined
by
the
voltage
breakdown
of
the
components,
While
the
CW
ratings
are
generally
determined by components heating.
The
following
chart
lists
the
power
rating
and
the
2:1
VSWR
bandwidth
of
this
antenna:
Band Power Bandwidth
CW SSB RITTY
40m 500 1500 700 40KHZ
20m 750 1500 1250 250KHZ
15m 1000 1500 1250 T00KHZ
10m 750 1500 1250 1.0MH
6m 300 750 300 2.6MHz
2m 200 300 200 TMHZ
The
weight
and
wind
load
of
this
antenna
are
15
pound
and
approximately
2
square
feet
respectively.

MEFJ-1796 Vertical Antenna Instructions
CHOOSING A LOCATION FOR THE ANTENNA
The best performance on receiving and transmitting will be obtained by mounting the antenna in
a clear location above or away from buildings, towers, feedlines, utility wires, and other antennas.
While your own ingenuity and particular circumstances will determine the final mounting
method, we'll pass along a few ideas for both permanent installation and portable operation.
WARNING Abvays mount this antenna so that it is out of the reach of adults as well as
children. The capacitance elements can cause injury and or severe RF burns.
« Never mount this antenna in a location that will permit unsuspecting people to come in
contact with the loading spokes or any other part of the antenna. .
« Never mount this antenna where a mechanical failure might allow the antenna, antenna
support and feed line to contact power lines or other utility wires.
« Always ground the feedline at the point where it enters a building to a aes earth ground fo
lightning protection.
e Follow the guide lines for antenna installations as recommended by the US consumer product
safety commission.
Permanent Installation
The ideal installation is a rigid pole or roof mount that puts the antenna completely in the clear.
If the ideal installation is not possible, choose the best compromise. TV mast, steel water pipe are
suitable mast materials. This antenna will mount on masts between 1 and 1-1/2" OD. The use of
soft or thin wall masts is not recommended Never use mast made of soft material or thin wall
aluminum, such as aluminum tubing and conduit.
The MFJ-1796 will perform quite well even at ground level, which means the lower capacitance
hat should be at least 5 ft above ground level on a short rigid mast. However, the antenna
installation MUST be protected (with non-metallic fencing) to provide personal safety and to
prevent damage to the antenna itself.
Portable Operation
This antenna may be disassembled to the extent necessary for transporting to a temporary
location. If possible, only remove the two HF loading coil assemblies. Leave the two main
elements with the 2 and 6 meter stub assemblies intact. Some retuning may be required after
moving the antenna.
Even for temporary or portable operation, do not be casual about selecting a suitable mast. If th
antenna falls it will be damaged and may cause serious injury. Whatever type of installation youl
choose, remember that the antenna should be installed where it can never be contacted by people
or animals.

MEFJ-1796 Vertical Antenna Instructions
TOOLS AND TIME REQUIRED FOR ASSEMBLY
The estimated assembly time for this antenna is two hours. Antenria assembly requires the
following hand tools:
1/4" nut driver
3/8" open end wrench
5/16" nut driver (or 1/4" blade standard screwdriver)
7/16" nut driver
7/16" open end wrench
Large wire cutters
#1 Phillips screwdriver at least 6" long or longer
#2 Phillips screwdriver
suitable eye protection
In addition, you will need two stable supports at least 30" tall (such as saw horses or trash cans)
and a short (6-8') temporary mast (1 to 1-1/2" OD) for temporary mounting during tuning.
MFJ-1796 PARTS LIST
As you unpack your antenna you should find the parts in the following list.
2 Fiberglass Coil Assemblies
Two bundles of wire capacitance spokes 28 short, 12 medium, (and 4 spare long spokes)
One bag of clamps: 10 hose clamps and 2 saddle bolts
5' upper radiator, 6061-T6 AL tubing, 1 1/8" OD with the 6 and 2 meter stubs inside
5' lower radiator, 6061-T6 AL tubing, 1 1/8" OD (this tube has two holes through it)
One bag of short 6-32 stainless screws (you will only use 40, the rest are extra)
small "L" brackets with holes one end
long "U" channel "L" brackets
flat fiberglass insulators
hollow white nylon insulators
solid rod fiberglass center insulator
split ring 1/4" washers
1/4" dia. 7/16" head bolts
1/4-20 x 7/16" nuts
20 6-32 x 1/2" stainless screws
20 6-32 x 1/4" nuts
8 10-32 x 3/8 nuts
es es tees Sp Beeson es Oe nee Oe ee ee ee a a a eo a ec
AMmaneN DB DB HL
For installation you will need some items not supplied with the antenna installation kit.
[] A 6'-8' rigid mast or other mounting pipe between 1" and 1.5" outside diameter. (suitable
materials include TV mast sections, galvanized iron pipe.)
[] Quality low-loss 50-Ohm short coax cable with PL-259 connectors.
[ ] Either an SWR/Power meter or Analyzer (MFJ-207, MFJ-249, or MFJ-259)

MFJ-1796 Vertical Antenna Instructions
SAFETY PRECAUTIONS
WARNING! You can be killed if the antenna, feedline, or the equipment used to install the
antenna accidentally contacts any utility lines. Never install an antenna near power lines!
L, Be careful while climbing and carrying the antenna. It is heavy enough to cause you to
lose your balance if it is handled too casually or if the epee spokes are snagged on a
gutter, ladder, tree limbs and so forth.
Mount the antenna high crouch so that it is out of reach. The ends of the capacitancd
spokes can cause eye injury, serious RF burns oF both.
Make sure that the mast is sturdy. cash to support: the 15 pounds weight and the wind
load of approximately 2 square feet.
ASSEMBLY AND INSTALLATION PROCEDURE
During assembly of this antenna refer to the labeled figures in this manual and the inside cover
figure. The assembly instructions tell you how to first install the balun and then connect the
upper and lower elements. Then the 2 and 6 meter stub elements are installed. Last the loading
coil assemblies are assembled and installed on the upper and lower elements.
If you do not wish to install the 6 and 2 meter stubs operation on the other bands will not be
affected. Skip steps 4, do not install the hose clamps in step 10 and skip steps 13-18.
After the antenna is assembled it should be checked and adjusted for resonant frequency and
SWR. It can then be mounted on a tower or rooftop and given final adjustments(see Timing The
Antenna section for detail).
NOTE: Wear safety glasses whenever working near or on this antenna.
Warning: Do not tighten the screws that connect the loading coil terminal lugs to the
capacitance hat rings or you will BREAK the fiberglass form. If the terminal lugs loosen
tighten the NUT down on the lug.
¢« Step-By-Step Procedure
[] t. Prepare a temporary ground-level mounting mast that will permit easy initial testing and
adjustment. Set up saw horses or any other stable support (plastic trash cans or folding
tables, etc.) near the mast.

MEJ-1796 Vertical Antenna Instructions
[ | 2.
[] 3.
Sort out the parts you have unpacked into groups of similar parts. Be sure all the parts are
available.
After examining the antenna parts, gather the tools needed for basic assembly. At the
minimum these consist of:
[ ] #1 Long Phillips screwdriver for capacitance spoke screws
[ ] #2 Phillips screwdriver for other 6-32 screws
[] 1/4" standard screwdriver or a 5/16" nut driver for hose clamps.
[ | 3/8" wrench for 6 and 2 meter stub nuts
[ ] Two 7/16" open end wrenches or one wrench and one nut driver for "U" BOLTS and
center insulator bolts.
[ ] Wire cutters for trimming capacitance spokes.
[ ] Safety glasses.
{]4. Assemble the four small "L" brackets to the 4 long fiberglass insulators with the 6-32 x
1/2" screws and the 6-32 x 5/16" nuts as shown in Figure 1.
i Short "L" Brackets
Hole
for
L
a
7
io
6
or
2
Meter
Stub
Ss
&
|
SS
= A to 6-32 x 5/8" Screws
tT) WD
Fiberglass Insulator ie 6-32 x 5/16" Nuts
Figure 1
[] 5. Bolt the top balun hole loosely to the top hole in the base mounting assembly with a 1/4-20
[] 6.
[] 7.
[] 8.
[] 9.
* 7/16" nut and the 1/4" x 7/16" head bolts. Use the hollow white nylon spacers to separate
the balun from the mounting bracket. Finger tighten only. See Figure 2.
Bolt the bottom balun hole to the bottom hole in the base mounting assembly as in Step S.
Tighten the balun bolts with a 7/16" wrench.
Bolt the coax connector assembly to the base mounting assembly with four 6-32 x 5/8"
screws and 6-32 nuts. See Figure 2.
Slide the bottom radiator (the one with two sets of holes) over the fiberglass rod with the
holes that are 2" from the end toward the base mounting bracket. Slide a hose clamp to the
bottom of the element. The radiator should butt against the insulating plastic of the base

MEF J-1796 Vertical Antenna Instructions
mounting bracket. Install a 1/4 x 7/16" bolt through the element and fiberglass rod and
tighten with a lock washer and 1/4 x 7/16" nut.
[] 10. Slide three more hose clamps over the bottom element. Tighten the hose clamp installed
in step 9 over the slit in the bottom element. This clamp will make the antenna more rigid.
[ ] 11. Insert the fiberglass center insulator into the bottom element and insert a 1/4" x 7/16" head
bolt with a lock washer through the hole. Thread a 1/4" x 7/16" nut on the other end.
Finger tighten only. See Figure 3. Slide a hose clamp over the center insulator. Tighten
the hose clamp on the slit in the bottom element. Slide another hose clamp over the
insulator.
[ ] 12. Slide the top 1 1/8" diameter element over the center insulator and install the 1/4" x 7/16"
head bolt and nut as in step 10. Tighten the hose clamp over the slit in the top element
until the element will not sway.
[ ] 13. Slide three hose clamps over the top element.
NOTE: The upper and lower stubs (U-channel "L" brackets) on each band should not be installed
perfectly in line. There should be enough offset so that the threaded ends won't touch if the stubs
are fully shortened. The alignment of the stubs will not affect operation. See Figure 5.
Figure 2 1/4" 20 x 7/16" Bolt
Bottom View of the
Base Mounting Assembly ——
~ 1/4-20 x 7/16" Nut \ |
/
2
1
5
<<
A
6-32
x
1/2"
Screws
ly
White
Nyion
a
Spacer
Balun
and
4 6-32 Nuts
Coax Connector
Assembly
Coax Enters this Side

MFJ-1796 Vertical Antenna Instructions
[] 14. Clamp the four long U-channel "L" brackets to the elements 1/4" above and below the
center insulator bolts. See Figure 4 and Figure 6.
[] 15. Mount the two short stubs by threading a 10-32 x 3/8" nut 1/2" from the end of the
threads, toward the elements unthreaded end. This will leave a large area of the threads
exposed at the end of the element. Add a second nut to sandwich the bracket between the
two nuts. See Figure 4. The two short stubs should be mounted opposite from the
balun. (See figure 5).
Figure 3
Top
Figure 4
Short 2 Meter
Stub Element
Long 6 Meter
Stub Element Element
mmm
U-channel
7
|
"L"
Brackets
Fi
([[naonenanncncuonne
\
V/A"
x
7/16
Bolts
We
Lock
he
|
1/4"
x
7/16
Waishers
|
insula
Nuts
Lsmnmonesononene
1
Element
Figure
5
5\
Put
6
Meter
Stub
Elements
Over
the
aod
oe
i)
pines
=
Elements
Top
View
A\\
Rs
of
Antenna
Note: Stubs are offset so that
threaded ends do not touch.

MFJ-1796 Vertical Antenna
[ ] 16 Mount the two long stubs by threading a
10-32 x 3/8" nut, 1/2" from the
elements threaded end. This will leave
only a small amount of threaded area
below the nut. Add a second nut to
sandwich the bracket between the two
nuts. See Figure 4. The two long
stubs elements should be on the same
side as the balun. ( See Figure 5.)
[]17.Install two long fiberglass insulators
over each long stub; one approximately
20" and the other 14" from the
unthreaded ends of the long stubs by
clamping them in place with hose
clamps. See Figure 6.
[]18.Install the remaining long fiberglass
insulators over the short stubs
approximately 5" from the outside ends
of the stubs. See Figure 6
40 m 20 Mm 158m
;
Figure 6
2 Meter
Stub Element
Instructions
|
6 Meter
Stub Element
Fiberglass
Insulators
Loading Assembly
x
\
\
\
Bend Bare Wire 1"
From Any Element if Necessary
8
Figure 7

MFJ-1796 Vertical Antenna Instructions
[ ] 19. Install the short 6-32 screws in the ring of both loading coil assemblies. Do not thread the
screws completely in. Put the medium capacitance spokes in the six holes in these rings
on both coil assemblies. Tighten the screws until the spokes are snug. At this point you
should be able to turn the coil assemblies over and they should balance on the long spokes.
USE THE #1 PHILLIPS SCREWDRIVER HERE.
[ ] 20. Install the screws in the next set of rings and install six short spokes in these rings.
[ ] 21. Install the next groups of four short spokes on each loading coil assembly.
[ ] 22. Check the bare wires running along the side of the loading coil assembly to be sure that
there is at least 1" of clearance between the bare wire and the capacitance spokes. It is
okay to bend the bare wire enough to clear the spokes properly. See Figure 7.
[ ] 23. Remove the nuts on the center insulator bolts of the main element and install thecenter
conductor lug of the coax under the upper element nut and the shield lug under the
bottom element nut. Hold the nut in place and turn the bolt head to tighten these bolts so
that the lug does not break off the end of the coax. Be sure to dress the coax so it loops up
in a drip loop so water cannot get into the end. See Figure 8.
qd |
A
he
*
'
Drip
Loop
Tum
This
Side
~~,
4
Bete
eee
fete
es
Put
Terminal
Lugs
”.
Shletel
on This Side
Figure 8

MFJ-1796 Vertical Antenna Instructions
[ ] 24. Use the three black cable ties to affix the coax to the antenna as illustrated on page 1.
Warning: To Prevent Arcking And Destruction Of The Coax Cable, Do Not Allow The Coa:
Cable To Come Within 1 Inch Of The Aluminum Base Mounting Bracket.
[] 25. Slide a hose clamp over the top element. Mount the top loading coil assembly to the
antenna by inserting the fiberglass form into the top element. Tighten the bus wire from
the coil assembly under the hose clamp. Make sure the loading coil assembly is secured.
{ ] 26. Mount the coil assembly with the angle mounting bracket three to four inches from the
bottom insulator of the antenna. ( see figure on inside front cover )
[ ] 27. Double check the tightness of all the hardware you installed and then mount the antenna on
the short temporary tuning mast.( 6 to 8 feet)
{ ] 28. Tune the antenna, see the next section.
[ ] 29. Mount the antenna in it's permanent location. Slight re-tuning may be necessary.
FREQUENCY AND SWR ADJUSTMENT
This antenna covers wider frequency ranges on the higher bands, and narrower segments on the
lower frequency bands. The 40 meter band has the narrowest range of operation (approximately
40 KHz) and is the most sensitive to adjustments.
The entire antenna must be accessible during initial coarse tuning and testing. Any repair or
adjustment to the antenna after it is installed on a tall support will make adjustments difficult and
time consuming. It is best to install the antenna on a short temporary mast or pipe that is located
in a reasonably clear location for tuning. The antenna should be mounted vertically with the base
of the antenna around six feet above ground to make tests and adjustments easy.
Hint:: The use of a small tripod will make tuning this antenna easy. With the help of an other
person it is easy to lean the antenna, while it is fastened to the tripod, to lower it and make th¢
necessary adjustments.
The SWR can be measured by using a transmitter and SWR bridge or an SWR Analyzer such as
MFJ-249 / MFJ-259. The best location to make SWR measurements is at the base of the antenna.
If the measurements are not taken at the base of the antenna, the antenna must be fed with a
reasonably short length of good quality 50 ohm coaxial cable to insure proper results. If using a
transceiver and SWR meter, set the transceiver to the lowest power possible to make
measurements.
10

MF J-1796 Vertical Antenna Instructions
Please read the following hints:
e The normal resonant frequency of this antenna is at or just below the bottom of each
amateur band. This allows the user to "trim', a small amount off theinside end of the
capacitance spokes to raise the resonant frequency. Conversely, adding a longer capacitance
spoke will lower the resonant frequency. Spare spokes are included in case you need to lower
the resonant frequency of the antenna. ‘
e If you suspect the resonant frequency is lower than your equipment can detect, for
example below 6.0MHz, take one 40 meter spoke entirely off the antenna (top and bottom
hats). make another attempt to measure the resonant frequency. If you still unable to find the
resonant frequency, check an other band. If non of these test produce a good SWR on any
frequency, substitute a 50 ohm load for the antenna to test the feed line. If the SWR checks
good, you will have to double check the antenna assembly for shorts or opens at the feed
point and the connector box.
e If the antenna operates normally higher than the band after one spoke is removed,
install all the spokes and trim one spoke simultaneously from top and bottom hats in one inch
steps until you find the resonant frequency within the range of your equipment.
e Once you find the resonant frequency, Use the chart located on the following page to
estimate the amount of spoke length to cut so the antenna will resonate at your favorite
section of the band.
IMPORTANT: Always start tuning on 40 meters and adjust each band progressively
higher in frequency
TUNING THE ANTENNA
ALWAYS REMEMBER: This antenna is a balanced dipole. If changes were
made to one side only, the dipole will be unbalanced. For that reason, any
changes you make on the bottom capacitor hat should be done in the same
manner on the top capacitor hat to keep the dipole balanced.
. Measure and record the frequency that the lowest SWR occurs on for each band. The lowest
SWR should be at or below the bottom end of each HF band. The SWR should be below 2:1 at
resonance on each band.
The following is a typical chart for initial measurements of a new antenna before tuning:
40M 1.6:1 at 6.99MHz 10M 1.6:1 at 27.97 MHz
20M 1.2:1 at 13.9MHz 6M 1.2:1 at 51 MHz
15M 1.2:1 at 20.85 MHz 2M 1.2:1 at 146 MHz
11

MF J-1796 Vertical Antenna Instructions
If the resonant frequency is lower than your equipment can detect take one spoke off ( top and
bottom hats) to raise the resonant frequency. Measure the resonant frequency and calculate the
approximate resonant frequency as if the spoke was in place using the chart on the next page.
Warning : Shortening the spokes from the looped end degrades safety and power
handling capabilities!
NOTE: Always tune the lowest frequency bands first
TUNING THE LOW FREQUENCY BANDS
NOTE: always trim the same amount of spoke length from both capacitor hats of the antenna
(top and bottom ) to keep the dipole balanced
40 Meter Band:
e Select a frequency 50 KHz below the desired operating frequency. Use this frequency as a
target.
e Measure the resonant frequency of the antenna at this band. determine the frequency shift
required by subtracting the initial frequency from the desired frequency. Use the results and
the chart below to determine the proper amount of spoke length to be cut.
e If the calculated amount of spoke shortening exceeds 8", cut one inch from the inside end of
all six spokes for each 8" calculated.
e Return to step 1. Keep repeating these steps until done.
Example: the antenna measure 6.95 MHz, the desired frequency is 7.25 MHz, less .05 MHz (50
KHz below desired frequency) for a difference of .2MHz or 200 KHz. This would require the
trimming of 8" from one spoke in each top and bottom hat. Instead, cut one inch from all 6
spokes ( top and bottom hats )and measure the resonant frequency. Assume the new resonant
frequency is close to the wanted one. A single spoke (from top and bottom hats) can now be
trimmed to adjust the antenna to resonance.
40 M: 1" trimmed off a pair of spokes equals approximately 25 KHz
20 M: 1" trimmed off a pair of spokes equals approximately 100 KHz
15 M: 1" trimmed off a pair of spokes equals approximately 175 KHz
10 M: 1" trimmed off a pair of spokes equals approximately 250 KHz
12

MEJ-1796 Vertical Antenna Instructions
Tuning 20, 15, And 10 Meter Bands
Now tune progressively higher frequency HF bands by using the same technique used for the
40 meter band. Set the target frequency 30 KHz lower than the desired operating frequency for
these bands. 20 meters must be the second HF band adjusted, 15 the third and 10 meters last.
After adjusting 10 meters go back and check the other bands. Tighten all spoke screws. ( Use the
chart above for cutting at each band.)
TUNING THE HIGH FREQUENCY BANDS (VHF)
The six and two meter bands are tuned by lengthening or shortening the threaded portion of the
stubs. See Figure 9. This adjustment is very coarse. If the frequency is still too low with the stub
element extension at a minimum, the unthreaded ends of the stubs can be trimmed. Once again
the lower frequency stub (6 meters) should be adjusted first.
6 Meter
2 Meter Element
After Decreasing Stub
Extension To Max, Trim
End to Raise Frequency
Increase Extension
to Lower Frequency
Decrease Extension
to Raise Frequency
Figure 9
The six meter stub covers from 50 to 54 MHz as it is adjusted. Be careful because the third
harmonic resonance of the six meter stub will show up as a low SWR on the third harmonic of it's
setting, usually between 150 and 160 MHz. The range of the two meter stub allows frequencies
as low as 130 MHz to be covered with the stub fully extended and 148 MHz with the stub fully
contracted.
Final frequency adjustments can be made by trimming spokes on the bottom hat only when the
antenna is permanently mounted. The minor adjustment of bottom spokes without the
symmetrical trimming of the top spokes is perfectly acceptable so long as the frequency is
changed less than 30 KHz on 40 meters and 60 KHz on the higher bands with the final
adjustment. The result of attempting to move the resonant frequency too far with only the bottom
spokes will be an increase in the SWR of the antenna at the resonant frequency.
13

MFJ-1796 Vertical Antenna Instructions
GROUNDING CONSIDERATIONS
Although this antenna is designed to operate efficiently without the requirement of an earth
ground, SAFETY GROUNDING MUST STILL be provided to protect equipment, property and.
persons from the hazards of lighting strikes and other weather related electrical discharges. In
addition the coaxial cable feeding the antenna should have the shield grounded to eliminate the
risk of any indoor equipment failure from allowing hazardous voltages from appearing indoors
and creating a shock hazard.
Adequate protection can be accomplished by grounding the shield of the coax where it enters the
building to a good earth ground or directly burying the cable in the earth for several feet before it
enters the building. The coaxial cable should be totally disconnected from the station during
threatening weather conditions for maximum lightning protection.
A less effective method of protecting station equipment is to install an in-line coaxial lightning
arrestor with a heavy duty ground wire to a suitable earth ground, or a safety switching system as
part of the basic ham station equipment.
MAINTENANCE
Your antenna is constructed of heavy duty non corrosive materials and should withstand normal
climates for many years. The use of some type of coaxial connector moisture protection is
recommended at the bottom coax connection and also around the center-feed connections,
especially in coastal areas where salty mist is commonplace.
GE makes a pure silicone grease called "SILICONE DIELECTRIC COMPOUND" that can
be applied SPARINGLY to the threaded area of the female connector. This compound, or even a
clear silicone heat sink compound, will prevent moisture from entering the connector through the
threads and protect the connectors from corrosion. THIS IS THE SAME TYPE OF SEALER
THAT COMMERCIAL ANTENNA INSTALLERS AND CATV COMPANIES USE WITH
GREAT SUCCESS.
A less desirable, but still adequate sealer is the automobile seam sealer commonly sold as "coax
seal". This is a semi-pliable black sealing compound.
When installing any "coax seal", NEVER completely cover the barrel of the coax connector. The
sealer should ONLY be placed near the junction of the threaded part of the chassis connector and
the knurled area of the male connector. This will leave the bottom of the male outer sleeve open
and permit the connector to "breathe" so it does NOT collect moisture!
IMPORTANT FOR COASTAL AREA OPERATORS:; It is advisable to use some type of silicon
spray ( circuit board type from Radio Shack ) on the capacitor rings to prevent corrosions
between the aluminum and the stainless steel screws Corrosion on capacitor rings tend make it
difficult to remove the spokes to retune the antenna.
14

MEJ-1796 Vertical Antenna Instructions
Technical Assistance
If you have any problem with this unit first check the appropriate section of this manual. If the
manual does not reference your problem or your problem is not solved by reading the manual, you
may call MFJ Technical Service at 662-323-0549 or the MFJ Factory at 662-323-5869. You
will be best helped if you have your unit, manual and all information on your station handy so you
can answer any questions the technicians may ask.
You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial Park Road,
Starkville, MS 39759; by Facsimile (FAX) to 662-323-6551; or by email to
[email protected]. Send a complete description of your problem, an explanation of
exactly how you are using your unit, and a complete description of your station.
15

LIMITED 12 MONTH WARRANTY
MFT Enterprises, Inc. warrants to the original owner of this product, if manufactured by MFJ Enterprises,
Inc. and purchased from an authorized dealer or directly from MFJ Enterprises, Inc. to be free from defects
in material and workmanship for a period of 12 months from date of purchase provided the following terms
of this warranty are satisfied.
1.
10.
11.
The purchaser must retain the dated proof-of-purchase (bill of sale, canceled check, credit card or
money order receipt, etc.) describing the product to establish the validity of the warranty claim and
submit the original or machine reproduction of such proof of purchase to MFJ Enterprises, Inc. at
the time of warranty service. MFJ Enterprises, Inc. shall have the discretion to deny warranty
without dated proof-of-purchase. Any evidence of alteration, erasure, or forgery shall be cause to
void any and all warranty terms immediately.
MFJ Enterprises, Inc. agrees to repair or replace at MFJ's option without charge to the original
owner any defective product under warrantee provided the product is returned postage prepaid to
MFJ Enterprises, Inc. with a personal check, cashiers check, or money order for $7.00 covering
postage and handling.
This warranty is NOT void for owners who attempt to repair defective units. Technical
consultation is available by calling the Service Department at 662-323-0549 or the MFJ Factory at
662-323-5869.
This warranty does not apply to kits sold by or manufactured by MFJ Enterprises, Inc.
Wired and tested PC board products are covered by this warranty provided only the wired and
tested PC board product is returned. Wired and tested PC boards installed in the owner's cabinet
or connected to switches, jacks, or cables, etc. sent to MFJ Enterprises, Inc. will be retumed at the
owner's expense unrepaired.
Under no circumstances is MFJ Enterprises, Inc. liable for consequential damages to person or
property by the use of any MFJ products.
Out-of-Warranty Service: MFJ Enterprises, Inc. will repair any out-of-warranty product provided
the unit is shipped prepaid. All repaired units will be shipped COD to the owner. Repair charges
will be added to the COD fee unless other arrangements are made.
This warranty is given in lieu of any other warranty expressed or implied.
MFI Enterprises, Inc. reserves the right to make changes or improvements in design or manufacture
without incurring any obligation to install such changes upon any of the products previously
manufactured.
All MFJ products to be serviced in-warranty or out-of-warranty should be addressed to:
MFJ Enterprises, Inc.,
300 Industrial Park Road
Starkville, Mississippi 39759 USA
and must be accompanied by a letter describing the problem in detail along with a copy of your
dated proof-of-purchase.
This warranty gives you specific rights, and you may also have other rights which vary from state to
state.