DX Engineering DXE-WA-BMB User manual

Balun Mounting Bracket for
COMTEK Baluns and
Wire Antennas
Patent Pending
DXE-WA-BMB
DXE-WA-BMB-INS Rev 0c
Shown with optional parts
© DX Engineering 2018
DX Engineering - 1200 Southeast Ave. - Tallmadge, OH 44278 USA
Phone: [phone] ∙ Tech Support and International: [phone]
Fax: [phone] ∙ E-mail: [email protected]

Page 2
Introduction and General Information
This custom made patented pending Balun Mounting Bracket
for top terminal COMTEK Baluns and Wire Antennas kit
includes two DX Engineering End Insulators (US Patent
No. D534,905) and all Stainless Steel Hardware. Using the
optional coaxial cable strain relief (DXE-CSR213-1 for RG-
213 sized coax or the DXE-CSR8X-1 for RG-8X sized coax)
with your optional dipole wire (DXE-ANTW Antenna Wire)
and DX Engineering rope, this kit is the ideal starting point
for building a quality coaxial cable fed single band resonant
dipole, folded dipole or off-center fed dipole. The custom
made mounting bracket will fit other manufacturers’ similarly
packaged Baluns.
The unique design provides minimum capacitive coupling to the wire and field surrounding the Balun
core plus a special UV resistant, strong black plastic compound. The bracket as well as the end
insulators feature an exclusive serpentine wire weave grip for insulated DX Engineering Antenna Wire.
This method of threading the wire provides a grip strong enough to permanently support the antenna
wires without the need for looping or wrapping the wire ends back on to the dipole wires. This allows
fast and easy field adjustments of antenna length without soldering.
This manual does not cover all the types of resonant dipoles that could be built using these components.
The type of resonant dipole to be built is limited only by your imagination. For more complete antenna
theory and for construction of the many different types of wire antennas possible, refer to textbook
material such as the "ARRL Antenna Book"which is also available from DX Engineering.
Features
All-in-One mounting bracket (Patent Pending)
Custom molded, UV resistant black poly-resin blend
Serpentine routing of dipole wires to ensure maximum grip without soldering or other
mechanical restraints
Includes two DX Engineering End Insulators (US Patent No. D534,905)
Easily mount a COMTEK balun with top wing nut terminals
Adapts easily to other brand baluns built with the same NEMA mounting box used by COMTEK
All Stainless Steel Balun Mounting Hardware
Manual Updates
Every effort is made to supply the latest manual revision with each product. Occasionally a manual will
be updated between the time your DX Engineering product is shipped and when you receive it. Please
check the DX Engineering web site (www.dxengineering.com) for the latest revision manual.

Page 3
Parts List
Qty
Description
1
Comtek Balun & Wire Antenna Bracket
2
DX Engineering End Insulators
4
6-32 x 3/4” long Stainless Steel Hex Head Bolts
8
#6 Stainless Steel Flat Washers
4
6-32 Nyloc Hex Nuts
Note: The following assembly instructions are based on building a typical
resonant dipole for 15 meters. Optional items include a COMTEK balun,
DX Engineering Antenna Wire, DX Engineering Coax Strain Relief, DX
Engineering Rope, DX Engineering Coaxial Cable, suggested Never-
Seez®for the stainless steel hardware and DX Engineering
weatherproofing materials for coaxial connectors.
Additional Items Needed, but not Supplied:
COMTEK Balun
DX Engineering Premium Antenna Wire
DX Engineering Coaxial Cable Strain Relief
DX Engineering Synthetic Rope
DX Engineering Coaxial Cable with PL-259 connectors installed
JTL-12555 Jet Lube SS-30 compound - used on the threads of Stainless Steel Hardware to prevent
galling (seizing) and aid in proper tightening

Page 4
Antenna Installation
Safety Considerations
WARNING!
INSTALLATION OF ANY ANTENNA NEAR POWER LINES IS DANGEROUS
Warning: Do not locate the antenna near overhead power lines or other electric light or power circuits,
or where it can come into contact with such circuits. When installing the antenna, take extreme care not
to come into contact with such circuits, because they may cause serious injury or death.
Overhead Power Line Safety
Before you begin working, check carefully for overhead power lines in the area you will be working.
Don't assume that wires are telephone or cable lines: check with your electric utility for advice.
Although overhead power lines may appear to be insulated, often these coverings are intended only to
protect metal wires from weather conditions and may not protect you from electric shock Keep your
distance! Remember the 10-foot rule: When carrying and using ladders and other long tools, keep them
at least 10 feet away from all overhead lines - including any lines from the power pole to your home.
Mounting Considerations
When planning the location of your antenna, consideration should be given to the height, location of
suitable support structures and feedline positioning and length.
Generally speaking, dipole antennas should be mounted as high as possible for best performance.
Antenna height will affect the exact resonance point, radiation pattern, and takeoff angle. The higher the
antenna, the lower the takeoff angle to the horizon, which increases the effective range of the antenna.
For DX, the minimum height above ground should be 1/2 to 1-wavelength at the lowest operating
frequency. On the low bands, this height becomes impractical for most hams. For example, an 80m
dipole at 70 feet is about 1/4-wavelength above the ground. This antenna would be good for local and
short distance communications, but not optimal for DX, due to the high takeoff angle and ground
absorption. A 40 Meter dipole at 70 feet is approximately 1/2-wavelength high and is likely to be good
for DX and less optimal for local or short range communications. For more information on antenna
design, feedline and radiation angles, consult a reliable text such as the "ARRL Antenna Book"which is
available from DX Engineering.

Page 5
Basic Assembly
Note: The following assembly instructions are based on building a typical flat
top resonant dipole for 15 meters. Optional items include a COMTEK
balun, DX Engineering Antenna Wire, DX Engineering Coax Strain
Relief, DX Engineering Rope, DX Engineering Coaxial Cable, suggested
Never-Seez®for the stainless steel hardware and DX Engineering
weatherproofing materials for coaxial connectors.
Using the included Stainless Steel Hardware, mount the COMTEK balun (in this example we’ll use the
COMTEK 1:1 Balun - part number COM-BAL-41130T) as shown below. Note: When installing
stainless steel hardware, it is suggested that JTL-12555 Jet Lube SS-30 be used to prevent thread
galling.
Mount the Balun on the side opposite the cupped areas of the dipole wire guides.

Page 6
When building a single band coaxial cable fed HF dipole antenna, you may easily use the formula
L = 468/F to determine the overall length of the wire (L in feet, F in MHz). The formula takes into
account the end-effect of the antenna wire to give you the overall length of the wire portion.
As an example, using the formula L = 468/F, the overall length of a half wave dipole for 3.800 MHz
would be L = 468/3.800 or 123.2 feet. Cut the overall length of the wire to 125 feet or more to include
the extra length for tuning. Then cut that in half to provide two dipole legs –each 62.5 feet long.
Use this theoretical formula length as a starting point to cut the wire, leaving about one foot extra on
each dipole leg for wire fastening and fine tuning adjustment to allow for anomalies and environmental
effects in your particular installation. Longer length dipole legs may be required for Inverted-V
antennas.
Both of the dipole leg ends should be measured and cut longer than necessary so you have enough wire
to wrap around the Balun terminals and End Insulators, plus a little extra for final tuning. It’s always
easier to cut excess wire rather than having to solder on extra wire when tuning.
In this example, we are making a 15 meter flat top resonant dipole. The lowest frequency on the 15
meter band is 21.000 MHz.
Example: 21.000 MHz (bottom edge of 15 meters)
Overall Length = 22.29 feet
Leg 1 = 11.145 feet
Leg 2 = 11.145 feet
Overall length would be 22.29 - BUT we add some extra for wire fastening and tuning
Therefore; cut the legs to 13 feet each
Longer length dipole legs (up to 2 feet longer) may be required for Inverted-V antennas.

Page 7
Trim approximately 1 inch of insulation from the two dipole wires that will connect to the COMTEK
Balun.
Route the dipole wire ends through the mounting bracket in a serpentine manner as shown below.
Note where the wire enters the bracket through the cupped area.
Loosen the connection hardware on the COMTEK balun.
Wrap one of the the trimmed dipole wire ends around the balun connection point between the flat
washers in a clockwise direction. Don not include insulation, just have bare wire under the washers.
Firmly tighten the balun mounting hardware wing nut.
Repeat this for the other wire and balun terminal.

Page 8
Install the optional DX Engineering Coaxial Cable Strain Relief - either the
DXE-CSR213-1 or the DXE-CSR8X-1 depending on the type of coaxial cable
used.
In our example we are using the DXE-CSR8X-1 Cable Strain Relief to be used
with the DXE-8X coaxial cable.
Refer to the detailed instructions that are included with the strain relief for
details on the assembly.
Connect the coaxial cable (in this example DX Engineering DXE-8X (with PL-259s attached) to the
bottom of the Balun.
This coaxial connection should be weather proofed using the DX Engineering TES-2155 TemflexTM
Rubber Splicing Tape with an overwrap of TES-06132 Scotch®Super33+ tape for a complete
weatherproof solution.
Detailed information on weatherproofing connectors is available on-line at www.DXEngineering.com

Page 9
Dipole Wires and End Insulators
The End Insulators are installed at the far ends of the dipole wires. One on each end. Route the dipole
wire in a serpentine manner as shown below. Note the wire enters the End Insulator at the cupped area.
Once tuning is completed at low power, and the dipole leg wires are trimmed to length you can add an
extra tuck in the wire end to provide even more gripping power on the dipole wires as shown below.
Wrapping and soldering is not required.
Attaching Rope to the End Insulators
DX Engineering Double-braided Polyester Rope SYN-DBR should be secured to the Balun Mounting
Bracket and the End Insulators (depending on your installation) using a non-slip knot. The rope hole
(diameter) on the Balun Mounting Bracket is 0.371" and the end insulators are 0.34".
One suggestion for attaching the rope to the End Insulators is shown below. The ends of the rope should
be cauterized with a small flame to prevent the rope braid from fraying.
Non-Slip Knot using SYN-DBR Double-braided Polyester Rope

Page 10
Support Line
The Balun Mounting Bracket’s top hole is used for the attachment of a support line (also referred to as a
messenger line) that is used to provide support for the antenna wire and feedline. The use of the
messenger line, which is strongly recommended, will reduce the stress on the element wires and keep
the antenna from stretching over time, which will change its resonant frequency.
When using trees for support, you may want to use counter weights that will allow the rope to move
when the trees sway in the breeze to avoid stretching or breaking your dipole. For more hints, consult a
reliable text such as the "ARRL Antenna Book" which is available from DX Engineering.
Ideally, the messenger line should attach to the same structure used for the dipole, only above it, forming
at least a 30 degree angle between the dipole and the messenger line to support the antenna as shown
below.
Flat Dipole Installation between trees using a Messenger Line
DX Engineering Double-braided Polyester Rope SYN-DBRis used for the messenger line by forming a
loop at the mid-point of the rope. Push the loop through the Center-T top hole, and pull the rest of the
rope through the loop..
Rope Loop for Messenger Line
The excess rope can be used to attach the antenna end insulators to the support structures. Use the same
structures used by the messenger line if possible. The ends of the rope should be cauterized with a small
flame to prevent the rope braid from fraying.

Page 11
The top support hole may also be used for rope to install it as an inverted-V.
Inverted-V Dipole –Tower Side Arm Installation
Tower side arm Universal Mounting Plates and Saddle Clamps are available from DX Engineering.
Tuning
Once the dipole is completed, raise the dipole to its operating position.
Attached an Analyzer (example: Rig Expert REU-AA-230ZOOM) and determine the resonant point on
the dipole.
It will probably be a bit lower than you want - this is good. You then need to trim a small piece from
each end of the dipole (about 1 inch) and re-measure.
If the resonant point is low - trim the overall length shorter
If the resonant point is too high, you have to add to the overall length.
Once tuned, you are ready to get in the air and make contacts.

Page 12
Technical Support
If you have questions about this product, or if you experience difficulties during the installation, contact
DX Engineering at [phone]. You can also e-mail us at:
[email protected]
For best service, please take a few minutes to review this manual before you call.
Warranty
All products manufactured by DX Engineering are warranted to be free from defects in material and workmanship for a
period of one (1) year from date of shipment. DX Engineering’s sole obligation under these warranties shall be to issue
credit, repair or replace any item or part thereof which is proved to be other than as warranted; no allowance shall be made
for any labor charges of Buyer for replacement of parts, adjustment or repairs, or any other work, unless such charges are
authorized in advance by DX Engineering. If DX Engineering’s products are claimed to be defective in material or
workmanship, DX Engineering shall, upon prompt notice thereof, issue shipping instructions for return to DX Engineering
(transportation-charges prepaid by Buyer). Every such claim for breach of these warranties shall be deemed to be waived by
Buyer unless made in writing. The above warranties shall not extend to any products or parts thereof which have been
subjected to any misuse or neglect, damaged by accident, rendered defective by reason of improper installation, damaged
from severe weather including floods, or abnormal environmental conditions such as prolonged exposure to corrosives or
power surges, or by the performance of repairs or alterations outside of our plant, and shall not apply to any goods or parts
thereof furnished by Buyer or acquired from others at Buyer’s specifications. In addition, DX Engineering’s warranties do
not extend to other equipment and parts manufactured by others except to the extent of the original manufacturer’s warranty
to DX Engineering. The obligations under the foregoing warranties are limited to the precise terms thereof. These warranties
provide exclusive remedies, expressly in lieu of all other remedies including claims for special or consequential damages.
SELLER NEITHER MAKES NOR ASSUMES ANY OTHER WARRANTY WHATSOEVER, WHETHER EXPRESS,
STATUTORY, OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS, AND NO
PERSON IS AUTHORIZED TO ASSUME FOR DX ENGINEERING ANY OBLIGATION OR LIABILITY NOT
STRICTLY IN ACCORDANCE WITH THE FOREGOING.
©DX Engineering 2018
DX Engineering®, DXE®, DX Engineering, Inc.®, Hot Rodz®, Maxi-Core®, DX Engineering THUNDERBOLT®, DX
Engineering Yagi Mechanical®, EZ-BUILD®, TELREX®, Gorilla Grip® Stainless Steel Boom Clamps, Butternut®,
SkyHawk™, SkyLark™, SecureMount™, OMNI-TILT™, RF-PRO-1B®, AFHD-4® are trademarks of PDS Electronics,
Inc. No license to use or reproduce any of these trademarks or other trademarks is given or implied. All other brands and
product names are the trademarks of their respective owners.
Specifications subject to change without notice.
DX Engineering
1200 Southeast Ave. - Tallmadge, OH 44278 USA
Phone: [phone] ∙ Tech Support and International: [phone]
Fax: [phone] ∙ E-mail: [e-mail]