Near Vertical
Incidence
Skywave
(NVIS)
Antenna
DXE-NVIS-8040
DXE-NVIS-8040S
DXE-NVIS-8040NM
DXE-NVIS-8040SNM
DXE-NVIS-INS Revision 1
© DX Engineering 2019
1200 Southeast Ave. - Tallmadge, OH 44278 USA
Phone: (800) 777-0703 ∙ Tech Support and International: (330) 572-3200
Fax: (330) 572-3279 ∙ E-mail: DXEngineering@DXEngineering.com
Introduction
DX Engineering’s Near Vertical Incidence Skywave (NVIS) Antennas for both 80 and 40 meters
are available in two models. The difference between the two models is the foot print size area
needed. The larger version the DXE-NVIS-8040 is a full size 80 and 40 meter NVIS antenna that
uses no coils. The footprint for this model is approximately 158 feet by 75 feet. The second version
- DXE-NVIS-8040S uses two coils on the 80 meter legs which shrinks the footprint to
approximately 75 feet x 75 feet.
Both versions operate virtually identical to each other and provide the operator with a complete kit
to get on the air in an emergency or other temporary communications event. The NVIS antenna can
also be permanently installed for every day use.
For those that have their own non-metallic 15 foot mast, you can purchase the NVIS antenna kits
with all the parts except the mast assembly. Part numbers for those antenna kits are: DXE-NVIS-
8040NM and DXE-NVIS-8040SNM.
NVIS
Near Vertical Incidence Skywave (NVIS) is a
propagation mode which uses high angle
radiation to send signals almost straight up to be
reflected back to Earth for very effective short to
medium distance communications. This mode of
operation makes it ideal for in-state
communications during disasters or other
emergency situations. The military has used
NVIS techniques for decades to provide short
haul communication with other units on the
ground.
NVIS only works at frequencies from 2 MHz to
10 MHz. The signal must penetrate the D layer of the ionosphere, and bounce off the F layer.
Lower-frequency signals will not penetrate the D layer; higher frequencies will not bounce off the F
layer at these sharp angles and just goes out into space. Remember the Maximum Useable
Frequency (MUF) For amateur radio operators, we're looking at 40 and 80 meters primarily for
NVIS use.
A good NVIS antenna will not work well at DX distances. Antenna gain is a zero sum game. There
is a fixed amount of energy radiating. If we push it all out in one direction (the near-vertical angles),
we have to take it away from another direction (the low DX angles).
Regular height dipoles or vertical antennas have a lower take off angle and your signal may be
heard three states away, but not in your state due to the skip zone. This skip zone is the area
between the maximum ground wave distance and the shortest sky wave distance where no
communications are possible. Depending on operating frequencies, antennas, and propagation
conditions, this skip zone can start at roughly 10 to 20 miles and extend out to several hundred
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miles, preventing communications with the desired station. The other term called ground wave is
where your signal does reach someone closer. A ground wave signal can go up to approximately 50
miles if conditions, including terrain and obstacles, are favorable.
Using no skip zone or ground wave, the NVIS mode is used for making reliable HF
communications below 10 MHz
effective for a range to 600 miles. The
NVIS propagation mode works best on
HF below 10 MHz since these high
angle radio waves are reflected back to
Earth. Most often a low dipole is the
best antenna to use and will provide
reliable communications. This makes a
NVIS antenna an excellent choice for
emergency communications and for
staying in contact with other amateur
radio operators in nearby locations.
Dipoles only exhibit directionality once they reach 1/2 wavelengths above ground. However, NVIS
antennas are located from 1/4 to 1/10 wavelength above ground.
Vertical RF energy radiated at a low enough frequency is reflected back to earth at all angles.
The effect is similar to taking your garden hose with a fog nozzle and pointing it straight upwards.
The water coming back down gives you an omni-directional pattern without dead spots. It's a
continuous circular radiation pattern coming back down. Since it is omni-directional, dipole
orientation is not important.
The higher the angle, the lower the frequency
needed to work properly. Therefore lower
amateur radio frequencies such as 40 and 80
meters are ideal for NVIS use. NVIS
generally requires takeoff angles of 70 degrees
or higher. Radio waves directed vertically at
frequencies higher than the critical frequency
pass through the ionized layer out into space.
Typical expected ranges are up to 300 miles
when using NVIS antennas which make them
ideal for close in communications (not for
DXing).
The DX Engineering versions of the NVIS antenna have been designed and tested in real-world
situations and found to offer great performance for NVIS communications on both 80 and 40
meters.
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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.
Fiberglass Information
The mast sections in this kit are fiberglass. Take normal precautions when handling any fiberglass
material. There may be fiberglass dust, slivers or particles present when the fiberglass parts
were manufactured. The use of typical fiberglass handling safety gear, (gloves, dust mask, eye
shield, clothing, etc.) when handling and working with fiberglass, is recommended. Use a damp rag
to wipe the parts. Do not use compressed air to clean fiberglass parts. Measures can be taken to
reduce exposure after a person has come in contact with fiberglass. Eyes should be flushed with
water and any area of exposed skin should be washed with soap and warm water to remove fibers.
Clothing worn while working with fiberglass should be removed and washed separately from other
clothing. The washing machine should be rinsed thoroughly after the exposed clothing has been
washed. Check with your local or state safety and/or environmental agencies for more detailed
precautions.
NVIS Features and Specifications:
Easy Assembly ideal for emergency set-up
Covers both 40 and 80 meter bands - ideal for NVIS
communication
Transports easily
Made with quality rugged parts for long service life
Tunable with modern transceivers that have internal tuners
Can be installed as a temporary or permanent system
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Parts Lists
Parts Common to Both 8040 and 8040S Models
Qty
Part Number
Description
1
DXE-NVIS-MAST
Tubes and Hardware for the NVIS Mast
(1) 2” OD x 4 feet long, fiberglass tube
(1) 1-3/4” OD x 4 feet long, fiberglass tube
(1) 1-1/2” OD x 4 feet long, fiberglass tube
(1) 1-1/4” OD x 4 feet long, fiberglass tube
(1) Compression Clamp 2” to 1-3/4”
(1) Compression Clamp 1-3/4” to 1-1/2”
(1) Compression Clamp 1-1/2” to 1-1/4”
(1) Band Clamp for, 2.250" OD (use 5/16” Nut Driver)
(2) Band Clamp for, 2.000" OD (use 5/16” Nut Driver)
(2) Band Clamp for 1.750" OD (use 5/16” Nut Driver)
(1) Band Clamp for 1.500" OD (use 5/16” Nut Driver)
(1) Black Vinyl Cap for 1-1/4” Fiberglass Tube
1
COM-BAL-11150T
COMTEK 1:1 Single Core Balun
1
DXE-NVIS-BMB
Balun Mounting Bracket with Stainless Steel Hardware
(2) Hex Head Nut, Nyloc, Stainless Steel
(2) Flat Fender Washer, Stainless Steel
(2) DXE-ECLS-150 Studded Band Clamp, Stainless Steel, w/ hardware
1
DXE-CSR8X-1
Cable Strain Relief Kit for 8X Coaxial Cable
1
DXE-8XDX100
RG-8X Coaxial Cable, 100 Ft, with PL-259 connectors
1
SYN-DBR-125-100
Antenna Support Rope, 0.125” dia, 100 FT
2
DXE-TGI-2
Glass Antenna Insulators (2 packages, total of 4 insulators)
1
DXE-TENTPEGS4
Tent Peg Ground Stakes, Aluminum, 4
DXE-NVIS-8040
Qty
Part Number
Description
3
DXE-ANTW-75
Premium Antenna Wire, 14 ga, Relaxed PVC, 75 feet per roll
Plus the common parts listed above
DXE-NVIS-8040S
Qty
Part Number
Description
2
DXE-ANTW-75
Premium Antenna Wire, 14 ga, Relaxed PVC, 75 feet per roll
1
DXE-NVIS-80RES
(2) Resonator Coils for the 80 meter NVIS-8040S antenna
(2) MSG-ADC03 Wire Strain Relief Clamp, 3 mm
Plus the common parts listed above
NOTE: For those that have their own non-metallic 15 foot mast, you can purchase the NVIS
antenna kits with all the parts except the mast assembly. Part numbers for those antenna kits are:
DXE-NVIS-8040NM and DXE-NVIS-8040SNM.
DXE-NVIS-8040NM DXE-NVIS-8040SNM
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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.
Tools Required
Wire Stripper
Soldering Iron and Solder
Utility Knife and Lighter (for rope)
Nut Drivers: 1/4”, 3/8”, 516”
Wrench: 7 mm (for the 80 meter coil strain relief clamps)
Pliers
Gloves (see information on Fiberglass Tubing on page 4)
Hammer (for Tent Peg Ground Stakes)
Assembly
Mounting the BALUN to the BMB BALUN Mounting Bracket
1. The BMB BALUN Mounting bracket comes with the hardware required to
mount the BALUN. As shown, mount the BALUN in place on the
Mounting Bracket using the four #6 hex head bolts, eight #6 washers and
four #6 Nyloc hex nuts.
Note: The cupped ends are facing the rear.
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