DX Engineering DXE-NVIS-8040 Manuale utente

Near Vertical

Incidence

Skywave

(NVIS)

Antenna

DXE-NVIS-8040

DXE-NVIS-8040S

DXE-NVIS-INS Revision 0

1200 Southeast Ave. - Tallmadge, OH 44278 USA

Phone: (800) 777-0703 ∙ Tech Support and International: (330) 572-3200

Fax: (330) 572-3279 ∙ E-mail: [email protected]

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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.

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

miles, preventing communications with the desired station. The other term called ground wave is

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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.

- 4 -

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

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

(4) Tent Peg Ground Stakes, Aluminum

COM-BAL-11150T

COMTEK 1:1 Single Core Balun

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

DXE-CSR8X-1

Cable Strain Relief Kit for 8X Coaxial Cable

DXE-8XDX100

RG-8X Coaxial Cable, 100 Ft, with PL-259 connectors

SYN-DBR-125-100

Antenna Support Rope, 0.125” dia, 100 FT

DXE-TGI-2

Glass Antenna Insulators (2 packages, total of 4 insulators)

DXE-NVIS-8040

Qty

Part Number

Description

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

DXE-ANTW-75

Premium Antenna Wire, 14 ga, Relaxed PVC, 75 feet per roll

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

- 6 -

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.

- 7 -

Installing the Coaxial Cable and Coaxial Cable Strain Relief

1. The DXE-CSR8X-1 Cable Strain Relief has the parts needed to mount to the

previous assembly. The assembly will be slightly different that what is described in

the DXE-CSR8X-1 instructions.

2. Connect one end of the DXE-8XDX100 coaxial cable to the BALUN.

Fully insert the PL-259 to the balun and tighten the collar.

3. Loosely mount the DXE-CSR8X-1 Cable Strain Relief bracket to the

DXE-BMB-4P bracket using the DXE-ECLS-150 Studded Band

Clamp, with a flat washer and a Nyloc hex nut as shown.

4. Loop the coax cable through the ‘P’ clamps and form approximately a 6”

diameter loop of cable.

5. Mount the ‘P’ clamps on both sides of the bracket using the hardware (1” hex bolt, 1/4” spacer,

three star washers, and Nyloc hex nut) as shown. Using pliers will help hold the clamps and parts

together while you get the Nyloc hex nut started.

6. Once the cable is aligned between the Balun and the first ‘P’ clamp, tighten

the Nyloc hex nut that holds the Studded Band Clamp at the balun end of

the bracket. Ensure the cable going through the ‘P’ clamps is properly

aligned and has the loop. Tighten all the parts holding the ‘P’ clamps in

place.

7. The completed DXE-CSR8X-1 Cable Strain Relief installation should look

as shown below.

- 8 -

8. Mount the second Studded Band Clamp to the top of the Balun Mounting Bracket using two

large Flat Fender Washers and one Nyloc hex nut as shown.

Preparing the 40 meter Wire Elements

1. Both models of the NVIS antenna (DXE-NVIS-8040 and DXE-NVIS-8040S) use the same

lengths of antenna wire for 40 meters.

2. Using one roll of the DXE-ANTW-75 Antenna Wire, cut the wire length in half so you have two

pieces of wire approximately 37 feet 6 inches long. Note - The test antenna after tuning had the

40 meter length as 32 feet 5 inches each. Until you perform tuning, do not shorten the 37-1/2

foot wires.

3. On each wire, solder one Ring Terminal as shown.

Preparing the 80 meter Wire Elements

Each model of the NVIS uses different lengths of Antenna Wire for 80 meters.

For the DXE-NVIS-8040 there are no coils used. The wire lengths are two 75 foot wires for 80

meters. Note - The test antenna after tuning had the 80 meter length as 61 feet each. Until you

perform tuning, do not shorten the 75 foot wires.

1. Using two rolls of the DXE-ANTW-75 antenna wire solder one ring terminal as shown on one

end of each 75 foot roll of antenna wire.

- 9 -

2. The DXE-NVIS-8040S uses two coils. There are four wires for 80 meters. After assembly,

each leg of the dipole will be approximately 32 feet. 16 feet in length between the BALUN and

the 80 Meter Coil and another wire, approximately 16 feet from the coil to the end insulator.

3. Cut one of the 75 foot antenna wire rolls so you have 4 pieces of antenna wire 17 feet long each.

4. On two of the wires, solder one ring terminal to each end of the wires as shown.

5. For the other two 17 foot wires, solder one ring terminal to one end of the wires as shown.

From this point on the wires will be designated as A, B, C, D to help make the assembly clear and

easy to understand.

- 10 -

Attaching the antenna element Wires to the Balun

Both models (DXE-NVIS-8040 and DXE-NVIS-8040S) use the same method for attaching the

antenna wires to the balun.

Wires Aand Bare connected to the BALUN for the DXE-NVIS-8040

Wires Aand Care connected to the BALUN for the DXE-NVIS-8040S

Attaching the 40 and 80 meter Wires for the DXE-NVIS-8040

1. Install one 40 meter wire (A) and one 80 meter wire (B) on each side of the Balun Bracket for

the DXE-NVIS-8040 as shown.

Note how the wires route through the three serpentine slots. Allow a bit of extra wire so there is

no strain on the wires when connecting them to the balun.

DXE-NVIS-8040

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