DX Engineering DXE-BFS-1 Manuale utente

Beverage Feedpoint Matching

System

DXE-BFS-1

Patent Pending

DXE-BFS-1-INS Revision 3c

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

The DXE-BFS-1 is a single-wire, single direction Beverage Feed System. This W8JI design is

immune to strong signal overload and core saturation common in multi-transmitter contesting

environments, and is used by winning contest stations and low-band DXers. The unit uses an

isolated-winding, matching transformer system to significantly increase the signal-to-noise ratio in

Beverage and other high impedance antennas.

The DXE-BFS-1 works with antenna impedances from 400 to 500 Ω.

Included with the DXE-BFS-1 is a 470 Ω, 2-Watt non-inductive

termination resistor that withstands nearby lightning strikes significantly

better than hard to find carbon composition resistors. DX Engineering has

replacement resistors available, part number DXE-ECM-R470-2.

The feedline impedance of the DXE-BFS-1 is optimized for 75 Ω,

however, any feedline between 30 Ωand 100 Ωcan be used. While not

intended for transmitting, the DXE-BFS-1 can withstand power levels of

20 watts continuously, 200 watts for 5 seconds or the power rating of the termination resistor,

whichever is less. The DXE-BFS-1 coaxial cable connection uses an industry standard CATV F

type connector.

The DXE-BFS-1 sets itself apart from competitive products by combining quality components and

superior technology inside a compact metal housing.

Features

100 kHz to 30 MHz operating range

Integral spark gaps built into the internal printed circuit board minimize damage from

lightning

Wing nut terminals eliminate soldering

Metal housings used for superior shielding and improved life

Flange-mount holes for easy mounting

Ground isolated secondary essential for building beverage arrays and can be connected with

normal or reverse phase

RoHS compliant assembly

The DXE-BFS-1 uses an isolated-winding, matching transformer system that significantly increases

the signal to noise ratio in Beverage and other high impedance antennas. This unit is immune to

strong signal overload and core saturation common in multi-transmitter contesting environments,

and is used by winning contest stations and low-band DXers.

Coaxial Cable and Connectors

The feedpoint matching system is optimized for 75 Ωfeedline. This allows the use of 75 ΩCATV

type coaxial cable and F style connectors. We recommend using high quality “flooded” 75 Ω RG-6

type coaxial cable, DX Engineering part number DXE-F6-CTL or DXE-F6-1000. Flooded coaxial

- 2 -

cables have the distinct advantage of automatically sealing small accidental cuts or lacerations of

the jacket. Flooding also prevents shield contamination and can be direct-buried. To ensure

weatherproof connections, use Snap-N-Seal connectors. DX Engineering part number DXE-SNS6-

25 contains 25 Snap-N-Seal connectors. The Snap-N-Seal connectors cannot be installed with

normal crimping tools or pliers, so an installation tool like the DXE-SNS-CT1 is essential for

proper connector installation.

Additional Requirements

Please note you will need the following items (not included in this package) to install and operate

the DXE-BFS-1 antenna:

Antenna wire: You will need a minimum of 3/8 wavelength ofwire of any gauge between #8 and

#20.

Ground rods: Use at least one 5-ft copper rod.

Insulators and supports: Insulators and supports are required to support the antenna wire 5 to 10 feet

above ground. Supports can be metallic but the antenna wire must be insulated from them.

Specifications

Operating Frequency: 100 KHz to 30 MHz

Input Impedance: 400-500 Ω

Output Impedance: 30-100 Ω (75 Ω recommended)

Common Mode Isolation: 20-30 dB (feedline and antenna)

Power Handling: 20 watts continuously or 200 watts for 5 seconds

Termination Resistance: 400-500 Ω

Installation

We strongly suggest that you read the entire DXE-BFS-1 manual before installing the antenna, and

make sure you understand the concepts outlined in the sidebar (below) that are critical to proper

operation.

Isolation

The DXE-BFS-1 operates on the principle of a transformer with isolated antenna and feedline

connections. This prevents the feedline from contributing unwanted electrical noise or signals to the

receiver. Many antenna enthusiasts unwittingly connect their feedline to their matching system

housing, not realizing that the practice simply makes the antenna longer and increases unwanted

signals. The DXE-BFS-1 solves this problem by insulating the connection lugs from the housing,

which also isolates the antenna from the feedline.

- 3 -

Performance Factors

For an effective Beverage antenna, you will need at least 3/8 wavelength of wire. Acceptable wire

types include galvanized or cadmium-plated steel electric fence wiring, stranded or solid copper

wire, and steel-core wires like copperweld. Avoid wire designed for welding applications. The line

with the best mechanical and electrical characteristics is generally #16 gauge copper clad steel

(copperweld) wire. Aluminum wires will work, but connections and splices are problematic due to

the formation of aluminum oxide.

Critical Installation Information

Transmitting The DXE-BFS-1 is designed for use in receiving antennas: do not transmit

through the DXE-BFS-1 with more power than the rating of the termination resistor (a 2-watt

resistor is included with the unit). This system will not be damaged by transmissions from

other antennas as long as the DXE-BFS-1 is more than one half wavelength from the

transmitting antenna and the power is less than 1500 watts.

Grounding To ground the antenna, run a wire from the –terminal of the DXE-BFS-1 to the

ground rod or rods. The antenna system is NOT grounded through the metal case. Feedline

terminals are engineered to be ground independent of the metal housing and whatever that

housing is mounted on. DO NOT ground the case to the antenna ground, since that will

connect the feedline shield to the antenna system and possibly increase noise or reduce

directivity of the antenna.

Termination The far end of the antenna must be properly terminated, or the antenna will not

have the best F/B ratio. Failure to terminate the antenna will generally result in a reduction of

S/N ratio as high as 20 dB, depending on noise arrival direction. For best results, use the

termination resistor included in this package.

Antenna Length

The chart below shows relative performance of Beverage antennas based on wire length:

Antenna Performance Based on Length

Antenna Length

160 Meter Band

80 Meter Band

40 Meter Band

20 Meter Band

120 Feet

Too Short

Marginal

Good

240 Feet

Marginal

Good

Best

Good

360 Feet

Fair

Best

Good

480 Feet

Good

Best

Good

600 Feet

Better

Good

Good - Marginal

720 Feet

Best

Good

Marginal

- 4 -

The antenna can be any length between 3/8-wavelength through multiple wavelengths, although we

recommend using lengths similar to those in the table above. In most cases, the DXE-BFS-1

performance is excellent even when the antenna is not cut to the ideal length.

Location

Beverage antennas work well and are easy to install; you can make reasonable height changes,

drape the antenna over tree branches, and deviate orientation by as much as 10

degrees. Metal poles will not affect the antenna’s performance as long as the

wire is insulated from the pole. Avoid placing the antenna near transmitting

antennas, power lines, large metal fences, or over buried cables. Install the

antenna wires 5-8 feet above the ground. It is not necessary to follow the

contour of the land because small hills, ravines and ditches generally do not

affect the antenna. Contrary to popular belief, sloping the antenna wire does

not improve performance. The picture shown uses typical electric fence wire

holders mounted on top of wooden posts with the beverage antenna wire

strung through.

Connections

The DXE-BFS-1 Feed Point unit has antenna terminals marked

+(positive) and - (negative). Normally, the +side goes to the antenna wire

and the - terminal goes to the antenna ground as shown in the drawing

below. When building Beverage arrays, phase can be reversed by simply

reversing the connections. The DXE-BFS-1 also has ground-isolated

secondaries which are essential for array construction. Do not ground the

case of the DXE-BFS-1 to the antenna ground system.

- 5 -

Grounding

Ground the ends with at least one five-foot copper rod. 3/4 inch copper water pipe is ideal. A five-

foot rod typically has 50-150 ΩRF resistance on 160 meters. For most soil types, you should use

two or more rods spaced at least five feet apart. Longer rods generally do not improve RF

grounding because RF skin depth prevents deep ends from having much effect. Do not connect the

coax shield to the antenna ground. Isolating the feedline and antenna grounds will prevent the

feedline shield from becoming an unintentional antenna ground and introducing unwanted signals

and noise.

NOTE: Be sure to use the wing nut terminal on the case for the antenna ground. The metal case is

NOT connected to the antenna ground, and should not be connected to the antenna

ground.

Feedline

The DXE-BFS-1 uses standard CATV “F” connectors. We recommend using DXE-SNS6-25

Watertight Snap-N-Seal F connectors and DX Engineering custom made high quality 75 Ω

“flooded” F6 type cables because they are generally high quality and have excellent shielding. Be

sure to use a coax sealant or install a rain hood over cable connections, and follow all appropriate

wiring codes for grounding where cables enter a building. Bury the feed cable for 10 feet or more

when approaching the feedpoint, or ground the feedline shield to a separate ground rod.

Termination

The far end of the antenna must be terminated, typically at 450 to 500 Ω, or the antenna will not

have the optimum F/B ratio. Failure to terminate the antenna always results in a reduction of S/N

ratio. S/N reduction can be as much as twenty dB, depending on the noise arrival

direction. A special termination resistor is included in this package. This high-

energy, metal composition resistor has stable electrical characteristics, almost no

inductance, and withstands severe overloads. DX Engineering has replacement

resistors available, part number DXE-ECM-R470-2.

Lightning Protection

This unit features small air gaps and wide foil trace areas, as well as entrance gaps at all feed-

through terminals. The gaps act as safe, short paths for lightning discharges. The DXE-BFS-1 is

normally immune to nearby lightning, although a direct strike might cause component failure. For

additional lightning protection, consider using a one-foot link of #26 wire between the antenna

terminals and the antenna. This wire will act like a fuse link and help protect against severe

lightning energy.

- 6 -

Simplified Testing

The DXE-BFS-1 feedpoint matching system is not only easy to use, it can also be tested in its

operating configuration. Just attach a standard SWR analyzer to test the antenna, the termination

and the DXE-BFS-1 as a single entity. Properly functioning systems will show a reasonably

constant SWR value over several bands. The SWR does not have to be low (it is typically under

1.8:1) but should change gradually over large variations in frequency

For more information about Beverage construction, see "ON4UN's book on Low Band DX'ing".

- 7 -

Alternate Radio Connection

The following diagram shows the DXE-BFS-1 connected

to a radio that does not have a Receive Antenna Input.

This set up allows switching between a transmit antenna

and the beverage antenna using the DXE-RTR-1A Receive

Antenna Interface. Refer to the DXE-RTR-1A Receive

Antenna Interface manual for more information.

- 8 -

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.

Optional Items

DXE-ECM-R470-2 470-ohm, 2 W Beverage Termination Resistor Lightning Damage Resistant, Pack of 10

This special non-inductive resistor can absorb extreme amounts of power for short periods

without damage. It has the highest surge immunity of any 2-watt leaded (with leads) carbon

or metal resistor. Metal-film and carbon-film resistors easily fail from even minor electrical

disturbances. Ideal for use as a Beverage terminator, the DXE resistor withstands nearby

lightning strikes significantly better than hard-to-find carbon composition resistors. It is

superior to carbon composition resistors in real life, retaining resistance value despite

exposure to heat and power surges.

DXE-ANTW-1000 #14 Insulated Antenna Wire, Multiple Antennas, 1000 Ft.

Use this wire to achieve top performance and long, trouble free operation. This antenna wire kit uses insulated wire that

is UV resistant and pays out easily, unlike the wire that is commonly available at the big box stores which coils and

kinks. It will last much longer in contact with the environment than bare wire.

Heavy #14 AWG stranded copper antenna wire

1000 foot bulk length spool

UV-resistant relaxed black PVC insulation

Reduces precipitation static

Long, reliable life

DXE-RPA-1 - Receiver Preamplifier 0.3-35 MHz

This is the best HF low noise amplifier available. The RPA-1 is optimized for 0.3-35 MHz operating range. The push-

pull amplifier design and robust components enable it to withstand high signal levels and operate when you need it

most. The dynamic range of the RPA-1 is better than most receivers. The RPA-1 is actually capable of providing

protection against high RF levels and ESD for many transceivers with un-switched,

unprotected receive antenna inputs!

The RPA-1 is suitable for indoor or outdoor installation, with the option of being powered

through the coaxial feed. The metal housing provides shielding and improved lifespan. The

unit uses RCA type phono jack and CATV F connector for the input and output

connections, and has a relay that automatically bypasses the amplifier when dc power is

removed.

Benefits:

Push-pull operation eliminates harmonic distortion

High quiescent current increases ability to handle strong signals without distortion or overload

Meticulous craftsmanship and durable components provide superior dynamic range

RCA type phono jack and type F connector ease installation

Simplified switching - automatic bypass eliminates gain when dc power is off

10-18 Vdc power using power connector or through the coax

10-18 Vdc through coax enables remote operation at antenna

- 9 -

DXE-PSW-12D1A - AC Adapter 12 VDC/1000 mA

The DXE-PSW-12D1A is an AC Wall Transformer Adapter to furnish 12 Volts DC at 1000 mA

from 110 Vac 60 Hz input, fused output. It features a standard 2.1 mm plug connection for 12 Vdc.

Outer connection is GROUND Center Pin is input for +12 VDC.

DXE-SNS6-25 Watertight Coax Connector, Snap-N-Seal for CATV F-6 Cable, 25 pieces

Snap-N-Seal is an environmentally sealed CATV F coax connector system for harsh environments. The connectors have

a unique, 360 degree radial compression system that offers the signal leakage protection required for high performance

receive systems.

Quad sealed system prevents moisture from migrating into the connection

360 degree radial compression provides superior RF integrity (-95dB typical, 60%

bonded foil cable)

Easy cable preparation

Connector to cable retention of 40 lbs minimum

Superb impedance match to 1 GHz

Manufactured of high quality 360 brass, cadmium plated with iridescent clear chromate

coating for maximum corrosion resistance

UV-resistant plastic and O-rings provide a reliable environmentally sealed connector

An installation tool, such as the DXE-SNS-CT1, to install the connectors. Normal crimping tools or pliers will not

work.

DXE-UT-KITF F-Connector Coaxial Cable Prep Tool Kit

This cost-saving kit provides a handsome, convenient carrying case complete with the DX

Engineering F-6 coaxial cable prep tools and accessories. It features a rugged, lockable

enclosure fitted with a precut foam insert with a home for each tool.

The DXE-UT-KITF kit provides the case complete with the following:

DXE-CPT-659- Stripping Tool for RG-59/F-6 size cable w/extra blades

DXE-SNS6-25 - Snap-N-Seal Watertight F Connectors - qty. 25 pcs

DXE-SNS-CT1 - SNS Connector Compression Tool

CNL-911 - Coaxial Cable Shears

DXE-CIT-1 - F Connector Tightening Tool

The case-only may be ordered as DXE-F6-CASE.

75ΩF-6 Style, Direct Bury Coax: Full Spool or Custom Cable Assemblies

DXE-F6-CTL 75ΩF-6 Style Direct Bury Coax, Per Foot

DXE-F6-1000 75ΩF-6 Style Direct Bury Coax, 1000 ft. Spool

We recommend using a high quality 75 Ω “flooded” F6 type coax. Flooded style cables have the

distinct advantage of automatically sealing small accidental cuts or lacerations of the jacket.

Flooding also prevents shield contamination and can be direct-buried. This low-loss cable features

dual shields and an 85% Velocity Factor.

Custom Cable Assemblies with connectors available - Call for details.

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