DX Engineering DXE-RFS-2P User manual

Receive Four Square System
DXE-RFS-2P
DXE-RFS-TS3P
DXE-RFS-TS3P-INS Revision 1
U.S. Patent No. 7,423,588
DXE-RFS-TS3P Components Shown
© DX Engineering 2010
P.O. Box 1491 · Akron, OH 44309-1491
Phone: [phone] · Tech Support and International: [phone]
Fax: [phone] · E-mail: [email protected]

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Table of Contents
Introduction 3
DXE-RFS-2P Receive Four Square Array Controller and Switch Package 3
DXE-RFS-TS3P Complete Receive Four Square Array Package 4
System Overview 5
Features 5
Prerequisite 6
Additional Parts Required, Not Supplied 6
Example of Array Performance 7
Site Selection 9
Proximity to Transmitting Antennas 9
Topographical Considerations 10
Site Selection in Relation to Noise Sources 10
Ground System 11
Lightning Protection 11
Sizing the Array 12
Four Square Layout 13
System Operational Overview 13
Installation 14
Active Antenna Elements 14
Station Feedline, Active Antenna Feedline and Delay Lines 15
Active Antenna Feedlines 16
Delay Lines 16
Control and Power Connections 18
Default Configuration 19
Alternate Configurations 21
Supplying Power Using the Feedline 21
Directional Control Using the Feedline 21
DXE-RFS-2 and Active Element Power 24
Directional Control 24
Internal Jumper Selection 25
Default Jumper Configuration Settings 25
Powering Through the Feedline 26
Directional Control Using the Feedline 26
Optimizing the Array 26
Front-to-Rear (Null) Optimizing 27
Normal Receive Four Square Operation 28
Receive Four Square Troubleshooting 29
Additional Receive Four Square Control Troubleshooting 31
Optional Items 33
Technical Support and Warranty 36
Figures, Tables, and Diagrams
Azimuth Patterns for an Optimized 40 meter Array 8
Figure 1 - Site Selection Clear Distance 9
Table 1 - Array 1500 Watt ERP Safety Distance 10
Table 2 - Array Side Lengths 12
Figure 2 - Layout of the DXE-RFS-TS2P Four Square System 13
Figure 3 - Active Element L1MF Jumper Locations 15
Table 3 - Examples of DLY3 Required Length 17
Figure 4 - Diagonal Dimensions 17
CC-8A and RFS Connectors 18
DXE-RFS-TS3P Default Connection Diagram Using Factory Jumper Settings 20
Diagram 2 - Alternate Configuration 22
Diagram 3 - Alternate Configuration 23
Table 4 - BCD Directional Control Matrix 24
Table 5 - Differential Voltage Control Matrix 25
Figure 5 - Jumper Locations and Default Settings 25
Operation Pattern Diagram 27

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Introduction
There are two packaged systems available:
DXE-RFS-2P - Receive Four Square Array Controller & Control Box
The DXE-RFS-2P is a sophisticated receiving system that uses time delay phasing rather than the
conventional narrow-band, frequency dependent phasing systems. The time delay phasing is
directivity-optimized to produce wider and deeper rear nulls and a narrower main lobe. The result is
that noise and undesirable signals are greatly reduced for a superior front-to-rear ratio (F/R). Better
control of phase and currents provides a cleaner pattern than found on available transmit four square
arrays.
The DXE-RFS-2P is optimized to use DX Engineering’s Active
Vertical Antenna Package, DXE-ARAV3-4P. The two products
together offer great F/R response over octaves of bandwidth. DX
Engineering’s Active Receive Antenna System offers excellent
receiving performance from 100 kHz to 30 MHz while using only a
102 in. whip as the antenna element. A unique design makes it vastly
superior to traditional active antennas in both strong signal handling
and feedline decoupling. This results in significantly better weak
signal reception due to lower spurious signal interference and
reduced noise.
Finally, this system offers greater reliability in receiving applications. The RFS-2 uses sealed relays
sized for receiving applications with silver contacts to prevent oxidation and contamination. Most
transmitting four square switches use large open-frame relays where the contacts are exposed to air
which can lead to contamination. Relays with brass contacts can oxidize leading to poor
conductivity.
Advantages of the DXE-RFS-2P Receive Four Square Antenna System over other small or
medium-size receiving arrays include:
•Reduced susceptibility to high angle signals compared to EWE, Flag, Pennant, and K9AY
antennas
•Excellent directivity in a small space for better signal-to-noise ratio
•Switchable in four 90 degree spaced directions
•Directivity over a very wide frequency range using DX Engineering active receive
elements DXE-ARAV3-4P
•Less physical space required than a Beverage antenna and active elements need only a
minimal ground system
•Enhanced relay contact reliability
The DXE-RFS-2P includes the DXE-CC-8A Receive Four Square Switch controller. The CC-8A
interfaces to the RFS-2 through a 3 or 4 wire cable to select one of four directions on the RFS-2
and to power the active elements. Economically priced DXE-CW9 is a 9 conductor Shielded Control
Wire which may be used.

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DXE-RFS-TS3P - Complete Receive Four Square Array Package for Normal
Spacing to Transmit Antennas
Complete Receive Four Square Array package for Close Spacing to Transmit Antenna
•W8JI design
•Operates from 100 kHz to 30 MHz
•Excellent directivity in a small space for better signal-to noise ratio
•Switchable in four 90 degree spaced directions
•Reduced susceptibility to high angle signals compared to EWE, Flag, Pennant, or K9AY
arrays
DXE-RFS-TS3P (U.S. Patent No. 7,423,588) is a complete Receive Four Square Array
Package for Close spacing to transmit antenna which includes:
•(1) DXE-ARAV3-4P Package of four Active Receive Vertical Antennas w/ Internal
Antenna Disconnect Relays
•(1) DXE-CC-8A 8 Position Control
Console
•(1) DXE-RFS-2 Receiving Four
Square Antenna Switch
•(1) DXE-TVSU-1A Time Variable
Sequence Unit
•(1) DXE-F6-1000 CATV F-6 Style
Coax, 75 , F6 Flooded for
Direct Burial, 1000' Spool
•(1) DXE-CPT-659 CATV F-6, RG-6
and RG-59 Coax Cable Stripper,
Includes 1 Replacement Blade
•(25) DXE-SNS6-25 Snap-N-Seal 75
Coax Connectors
for CATV F-6 Cable
•(1) DXE-SNS-CT1 Crimp Tool for
Snap-N-Seal 75 Coax
Connectors

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System Overview
The DXE-RFS-2P is an advanced four square receiving system that uses four symmetrically spaced
elements to provide switching for a 4-direction receiving antenna system. This unique system uses
time delay phasing rather than the single band phase shifting used in traditional four squares. When
used with active receive elements, this time delay phasing scheme provides the correct phase
relationship across a wide frequency range and useful front-to-rear ratio (F/R) response over octaves
of bandwidth.
This system uses directionally-optimized time delays to produce wider and deeper rear nulls. Wide
null areas and a narrow main lobe greatly reduce noise and undesirable signals.
The system is more reliable than a conventional transmitting four square system in receiving
applications. Most transmitting four squares use large, exposed open-frame relays which can
become contaminated or corroded. This system uses sealed relays; contact size is optimized for
receiving applications.
Features
Advantages of the DXE-RFS-2P Receive Four Square Antenna System over other receiving arrays
include:
•Seamless stainless steel RFS-2 enclosure, for enhanced weather resistance
•Reduced susceptibility to high angle signals compared to EWE, Flag, Pennant, and K9AY
antennas
•Excellent directivity in a small space for better signal-to-noise ratio
•Switching of four 90 degree spaced directions
•Directivity over a very wide frequency range using DX Engineering’s Active Receive
Antennas
•Requires less space than a Beverage antenna. Active elements need only a minimal ground
system
•Using active elements, system allows close proximity to transmit antennas using
transmit/receive sequencer
•Enhanced relay contact reliability

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Prerequisite
This manual covers both the DXE-RFS-2P stand-alone unit and the DXE-RFS-TS3P system.
This manual will describe the DXE-RFS-TS3P total system package in detail.
The DXE-RFS-3P includes the RFS-2 Receive Four Square Switching Unit and the
DXE-CC-8A Control Console.
The DXE-RFS-2 includes just the Receive Four Square Switching Unit. The stand-alone
RFS-2 unit must be connected with the appropriate power and switching voltages as defined in the
Control & Power Section of this document. The RFS-2 can also be used with passive elements.
The DXE-RFS-TS3P is a sophisticated system that has critical control voltage and
three delay line connections.
Failure to make quality feedline or delay line connections might result in an array
that does not work or performs poorly.
Additional Parts Required, Not Supplied with the DXE-RFS-TS3P
Four-Conductor Power and Control Cable for RFS-2, Default Configuration
4-conductor cable (3 plus ground), 22 gauge minimum. Alternate configurations use a
1-or 2-conductor cable. Economically priced DXE-CW9 is a 9 conductor Shielded Control Wire
which may be used.
Additional Parts Required, Not Supplied with the DXE-RFS-3P
DXE-CAVS-1P Mounting Clamp for RFS-2
Pre-drilled mounting bracket accepts pipe sizes from 1/2 inch to 1 3/4 inches.
Four-Conductor Power and Control Cable for RFS-2, Default Configuration
4-conductor cable (3 plus ground), 22 gauge minimum. Alternate configurations use a
1-or 2-conductor cable. Economically priced DXE-CW9 is a 9 conductor Shielded Control Wire
which may be used.
75 Coax Cable (CATV F6 Style), Connectors and Installation Tools
When calculating cable length, include connections from the phasing unit to each active
element, the 3 delay lines and the distance to the operating position. You must use 75 coax
with a known velocity factor (VF) for all connections.
We recommend using a high quality, 75 “flooded” F6 type coax, such as
DX Engineering part number DXE-F6-1000. Flooded-style cables automatically seal small
accidental cuts or lacerations in the cable jacket. Flooded cables also prevent shield
contamination and can be direct-buried.

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Feedline connections must have good integrity and be weather resistant. We recommend
Snap-N-Seal type F connectors. The complete DXE-RFS-3P system, including feedline
connections, requires 16 type F connectors. DXE-SNS6-25 contains 25 Snap-N-Seal
connectors, enough for the entire array plus nine spare connectors.
Note: The DXE-CPT-659 stripping tool prepares F6 style cable for
connectors in one easy and clean operation and comes with an extra
cutting cartridge.
Snap-N-Seal connectors cannot be installed with normal crimping tools or pliers.
The DXE-SNS-CT1 is an essential tool for proper connector installation.
Note: DO NOT use pliers or other tools to tighten the type F connectors;
they do not require high torque to make a good connection. Damage to
the various units may result and is not covered under warranty.
Example of Array Performance
Dedicated receive antennas have better signal-to-noise ratios. Directing the antenna away from
noise sources or toward the desired signal path is the primary benefit. Antenna gain is a secondary
advantage. As frequency increases, the fixed array size becomes electrically larger in terms of
wavelength. The increased electrical spacing produces higher sensitivity (average gain) even though
front-to-rear ratio only changes slightly. On the low bands, once the receiving system limits on
external noise, antenna directivity (F/R) is the only thing that affects the signal-to-noise ratio.
An average Beverage antenna exhibits about -6 dB gain. You would need two reversible Beverage
systems to obtain 4-direction selectivity and you still would be limited to one or two bands. The
DXE-RFS-3P system occupies less space, is much easier to install, is less conspicuous and operates
over a wider frequency range with similar or better performance.
A test array, constructed at DX Engineering using the DXE-ARAV3 Active Elements and a side
length of 35 feet, showed excellent performance across a wide frequency range. This side length is
optimal for 40m, according to Table 2. The array worked from 3 MHz to 15 MHz. As shown on the
following page, the patterns stay clean with good directivity and front-to-rear performance. The
elevation angle is 15 degrees for all patterns. Amplification is required below 3 MHz.
Note: The DXE-RFS-TS2P Receiving system must be separated from transmitting or
other antennas and structures (particularly metal) by at least 1/2 wavelength.
Less separation may cause significant pattern distortion and the introduction of
re-radiated noise into the system. This becomes apparent as reduced front-to-
rear directivity in one or more directions or a higher noise level.

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In a different test array with 50 ft side lengths, optimum performance occurred between
3 and 4 MHz. Performance on 7 MHz was also excellent. Amplification was used below
2 MHz. The highest usable frequency was 10 MHz. This array also produced usable F/R ratios
down to the lower end of the AM broadcast band (600 kHz).
Increasing the array size increases its sensitivity on the lower frequencies, sliding the performance
curve toward the low frequencies and potentially eliminating the need for amplification.

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Site Selection
Site selection is important. The DXE-RFS-TS3P system can be positioned as close as 1/10
wavelength to transmitting antennas. The DXE-ARAV3-4P Active Elements are bypassed to
ground when power is turned off. A programmable sequencer, such as the DXE-TVSU-1A, is
required for close spacing requirements. The DXE-TVSU-1A is included in the DXE-RFS-TS3P
complete Receive Four Square Array Package.
Significant pattern distortion or coupling may result from close spacing. To prevent pattern
degradation or re-radiation of electrical noise or other interference, separation of 1/2 wavelength (at
the lowest operating frequency) is ideal. See Figure 1. The goal is to do the best you can by
balancing all the factors.
1/10 wavelength is the minimum distance to any transmitting antenna
from the Four Square perimeter. 1/2 wavelength is the best distance to
prevent coupling to other antennas.
Figure 1 - Site Selection Clear Distance
Proximity to Transmitting Antennas
The DXE-ARAV3-4P active elements and your transmitting antenna need only minimal physical
separation to maintain safe power levels when the DXE-TVSU-1A sequencer is used. With 1500
watts output and a unity gain (0 dB) antenna, the closest active element can be 1/10 wavelength
from the transmitting antenna at the lowest transmitting frequency. Doubling the protection distance
quadruples safe power levels. See Table 1.

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For example, transmitting legal-limit power output (1500 watts) into an ideal four square
transmitting antenna produces about 6,000 watts ERP (6 dB gain). Because of the increased radiated
power level, nearly 1/2 wavelength minimum spacing between the transmitting and receiving
antenna arrays is required.
Table 1 indicates minimum safe distances from transmitting antennas with 0 dB, 3 dB and
6 dB gain (ERP) using a 1500 watt transmitter. Your actual measurements may vary according to
location and proximity to various objects.
Band Unity (0 dB) Gain 3 dB Gain (2x) 6 dB Gain (4x)
160m (1.8 MHz) 55 ft 110 ft 220 ft
80m (3.5 MHz) 28 ft 56 ft 112 ft
40m (7.0 MHz) 15 ft 30 ft 60 ft
Table 1 - Array 1500w ERP Safety Distance
Topographical Considerations
Flat land is best. Erecting the receiving array on sloped land or steep hills may degrade
performance. To avoid pattern degradation, antenna elements must have reasonably similar
elevations. It's recommended the ground height difference between any element in the array be less
than 10% of the array diameter. For example, a 60 foot diameter array should be within six feet of
level. Every effort should be taken to make the elements symmetrical. Elements should all be
identical in construction and grounding, and should be mounted above any standing water or snow
line but as close to the ground as possible. In general, the system will not be affected by trees or
foliage as long as the foliage does not contact the element. Ideally, in important receiving
directions, there should be a clear electrical path for at least 1 wavelength. The site should allow a
ground system to be evenly distributed around the antenna, if one is required.
Site Selection in Relation to Noise Sources
Because the array is directional across its corners, use this example as a guide: If you have a noise
source and if your primary listening area is northeast, locate the array northeast of the dominant
noise source. This ensures the array is looking away from the source of noise when beaming in the
primary listening direction. The second-best location for the array is when the noise source is as far
as possible from either side of the array. If you look at patterns, the ideal location for the array is
one that places undesired noise in a deep null area.
If your location doesn’t have the usual noise sources (power lines, electric fences, etc.), locate the
array so that your transmitting antennas and buildings are off the back or side of the receiving array.
Noise that limits the ability to hear a weak signal on the lower bands is generally a mixture of local
ground wave and ionosphere propagated noise sources. Some installations suffer from a dominant
noise source located close to the antennas. Noise level differences between urban and rural locations
can be more than 30 dB during the daytime on 160 meters. Nighttime can bring a dramatic increase

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in the overall noise level as noise propagates via the ionosphere from multiple distant sources. Since
the noise is external to the antenna, directivity can reduce noise intensity.
Consider these things about noise sources:
•If noise is not evenly distributed, performance will depend on the gain difference between
the desired signal direction (azimuth and elevation) and average gain in the direction of
noise.
•If noise predominantly arrives from the direction and angle of desired signals (assuming
polarization of signals and noise are the same) there will be no improvement in the signal-to-
noise ratio.
If the noise originates in the near-field of the antenna, everything becomes unpredictable. This is a
good case for placing receiving antennas as far from noise sources (such as power lines) as possible.
Ground System
The ARAV3-4P Active Elements work well with just a single copper ground rod placed as close as
possible to the mounting pipe. The mounting pipe can be used as the system ground if the pipe is an
adequate ground. It is recommended that a 3/4" or larger rigid copper water pipe, although
conventional copper coated steel rods may also work. Depending on soil conductivity, you can
expect better performance with multiple ground rods spaced a few feet apart. Increasing ground rod
depth beyond 5 ft rarely improves RF grounding because skin effect in the soil prevents current
from flowing deep in the soil. Avoid ground rods less than 5/8" O.D. A good ground system
improves the array performance and enhances lightning survivability. It is important that each
ground system be the same for each active antenna in the array.
You can test ground quality by listening to a steady local signal. Attach 15 ft of wire laid in a
straight line (away from the coaxial feedline) to the initial 4 ft to 6 ft ground rod. If you observe a
change in signal or noise level, you need to improve the ground. A second rod spaced a few feet
away from the first one may correct the problem or 10 to 12 ground radials, each 15 ft long, should
provide a sufficient ground system for most soil conditions. If a good ground cannot be established,
use an optional DXE-RFCC-1 Receive Feedline Current Choke that will further decouple the
feedline from the antenna and reduce common mode current and associated noise from the feedline.
Lightning Protection
While amateur radio installations rarely suffer damage from lightning, the best protection is to
disconnect electrical devices during storms. The key to lightning survival is to properly ground
feedlines and equipment and to maintain the integrity of shield connections. A proper installation
improves lightning protection and enhances weak signal receiving performance.
Consult lightning protection and station grounding information in the ARRL handbooks, or by
referring to the NEC (National Electric Code). The DX Engineering website also has technical and
product information listed under “Lightning Protection and Grounding.” Use lightning surge
protectors for the coax feedline and control lines.

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Sizing the Array
When using active elements, the array side length can be as small as 1/10 wavelength and up to
about 1/2 wavelength on the highest frequency to be used. Sizes below 1/10 wavelength result in
unusable array sensitivity in the most desired bands. Making side lengths larger than 1/2 wavelength
on the highest frequency will split the main lobe and cause pattern and front-to-back degradation.
Determine the size of the array by considering the availability of appropriate space, frequency
coverage desired and the near proximity to undesirable noise sources, transmitting antennas and
other structures.
If there are no space constraints, follow the array side length recommendations in Table 2 for
excellent performance. Side lengths longer than the optimal lengths shown will move the peak
sensitivity of the array toward the lower frequency. For example, if you are most interested in 160m
performance with occasional use on 80m, make the side lengths longer than the optimal 98 feet
shown for 160m and 80m. This will improve 160m performance, reduce sensitivity on 80m
somewhat, but less than sizing the array exactly for 160m.
Band Freq - MHz Optimal Side
Length in Ft
Min. Side
Length in Ft
Max. Side
Length in Ft
160 1.83 135 54 270
80 3.60 70 28 140
40 7.10 35 14 70
160, 80 1.83, 3.60 98 40 192
80, 40 3.60, 7.10 50 20 98
160, 80, 40 1.83, 3.60, 7.10 70 28 137
Table 2 - Array Side Lengths
If you have limited space, a carefully installed and amplified DXE-RFS-3 can be used on multiple
bands with very small side lengths. At smaller side lengths, careful construction using precise
measurements is critical. On a fixed-size array, as frequency is decreased, the array signal output
decreases along with array sensitivity. Eventually the received ambient noise signal level will
decrease to a point where it is below your receiver’s noise floor. This comes from two effects:
•Elements become electrically shorter, reducing element sensitivity
•Element spacing becomes smaller in electrical degrees, reducing array sensitivity
Side lengths at 1/10 wavelength on 40m would only be 14 ft. Although usable, amplification would
be required. In addition, the construction of a very small array is extremely critical. Side lengths
must be perfectly symmetrical. The delay lines must be directly measured for electrical length and
cut to exact lengths. The ground system must be effective. Even at this small spacing, the array will
have useful front-to-rear performance and directivity!

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Four Square Layout
The array antenna elements should be arranged in a square, use Table 2 for guidance in choosing
the best combination of frequency coverage and side length dimensions.
•The diagonal corners of the square should point in the most desirable receiving directions.
Element 1 is the default forward element, Element 3 is the rear or null element.
•Performance of the RFS-2 can noticeably decrease if structures radiating even small
amounts of noise or signals are within 1-wavelength of the array
Figure 2 - Layout of the DXE-RFS-TS2P Four Square System
•Measure side-to-side and then corner-to-corner to ensure the element locations are square.
•Normally the RFS-2 phasing unit is installed near the center of the four array elements, above
any standing water or snow line, with the connector side facing down. The placement of the
RFS-2 unit is not critical, however, the feedlines to each of the active elements must be equal.
•If you mount the RFS-2 on a wood post, it should be grounded to a separate ground rod.
System Operational Overview
The DXE-RFS-3P system is comprised of the DXE-CC-8A Control Console and the DXE-RFS-2
Control Unit. These units interconnect and work together using factory default settings. If you
purchased only the DXE-RFS-2 Control Unit, you must provide the power and switching voltages
to the DXE-RFS-2. Please refer to the appropriate tables and the configuration diagrams in this
manual for details.
The DXE-CC-8A Control Console supplies the nominal +12 Vdc operational voltage as well as the
+12 Vdc BCD control voltage. The operational voltage powers the DXE-RFS-2 Control Unit which
subsequently powers the active receive elements. The BCD switching voltages cause the
DXE-RFS-2 to change the receiving direction of the array.

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The DXE-CC-8A Control Console is configured by default to output the BCD control voltages
needed by the DXE-RFS-2. Only the last four positions of the DXE-CC-8A are used (LEDs 5
through 8) because the DXE-RFS-2 only requires a 2-bit BCD control logic. The array is powered
when the DXE-CC-8A has selected LED 5, 6, 7, or 8. The default direction for the array (toward
Element 1) is selected when LED 5 on the DXE-CC-8A is illuminated. When positions 6 to 8 are
selected on the CC-8A, the array switches directions according to the directional control matrix in
Table 4.Refer to Diagram 1for default connection details.
The DXE-RFS-2 distributes the operating power to the active elements through the individual
element feedlines. The active elements do not work without power. Cutting power to the
DXE-RFS-2 also cuts power to the active elements which causes the DXE-AVA-3 to ground the
vertical element. Operating with the DXE-TVSU-1A Sequencer (inserted into the CC-8A "C" to
the RFS-2 "C" terminal) makes this power switching function automatically.
An alternate configuration, which uses the feedline coax for either the operational power or the
directional control voltages, can be used. This configuration requires internal jumper changes in the
DXE-RFS-2, along with additional hardware to couple the proper voltage to the feedline. For
directional control through the feedline, the DXE-RFS-2 requires +12 Vdc, 12 Vdc and 12 Vac.
The DXE-FVC-1 Voltage Coupler can be used to supply these voltages. Operational voltage is a
nominal +12 Vdc, which can be provided by station power if a 1A in-line fuse is used.
In any alternate configuration, do not use coax or other conductor for more than one simultaneous
use. Refer to Diagram 2 for connection details of one of several alternate configurations.
Installation
The DXE-RFS-2 Control Unit can be mounted to a galvanized pipe driven into the ground. The
DXE-RFS-2 unit has been pre-drilled to accommodate up to a 2 inch OD pipe using an appropriate
clamp. If pipe mounting is desired, the optional DXE-CAVS-1P V-Bolt Saddle clamp for pipe from
3/4" to 1-3/4" inches OD is recommended, or DXE-CAVS-2P V-Bolt Saddle Clamp for 1" to 2"
OD pipe. The controller can also be mounted on a sturdy wooden post, but provision for grounding
the DXE-RFS-2 unit must be made.
The DXE-RFS-2 is designed to be used with the DX Engineering Active Vertical Antennas or it
can be used with passive elements. The user manual included with the active elements has
instructions for assembly and installation. As noted in that manual, the active elements should be
installed as close to the ground as possible but above any standing water or snow line. Ground the
ANT– (negative) terminal to an adequate ground.
Active Antenna Elements
If you are planning to use the array on 160m, a jumper in the active antenna matching units should
be changed. Placing a jumper on L1MF will peak the array sensitivity response for use on 160m,
with little effect on 80m, when the recommended array side lengths in Table 2 are used. When

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doing this the sensitivity for the AM broadcast band will be reduced. All four active elements in the
array must have identical jumper settings.
For access to the jumpers in the active matching units, remove the 2 screws on each side of the case
and remove the bottom. The circuit board and jumper headers will be visible, as shown in Figure 3.
By default, there are no jumpers across any pins. Place a jumper across L1MF. Do not jumper any
other positions. See the Active Antenna User Manual for more information about additional peak
response jumper settings.
Figure 3 - Active Element L1MF Jumper Locations
Please read the manuals for the DXE-ARAV3 Active Elements and DXE-CC-8A Controller so you
understand their operation before proceeding.
Station Feedline, Active Antenna Feedline and Delay Lines
The weakest link in an antenna system, such as the DXE-RFS-3P, is often the coax cable
connections. All connections must be high quality and weather tight to prevent contamination and
corrosion, which can cause the feedline impedance to change. This can affect the signal-to-noise
ratio and the directivity of the array. In addition, the DXE-RFS-2 uses the shield as a ground return
path for the active element power.
Note: The total loop resistance of the ground path must be under 30 Ωfor reliable operation.
If the resistance of the shield increases due to contamination, the active elements may not function
properly. Any splices in the feedline should be high quality and entirely weather tight. Do not use
splices in the delay line cables. The DXE-RFS-3P system has been designed to use only 75 coax.
High quality, flooded 75 CATV F6 type coax is recommended. DXE-F6-1000 Flooded cables
automatically seal small accidental cuts or lacerations in the jacket. Flooded cable also prevents
shield contamination and can be direct-buried.
DX Engineering offers an inexpensive preparation tool, part number DXE-CPT-659, that readies
the coax for connectors in one operation and comes with an extra cutting cartridge. To ensure
weather tight connections, use DXE-SNS6-25 Snap-N-Seal compression style connectors. DXE-
SNS6-25 contains 25 Snap-N-Seal connectors, enough for the entire array plus some spares. The
Snap-N-Seal connectors cannot be installed with normal crimping tools or pliers, so you must use

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an installation tool like the DXE-SNS-CT1, available from DX Engineering, for proper connector
installation.
Active Antenna Feedlines
Use 75 coax from each antenna element to the DXE-RFS-2. The four feedlines from the DXE-
RFS-2 phasing unit to the active elements can be any length needed to accommodate the size of the
array, but must all be the same length, velocity factor and type. Note the orientation and numbering
of the elements by using Figure 2.Be sure the appropriate antenna element is connected to the
proper ANT connector on the phasing unit. The default (zero control voltage) forward direction is
towards Element 1. Element 3 is the rear or null direction.
Delay Lines
The DXE-RFS-2 uses a time delay system, not a traditional phasing system. Delay line lengths are
dictated by array dimensions rather than operating frequency. This results in phase being correct for
a rearward null at any frequency. This system is especially effective when used with DX
Engineering ARAV active elements. User-supplied passive elements can also provide exceptional
performance for single or dual band operation where high dynamic range is required.
The DXE-RFS-2 phasing unit has three sets of delay line connections marked DLY1, DLY2 and
DLY3. Each of these connection pairs will have a specific length of coax acting as a jumper
between the two connectors. Jumper electrical length is critical. Careful measurements and the use
of 75 coax with a known Velocity Factor (VF) is very important.
Solid Teflon® or polyethylene dielectric coax cable has a VF of approximately 0.66. Foamed coax
cables typically range anywhere between 0.75 and 0.90 VF, depending on the ratio of air-to-
dielectric material in the cable core.
If you do not know the VF of the coax you are using, you must directly measure the electrical
length of the coax you have or obtain cable with a known VF. The DX Engineering
DXE-F6-1000 75 coax has a nominal VF of 0.85. For best performance, the coax for the delay
lines should be from the same batch or spool.
The first step is to determine the required electrical length of DLY3. This is based on the corner-
to-corner or diagonal distance between two diagonal corner elements of the square forming the
array. You can directly measure this distance, or it can be calculated by multiplying the side length
of the array by 1.4142. The electrical length of delay line DLY3 should be slightly shorter than the
actual physical distance between the two diagonal corners of the array. An electrical length 95% of
the physical distance works well (diagonal distance times 0.95). Table 3 shows these calculations
for three common side lengths.

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Side Length in
Feet
Diagonal
Physical Length
in Feet
Factored 0.95
Electrical Length
in Feet
DLY3 Physical Length
in Feet (0.85 VF)
135 (160m) 190.9 181.4 154.2
98 (160m & 80m) 138.6 131.7 111.9
70 (80m) 99.0 94.0 79.9
Table 3 - Examples of DLY3 Required Length
After calculating the required electrical length, you must include the VF of the coax being used
when determining the correct physical length of DLY3. Multiply the factored electrical length by
the VF. The result is the correct physical length for DLY3. See Figure 4 and the sidebar for an
example. Note: These calculations are in feet, not feet and inches.
To find the physical length of DLY3, calculate the
diagonal length of the array by either directly
measuring the diagonal or by multiplying the array side
length by 1.4142. DLY3 will be significantly shorter
than the actual physical length. The diagonal length is
first multiplied by 0.95. This gives the factored
electrical length for DLY3. Next, multiply the DLY3
electrical length by the VF of the delay line coax. The
result is the correct physical length for DLY3.
Figure 4 - Diagonal Dimension
For Example: An array with 90 foot side spacing, the diagonal length is 127.3 feet. The 0.95
factored physical length for DLY3 electrical length is 120.9 ft. Multiply 120.9 ft.
by 0.85 (the VF of DX Engineering 75 coax).
The correct physical length for DLY3 is 102.77 feet, or 102 feet 9 inches.
Delay lines DLY1 and DLY2 must be half the length of DLY3. Make DLY1 and DLY2 as close to
half the physical length of DLY3 as possible. To avoid performance degradation due to inconsistent
coax construction, all the delay line coax should be cut from the same spool.
Delay line cables can be neatly coiled in a 1-1/2 ft diameter coil. Support the weight of the cables
by taping or securing them to the support pole or mast rather than allowing them to hang from the
connectors.

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It is important to use 75 feedline to the operating position from the DXE-RFS-2. Do not use
amplifiers, combiners, filters or splitters that are not optimized for 75 systems.
Control and Power Connections
Prior to installation, you should decide if you want to use the factory configuration or an alternate
one. If you have the DXE-RFS-3P system, with the DXE-CC-8A Control Console, no other
equipment is needed for powering the DXE-RFS-3P, the active elements or controlling the receive
direction of the DXE-RFS-3P. The DXE-RFS-3P has been factory-set to work with the
DXE-CC-8A. If you have a stand-alone RFS-2, several configuration options need to be considered
before installation.
J12 is the 5-terminal connector plug on the front panel of the DXE-RFS-2. It is labeled G A B C G.
G Ground. Both "G" terminals are common ground
A &B 2 bit BCD directional control inputs
C Operational power from the DXE-RFS-2 and active
elements
Depending on jumper configuration, terminal C can also be used for directional control using
differential voltages. The coax must then be used to supply operational power.
The DXE-CC-8A uses the same 5-terminal plug labeled “BCD”. The terminals use the same
names.
CC-8A RFS-2
On both the DXE-CC-8A and the DXE-RFS-2, the green connectors are in two parts and the top
part can be removed by pulling it straight off. This will allow easier wire replacement or servicing
as needed. When pushing the connector back in place, ensure you press straight inward.

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Default Configuration
The DXE-RFS-2 default configuration uses terminals A & B for the BCD directional control
interface and terminal C for operational and active element power. The DXE-CC-8A provides the
operational power as well as the 2-bit BCD interface used for directional control. A user-supplied 4-
conductor cable is needed to connect the DXE-RFS-2 and the DXE-CC-8A.
Choose a 4-conductor cable (3+ ground) of at least 22 gauge for lengths up to 1500 feet. If you use
a cable with more conductors, it is a good idea to tie the unused conductors to ground. Use point-to-
point wiring, matching the terminal labels at each end. Economically priced DXE-CW9 is a 9
conductor Shielded Control Wire which may be used.
DXE-CW9 is made of 24 AWG wire. Since the DXE-RFS-2 needs four lines, the DXE-CW9
could be doubled up (example: orange & orange/white wires connected together at both ends) to
increase the wire gage size and increase the length of operation.

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DXE-RFS-TS3P Default Connection Diagram Using Factory Jumper Settings
Shown with optional DC Pass Through Lightning Protection, optional DXE-RFCC-1 Feedline
Current Choke, and optional DXE-RPA-1 HF Preamplifier