Transmit Four Square System
Phasing Unit and Four Square Control Console
DXE-TFS Series for 160, 80 or 40 Meters
DXE-TFS4-160B, DXE-TFS4-80B, DXE-TFS4-40B
DXE-TFSB-INS Revision 1e
© 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
Table of Contents
Introduction
3
System Overview
3
Features
4
Required Parts Not Included
5
System Discussion
5
Vertical Antenna Selection
7
Warning
7
Overhead Power Line Safety
7
Installation
8
Suggested Installation Sequence
8
Site Selection
8
The Four Square Layout
8
Topographical Considerations
11
Site Selection in Relation to Noise Sources
11
Mounting the Four Square System Phasing Unit
12
Antenna Feedline
13
Control Wire Connections
15
Radial System
16
Tuning the Vertical Antennas Radial System
18
Four Square Control Console Front Panel
19
Four Square Control Console Direction Label
21
Four Square Control Console Rear Panel
22
Four Square System Phasing Unit Connections
24
Typical Transceiver / Amplifier Connections
25
Lightning Protection
26
Turn On and Test
26
Power ON Relay Exercise
26
LED Brightness
27
Using the Transmit Four Square System Phasing Unit
27
Manual Updates
28
Technical Support and Warranty
28
2
Introduction
DXE Model
Band of Operation
DXE-TFS4-160B
160 Meters
DXE-TFS4-80B
80/75 Meters
DXE-TFS4-40B
40 Meters
System Overview
DX Engineering's TFS4 series of Transmit Four Square System Phasing Units bring together the
highest level of engineering excellence with the practical realities of operator convenience and ease
of installation.
The Transmit Four Square Series System Phasing units are currently available only in monoband
versions for either the 160, 80/75 or 40 meter bands. Check DXEngineering.com for the latest
models.
The DX Engineering Transmit Four Square series System Phasing Unit is easily dropped into your
quarter-wave spaced vertical 4-square array to provide optimum directional control.
The system will allow the operator to receive or transmit with gain in any one of four directions
with good front-to-back ratio, or in a single high efficiency omni-directional pattern with a push of a
single button. This combination is a great tool which permits you to transmit and listen "all-around"
unhindered by pattern nulls, and then select the best direction for signal reception and noise
rejection.
The standard four square array uses four ground mounted 1/4-wave vertical antennas positioned at
the corners of a square land area that measures 1/4-wavelength on a side. The antennas must be
located as described in the installation section to provide switchable patterns in desired directions.
The forward lobes are reasonably wide eliminating the need for precise aiming while also providing
coverage of in-between directions.
The four vertical antennas must be resonant in the desired band of operation. Each vertical element
must be directly fed through 1/4-wave long 75Ω transmission lines. Do not use additional matching
components or decoupling devices like baluns or coils between the centrally located Four Square
System Phasing Unit and the verticals, as additional transmission lines can reduce array
performance. The vertical antennas must be series-fed at the base. The verticals must be 1/4-wave
long or electrically 1/4-wave and must be resonant. DX Engineering offers vertical antennas that are
well suited for this application. Above all, a properly designed and installed radial system is
necessary for maximum system performance. Detailed information of the entire array follows in the
installation section.
The four 30-40 Ω feedpoint vertical antennas are connected to the Four Square System Phasing Unit
by electrical 1/4-wavelength 75Ω cables foam dielectric cables. Coaxial cable velocity factor must
be high enough to allow the cable to physically reach the Phasing Unit. The recommended coaxial
cable for this application is DXE-11U. This is an RG-11/U type foam dielectric cable with a
3
velocity factor of 84% (0.84). During phased array operation, due to mutual coupling, each vertical
antenna has a different operating impedance. This means transmitter power is not evenly divided by
the Four Square System Phasing Unit. The highest effective power into any element feed cable is
approximately half of the applied power, which means the overall system can handle approximately
twice the 1:1 SWR 75Ω cable ratings when used in this application. Properly prepared 1/4-wave
cables may be ordered from DX Engineering Customer Service.
If you already have a four square array with a Comtek or similar hybrid controller and would like to
improve overall performance, add the power handling capability and Omni feature of the DX
Engineering TFS4 Transmit Four Square Series, which is essentially a direct replacement system. A
slight shift downwards in optimum performance frequency may result from this substitution.
Control is accomplished using a four-wire control cable to perform all the necessary switching
functions when connected to the included DXE-CC-4SQR Transmit Four Square Control Console.
Optional DXE-CW9 CAT 5 control cable is available from DX Engineering. Push-button switching
allows instantaneous direction change. Your amplifier keying or relay line should be routed through
the control console. This prevents catastrophic failures caused by relay transfer while the amplifier
is activated. The DXE-CC-4SQR Control Console allows you to call for pattern changes while
transmitting without damaging relay contacts.
Features
Four Directions PLUS Omni - versatile operation
5 kW CW Power Rating - high reliability
10 kW PEP SSB
Hot switching lockout - disables amplifier during directional changes
Drop-in replacement for Comtek - easy upgrade
Proven DX Engineering RF Relays - high performance
RF Shielded Weatherproof Housing - unique protection
Custom label with four compass direction sets for the Control Console
Relays cycle during Power-On
The DX Engineering Transmit Four Square system consists of a Transmit Four Square Control
Console that has four momentary contact light-touch push-button switches for direction control and
one push-button for omni selection. There is a toggle switch for power on/off, and four variable
brightness green LEDs (light emitting diodes) to show the system's current direction. A custom
label for the Control Console to indicate four antenna directions. During Omni operation, all four
LEDs light at the same time. A 2.1 mm DC power cord is supplied with the unit.
The custom made Four Square System Phasing Unit must be located at the center of the four square
antenna system. Also included is a DXE-SSVC-2P V-Clamp for mounting the Four Square System
Phasing Unit. Note: JTL-12555 Jet-Lube SS-30 Anti-Seize should be used on all clamps, bolts and
stainless steel threaded hardware to prevent galling and to ensure proper tightening.
4
Required Parts Not Included with the TFS4 Series
Part Number
Qty
Description
DXE-Q75-160-4P
4
1/4 Electrical Wavelength 160 meter 75 Ω coaxial cables with PL-259 connectors
on each end. Customer to specify center frequency.
DXE-Q75-80-4P
4
1/4 Electrical Wavelength 75/80 meter 75 Ω coaxial cables with PL-259 connectors
on each end. Customer to specify center frequency.
DXE-Q75-40-4P
4
1/4 Electrical Wavelength 40 meter 75 Ω coaxial cables with PL-259 connectors on
each end. Customer to specify center frequency.
Four quarter-wave resonant vertical antennas for your selected band
Four DXE-RADP-3 Radial Plates plus extra DXE-225RT-20 Ring Terminal Kits and DXE-
RADP-1HWK Radial Plate Wire Attachment Hardware Kits
Four DXE-SSVC-2P V-Clamps - One for mounting each of the four DXE Radial Plates
DXE-RADW - Bulk radial wire and kits
Radial Cross Bonding Copper Strap - DXE-CS2-100
Coaxial Cable - 75 Ω - DXE-11U foam dielectric (or equivalent)
Single replacement, or sets of four, custom made 1/4 electrical wavelength cables with PL259 connectors are available from DX Engineering:
Control Cable - DXE-CW9 CAT 5 UV resistant (or similar)
Dummy Load - 50 Ω - 200 Watts or greater and 50 Ω feedline for the dummy load.
A Vectronics DL-650M Dummy Load is available from DX Engineering.
The VEC-DL650M Dummy Load simulates an accurate 50 Ω antenna up to
650 MHz, enabling you to test your transmitter without radiating a signal on
the air. DC to 650 MHz. Handles short-term RF power up to 1500 watts.
Dummy Load coaxial cable is available in any custom length with PL-259
connectors attached. Call DX Engineering for custom lengths of either RG-8X or RG-8U
System Discussion
A four-square antenna array is a single band directional antenna system. It uses four current-fed
vertical antennas positioned at the corners of a 1/4-wavelength on a side square. In order to produce
deep nulls each element must have equal currents and proper phase shift. Each element is excited
through a 1/4-wave 75 Ω feedline. The unique characteristic of a 1/4-wave transmission line is that
equal voltage at the source end will always produce equal currents at the load end, and the net phase
shift will always be constant regardless of line SWR. This unique combination is not true for any
other length of transmission line, except a very low-loss line that is an odd 1/4-wave long. The 75 Ω
line, since it is mismatched at the antenna, also transforms the impedance of the element.
The Four Square System Phasing Unit contains unique circuitry that, in combination with the
transmission lines to each element, cancels reactance and supplies each feedline with approximately
equal voltage and near ideal phase shift.
The TFS4 series Four Square System Phasing Unit provides four switchable unidirectional cardioid
patterns, along with the unique addition of a switch selection for an omni-directional pattern.
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The SWR bandwidth and directional performance bandwidth of this system is highly dependent
upon the characteristics of the vertical elements used in the array. The Four Square System Phasing
Unit is a switchable modified hybrid coupler. It provides proper currents and phase at each antenna
element when the correct electrical length 75 Ω feedlines to each vertical antenna are used.
Each of the four vertical antennas used in the Transmit Four Square system must be very similar to
each other. If the elements have different impedances or radiation characteristics, system
performance will suffer.
Each side of the square must be 1/4-wavelength in free space at the desired operating frequency. For
example, each side must be 64.7 ft for a center frequency of 3.800 MHz.
Note that the free space formula 246/f (MHz) is used for array spacing - not the more familiar 234/f
(MHz) used for antenna element lengths, which takes element end effect into account.
Note: Array spacing is important in providing the deepest rear null – commonly observed when
checking the front-to-back ratio (F/B).
The TFS4 Four Square System Phasing Unit is placed in the physical center of the square, where
exactly equal 1/4-wavelength 75Ω coaxial cables connect each vertical element to the Four Square
System Phasing Unit. Note that the cable lengths are different from the free space length of the
square sides. This is because the cables have a different velocity factor than air. Radio frequency
signals move through the cables slower than they move through air.
For best performance, you should install a good ground radial system. 32 straight radials, most
about 1/4 wavelength long, are recommended at each of the four vertical antennas. Some of the
radials will cross in the middle of the array. These radials may be allowed to cross if well-insulated
from each other at crossing points, but it is better if they are bonded as described in the installation
section. Either method will provide suitable performance. What cannot be tolerated are poor or
intermittent connections between radials.
As with any properly installed quarter-wave vertical antenna, signals arriving at lower angles of
radiation will be enhanced more than very high angle signals. Phasing is optimized for very low
wave angles. This means array directional performance will generally be better on more distant low
angle and on local ground-wave signals.
While greatly dependent on many variables, (such as the radial system, angle of arrival of signals,
etc.), the gain of a properly designed and installed four-square array will be on the order of 5 dB
over a single vertical element.
Typical F/B ratios will approach or exceed 25 dB, minimizing interference from the side and rear
directions. See various reference books such as "ON4UN’s Low Band DXing" for more in-depth
discussion of four-square theory and performance.
6
Vertical Antenna Selection
DXE-7580FS-VA-2
DXE-7580FS-VA-3
Band
80
80
Element Size Range
3” to 0.25” OD
4” to 0.5” OD
Power Rating
5,000 W SSB & CW
5,000 W SSB & CW
Bandwidth at 2:1
557 kHz
593 kHz
Height
68 feet
68 feet
Wind Survival
92 mph, Self Supporting*
112 mph, Self Supporting*
Pivot Mount
Heavy Duty Pivot Mount
Heavy Duty Pivot Mount
To provide optimum performance four vertical antennas of identical design are required. Each of
the four vertical antennas used in the Transmit Four Square must be identical. If not, peak
performance may not be obtainable. The vertical antennas must be spaced in a square according to
wavelength and have good radial systems installed. Anything less could cause serious performance
degradation.
The following DX Engineering monoband vertical antennas are an ideal match for top performance
in a four square array system.
* Depending on your environment, guying of any vertical antenna is recommended
Table 1 - DXE Monoband Vertical Antennas
For operation on 160 meters, the customer must supply the four vertical 160 meter resonant antenna
system. There are a number of vertical resonant designs available for operation on 160 meters. See
various reference books such as “ON4UN’s Low Band DXing”, the “ARRL Antenna Book” or other
reliable text for details.
WARNING!
INSTALLATION OF ANY ANTENNA NEAR POWER LINES IS DANGEROUS
Warning: Do not locate the antennas near overhead power lines or other electric lighting or
power circuits, or where they can come into contact with such circuits in the event of an accident or
mechanical failure. NEVER INSTALL AN ANTENNA WHERE IT CAN FALL INTO OR
ACCIDENTALLY TOUCH a power line. Very serious injury or death can result from contact with
utility lines.
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
7
advice. Although overhead power lines may appear to be insulated, such coverings are not intended
246
L in Feet =
▬▬▬
MHz
to nor can they be relied on to protect you from electrocution.
Keep your distance! Remember the 10-foot rule: When carrying and using ladders and other long
tools, keep the falling distance at least 10 feet away from all overhead lines - including any lines
from the power pole to your home. Your local utility will advise you if an antenna location is safe
or not.
Installation
Suggested Installation Sequence
Site Selection
Antenna Selection
Mounting post installations
Feedline and control cable installation
Radial System Installation
Antenna Installation and tuning
System phasing unit installation
Coaxial Cable and control wire connections
Testing and operation
Site Selection
Select a mounting location clear from power lines, structures and other antennas. Pay special
attention to overhead power lines, utility cables and wires. Vertical antennas should be mounted
well away from local noise sources or large metallic objects that might re-radiate noise and affect
the tuning, radiation pattern or SWR. When using the DX Engineering Tilt Base, determine the
direction you want the antenna to tilt down and make sure there is adequate clearance. There should
also be a clear area for guying and radial systems extending away from the four antennas.
The Four Square Layout
The four monoband vertical antennas making up the four-square system must be properly
positioned. You must adhere to the dimensions shown in Table 2 for optimum performance. The
placement of the four vertical antennas in relation to each other is somewhat critical. If more than
five percent out of specification, system performance can suffer. The formula for determining the
distance between each antenna (1/4-wavelength) is:
For four square arrays use 246 divided by the Frequency in MHz = Length in feet
8
Other spacing close to this value may work, but the characteristics of the main lobe will change
Band
(Meters)
Typical Center
Frequency
(MHz)
Distance between
antennas (1/4-wavelength)
at the Center Frequency
Meters
Feet
160
1.830
41.0
134.4
1.845
41.0
133.3
1.950
38.5
126.2
80/75
3.550
21.1
69.3
3.560
21.1
69.1
3.575
21.0
68.8
3.650
21.0
67.4
3.710
20.2
66.3
3.795
20.0
64.8
3.985
19.0
61.7
40
7.030
11.1
34.9
7.040
11.0
34.9
7.110
11.0
34.6
7.150
10.4
34.4
7.225
10.3
34.0
gain, directivity and front-to-back. Time spent in laying out a symmetrical installation will pay solid
dividends. The system is forgiving, but the best front-to-back is obtained when symmetry is
maintained and with each element resonant on the same frequency and with each antenna base at
the same elevation.
The following chart shows various calculations depending on the desired center frequency. The
frequencies shown here are various CW, DX, and SSB frequencies used in the American Radio
Relay League Band Plan:
Table 2 - TFS4 Four Square Vertical Antenna Spacing
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