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BevFlex-4X Quick Start Guide
Revision 1.01
July 16, 2020
Congratulations on purchasing the most versatile low band, low noise receive antenna system ever! The
BevFlex-4X is an updated and lower priced version of the unique W8GNM BevFlex-4. With the BevFlex-4X you
can build an above ground Beverage, Beverage on Ground (BOG), EWE, Flag, or a VE3DO type antenna. The
BevFlex-4X also allows you to reverse the antenna direction by simply throwing a switch. The Beverage and BOG
configurations permit placing the feed point at any point on the antenna while still using the entire length of the
antenna. Conventional Beverage designs can only be fed from the ends.
This Quick Start Guide gives you the basic information needed to set up your BevFlex-4X system. A full manual is
available online at www.unifiedmicro.com.
System Components
The BevFlex-4X has four modules. There are two Terminator units, a Feed Unit, and a Switch/Control Unit. The
Terminators and Feed Units are mounted outside as part of the antenna system, and the Switch Unit is installed
inside the shack to control the receive direction.
Terminator Units
The terminators transform the impedance of the antenna to 75 ohms and couple the signals to the transmission
feed lines. In the case of Beverage and BOG configurations, the antenna is made of RG-6 coax. The outer shield
acts as the receive conductor element, and the internal conductor in conjunction with the shield form a
transmission line which is part of the feed system.
Different antenna types have different impedances that must be matched to 75 ohms. The two stainless screw
terminals have different purposes depending on the antenna type. Two jumpers inside the box select
transformer taps to provide the correct impedance match. The default factory configuration is for
Beverage/BOG/VE3DO. The jumpers need to be changed if you are building a Flag or EWE antenna. Details are
covered in each antenna configuration section. Be sure the cover is replaced in the correct orientation if you
change the jumpers. The bottom of the label should be on the side of the F connector.
The Terminators also contain a gas discharge tube to give added protection from voltage surges. No antenna will
survive a direct or nearby lighting strike, but these devices do provide added protection. Always disconnect your
antennas if there is a chance of lightning.
Feed Unit
The Feed Unit takes the signals brought back from the Terminator Units on the coax and separates the signals
from the two directions. In the case of Beverage/BOG configurations, the Feed Unit couples the signals from the
two directions of the RG-6 coax that act as both the antenna and part of the feed line. The outputs of the Feed
Unit are two RG-6 coaxial cables to the shack and Switch Unit. It is important to keep track of which cable is
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which, and the correct connections to the Switch Unit will depend on the antenna type. The Feed Unit also
provides Ohmic and common mode RF isolation of the antenna from the feed lines back to the shack.
There are no user options or other configuration actions needed inside the Feed Unit.
Switch/Control Unit
The Switch Unit has two purposes. The first is to select between the forward and reverse directions. All the
antenna types supported have a single main lobe in the forward direction. That direction will be selected when
the front panel switch is in the Forward position. Changing the switch to the Reverse position will select a lobe
180° from the forward lobe direction.
The second purpose of the Switch Unit is to terminate the unused direction. Proper BevFLex-4X operation
requires a 75 ohm termination of the coax not selected by the switch. If you have a different receive antenna
switch you wish to use, it will have to terminate the unused feed line with a 75-ohm resistor.
The Switch Unit has additional protection for the receiver. A diode array clamps the signal voltage to the
receiver input. A 50ma fast blow fuse protects against over currents including accidental transmission power
into the receiver connector. While these provide additional protection, they are not guaranteed to prevent
damage to receivers. A third-party receiver input protection device is recommended, especially if your receive
antenna is near a transmitting antenna.
There are two jumpers for selecting options on the Switch Unit circuit board. Most users will not need to
change them.
G1: The Switch Unit has a transformer to provide DC and common mode RF isolation between the BevFlex-4X
antenna and the receiver. Common mode currents on the feed lines create additional noise. Some users may
prefer to connect the grounds from the two antenna feed lines to the ground of the coax going to the receiver
input. Soldering a wire between the two solder pads of G1 will connect the shields. The factory default is for G1
not to be installed.
G2: This jumper position provides a method to bypass the 50ma fuse in the line to the receiver. Inserting and
soldering a wire to the G2 pads shorts out the fuse. The factory default is for G2 not to be installed.
Figure 1. The yellow lines show installation points of optional jumpers.
Note that the coax cables between the Switch and Feed Units must be connected correctly to be receiving in the
indicated direction. If you get the coax cables reversed between the Feed and Switch Units, you will be receiving
in the opposite direction from what the switch indicates. If that happens, switch the two input cables on the
back of the Switch Unit.
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General Installation Guidelines
The BevFlex-4X was designed to give maximum weather protection to its outdoor units. They are encased in
NEMA rated cases with gasketed lids. The F type coaxial connectors are sealed to the case. The terminal
hardware on the Terminator Units is stainless steel. The internal circuitry is given a conformal coating to provide
additional protection from corrosion. Ultimately, weather protection is difficult to maintain, and proper
installation will go a long way in providing a long service life for your BevFlex-4X.
Mounting
The Terminator and Feed Units must be mounted with the F connectors pointing downward so water will drain
away from these connectors.
Connections to the Terminator screw terminals must have the connecting wires either drop down or have a drip
loop. Do not have the wires coming in horizontally or from above the case.
Similarly, if the coax cables must be routed at or above the Feed or Terminator unit level, allow several inches of
a loop to prevent water from flowing to the F connectors. Always seal coax connections.
Figure 2. Proper Terminal Unit mounting. Wires and coax must come from below the Terminal so water runs
away from the connections. Wires must have stress reliefs if they will put tension on the connectors. Wires
coming from the side or from above must have a drip loop. Weather proof the connections. Coax
connections to the Feed Unit must also drop down. Use drip loops where necessary on the RG-6 coax
While rugged, the BevFlex-4X outside units are not designed to handle the forces that attaching cables and wires
might put on the connection points. Always provide strain relief before connection to the BevFlex-4X modules.
Antenna Configurations
This section shows how to configure your BevFlex-4X for the supported antenna types. It is assumed the reader
is familiar with these antennas types and has decided which type of antenna they want to build and have
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selected the site to install the antenna. Each type of antenna has its advantages and disadvantages regarding
performance, space needed, support structures, and other factors.
If you are not familiar with these antennas, more information is available in the ARRL Antenna Book, ON4UN’s
Low Band DXing book, and many online resources. Note that none of these sources covers the BevFlex-4X
directly. If you build your BevFlex-4X version of an antenna with similar dimensions, you will get similar
performance to the traditional design. You get two switchable directions with the BevFlex-4X antenna and more
flexibility on feed point location with Beverage type antennas. These are features not available with most
designs described elsewhere.
Beverage/BOG
The classic Beverage antenna is an elevated, terminated wire placed 7’-10’ above ground level. Typical lengths
are 300’-1000’ or even longer. The BOG or (Beverage on Ground) is similar except the wire is placed right on the
ground or buried slightly below the surface of the ground. The typical lengths for a BOG are 100’-240’ feet long.
A BOG of a given length will have better characteristics than an elevated Beverage of the same physical length
due to the velocity of the radio wave being lower in the ground, but the signal strength received by a BOG is
about 10dB lower than from an elevated Beverage. The signal levels can be improved by mounting the BOG an
inch or two above ground level when it can be protected from being a tripping hazard. BOG lengths between
100 feet and 240 feet generally work well with 225 feet being the optimum length for 160m operation over
normal soil.
The BevFlex-4X replaces the Beverage wire with inexpensive RG-6 coax. Instead of a resistor termination end
and a feed point end, the BevFlex-4 has identical Terminator Units on each end. You may install the Feed Unit at
any point along the length of the antenna coax. Normally it is placed at the point nearest the shack to reduce
the length of the feedlines. The entire length of the antenna coax is always active regardless of Feed Unit
placement.
The Beverage/BOG block diagram shows the basic configuration of the BevFlex-4X system used as one of these
antennas. Because of the different impedances of the two types, the Terminator wire connections points to the
ground rods are different. Leave the other Wire Terminal unconnected.
Receiver
Control Unit
Coax
RG-6 Coax
RG-6 Coax
Ground Rod
Ground Rod
Ham Shack
Terminator Unit
Terminator UnitFeed Unit
Ant
Rev
Ant
Fwd
A OUT
B OUT
RX
Forward
Reverse
BevFlex-4X Block Diagram - Beverage/BOG Configuration
RG-6 feed lines to shack
Any length, do not need
to be the same length
Typical Antenna lengths:
Beverage: 200 ft to 1000 ft, elevated 7-10'
BOG: 100 ft to 300 ft, on ground or buried 1-2" deep
FWD IN
REV I N
Feed unit may be placed at
any point between terminators
REV END
FWD END
Direction refers to direction
of main receive lobe.
Antenna Type
Ground Rod connection
Elevated Beverage
Wire Terminal 1
BOG
Wire Terminal 2
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The Terminator internal jumpers must be set to the Beverage/BOG settings. This is the factory default
configuration. See the section on Terminator Configuration if you are not sure of the configuration of your
Terminators.
EWE
The EWE is a wire antenna in the form of an inverted U. Its advantages are a fairly small space requirement and
simple 10’ supports. It is reported to work best over soil with poor conductivity. The standard EWE has a feed
transformer at the end of one of the vertical sections and a terminator resistor at the end of the other vertical
section. The BevFlex-4X version places a Terminator at the bottom end of each vertical section. This
arrangement allows for instant direction switching.
The Terminators must be configured for the EWE/Flag settings. See the section on Terminator Configuration to
set the jumpers. Also, note that the connections between the Feed Unit and Switch Unit are reversed compared
to the Beverage/BOG connections.
Receiver
Control Unit
Coax
RG-6 Coax
RG-6 Coax
Ground Rod
Ground Rod
Ham Shack
Terminator Unit
Terminator Unit
Feed Unit
Ant
Rev
Ant
Fwd
B OUT
FWD I N
A OUT
REV I N
RX
Forward
Reverse
BevFlex-4X Block Diagram - EWE Configuration
RG-6 feed lines to shack
Any length, do not need
to be the same length
Direction s
#12 Antenna Wire, 30 ft to 40 ft typical length
Top wire elevated at 10'
REV END
FWD END
Note: Feed line connections
are reversed for EWE, Flag,
and VE3DO configurations.
Directions indicate direction
of main receive lobe.
Terminator Connection
Connection Point
Wire Terminal 1
Ground rod
Wire Terminal 2
Antenna wire
Flag
The Flag antenna style is like the EWE except an elevated wire closes the loop instead of the ground as in the
EWE. The Terminator mounting locations are in the center of the vertical wire sections.
The Terminators must be configured for the EWE/Flag settings. See the section on Terminator Configuration to
set the jumpers. Also, note that the connections between the Feed and Switch Units are reversed compared to
the Beverage/BOG connections.
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Receiver
Control Unit
Coax
RG-6 Coax
Ham Shack
Terminator Unit
Terminator Unit
Feed Unit
Ant
Rev
Ant
Fwd
B OUT
FWD IN
A OUT
REV I N
RX
Forward
Reverse
BevFlex-4X Block Diagram - Flag Configuration
RG-6 feed li nes to shack
Any length, do not need
to be the same length
Directions
#12 Antenna wire
#12 Antenna wire
Lower wire 10' above ground
34' Typical
flag horizontal length
8' Typical
8' Typical
RG-6 Coax
Direction indicates direction
of main receive lobe.
Note: Feed line connections
are reversed for Flag, EWE,
and VE3DO config urations.
FWD END
REV END
Terminator Connection
Connection Point
Wire Terminal 1
Ground rod
Wire Terminal 2
Antenna wire
VE3DO
The VE3DO is similar in form to a Flag antenna but uses shorter supports. The Terminators are placed at the
center of the bottom wire element near the ground. The Terminator jumpers must be configured to the
Beverage/BOG setting. This is the factory default setting. See the section on Terminator Configuration to set the
jumpers.
Receiver
Control Unit
Coax
Ham Shack
Terminator Unit
Feed Unit
Ant
Rev
Ant
Fwd
B OUT
FWD IN
A OUT
REV IN
RX
Forward
Reverse
BevFlex-4X Block Diagram - VE3DO Configuration
RG-6 feed li nes to shack
Any length, do not need
to be the same length
Directions
#12 Antenna wire
Lower side ground height: 12"-24"
12" optimized for 80M, 18"-24" optimized for 160M
Horizontal length: 20'-40'
40' optimized for 160M, 20' opt imized for 80M
Terminator Unit
10'
Terminato rs placed nea r Feed Un it
Ground Ro d
REV END
FWD END
Note: Feed line connections are
reversed for EWE, Flag and
VE3DO config urations.
Directions indicate direction of
the main receive lobe.
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Terminator Connection
Connection Point
Wire Terminal 1
Ground rod
Wire Terminal 2
Antenna wire
Terminator Configuration
The Terminator uses internal jumpers to select taps on the impedance transformer to match the impedance of
the antenna type you are building. The factory default setting is for Beverage/BOG/VE3DO configurations. You
will need to change them if you are building a Flag or EWE version.
Antenna Type
G1 Jumpers
G2 Jumpers
Beverage/BOG/VE3DO
2-3
1-2
EWE/Flag
1-2
2-3
Figure 3. Bev/BOG/VE3DO Jumper Configuration Figure 4. EWE/Flag Jumper Configuration
If you are unsure of a Terminator configuration, you can test it with an ohm meter without opening the case.
Check the resistance between the F connector threaded barrel (shield) and one of the Screw Wire Terminals. If it
shows a low DC resistance, the unit is configured for Beverage/BOG and VE3DO type antennas.
Be sure to put the cover on the proper way after changing the jumper configuration. The bottom of the label
goes to the F connector side.
Additional Information
Warranty
The BevFlex-4X is warranted for parts and workmanship for a period of one year from the time of purchase.
Unified Microsystems will repair or replace failed units at its discretion. Physical or lightning damage is not
covered under warranty.
Unified Microsystems may make changes to the design or specifications without notice.
Support
Support for Unified Microsystems products is available by email. w9xt@unifiedmicro.com Include the product
name (BevFlex-4X) in the subject line to prevent your message from being lost in the spam.
Disclaimer
Installing antennas can be dangerous. Use caution when installing your BevFlex-4X antenna system. Stay away
from power lines. Unified Microsystems is not responsible for injuries sustained while installing its products.
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Always disconnect your BevFlex-4X antenna and all other antennas when not operating to prevent lightning
damage. Unified Microsystems is not responsible for injuries or equipment damage due to improper installation,
lightning or similar events.
Unified Microsystems
PO Box 133
Slinger, WI 53086
www.unifiedmicro.com
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