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BALUNS, UNUNS & Line Isolators


In addition to matching the feed-line cable to the antenna for maximum transfer of RF energy, the BUXCOMM MasterMatch BALUNS improve the radiation pattern for more predictable coverage. See with and without patterns above.


To prevent excesive heat, we never use an Air-Core antenna BALUN.  We use multiple cores in our BALUNs for several reasons, one being: to reduce or eliminate common mode currents within the antenna system.  If the common mode impedance at the feed point is anything above 450 ohms reactance, the balun can introduce serious common mode currents.

Current vs Voltage BALUN Specifics

There are two kinds of BALUNs: voltage baluns and current BALUNs. Both accomplish the same thing. The difference in these two BALUN type are the way they are wound. A voltage BALUN produces equal voltage with opposite polarity at its output. A current BALUN (preferrred) provides equal currents with opposite polarity at its output.

Other BALUNs provide a step-up or step-down impedance transformation. A 4-to-1 BALUN {BuxComm cat# B2KC41} steps up the impedance four times. It will transform a 50-ohm impedance to 200 ohms. This type of BALUN transformer is used at the output of tuners to increase the tuning range of a tuner 4 times. If a tuner without a BALUN can match 500 ohms, a 4-to-1 BALUN will increase the range of impedances it can match to 2000 ohms. Many hams think the 4-to-1 BALUN is used to match 50 ohms to 450-ohm ladder-line: It is NOT. It takes a 9-to-1 balun to match 50 ohms to 450 ohms, and it is not important to match the impedance to ladder-line. {BuxComm cat#B15KC91} (I.E. 450 divided by 50 = 9, thus a 9 to 1 ratio). Because most longwire antennas ar 400 to 500 ohms at the feedpoint a 9 to 1 BALUN is most often used.

A balun should always be placed at the input end of ladder-line or open wire feeders to prevent feed-line radiation. When using ladder-line a step up balun is commonly used although a 1:1 balun will provide some isolation.

The BALUN Application Rule of Thumb:

1 to 1 BALUNs are used mostly with center-fed dipoles.
2 to 1 BALUNs are employed with high-frequency Quads and loop antennas (above 40 meters). 
4 to 1 BALUNs are commonly used with Windom's, Off-Center fed, and Sky-wire loops cut for 75/80 and 160 meters.
6 to 1 BALUNs are sometimes used with antennas that are fed with 300 ohm feed line. 
9 to 1 BALUNs are the BALUN of choice when feeding end-fed, long-wire antennas.
The 9:1 is also preferred when feeding a T2FD antenna that has a 450 ohm balanced terminating load at its center.

Here's the got'cha; When feeding mobile antennas that are end-fed, use coax cable, HOWEVER, the feed-point impedance of most (bottom) end-fed mobile antennas is somewhere between 15 and 35 ohms. To remedy this requirement, we have developed the B1K5022 UNUN. 

Where a VHF or UHF yagi is in use, improved transfer of energy is realized when using the B1VBALUN.  In rare cases. the 12 to 1 BALUN will be necessary when feeding an antenna with 600 ohm open-wire, transmission line.  A 16 to 1 BALUN is sometimes used with Rhombic antennas that employ 800 ohm termination balancing network resistors at the far side apex.

BUXCOMM  is  BALUN  Headquarters.
BUXCOMM BALUNS are made in the Commonwealth of Virginia

We highly recommend using CoaxSeal, CS104 on all BALUN and UnUn
terminals and attachments.
Any BALUN installed out-of-doors is subject to harsh
weather, hard driving rain, and heavy winds. These conditions can allow
moisture to develop inside a BALUN when the connections are not sealed.

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