4:1 Baluns/Ununs

4:1 Baluns and Ununs are available in kit form or assembled form in a weatherproof  Current Unun and Balun Enclosure which we call CUBE Baluns™ and CUBE Ununs™. All 4:1 Baluns/ununs are ferrite toroid baluns and the kit forms can be configured as a balun with balanced output of 200 ohms or as ununs with one side grounded.

4:1 baluns are designed for 50 ohm input to 200 ohm output (either balanced or with one side grounded).

4:1 Baluns are useful between balanced lines for center fed Zepps, Off-center fed (OCF) dipoles with coax, G5RV antennas, full wave loops, NVIS dipoles that are close to ground and have impedance levels near 200 ohms or high impedance feeds for log periodic beams.

4:1 ununs are useful between coax and vertical antennas, monopole verticals or long wires with load impedances near 200 ohms.

KITS

4:1 250-Watt Balun/Unun Kit

BA-4-250
Assembled BA-4-250

Model BA-4-250 is a 4:1 balun/Unun kit used to translate a 50 ohm input up to 200 ohms at power levels up to 250 watts when used with a matched load. With a matched load the SWR will not exceed 1.2 over the frequency range 1.8 to 30 MHz.

The kit consists of a F140-61 ferrite core, two colors of  1000-v insulated wire.  a UHF connector with stainless steel hardware, and an instruction manual with directions to connect the kit as a 4 to 1 balun (balanced coax to balanced antenna like zepp or from 450 ohm feeder line to coax for a tuner) or 4 to 1 unun (unbalanced coax to unbalanced antenna like end fed or random wire).

This 4:1 voltage balun is very useful for OCF dipoles with a vertical radiating element where you want the shield to radiate on the vertical element.  At the end of the vertical element, you will need a 1:1 balun to STOP the common mode current from radiating down the rest of the coax. DO NOT use a 4:1 current balun at the antenna if you want to have radiation from the vertical element – use a 4:1 voltage balun and a 1:1 balun at then end of the radiating element (the vertical element gives a degree of vertical radiation for improved DX operation from your OCF).  If you do not use a vertical element, then use the assembled 4:1 current balun shown below which will prevent radiation on the coax.

This balun will also transform at 4:1 for a wide variation of load impedances.  Shown below are AIM 4170 SWR results for a 200 ohm load.  This balun gives near perfect transformation through 30 Mhz  with a SWR under 1.25 .  Light blue vertical bars are ham bands starting at 160 meters at left to 10 meters at right.  Antenna loads are never a perfect 200 ohms on all bands, but vary in a range.  Use this balun with a 135 degree vertical whose feed point impedance is near 200 ohms (See ARRL handbook) and with only 6 radials you get as high as 89% efficiency verses less than 60% efficiency with a quarter wave vertical and many more radials.  Also remember to get a 1:1 balun for the shack on the other end of the coax to keep radiated and unwanted common mode current out of your receiver (and reduce your noise levels).  Check website for various options.

 BA-4-250 SWR 1-31 Mhz

Model BA-4-250…………$17.50

+$10 S&H. Tax in Calif.

 Note: $10 S&H is “per order”. Order more than one or add other items and S&H is still $10.

Need an enclosure box?  Here is the one we use on all of our CUBE Baluns™.  Part # CB-BOX   Price $9.50.  Includes box only. Use SO-239?s supplied with balun kit or supply your own connectors

Balun Enclosure Box with SO-239 shown installed.  Box is delivered without holes drilled.
Balun Enclosure Box with SO-239 shown installed. Box is delivered without holes drilled.

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4:1 1500-watt Balun Kit – Great for Tuner Balun (ladder line to coax)

BA-4-1500 Connected as Balun

BA-4-1500 Connected as Balun

Purpose. This kit is designed to convert from coaxial cable to ladder line at full legal amateur power at 100% duty cycle from 1.8 to 30 MHz. It provides conversion from unbalanced coax to balanced ladder line and gives a 4:1 impedance step-down to reduce impedance seen by the coax, allowing the tuner to easily match the antenna.  Based upon the classic “McCoY” antenna tuner Ruthroff balun used for over 60 years!

Application. A zepp dipole can be used as a multi-band antenna by using an antenna tuner to convert the impedance to 50 ohms for the transmitter.  The zepp is usually fed with 300-600 ohm balanced line feeders and, as long as the feedline length is an odd number of 1/8 wavelengths at the fundamental frequency (468/f (mhz), the impedance at then end of the feeders will generally be in the 100-500 ohm range.  The  BA-4-1500 is designed to operate over a range of 200-500 ohms and convert these ranges to 50-125 ohms impedance which can be easily matched by an antenna tuner at then end of the coax.   Coax length should be kept to less than 10 feet due to the potentially high SWR (and coax losses) that may occur on the coax.  Of course the ladder line changes the impedance seen at the balun depending on its length. But there still is a wide range of impedances seen from band to band and a very rugged balun, such as the BA–4-1500 is required to cope with it.  The impedance conversion is not uniform for the 1-8-30 mhz range but is adequate for most tuners to match the transmitter/transceiver.  If a more uniform match is needed from 1.8 to 30 Mhz, we suggest the assembled and tested CB-4-5000 which is also rated for 5KW (see below).

Model BA-4-1500. Kit consists of two type T200A cores, two colors of #14 1000-v insulated wire, a UHF connector with stainless steel hardware, and winding instructions with directions to connect the kit as a 4 to 1 balun (balanced antenna to unbalanced coax) or 4 to 1 unun (unbalanced coax to unbalanced antenna).  The advantage of iron powder cores in the tuner application is the tolerance to withstand VSWRS considerably higher than 2:1 without any harmful temperature rise (like ferrite baluns).  Furthermore, the wire doesn’t heat up; however the core does via dialectric heating (that’s why we use two cores in this design).

This balun will also transform at 4:1 for a wide variation of load impedances.  Shown below are AIM 4170 SWR results for loads from 200 to 600 ohms.  This balun gives adequate transformation through 25 Mhz and acceptable transformation for an antenna tuner to tune in the differences from 1.8-30 Mhz.  SWR under 3:1 for most loads for selected frequency ranges.  Light blue vertical bars are ham bands starting at 160 meters at left to 10 meters at right.  Antenna loads are never a perfect 200 ohms on all bands, but vary in a range.  Get the BA-4-1500 balun to do the job right when converting from tuned feeder to coax.  Also remember to get a 1:1 balun for the shack on the other end of the coax.  Check website for various options.

 

BA-4-1500 Tuner Balun with loads of 200-600 ohms. SWR in red and Z input transformation in green.

BA-4-1500 Tuner Balun with loads of 200-600 ohms. SWR in red and Z input transformation in green.

Operate open or in a case of your choice. It is for use from 160 through 10 meters at full legal amateur power at 200-400 ohm impedances.

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BA-4-1500 Kit

 

Model BA-4-1500…………….$28.50

+ $10 S&H. Tax in Calif.

Note: $10 S&H is “per order”. Order more than one and S&H is still $10 (USA only).

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ASSEMBLED

 5000 Watt rated 4:1 CUBE Balun™ – Model CB-4-5000DC

This high power 50:200 ohm dual core current balun is actually designed for a 65:260 ohm making it useful for 75:300 and 50:200 ohm ranges.  We have measured it at 100, 200, 300 and 400 ohm loads with satisfactory conversion results capable of tunable SWR under 2:1 with an antenna tuner.  At 50:200 it has a virtually flat 1.2 SWR from 1.5 to 40 Mhz and has been used very successfully with a 160 meter OCF antenna (20% offset feed point).  With dual cores you get great frequency range, equal current in each leg and very conservative 5KW rating with Thermaleze™ wire covered with Teflon™ tubing for extra high voltage rating near 10,000 volts.

This balun is our top rated for OCF antennas, folded dipoles, Zepp, longwire, and multiband delta loop antennas.  A real workhorse with built in choking action for common mode rejection.

Housed in a 4” x 4” x 2” waterproof housing with SO-239 input and stainless steel eyebolts on the side with 12” wire tails for ease of connection to your wire antenna.

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CB-4-5000 5KW PEP, 1.5-30 Mhz Dual Core Toroid Current Balun

 

The CUBE Baluns™ are built to order and typical build time is two days after order received.

Model CB-4-5000DC (Dual Core – Balun)                  Price $65.00 (introductory price)

Model CU-4-5000DC (Dual Core – Unun)                  Price $65.00 (introductory price)

+ $10 S&H. Tax in Calif.

Baluns include side eye bolts (shown) for antenna connection, top eye hook (not shown) for halyard hoist, and 12″ wire tails for antenna connection

Note: $10 S&H is “per order”. Order more than one and S&H is still $10 (USA only).

The CB-4-5000 makes an excellent replacement for the MFJ OCFD antenna matching units that can not take high power – see testimonial below from a Flex Radio user who monitors multiple bands simultaneously from his OCF with the CB-4-5000.

Hi Bob,

Radio: Flex-6700 running barefoot -10 to 100 Watts max.
Antenna: MFJ-1216 – 160/80 meter OCFD wire antenna with matching network.
Elevation: Over 60 feet AGL – fully extended.
Installed: Mid November 2013

I operate mainly on the digital modes running less than 50 Watts.  All of the sudden after a few days operating with this antenna, I start to have RFI and my radio was acting up; such as changing bands, SWR changing values, radio failures and turning off. However, when I used my Hy-Gain 18 HT vertical on the same band none of the abnormality occurred.
I contacted MFJ and confirm that what I was noticing was a failure of their “matching network” AKA balun.  They offered no solutions. Then I contacted Palomar Engineers and bought the 1:1 new toroid RF beads.  I called Palomar Engineers and I happened to talked to you directly; regarding the on going issue with the MFJ antenna. I found out that the 1:1 balun was not what I needed (I was miss-informed by MFJ that it was 1:1 matching network.)
You offered to make the required balun 4:1 and the rest is history.

Here are my findings:

1. No more RFI displayed on the monitors.

2. Radio not acting up or turning off.

3. The SWR at 160/80 meter is 1.2:1

4. No antenna tuner required.  (radio goes to Bypass automatically.)

5. Worst SWR is on 10 meter with a 2:1 but still usable, with antenna tuner 1.5.

6. One happy OCFD user!

Thanks to Palomar Engineers design and engineering for solving this issue.

73, Ernest – W4EG