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Balun Designs

Model 4124 - 4:1 Tuner Balun 1 - 45 MHz 5kW


Model 4124 - 4:1 Tuner Balun 1 - 45 MHz 5kW

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Product Description

Jerry Sevick (W2FMI) specifically researched and designed this balun to provide a very constant 50 ohm input impedance on the lower frequencies where most baluns can drop by 20-40%.  In addition, the Thermaleze wire/Teflon tube windings on a large iron powder core allow the balun to handle large swings in impedance and high temperatures with ease. 

All of these features make the unit very unique and rugged while literally providing the best of both a current and a voltage winding design when used with a balanced antenna.  This model is especially effective on the low bands and can provide enhanced matching capability where other baluns fall short. 

If you have a tuner with a bad balun or a homebrew tuner in need of an excellent 4:1 balun, this is the perfect model. The model 4124x has no enclosure or connectors and provides a balun that is extremely rugged, almost immune to heat and can handle the full HF frequency spectrum. 

Balun Designs offers this unique balun using a three inch double height core. This larger size provides the necessary increase in inductance for enhanced performance on the low bands while maintaining the same wide bandwidth up through 54MHz.  Dr. Sevick's research showed that, when used with a balanced antenna, this balun provides current balance normally found only in a current winding.  This design can be used with doublets, extended Zepps, large skyloops and is a good replacement balun for Super Loops.

Please review the impedance curves in the graph below to better understand the efficiency and response of this balun.

Click to Enlarge



  Core Material   Large 3" DOUBLE HEIGHT iron powder toroid for excellent low frequency performance.
  Core is coated and sealed for long term durability.
  Winding Type  Single bifilar wire pair wound as 4:1 tuner balun.
  Winding Material   Heavy gauge polyamideimide Allex 240 Winding Wire
  Windings are inserted into Teflon tubes increasing total breakdown to 10,000 volts.  
  Power Rating   1 to 35 MHz - 5kW, 7kW intermittent.  35 to 54 MHz - 4kW.  
  All ratings based on resonant load. High SWR will reduce power handling ability.
  Useable Frequency   1 to 45 MHz
  Insertion Loss   Less than .02db
  Connectors   SO-239 connectors are silver plated with Teflon insulation.
  Studs and eyebolts are 1/4 inch.
  Alternate connectors and Mounting Options are available in the Accessories section.
  Hardware   All Stainless Steel
  Enclosure Type   NEMA rated 4x marine grade junction box for outdoor installations.
  Cover utilizes integral neoprene gasket for weatherproof integrity.
  Dimensions   4x4x2 inches for main body of unit
  Additional Info   Very high efficiency (98-99%). 
  Iron powder core is very tolerant of high temperatures.

Installation Notes