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Balun Designs

Model 55131 - 55:1 for End Fed Half Waves - Up to 1kW


Model 55131 - 55:1 for End Fed Half Waves - Up to 1kW

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Product Description

For those that enjoy the LNR and Hy Endfed antennas, but want to run more power, Balun Designs now offers an excellent alternative.  Built with the same craftsmanship as all our other units, this new model will allow you to either replace your current matching unit or construct a new higher power end fed half wave antenna. We have also installed an additional stud which can be used for a separate counterpoise rather than forcing the use of the feedline's coax shield.  The suffix "e" configuration also includes the wire clip as shown but does not include wire. Wire is shown for demonstration purposes only.

Most end fed half wave antennas have an impedance between 2500 and 3000 ohms so we have designed a unit to fall in the middle of this range.  Creating a very low SWR match is accomplished by adjusting the overall length of your antenna. The capacitor as shown in photos may change depending on availability.

Caution: When used at full power rating of 1kW, the antenna must have a low SWR on the band selected and be used on a 50% duty cycle.  Any SWR measurement taken with the transformer at the feedpoint should not exceed 1.5:1 with NO tuner in use.  There are numerous configurations available online that will accomplish this on multiple bands (Google search "end fed half wave antennas").  If the transformer is used with an external tuner in conjunction with a single wire antenna typically 130-135 feet in length, power should be reduced on those bands that show an SWR above 1.6 to 2:5 without the tuner.  A level of 500-600 watts is the maximum with a further reduction on any band measuring above 3:1.

If you would like to use high power up to legal limit with a single end fed wire antenna (not necessarily a half wave) consider using our Model 9135 along with one of the wire lengths shown in the Installation Notes.





  Core Material   Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
  Cores are coated and sealed for long term durability.
  Winding Type   Stacked cores with winding configured as 55:1 auto transformer
  Downward impedance transformation by factor of 55, i.e. 2750 ohms to 50 ohms.
  Winding Material   14 gauge Superior Essex Heavy build polyamideimide Allex 240 Winding Wire
  Windings are inserted into Teflon tubes increasing total breakdown to 10,000 volts.  
  Power Rating   1.5 to 31 MHz - up to 1kW intermittent (50% duty cycle)
  Useable Frequency   1.5 to 31 MHz
  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
 Dimensional Drawing of Standard Enclosure