Model 64131e - 64:1 & 49:1 - 80-10m EFHW - Up to 1kW

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  • Model 64131e - 64:1 & 49:1 -  80-10m EFHW - Up to 1kW
  • Model 64131e - 64:1 & 49:1 -  80-10m EFHW - Up to 1kW

Vacation Closure until Aug 4th


For those that enjoy half wave end fed 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 wire rather than forcing the use of the feedline's coax shield

In addition, this model provides both a 49:1 ratio PLUS a 64:1 ratio for those who find their particular installation has a higher feedpoint impedance. Please note that both ratios cannot be connected to an antenna at the same time.

This transformer is designed to be used with an end fed half wavelength of wire only.  The length should be calculated based on the lowest frequency to be worked.  So for example 80m could range in length from 120 to 133 feet.  Use with other lengths can potentially damage the transformer depending on power level in use. 

Attaching a counterpoise wire to the common point of the auto-transformer provides the antenna radiator something to push against rather than the coax shield. The counterpoise wire does not have to be similar in length to the main radiator and the antenna works best with counterpoise length of 0.05 λ on the lowest band the antenna is cut to.  This calculates to ≈ 12.5 feet for an 80m end-fed.

"Just received my new 64131 yesterday and was anxious to see how well it performed.  I connected it to a 33’ wire running from my balcony, through the trees, and ran WSPR overnight to check things out.  Performance is ASTOUNDING, far exceeding my expectations.  I have included a screenshot showing the stations that reported spotting my 200 mw beacon over the last 16 hours.  The WSPR map is so dense it looks like the US and Europe are just big blobs of color. At this point, I’ve only used the 49:1 tap, but plan to take the 64131 whenever I operate portable.  Having the option to switch rapidly between 49:1 and 64:1 should prove to be a really nice feature.. Thank you so much for such a great product!

P.S.  Antenna details:
Approx. 33 ft #18 insulated copper wire (20m half wave)
Avg height: 20 ft.
Counterpoise:  1 meter coax (0.05 x wavelength) connected between 64131 and Balun Designs 1115d Isolation /Choking balun
SWR measured at feedpoint:  1.1:1"



"I received my third balun from Balun Designs this afternoon.  Following the directions exactly as specified (0.47wl / 0.05wl matching counterpoise) and drilling two weep holes in the appropriate position, I had a 10 meter EFHW antenna up in less than ten minutes.  I made just a touch over 100 QSOs today with the new unit.  I'm consistently pleased with the quality and ease of use of Balun Designs products and look forward to my next purchase in the future.

Thank you!


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 or high digital use such as FT8.

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 49:1 auto transformer
  Downward impedance transformation by factor of 49.
  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   3 to 31 MHz - up to 1kW intermittent (50% duty cycle)
  Useable Frequency   3 to 31 MHz
  Insertion Loss
  0.3 to 1.65 db based on frequency
  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
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