Model 36130 - 36:1 for EFHW, 150 watts

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  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
  • Model 36130 - 36:1 for EFHW, 150 watts
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After much research and testing, a new transformer design for End Fed Half Wave (EFHW) antennas has been achieved. Developed by Bob Glorioso, W1lS and Bob Rose KC1DSQ, they discovered that most transformers for EFHW antennas used higher impedance transformations than necessary and were wound in a way that limits the high frequency response of the transformer. By utilizing their capacitive loading technique developed for OCF antennas, they created an EFHW antenna with low SWR on all bands 80-10m. In addition to their capacitive loading, the "Bobs" also found the most important thing to make EFHW antennas  work consistently on all bands was the need for a properly sized counterpoise as shown in the diagrams above.

For optimum performance with this new design, a quality 1:1 choke balun is integral to the overall installation. Depending on your decision for which counterpoise option you will use, the choke balun is installed either immediately behind the EFHW transformer or at the end of the coax length recommended when using the coax shield as your counterpoise.  All air wound coax choke (aka Ugly balun) and many commercial units are unable to provide adequate choking for proper operation of this unit.

We are offering the transformer either by itself, with just the excellent surface mount load or with both the load and our new dual core model 1110du choke balun that provides 30-36 db of suppression for 80-10m.

The SWR plots shown are applicable ONLY when capacitive loading is used as described in the article referenced below.


The enclosure for our low power units is small, lightweight and portable but is not weatherproof  and not intended for long term or permanent outdoor use. If used in a permanent outdoor installation, additional attention must be given to weatherproofing and strain relief. Damage caused by such use is not covered under our warranty.

Complete design and installation recommendations are available using the link below to view the authors' CQ article. 
Please be sure to carefully follow the Installation Notes when installing the choke balun.

Installation Notes


  Core Material   Medium mix permeability toroid by Fair Rite Products for maximum bandwidth.
  Winding Type   Single toroid with winding configured as 36:1 auto transformer
  Downward impedance transformation by factor of 36.
  Winding Material   16 gauge Superior Essex Heavy build polyamideimide Allex 240 Winding Wire 
  Power Rating

  3 to 31 MHz - up to 150watts intermittent (50% duty cycle)  FT8 - 50 Watts

  Useable Frequency   3 to 31 MHz
  Insertion Loss
  0.3 to .5 db based on frequency
  Connectors   SO-239 connectors are nickel plated with Teflon insulation.
  Alternate connectors and Mounting Options are available in the Accessories section.
  Hardware   All Stainless Steel
  Enclosure Type
 Polycarbonate (ABS) enclosure with bottom plate that fits flush with the case.
 Bottom plate is an exceptional fit that can be easily weatherproofed if desired.
 Dimensions   Very compact and lightweight 3x2x1.5 inch -  Link to dimensional drawing
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