Model 36130 - 36:1 for EFHW, 150 watts
- Calculated at Checkout
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 found it 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 commercial will NOT provide enough 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 a special dual core model 1110d choke balun that provides 30-36 db of suppression for 80-10m.
The enclosure for our low power units is small, lightweight and portable, but 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.
|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.
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|