Let's Build an EFHW Antenna
If you attended Field Day 2022, you may have been one of the students that learned how to build an end fed half wave Antenna and actually got to build one and take it home. For those that were not able to do so, this page is for you. Building antennas is a fun learning experience for any ham operator and one that will serve you well for many years. Knowing how to build an antenna also saves you a bit of money from buying the commercial ones online that can range from $40 up to $180.
It is just an overall good skill to have under your belt.
As promised in the class, I am making the build details available to you if you so choose to build one. They are not hard to assemble and with a few minor skills you are going to end up with a very nice antenna.
Supplies for building an EFHW Antenna
Some of the items below are links to purchase supplies from reputable dealers
- 68 feet - Antenna Wire 22-24AWG - Sotabeams - $19 shipped to your door - LINK
- Alternative Wire: Stealth Wire is also a good choice ------> LINK
- 140-43 Toroid (This will match the one used in the class and is locally available) LINK
- 240-43 Toroid (If you want to be able to push more power) LINK
- 3.5 ft - Magnet Wire - Amazon is a good source. For the 140-43 use 18-20 gauge, for the 240-43, use 16 gauge
- Wire Winder Assembly STL File (3D Print) - LINK
- 100Pf 10KVDC Capacitor - LINK | Alternatively, you CAN use a 100Pf 4KV Capacitor instead
- 100Pf 15KVDC Capacitor - LINK
- 8-32 Screw 1 1/4" (1), #8 washers (2), 8-32 Wing Nut (1), 8-32 Nut (1)- Find at Home Depot or Lowes
- SO-239 Bulkhead connector W Ground ring - Check EPO, Amazon or Ebay
- S-Biners - for easy deployment on a pole , etc... - LINK
- Fiberglass Pole for Deployment - I use Spiderbeams poles 10M- LINK
NOTE on 3D Printing the Winder
Living in a hot climate area like Texas, things tend to melt. I highly suggest that if you are going to 3D print this, that you use Tough PLA. It is rigid and heat resistant. That last thing you want is for the SO-239 to fall off your antenna while operating. I used 100% infill on my print and it took my Creality CR10-S about 7 hours to print the winder. No adjustments need to be made and you can print it as it. However, if you wish to experiment and are good with 3D software like Tinkercad, feel free to modify it to your needs.
Tools You Will Need
- Soldering Iron and Solder
- Wire Snips & Wire Strippers
- Pliers
- Sand Paper or Emory board
- Drill & Drill Bits
- A small stick, a micro screwdriver or you can use your drill carefully to wind the wire in part of the build
- Antenna Analyzer - I prefer the Rigexpert for the quality and precision, but you can also use a NanoVNA or an MFJ Analyzer which will be cheaper in cost.
Build Instructions
PART 1
- Measure antenna wire 4.5 inches and double over
- Using larger of the ring terminals, pass wire through and loop over ring
- Crimp
- Attach the loose end wire to the smaller ring terminal
- Crimp and solder
PART II
- Measure out 8 inches of magnet wire and fold over
- Measure up 2.5 inches of the loose end wire and bend 90 degrees (see video), carefully hold with pliers and twist the loop
- Snip off loop after twist is complete
- Wind Toroid keeping your windings tight to the toroid and NOT overlapping or kinking up the mag wire(see diagram)
PART III
- Install SO-239 to wire winder paying attention to direction of ground tab
- Mount Toroid with zip ties
- Measure toroid wires to each of the SO-239 terminals, make your cuts
- Scrape off magnet wire coating on all three wires (TX, GND & ANT)
- Snip capacitor and prepare for solder
- Solder toroid twisted wires and capacitor to ground ring
- Single wire and capacitor go to center connector on SO-239
- Hot Glue SO-239 connections and wire (Optional)
- Attach Antenna wire to antenna frame winder (See Video for Sequence)
**TUNE ANTENNA TO THE MIDDLE OF THE GENERAL PORTION OF 40M BAND 7.237
You should be good for 40, 20, 15 & 10 Meters.
Enjoy your EFHW Antenna!
