20/30/40m End-Fed Half Wave Antenna EFHW
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20/30/40m End-Fed Half Wave Antenna

September 6, 2020

This project was inspired by George Cooley (NG7A) whom I met as a guest speaker during one of our Morse Academy sessions. He described his favorite goto SOTA antenna he uses during his own activations.

The technical description and build instructions are described on his web site in an article entitled: SIMPLE BACKPACK HF ANTENNA -- GET ON THE AIR IN JUST 15 MINUTES.

My project takes his idea and implements it in a slightly different way with the goal of getting the same results.

Building The Matching Transformer

There are a couple of ways to wind this FT-140-43 and different types of wire that can be used. Those methods are discussed in the NG7A article. My decision was to use a classic winding technique of twisting the primary and secondary for the first number of turns. I used a 24 gauge copper enameled magnet wire I purchased on eBay but I could have used any kind of wire. I prefer the magnet wire because it keeps its shape more than other types of wire.

Following the instructions provided in the NG7A article, I tuned the transformer to the 33 feet of wire by gradually removing 9 turns from the secondary winding leaving 15 turns.

I could not get down to a 1:1 SWR like in the NG7A article but I got it down to about 1.17:1. Considering that this was a 33-foot vertical antenna mounted on a 28-foot travel mast, the wire was not perfectly vertical, the type of wire I was using was a Kevlar-reinforced Antenna Wire of 6x26ga strands wound around Kevlar fibers, a wire of unknown velocity, a different brand of antenna analyzer, etc, I had to settle on a slightly higher SWR than what was achieved in the NG7A article.

The goal was to tune the transformer to the lowest possible SWR. The result I obtained was good enough for now.

For the tuning exercise, I soldered a BNC connector to the primary of the transformer and soldered the secondary directly to the 33-foot wire. To improve portability and robustness, the transformer assembly needed to be put into a box of some kind.

I found a junction box on Amazon that was perfect for the task of, providing a chassis mount for the BNC connection and a way to firmly attach the antenna wire to the transformer with enough strain relief that the box could be suspended from the wire. I used an eyelet and a tent guy line tightener I had in my junk box.

The wing nuts are used for connecting the antenna and an optional counterpoise to the junction box.

Tuning the Antenna on 20m

Once the transformer is tuned and connected to the wire, the antenna needs to be tuned to resonance for the 20 meter band. In his article, George recommends tuning for the best SWR at the resonant frequency of 14.060Mhz. Looking at the bandwidth I had on this antenna, I tuned it 50Khz higher, 14.110 for an SWR of 1.39:1

Building the Coils

There are two coils to build, and insert 5 feet from the end of the antenna. I had a really good experience trying different methods of building air core coils. I spent hours playing with stuff but came to the conclusion that the best coil for this antenna had to be rugged, light weight and it needed to be strong enough to hold the weight of the rest of the antenna on a windy day or yanked from trees or whatever from either end of the antenna.

The Kevlar reinforced wire use for this antenna was rated at 125 lbs. The coil assembly needed to match the strength of the wire it was attached to. I opted to build the two coils on one piece of thin walled PVC pipe of about 8 inches in length. This is a divergence from the original NG7A design which uses two separate coil assemblies.

The plan was to make one coil with tapped sections for the different bands.

The 30m Coil

Following the instructions, I cut 5 feet of wire off the end of the antenna, taped it to the end of my PVC and I wound and tested the first coil to resonate the antenna on 30m. After a few hits and misses, I finally got it right and found an SWR of 1.7:1 at 10.100Mhz. It took 39 windings to reach the sweet spot, two more than mentioned in the NG7A document.

This is where things get a little strange. This best SWR can only be achieved with the wire straight down and taped to the mast at about a foot from the ground. The picture of my antenna shows the tape that I used to hold it together. I suspended the transformer and the feed line on the end of one of my walking sticks.

On a slope, the best SWR achieved was about 3.5:1 or more depending to the angle of the slope. Enters the counterpoise. By adding a counterpoise, I could stabilize the antenna to an SWR of about 2.0:1 no matter what angle of slope I had. The optional counterpoise was a good idea. Without it, everything around the antenna is the antenna, including the tester and they guy holding it.

The 40m Coil

Keeping true to the documentation, I wound 60 turns of wire on my PVC and tested it. By the time I was done, I had 57 turns of wire, the same number of windings as the 40m coil in the NG7A paper.

On 40m the antenna worked really well as a sloper or tied to the mast. With the counterpoise, it was very stable and easy to measure. I took off the counterpoise to see if it would change the resonance and it didn't so there... this makes the counterpoise a mysterious option for the twilight zone's 30m band. My best SWR on 40m was 2.37:1 at 7.100Mhz. Not bad, good as is or even better with my built-in ATU.

Mechanical stuff

The coils I made are taped using Super 88 electrical tape. The PVC I used is the same PVC I used for making a twin-lead J-Pole vhf/uhf antenna I have on my house. The external diameter is 1.1" and it is sold only at Lowes as a 3/4" Light PVC.

I installed 3 taps on this long coil using standard electrical spades, crimped and soldered. I use a good quality alligator clip for connecting the 5' end of the antenna. I added some strain relief on both ends of the PVC but adding a couple of holes, 1 cm apart, into the pipe to feed the antenna wire through. I added a Velcro strap to wrap the coil around the mast to stop it from flopping in the wind.

All in all I am quite happy with the coil I made.

Test Environment

I built, tuned and tested my new antenna using a SOTABeams Travel Mast, 28 usable feet high, and a SOTABeam Guying Kit to hold up the mast. The bits and pieces and the winder that come with the kit are really useful for building this antenna.

Notice the piece of tape one foot up from the bottom? That's my Twilight Zone tie down... I used a collapsed hiking pole to hold my feed point above the ground. I used a 4-foot bnc cable and my MFJ 225 antenna analyze that is laying on the ground in the foreground. The temps that day were over 100F. It was a sweat building exercise.

Test Results

These are the measurements taken at various steps of the way.

 Band Frequency SWR
---- ---------- ------
20m 14.110 Mhz 1.27:1
30m 10.101 Mhz 1.71:1
40m 07.100 Mhz 2.37:1

These measurements are "best of" measurements. There are many variables that can change these numbers such as soil, moisture, proximity of other objects, counterpoise in some instances etc.

No matter how hard I worked at it, this antenna will probably need a tuner but in a pinch it will work without one if it is treated with "respect and understanding" for the quirks I noticed when testing it.

The Final Assembly

This is the resulting assembly with the antenna and the guy lines wrapped up around the winder that comes with the guying kit. This antenna is very portable, weighs in 15.8 Oz. including the stakes, the guys and the bag to hold it all!

Not bad!


  1. “Homebrew Your Own Inductors,” by Robert H. Johns, W3JIP, QST, Aug 1997
  2. "The Real SWR Page"
  3. "EFHW"
  4. "Specs for FT140-43 RF Toroids"

Parts List

Description Qty
¾ inch Class 200 PVC pipe (Lowes) 8"
22 AWG Gauge Enameled Copper Magnet Wire (eBay) 5'
FT-140-43 (kitsandparts.com 1
Kev-Flex Stealth Kevlar-reinforced Antenna Wire (eBay) 75'
Tulead Junction Box Case 2.52"x2.24"x1.38" 1
BNC Female Chassis Panel Mount Solder Nut Bulkhead Jack(eBay) 1
Liberty Mountain Aluminium Guyline Adjuster (Amazon) 1
Alligator Clip (Amazon) 1
Tulead Junction Box Case 2.52"x2.24"x1.38" 1
BNC Female Chassis Panel Mount Solder Nut Bulkhead Jack(eBay) 1
8-32 x 34" Long screw 2
8-32 Wing Nut 2
8-32 Hex Nut 4
#8 Lock Washer 2
Eyelet to suit 1
3" Nylon tiewrap 1
Roll of Two-Sided tape (PVC wire wrap grit) 1
14 gauge Electrical Spade 3
Sotabeams Multifunction Guying Kit MFGK-103 1


  1. Box cutter
  2. Wire strippers
  3. Long nose pliers
  4. Phillips screw driver
  5. Wire cutters
  6. Solder and Soldering iron, low wattage
  7. Drill and drill bits
  8. PVC Cutting tool
  9. Optional epoxy and thread locking fluid to ensure nothing loosens up with use wile on the trail
  10. Roll of Super 88 electrical tape