"The Simple Build" 80, 40, 20 Meter EFHW Shorty Antenna

 

 

 

 

By Tim Wallace, VA7PD

Let's get started!

Whether your building an EFHW antenna for your yard or for portable use, this antenna will do the job for you very well and can be used horizontally or as a sloper. The entire length of the antenna is slightly less than 75 feet with the 80 meter portion providing 50 khz bandwidth. This project is modeled on M0MSN's 80m EFHW build on YouTube, thanks Mike!

Check out the photos to get a better understanding on how to build this cool project.

Step 1:
Wind the 80 turn coil with 18 gauge magnet wire. Leave a few extra inches hanging out before starting the first turn, then while winding keep the wire tight with each previous turn. I like to tape the first few turns just to help keep windings tight. When you have 80 turns wound, keep an extra few extra inches hanging out, then tape that end as well, this will keep the whole coil from loosening. Next drill two holes in each end of the tube and install anchor points and solder ring crimp terminals with insulators removed (see photo). I used solid copper wire for the anchor points but you can use the 14ga stranded copper wire if you have no solid wire. Next solder the wires at each end of coil to corresponding anchor. Don't forget to remove enamel insulation from wire ends either scraping with a knife or using some sand paper before soldering. If you have an LCR meter you should get a reading across the coil of approx 110 uH. Then wrap coil with electrical tape to protect the wire.

Step 2:
Cut 66 feet of 14ga speaker wire (40m) portion of antenna and solder two ring crimp terminals to the input end of the antenna (see photo). Hold off installing ring terminal to the far end until you prune the wire to the exact length producing lowest SWR on desired portion of 40m. You will want to prune the 40m section with coil attached, I twist the end of the wire thru the coil's ring terminal till I'm done pruning, then I install the antenna ring terminal with solder then install coil to antenna with a stainless steel machine screw and nut.

Step 3:
Cut 74 inches of 14ga speaker wire for the 80m portion and install ring terminal then attach to coil with machine screw and nut. Prune far end of 80m wire for middle of desired portion of the 80m band then install ring terminal connector. I use #36 braided nylon decoy line to suspend the antenna, but you could use any kind of cordage as long as it's non-conductive. Remember, you may get some stretching using speaker wire. I recommend 18ga Poly-Stealth copper clad steel aerial wire but its very expensive. Your final measurements will probably be a little different than mine due to differing height above ground and soil conditions.

My tuned numbers using my 64:1 transformer:
80m Resonance 3.7 Mhz, SWR 1.7, resistance 53 ohms.
40m Resonance 7.14 Mhz, SWR 1.1, resistance 55 ohms.
20m Resonance 14.0 Mhz, SWR1.7, resistance 42 ohms.

73 de Tim

Disclaimer: These are projects that I build for myself and don't mind sharing with like-minded hobbyists. Comments, feedback, etc. please contact me at va7pdz@gmail.com

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