A shortened, 20-foot  half wave vertical
With toroid loading coils
June 21, 2007


This is an idea I have wanted to try for some time. It is a shortened, end-fed half wave antenna that I will use on my backpack and marine mobile outings. Normally I use PVC tubing to make the loading coils. This time I replaced them with small toroid coils. For each coil I glued two T50-2 cores together and wound 25 turns of #24 ga. enamel wire. Actually I started with extra wraps then removed turns until the antenna centered on 14.250MHz. I would have preferred to use heavier wire and larger cores, but it was what I had in the junk box. Here is a closeup of the tiny 1/2" coil against the Cabelas 20-foot support pole. The ename wire at the bottom is twisted from the extra wraps being unwound from the core. I may shrinkwrap the coils later to protect them from the elements. How did it work? See report below the next photo. . . .


I had only a short time to test the new antenna this evening. With five watts from my Yaesu FT-817, I made it from Colorado to Washington D.C. and Dan, NE3Z, who sent me a 5x6 report. This was excellent considering the SFI was 66, the K index was 3, and there was deep fading on the band. Afterward I called CQ and was picked up by AB3DD/mobile in Maryland. He gave me a 5x4 from his car compared to his 5x6 mobile signal.

I was in the front yard surrounded by 35-foot trees on either side and the house just fifteen feet away. The tuner was my homebrew parallel match unit seen here at the bottom of the page. I noticed in tuning that, unlike my larger PVC core coils, I had to retune as I moved across the band, indicating a higher Q value in the toroids.

Below the next photo are the dimensions I used to make the antenna. I hope to try this on 30 and 40 meters and maybe use plug-in coils.


I used #24 ga. stranded wire for the antenna itself. Why 24 gauge? Because I bought a 5,000-foot roll at a hamfest for $10. There are three sections of wire. The center length is 10 feet, 8 and 3/4 inches. The two coils attach at the ends of this wire. Then, the two outer wires are both 4 feet, 4 and 5/8 inches long. The antenna is fed at one of the ends. The actual total antenna length is 19.5 feet to fit the fiberglass pole I will use while operating pedestrian mobile.

----------------///------------------------------------///----------------[M] <match unit

Jake,  NØLX

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