Credit for image.

I wanted to share an antenna build I found in a military book about ship antennas.

It is basically a 50′ wire and a 4:1 UNUN with a short ground wire.

For the radiating wire, I chose a 50′ section of #10 THHN.

To build the UNUN, I bought a FT240-43 Torroid and a waterproof Box from Amazon.

You will need one SO-239 connector which can be can be found here.

I drilled and mounted my hardware into the box as pictured below.

I like to use copper strap to tie the ground and SO-239 together. (Instead of the coax in the diagram)

It can be bought here for $4 per 10′.

Winding the torroid is 15 simple bifilar turns. I like to use this silicone wire.

If you follow the diagram, the wound torroid  should turn out like this…

It mounts in the box like this…

Chris and I used the air cannon to hang the 50′ vertical in a tree. A folding knife was used as a ground rod.

N4CPW making 40m contacts.

Video of 80m in early morning…




It was impressive how effortlessly the LDG auto-tuner matched 80/40/20/17/15/10. Looking back, I should have tried to tune 30m and 60m, but was taken into the distraction of chasing easy contacts on 80/40/20. I also should have tried the IC-7300’s internal tuner, but again, blame the aforementioned good time for not doing so. I should have run WSPR too. Darn.

N4CPW took the “UNTENNA” with him for further testing.

Maybe we can get the answers to those questions from him in a future update.


UPDATE: 72′ radiating wire vastly outperforms 50′ wire on 80m, and allows a good tuner to use 160m.

We call this version the KW4RD antenna because it was developed with extensive testing by Ronnie Flemings.

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