The End-Fed Eighth-Wave (EFEW) Wire Antenna – A Figment of My Imagination

I am a huge fan of the compromised antenna. I like to bring the power on my transceiver down from 100 watts to virtually none simply by using a highly wasteful, inefficient antenna system. And its all because my need to operate out in the wild with the simplest, easiest deployment method far exceeds my desire to be fussy about my antenna. And then AA1F started successfully making POTA activations on 80M with his commercially produced 20M end-fed halfwave antenna (using an antenna autotuner). And I thought to myself, well if a half-wave of 20M is an eighth-wave of 80M, would an end-fed eighth-wave of 40M work on 40M?

So, I went ahead and built a 5M radiator (about 15 1/2 feet in length) and attached it to my homebrew 49:1 unun and strung it from one fence to the other in my backyard, about 4 to 5 feet off the ground. Electrically, the radiator appears slightly long on 40M (meaning the trough of the SWR curve around the 40M band is slightly lower in frequency than I would have liked to see), but the SWR sits around 4:1 across the band regardless. This means that with an autotuner, it is a perfectly matchable impedance. The SWR graph is below. Remember on the RigExpert Zoom analyzers, each blue vertical band represents a ham band.

And for comparison, the SWR graph (below) for the diy 20M end-fed halfwave antenna is electrically long at 20M, electrically short at 40M, and has a dip between 5-10 SWR at 160M. If the length of the radiator was corrected to be resonant at 20M, would the 160M dip reside closer to 80M? The commercially produced 20M end-fed halfwave that AA1F favors does have an SWR dip of around 5:1 at 80M.

Now I just need to see if I can make a 40M contact on this 40M end-fed eighth-wave (EFEW) antenna. There are some real benefits to having a short antenna for portable ops, and it would be really neat if this works. Because a 20M wire antenna that is little over 8 feet in length is kinda dreamy too.

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