https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/

https://qsl.net/nf4rc/2020/ResonantEndFedUnUnConstructionManual.pdf

https://noji.com/hamradio/pdf-ppt/noji/Noji-Article-80-10-EF-HW.pdf