How efficient is the best 100w End Fed Half Wave Core when stacked for QRO? #hamradio #antenna

Link to the 2643251002 core on Mouser https://www.mouser.co.uk/ProductDetail/Fair-Rite/2643251002?qs=MLldULe7zY21cbRcW1YXeQ%3D%3D Link to the spreadsheet of results https://docs.google.com/spreadsheets/d/1OCBE5aVc_kkPXRaPDy-xGL7LLEAjUilN/edit?usp=drive_link&ouid=111484348574912642065&rtpof=true&sd=true How to measure core efficiency with the back to back method https://youtu.be/TZjY2Jim7fY