Bret from YouTube channel SurvivalComms published a comparison of several EFHW transformers. He too found the Fair-Rite 2643251002 to be a superior performer.
My only critique is that back-to-back testing of transformers isn’t good for absolute testing of transformer loss. Testing this way includes mismatch loss that would otherwise be cancelled out by a tuned wire. The mismatch loss I’m referring to is like running a high SWR coax on your coax and exaggerates how lossy these are.
Bret’s testing is a good relative comparison though and his thermal testing clearly shows how lossy the common design on an FT-240-43 toroid is. I need to get around to some thermal testing on my 81:1 UNUN.
Having passed around my EFHW design for some third party testing I will say a high efficiency design isn’t for everyone. More thoughts on that in a future post.
73,
Padre
The Orderwire 