HAM RADIO: The 64:1 EFHW Transformer build. 49:1 and 64:1 UnUn builds

For those confused why 8:1 turns ratio becomes a "64:1" transformer, it's because the voltage ratio is in proportion to the turns ratio, and the current ratio is in inverse relation to the turns ratio, so the IMPEDANCE ratio is in proportion to the turns ratio SQUARED. In this example, the voltage on the secondary will be 8x higher, and thus (conservation of power, sort-of) the current will have to be 8x less (as power is conserved, ignoring losses), so the impedance at the secondary Z = E/I = 8x / (1/8x) = 8x8 or 8^2 = 64x. So 50-ohms nominal would become 3200-ohms. Thus approximating the characteristic impedance of a half-wave antenna over real ground.

Would ,like to see a sweep with a VNA .

Thanks for this video and detailed explanation of how everything connects.

Excellent craftsmanship as always Mike ! Keep the videos going they are worth waiting for .

Thank you You where very clear, Concise, explained the calculation formula well

Fantastic build! Looking forward to the testing before I wrestle with the wire hahaha!

What a beautiful piece of work... 👍👌

Hello Mike, enjoyed winding this Transformer this morning and getting tangled up in wire and twine! Measure twice cut three times haha! I used 2mm wire but forgot that twisting the wire shortens it a bit, third time success. That’s a great way to twist the wire with a drill. 2mm wire is the absolute max to use although winding it wasn’t too difficult. Thanks for your videos on previous projects. 73 Alex M0KVA

Beautiful work!

Great vid Mike, I have been looking at building a 49:1 for /p on holiday. This looks really nice though in the clear lid box.

Excellent video. Very educational. Please do the LED version.

amazing video - soso helpful! i am intrigues to see finally what the difference between 3 to 24 turn VS 2 to 16 turn is ! thank you for doing this - this is GREAT Clear, detailed amazing

Gracias por el vídeo. Un like para tí.

Nice job Mike. I sure do like the clear top case. Every time I go out and check my EFHW I have to take the cover off. The clear top case would make checking my EFHW so much easier. 73 Joe

Great !!!

thank you for your educating videaos,..super glue between the toroids would be helpful

Hi Mike, Excellent job winding the toroid with the enameled wire. Didn't notice if the box has a seal for the lid. If it doesn't, wrap the seam with electrical tape. You and the family stay safe. 73 WJ3U

Have you checked the coverage and insertion loss above 14MHz, the 3 turns/24 turns on two 240-43 cores are good only for 160-30m.

I have ordered the EFHW 8010 kit from HF kits via ARRL. I have been interested in the EFHW for portable work as it can be resident on all the bands. I will need to make decisions on the low bands (SSB or CW) because of the high Q factor. Nice build

0:27 "...three primary followed by 21 secondary..." <- Odd description. If the first three turns are bifilar and thus include both primary and secondary wires, then it's confusing to refer to them as if they're only "primary". In fact, in the usual construction, those first three bifilar turns are both primary AND secondary. The subsequent turns are a continuation of the secondary. Minor nitpick. :-)