EFHW Transformer - without capacitor: alternative winding pattern

Great video again, Manuel. I never done KN5L method on FT82-43, only on FT114-43 and FT140-43. I noticed that efficiency on single FT114-43 was 86-89% 28:4turns, but the same KN5L method on 2xFT114-43 was 92-93% on 80-15m and 89% on 10m band. I think it is worth trying stacked FT82-43.

without a capacitor is better for wide band operation !

Awesome video, thank you for the idea! I used a FT114-43 I am on a peak today with contacts Arizona to Florida. It works great!

what value for your dummy load over antenna and earth terminal please ? the resistor ?

Could the ohmic loss in the primary be a reason for low efficiency when tested with 5W input? It's half the thickness of a traditional bifilar winding and will be carrying 7x the current of the secondary.

Can i do with 140/43 toroid? Thank's

👍Thanks for sharing.
Is that x5 15K parallel resistors (3K) load you have?
I have made some UNUNs for EFHW where I ended up doing a similar thing to get a good match. In my case, I wound the primary turns over the secondary turns.

Nice experiment, why is there only one connector (Antenna) ? There should be another connector for the receiver, right? How does this work?

Thanks for the video!

Hello, the main measure is missing: the insertion loss!
Assemble a second identical transformer and connect the two high impedance secondaries together. The primaries will go to the two ports of the VNA. Measure the transfer loss (Gain) and divide by two. Those who do not have a VNA can do the same test with an rtx, a power meter and a dummy load. Let us know. 73s.

Danke

I'm loving these! Thank you for sharing!!

Excellent work winding the core, Manuel!👍
I know your fingers must have been approaching ‘cramp-threshold’ after all those previous attempts!👀
Mine would have been.
Hope the TX results will be fruitful.
These videos really give a boost to real-world QRP ops!
73

Nice video. Please, AWG number? Thanks, Friend. 73 PU2AOO

Merci Manuel! I’m anxious to see you measure the real losses at 5 watts. I am starting to think that the losses on the transfo for efhw are enormous, and nobody realizes it. Good work Manuel, Best!

While I'm sure you can add sufficient capacitance by increasing the inter-winding capacitance this way, what I am curious about is any efficiency differences between the 2 different coil making methods, the bulk capacitor vs distributed capacitance. I have lots of capacitors on hand to use, but I'd like to use whichever method works best. Would you do an efficiency test for us in order to compare the 2 coils when you have an opportunity? Thanks.

I enjoy this series! vy 73 de Mike

Thanks for the video Manuel! I tested the KN5L windig after your hint as well this afternoon. And compared it with the "normal" 3to21 and 4to28 winding on a Würth core (similar size as a ft82). With the KN5L winding and 4to28 I got good results and even better with a 33pF capaciator. The würth core has a lower AL than the Amidon. I will test tomorrow also your Suggestionen of 3to21.
But according AF7NX, there is maybe one general downside with this winding pattern.
You will physically cross the low site (GND connection) wire with approx. 1/3 of the high site wire on the core. So this wires are very close and can have voltage difference of >210Vpp @10W and more. What do you think?
73 de Jan

Well, now to dig out my spare cores and . . . Thanks for the hints. 73 de W8IJN

That is something new to me hehe. In the notebook now for more experiments to make 😁. Thanks for sharing. 73