Antenna building #2 - EFHW Antenna - figuring out the right core size

00:00 Introduction
00:40 Transformer core sizes
01:58 SWR measurement over artificial Load
02:33 Insertion loss measurement
03:14 Insertion Loss under power
03:38 Thermal cam under power
05:14 Insertion loss with NanoVNA
06:02 discussing results SWR
08:16 discussion NanoVNA insertion loss results
09:12 Power loss in broadband transfomer
10:25 discussing measurement under Power
11:07 comparison NanoVNA / Power measurement
12:20 core heating
12:35 conclusions
15:34 wrap up / outro

Link to Jan´s GitHub:

[MYtimeNspace]

Great job i found simular results also by putting them back to back using a VNA.
Many videos telling you to twist the primary windings of 49 to 1 I found that this causes high losses in the 10 meter band. I also found it necessary to vary the turns depending on core size.
Happy to see someone else verifying the work I have done. Your a better man than I, as I haven't had the time to publish anything. Great job!!!
Rob A N7RBC

[Dazzwidd]

Excellent research, great job. I love it when people go the whole 9 yards to answer questions like this

[mervmartin]

Thank you very much for making this study of EFHW un-uns

[mikeramsey]

Definitely interesting video. Seeing how hot those small cores got was mind blowing.

[phildurall]

Wow Manuel! What an eye opener! Thank you for staying the course and putting in so much work to discover and document this. Real food for thought when running QRP and impacting the effective radiated power so much by introducing a matching device like this. 73 - KF6IF

[hughdavies]

I appreciate all the work and effort you put into your videos. Great help and resource for the hobby.

[johnwest]

Thank you for taking the time to wind these cores and documenting the results. It looks like the differences in the physical winding between the step-up and step-down transformers may have affected the SWR numbers.

[raybans]

Good engineering, Manuel. I will ejoy learning from your experiments. Especially valuable for me was the insertion loss and LOSSES POWER is applied, where core heating becomes a problem. I have always wondered about this.

[TheCrakkle]

Very nice work, was pleasantly surprised at you aproach.
Very nice to watch.

[davemartin]

Thank you for all the work you did winding the cores and building the spread sheet. This is very useful information. I knew wideband transformers were not lossless but didn't think they would be as lossy as they are. Thanks again. Dave K2ZU

[alanb]

Thanks for looking into this. One thing we learn here is to avoid making assumptions without data. In the same vein we should not assume tuner loss values, they vary dramatically depending on the actual situation, configuration and settings and can be low or high. Tuners are easier to model than transformers, so we can mathematically get some data on tuners and we need to include that, as well as feedline losses in any comparisons of antenna systems. Also concentrating on a smaller frequency range we can optimize for lower losses. Trying to handle "all bands" isn't necessarily the right goal. We have better options for higher frequency bands with small antennas, there's little need to make the 80-30 meter antenna work on 20 and up. 73 de w6akb

[ianxtreem]

This is really great stuff. Thank you. You are helping me learn a lot about practical antenna implementation.

[vetinger]

Thanks for R&D and sharing results! "73"

[AlexandrGubanov]

Thank you! You made a great job. Your reseach asked for my question about efficience of the wide band transformers. Even at QRP power the losses are big and make a heating.

[willian.direction]

I used my endfed for the last SOTA and found I sit in one spot all the time and get a sore body. After my hikes up its nice to jump up and swap links on my dipole and that lets me stretch out a bit during the activation. By fluke I had a FT 82 43 to make my EFHW and it seems to run quite cool. Thanks for all the good work setting that all up and sharing with us the results. vk5cz ..

[DonzLockz]

That's a lot of building and testing. Thanks for sharing this with us, very helpful.👍🤓

[MMOPXFieldRadio]

Very well done Manuel 👏. I'm now working on a workable solution for the larger core I have been testing for insertion loss. It turns out that this what my myantennas use for their 250w (100w Continuous data) version. I need to get one of those digital power meters and I can do the "under load" test.

[frankamato]

Excellent approach and thorough findings of results!
Best overview of the UnUn operation and efficiency…Have not seen such complete testing of its parameters!
Certainly good to know for QRP RF and DC supply power issues.
73 WA4ITD

[kevinnicholls]

Thanks for sharing your investigations and creating a very informative video. The measurements at 5w with a power meter and a thermal camera were a great idea.
While 20% losses sound terrible, it isn't necessarily a reason to abandon the EFHW for portable use, as some would have us believe.
For comparison, I regularly use a resonant linked dipole as an inverted V, with the apex around 5m. On the 40m band this has a feed point impedance of around 20 ohm, due to the low height, leading to a 1.6dB loss in my 10m of RG174, and around 30% signal loss. It works just fine but probably isn't as efficient as an EFHW!
The EFHW presents a feed point near to my operating positions so I can use around 2m of RG58 coax.

[KYLEE-je]

Very good result of efhw baluns. I think you had better wound 3 turns reduce to 2 turns for the primary of balun. Look at the most right for the input power of 10 meter at 27 line. it is less than another band input power. the primary wound will good by increase widing turns at low frequency band. but high frequency band will bad responce. Thank you.