EFHW transformer re-visited: improved core material & easier efficiency measurement

Part 1: Demonstrating a (easier) measurement method to determine broadband-transformer efficiency. Confirming older measurements and testing new core material, that improve efficiency of the EFHW-Transformers.
Part 2: (upcoming - not yet published): Effects of winding patterns and how to reduce bad SWR.
Sources:
1. github.com/DG1JAN/UniBalun
DG1JAN´s GitHub with Antenna PCBs, his own measurement reports and his genious excel sheet.
2. www.ai6xg.com/post/evaluating...
The source where Jan got his idea from.
3. • Best Ferrite Core For ...
MM0OPX / Colin´s original Video, recommending the big fair-rite core for 100W EFHW Transformers.
4. • Antenna building #2 - ...
My first Video, where I was trying to figure out the right core material, size and measurements.

[@MM0OPXFieldRadio]

First class video Manuel. Very well explaned. I hadnt seen Jans spreadsheet but he did kindly share his 1001 core results with me a few months back and they were within 4% of each other if I remember correctly. I cant take any credit as I have said before as I discovered this core as well as a QRP one via @evillairelectronics. My knowledge does not hold a candle to yourself or Jans. They say its better to be lucky than be good and that applies to me. I'm just glad to see others out there doing these experiments challenging the norm looking to improve. I look forward to your future experiments.

[@dl2man]

Thanks Collin ! We are all just one big community with the purpose to learn from each other. That´s, what I love about HAM Radio ! 73 Manuel; DL2MAN

[@johnwest7993]

Manuel, some thoughts that apply to all such recent amateur RF testing: I'm very pleased to see hams digging into these things, as I believe that learning about RF electronics is the heart and soul of amateur radio. But after reviewing multiple tests conducted by multiple hams over the last few years I do want to mention that the physical environment surrounding anything RF affects the result of any testing. Theoretical numbers used as references in our testing are absolute, sometimes calculated in entirely free space, not even over ground. But the real numbers vary with each installation, even with what the core is attached to. How high is the end-fed antenna actually mounted above the ground? What is the composition of the soil over which it is hung, and what is the band of operation we are on at that height, meaning what is the actual impedance, (of an antenna that will likely not be entirely parallel to the ground in any event.) These things have substantial interactions with the antenna characteristics themselves. That's why you will get a very good SWR at one POTA site but a poor one at a different site, with the antenna hung somewhat differently over different soil. The ground composition and reflections are part of the antenna system. We have little control over those variables, but we really need to stop thinking in terms of efficiencies of just the 'things', and start to think in terms of efficiencies of 'installations', and try to make our testing as realistic as possible, or at least more appropriate, keeping in mind that our testing will also be considered to be an 'installation'. A few things we do have control over are the shapes of the cores, the materials they are composed of, the winding patterns, the gauge of wire used for the winding, what materials our cores are mounted on, (is it a bare plastic? Is it copper-plated PCB material? Is the core mounted right against its surface? Is it on its side, or standing up?) And is a 49 to 1 winding better than a 64 to 1 winding? These things matter. They affect our test results, and our installation results, our RF efficiency. These specific things are determined by us, not the external situation. Yet I don't see any tests that fully compare these items, tests that are actually comparing apples to apples of the things we do have control over. I don't even know if some tests are being conducted with the cores mounted on copper-plated PCB material, on plastic, sitting on a wooden table, hung in the air, or sitting on a stone floor. That question of, were the cores laid down, or stood up on the material? That matters. These things matter. They all matter. They can significantly affect RF fields and efficiencies. Or if they don't, we need to know that, too. Knowing what doesn't matter is as important as knowing what does. As hams, I find that such information is seldom included with our test results, or worse, it varies from test to test, so we cannot really get much useful information from such testing. We are all hams, 'amateur' radio operators, not professional RF engineers spending a couple of months designing and optimizing a communications system for s particular installation. We don't take soil samples. We don't include the serial numbers of the test equipment we use to determine our experimental results. We don't typically have advanced, or any degrees, and most importantly we don't get paid to conduct our tests,. But if we as hobbyists are going to take the time to conduct tests and publish our results, we all need to at least understand what parameters affect the results of our tests and identify them for our testing purposes so that we can make useful apples to apples comparisons, progress in our understanding, and make sure we don't send others off in the wrong direction. Many, if not most of us now have NanoVNA's, and they can do impressive RF analysis, so we have no good excuses. Even as unpaid hams, we all need to up our game a bit in order to advance our hobby. As always, thanks to you and Guido for doing just that.

[@dl2man]

John, Thank you for that comment. I could not agree more, and as a native speaker you anywaycan express yourself way better than me. All I can say is: Wait for it. Wait for the next Video..... That will solve all this contradictions ;) And Johne: thanks for your long term support ! Really appreciated ! 73 Manuel; DL2MAN

[@KO4VNX]

This is exciting, we're getting better and better efficiency every time you update us!!!

[@labcat73]

Thanks Manuel! Very interesting and not having to wind two transformers saves a lot of work. Now we can vary the assumed antenna impedance between 2k and 3.5k, the compensation capacitor with a Trimm C and the windings - spread over the core or densly wound and investigate the effects. Endless fun ahead over the winter months... But as you said "because time" is always my biggest problem with these things as well... 73 Tobias DL3MHT

[@markusm.lambers8893]

Manuel, interesting to see, what we can do, altering some small 'things', ... ! I am very interessted to see the next video, to 'make things better', in the comming future! It only can go better. Most of my 'outdoor' radio preformances are done with OCFD and/or a MoreGain-antennas, by now ! Maybe to overthink some antenna-devices. 73/72 de Markus - db9pz (JN39fq - 3miles/5km east of LX)

[@KO4VNX]

I think you look like Frederick I with that hair on your face, I fully endorse this!!!

[@philipwells2793]

With this method, if I am not mistaken, the impedance you use in the test is the same as your antenna. This may not be the case. The back to back method makes no such assumption, but tells you which core+winding method is efficient. You then need to have the best winding ratio to match your antennas impedance. In reflection if you have correctly estimated your antennas impedance, then this single core method is much easier having only to wind one core. You can then change your winding pattern, core, and capacitor to find the best design. I recently made an unun and measured its efficiency using back to back method following Evil Lairs recommendations (related to Colin's) and got some very nice results of >80% across HF. Will experiment more. 73's

[@dl2man]

Thanks for your comment. The impedance is the assumed antenna impedance. It just provides a higher ohmic referenc, so everything is compareable. We will get to this soon (in the next video), as the Antenna Impedance is extremely dependent on elevation height. So we might need to have some adjustability available to adress all those cases. 73 Manuel; DL2MAN

[@DL1GKC]

… that‘s where the Fuchs or other EFHW tuner with variable C will come into play. It will eliminate those external influences as opposed to the broadband transformers used in EFHW antennas. 73 de Chris DL1GKC

[@dl2man]

@@DL1GKC Fuchs turns my beatiful Multiband setup into monoband, and tuner causes also losses. But there´s a simple solution and this is what we´re going to look at in the next video....

[@gac231]

I did not understand what you mean by "half 100pF" on the ...0601/1101 ferrite combination and did not see this notation in DG1JAN. What does it mean? Excellent and very helpful measurements, thank you.

[@dl2man]

I see.... The "half" was not related to the capacitor. It was a remark for me how the winding was done. All the other UnUns are wound according "W1JR Scheme", passing through the core after half of the required turns, then continuing in the opposite direction. By that W1JR covers almost full core. "Half" means: Only half of the core was wound with all of the windings. In a "half moon pattern". 73 Manuel; DL2MAN

[@oncomics1128]

I'm certainly open to new methods. If the trend is different are we only gaining precision?

[@dl2man]

The Trend is the same. This was confirmed. What we gain is: Not needing to wind 2 Transformers. And with the Test Jig, I also don´t need to put a capacitor or SMA Socket on the UnUn. I just screw the UnUn in the terminal connectors, start the measurement, feed the excel sheet and have my result. On Top it provides a real efficiency curve, while I manually tested at 4 Data Points only before. Providing an accurate, more complete picture of whats happening. 73 Manuel; DL2MAN

[@sm6moj30]

Brilliant work, Manuel. What is the power rating of the FairRite cores?

[@dl2man]

I did not test. The big 1002 core is certailnly good for safe use with 100W and 100% duty cycle. The smaller cores will handle anything from QRP to 100W with some restrictions. Try it and observe if it heats up in practice. If it does: Use bigger cores.

[@chrisherd991]

Hi thank you for this. Is it possible to try stacking two of the same core stacked one on top of the other to wind the transformer? If you want to play with the capacitor make one out of a length of coax. If you have access to a LCR meter is the 2k4 load purely resistive?

[@dl2man]

Stacking cores.... Maybe I´ll try that. But I´m more interested in the effect of winding pattern. My Load is not purely resistive, as shown at 10:18. This is, why the Load was measured/captured and this "load measurement" was used in all of the UnUn measurements to compensate it.

[@chrisherd991]

One more thought would be use a transmitter. Run it key down and use an infra red thermometer to see if the core is warming up. My guess is that is what causes the efficiency numbers.

[@dl2man]

You should have watched my first Videos about EFHW Transformers to understand, why this Video was a "re-visit" of that topic ;)

[@2EOGIY]

How much extra can we squeeze if we get a 50-ohm input impedance? You can use an online parallel wire impedance calculator and put enough heat shrink tubes on top of magnet wire to keep an even distance on the primary winding's first 2-3 coils.

[@dl2man]

I´m sorry, I don´t understand the question... Could you maybe explain a little bit more what you mean ? 73 Manuel; DL2MAN

[@2EOGIY]

​ @dl2man If you wind a primary coil in a perfect parallel way to a secondary one, in other words, create a 50-ohm ladder line. I quickly checked with the online calculator, and the spacing for AWG16 (or 1.02mm dia. or 0.923mm^2) should be 0.293mm, about the thickness of the single thermal shrink tube, to have a 50-ohm impedance. If you put on a single shrink tube isolation on the primary wire, another one on both to keep them together will result in a 50-ohm line on that part where two wires are wind next to each other. In this case, I'm talking about the classical transformer, not the autotransformer.

[@dl2man]

@@2EOGIY I don´t think this works, as the core dictates the impedance.... once your former 50 Ohm line is on there.

[@2EOGIY]

@@dl2man ratio between the first two turns of the secondary winding and primary winding that consists of two turns should be 1:1 regardless of the core

[@dl2man]

@@2EOGIY a) I have already proof by measurement, that there´s no significant difference between real transformer and autotransformer b) the ratio between primary and secondary is not 1:1, because you can not dismiss the rest of the secondary. If you would build a 1:1 Transformer, maybe.... c) the impedance of the primary coil alone is determined by the amount of windings and is further frequency dependent from core material. d) The impedance "seen" by TRX or NanoVNA is dependent from the load on the secondary. You can easily check that with a Poti on the secondary, while connecting your NanoVNA to the primary.

[@philipwells2793]

One thing I have had difficulty in finding out is what size of magnetic wire should be used for a given power. I know it will depend on mode, and what might be considered an acceptable loss due to heating. Large diameter wires will have less heating but are harder to wind and that in itself might lead to a lower performance, especially if you are trying to go for a tight winding pattern.

[@dl2man]

Rule of thumb would be: Use the biggest wire you can fit there, that can be decently handeled. From my own observations I know, that core is usually heating up more than the wire. What I do: For QRP 0,4-0,7mm^2 and for 100W: 1-1,5mm^2.

[@philipwells2793]

@@dl2man Thank you very much for your detailed response. Greatly appreciated.

[@hb9vqq533]

I wonder how much of a difference this makes in reality out in the field? Do 15% more efficient transformers make a notable difference on an EFHW?

[@dl2man]

That´s a very good question. In Terms of S-Bar: Probably not. But as a portable qrp station, I want to get as much of my 5W as possible. Why waste 1W in form of heat from my signal, if I can use it ?

[@K6ARK]

Efficiency is not all that matters. An EFHW wire is not a constant value resistor, and a non-linear response from a transformer could actually work better than one that matches perfectly to a 2.4k ohm resistive load. It is definitely worth reviewing the winding patterns, turns ratios, and toroids for which will be more efficient and allow for smaller matching units without overheating, but I wouldn't expect noticeable differences in performance from a perspective of contacts that you make or stations you hear.

[@jertres2887]

minor Typo: it’s not 58430000601, there is one too many 0, it’s 5943000601 and yes that’s an FT82-43 5943001101 is not an FT114-43, it is an FT-50A-43 pretty sure, 73 Jer aa1of

[@dl2man]

Without having it checked, I assume you´re right. I just used the last 3-4 digits in order to seperate them. 5943000601 is not very catchy ;)

[@jertres2887]

@@dl2man the full number let’s one search for and then order part for those who are interested. Yes, much too awkward to use in in conversation.

[@matthiasjahn5761]

Man kann auch deutsch sprechen das steht dir besser!! GRÜßE

[@dl2man]

Man kann auch Englisch lernen.... Das hilft bei der Völkerverständigung. Grüße.... P.S: Dieser Kanal ist seit Tag 1 englischsprachig. Für einen Zweitkanal habe ich keine Zeit und unter Funkamateuren setze ich voraus, daß man englisch kann.