An efficient 40-10m EFHW antenna for portable ops

Full details on github github.com/evi...

[@evil_lair_electronics]

View count really went up this afternoon, like this got linked somewhere maybe.

[@DaveW6OOD]

Perhaps MM0OPX 😊

[@daveN2MXX]

It is nice to watch a video on KZbin from someone who actually knows what they are talking about for a change. Nice job.

[@MM0OPXFieldRadio]

Excellent video once again 👏. I admire your tenacity to keep loses to an absolute video. I am getting repeated emails from people asking if what the transformers look like with a resistor across it. You have explained that perfectly here. Keep on truckin 👍

[@Steve-GM0HUU]

👍Thanks for sharing this. Some interesting things to try out. There is more to an effecient antenna system than low VSWR at the transmission line feedpoint.

[@wd8dsb]

Big follower and fan of yours. Wound 2 identical 49:1 transformers using the 61 material. Used plastic coated wire, separate primary and secondary windings, not twisted but bifilar wound, and close space turns. Back to back transformer test results very similar to yours. Back to back results: 7.088 MHz = -0.23 dB, 7.285 MHz = -0.20 dB, 14.07 MHz = -0.21 dB, 21.15 MHz = -0.53 dB, 28.23 MHz = -1.08 dB (divide these results to get individual transformer loss). Calculated efficiency on 40 meters 97.3%. Also tested back to back connected transformers on the bench running 100 watts CW and just noticed slight increase in temperature when touched by hand. Thanks, Don (wd8dsb)

[@labcat73]

Thanks man! I finally scored a win at Mouser and ordered a few of the "chunky" cores. Ready to follow in your and Colins footsteps and become a real Pert - In contrast to an "Ex-Pert" 😉🙃

[@survivalcomms]

Another excellent video. I really enjoyed it . There is so much baseless groupthink in social media its refreshing to see someone willing to tell it like it is and put their money where there mouth is. Bravo ! Thanks for sharing !

[@Aimsport-video]

Truth. You absolutely rock. People, this man speaks wisdom. My experiments concur with your findings and approach. Your videos inspire me to experiment even further. My free time trembles in fear every time I watch one of your videos. Your work and those of just a few others have encouraged me to try unconventional windings, to dig deeper for correct interpretation of objective measurements, and to go for it no matter what the “experts” say. Can’t wait for more of your videos.

[@robertvantichelt6448]

I picked up a few of the 43 mix cores. They fit perfectly in a plastic 35mm film can with room for the windings. BNC connector on one end and I'm set.

[@michaelb761]

I had several of your boards printed and have built several versions of this efhw design with excellent results. thanks for your hard work.

[@evil_lair_electronics]

Great to hear!

[@paulmadsen51]

Man, thanks so much for doing these videos! As someone who enjoys building my own antennas and transformers, the information you publish is incredibly valuable, and I really appreciate your critiques of the status quo with regards to the conventional "wisdom" of transformer building. Awesome channel! 😁👍

[@hvh2sa]

Great stuff, excellent video 👏. I tested your winding scheme with my TX36/23/15-4C65 cores from DX-Wire here in Germany, and I measured the loss with two setups, using your test method. Now I know the loss: 40m not usable (-1.79dB), 30m somehow ok (-0.86dB), 20m-10m good (0.35dB to 0.55dB). Much better than my former setup 👍

[@krzysztofp9316]

Hi, you convinced me with this video and the results you showed. I have such a core for the transformer you made for this antenna, so I'm getting to do one. Thanks for everything and greetings from Poland.

[@johnemmons9087]

As a newbie, I have one word...WOW!

[@richardholmes9469]

Thanks for the video. Respect. Have you tried loss measurement using a resistive terminator on the output, 2400R and then into port-2? I may be wrong, but I believe Owen Duffy uses this in his measurements? Also, and with the greatest respect, the loss on 80m is kind of indicating it needs more primary turns - then in my experience, 10m performance will be worse - of course happy to be proven wrong and learn.

[@evil_lair_electronics]

Yes, I've considered doing some testing in that way. It's much more of a hassle. I will probably do that with a couple of transformers and also put the same ones in pairs on a soldered jig keeping all of the leads as short as possible so that the comparison of the two tests would be the fairest. I know my quick change jig for testing pairs introduces a small amount of loss on 10m as I have seen it more than once when comparing with everything soldered and short leads. Only a very small amount in the 10m range, all of the rest of the loss graph still matched. Plus you are going to have that same kind of variance depending on how long the leads are when the transformer and capacitor are put in an enclosure, exactly why I created the circuit boards. As for primary turns that is correct, which is why with an unknown ferrite like this one was, first I will start it off with a 3T/27T wind. That way I can test it, remove turns from each end, retest, see what it likes the best. Much easier than winding 2T/14T then having to completely start over to get more turns. In this case, yes it looks acceptable for 80m when it has 3 primary turns. However it starts to get lossy on 15m, then 12m and 10m are in the toilet. And that's fine, something small/portable like this, I don't think portable users are likely to use 80m anyhow and it's really nice with 2 primary turns. After winding hundreds of different transformers, maybe over a thousand by now, I have yet to see a 52 or 61 mix that can efficiently cover 80-10m, they are always narrower and will miss either the bottom, top, or both.

[@CigarsOnTheAir]

Great video, well done and i learned a few things. Thanks so much for sharing this video and for your efforts making it. Cheers and 73!

[@K5azz]

Thank you! Very informative/enlightening...

[@alexdokic5567]

Thanks for sharing your knowledge in this very interesting video, you can thank Colin for directing me your way and thinking outside the box! 73

[@philipwells2793]

Great job and a github page as well!

[@75ohmHAM]

The world would be lost without your wisdom, please dont take it with you ❤

[@Yesindeed-dk9lz]

Cannot thank you enough for this. Everything now is opinion and self promotion; it's a relief to find a source of documented, tested and reproduceable truth. Science, not opinion! A couple of technical questions for you to consider: First, what is the effect of the choice of wire used in the toroid? Obviously, you want the wire to be large enough to handle the anticipated load (matched and unmatched), but what effects occur with smaller or larger wire, enameled or insulated in some other way? Second, the wrapping technique. Everything I've read suggests that the lowest loss occurs when the wire is VERY tightly conformed to the surface of the toroid core, and windings are physically touching and parallel inside (and even outside) the core. Can you confirm that? As I've wound my cores, I have noticed major performance changes if I fail to observe these rules. Thanks again, and keep up the good work!

[@evil_lair_electronics]

Hi. I've never used anything but magnet wire. Nothing scientific about how I choose the size, it's just what seems it would fit the particular size of ferrite and not be so small that it would concern me with the anticipated power level. If larger was desired I have wound these same size transformers with 18awg before and there is certainly room to go larger than that. However, the larger the wire, the more difficult it becomes to tightly wind it to the ferrite and have all the turns tight together. I agree with you 100% that tight windings show lower losses, mine are always all touching on the inside. This is a good argument for only using magnet wire also, as wire with insulation is going to spread them farther apart.

[@Bobsbbq]

I feel like I just heard the gospel for the first time. I feel so mislead lol. I have a nanovna v2.2, can I use this to do the same measurements? I think it would make a great video showing people how to check their own on a nanovna. Thanks for your videos.

[@sv2dsy]

Another excellent video...thanks a lot mate.

[@learnhamradio]

Looks good on 60M too, OM. Nice work!

[@tipex]

Great video, everything was well explained, thank you! I'll buy some toroids and do some testings.

[@enginedave]

Phenomenal video. Great ideas. Great improvements. I love it.

[@polzovotel]

Thank you for the video and ideas! What enamel wire did you use?

[@evil_lair_electronics]

I used 22ga but you could easily move up to something like 18 or 16ga if you wanted to.

[@drvigg9083]

Thank you for injecting a lot of common sense into this topic. Please clarify some details on the coil you have at 2m from feed. I believe you said 9 turns on a 28mm PVC form. I want to double check on this, because there is nothing on the Schedule 40 size list that's 28mm OD. Nominal 3/4" is under 27 mm OD; the next size up (1") is over 33 mm OD. Are you using something other than a Schedule 40/Schedule 80 size form? Would appreciate clarification. Thank you!

[@evil_lair_electronics]

Hi, it's a 1/2" PVC conduit coupler, not pipe, that is what it measured at. Don't get hung up on the exact diameter or how many turns or your tuning will never be right same if you try to just copy the overall antenna length it won't tune right either. It all needs to be tuned in your environment. It's going to vary with whatever wire you use, so adjust the number of turns to bring 10m and 15m down to where you want them.

[@drvigg9083]

@@evil_lair_electronics Got it! TU + 73 OM!

[@drvigg9083]

@@evil_lair_electronics TU OM; understood. One still needs a departure point - a place to start. You know the adage, I'm sure: Cut long and trim to suit. For that shape coil, inductance doesn't change much with number of turns or diameter as long as the length of wire coiled up is unchanged.

[@Wowfacter]

Going to pursue building same, as I like everything from low loss ferrite to case to the connect points. Am I correct that you glued the bottom of the wound core to the bottom of the board with what looks like Black RTV??? Also, can you provide a picture on GitHub or here of the actual tap point attachment at winding 2.

[@evil_lair_electronics]

No glue, just the 2 tie straps holding it on the board. When I am winding the wire onto the ferrite, after making the first 2 turns, I scrape the area of the wire which will be on the outside of the ferrite, then loop it around the end of a toothpick and continue to wind the rest of the transformer. So I then have that little loop sticking out, already scraped ready for the tap wire to be soldered to it.

[@Wowfacter]

Makes sense, and good use of toothpick. Thanks. @@evil_lair_electronics

[@allanjones4283]

Q. I'm a new HAM and this will be my very first antenna build. QUESTION: Which outside turn does the tap/loop go? (2nd or 3rd) 2:55 ? I've ordered all the parts - Thankyou! 73.

[@evil_lair_electronics]

The correct way is to count the turns through the center of the ferrite, so it would be after 2 passes through the center.

[@allanjones4283]

@@evil_lair_electronics Thankyou. I was getting a bit confused by it. Awaiting parts to arrive in Australia/VK and shall let ya know 🙂

[@cthoadmin7458]

When is evil lair going to show us how to build the ultimate 10m qrp antenna, now 10m is smokin'? Lot of talk about J-pole versus 5/8 lambda versus dipole etc. etc... but which is best for qrp?

[@allanjones4283]

That's their fun of our hobby..... Try them all 🙂

[@robertvantichelt6448]

Build the transformer. Cut a length of wire resonant on the 20m band. Then set it up as a 10m half square on a beach near salt water. Have fun all day long working DX

[@DuhBiggestDog]

I agree that the SWR using a resistor across the terminals of the transformer will not give you a valid picture of the real world when there is an antenna on the terminals. However, I don't agree that it is a waste of time using a carbon resistor to check your work. If you have just wound what you expect to be a 4:1 bifilar transformer I think most people would want to test it on the bench with a 200 ohm load to see if it looks like 4:1 on the other end. What's the alternative, put it in a box, haul everything up 30' or more and hope for the best?

[@evil_lair_electronics]

I'm already bench testing a pair of them for loss. So if there was something like a short or open that happened during construction I would see it during that test.

[@stevewithnell911]

@@evil_lair_electronics A good S11 measurement is the o/c and s/c conditions. That provides good and valid insight into transformer performance. I suspect the key to your improved performance is that it reflects the need for the ferrite core height to be greater than its width. The internal wires running up the core are doing the good work, the wires across the top and bottom of the core cause most of the trouble. The classic FT240-43 single core build ignores the science.

[@vk4foo]

Nice and neat.

[@Nathaniel7420]

Thank you.

[@allanjones4283]

QUESTION: Thankyou for a great video.... What is the effect if magnet wire is not as close as yours but tight wind?? Cheers.

[@evil_lair_electronics]

Thank you. My experience has been that spreading the turns out showed more loss 100% of the time no matter what size/mix of ferrite I was using..

[@allanjones4283]

@@evil_lair_electronics Thankyou. I'm a noob HAM. Made 1st transformer, it was a disaster, did another, still bad just better. I'll try again and might use PTFE just to learn from -- I know it's not as efficient as magnet wire.... Cheers.

[@geirha75]

Thanks for excellent information. Will 2661102002 work with 100W ( ft-891 )?

[@robertvantichelt6448]

Based on the weight of the core 55g. The ones I actually measured are 58g you should be able to do 120-140 watts cw ssb and maybe 50-55 watts ft8. Depends on band and swr etc. That is just a quick guess. Someone chime in with actual field performance

[@GoonyMclinux]

​@@robertvantichelt6448I did 47 watts ft8 on 40-10 meter for about 30 hours straight on that core and it was fine, but that was near resonance and not off band.

[@K6SUD]

Excellent video!

[@phurla1]

Great video. How did you use a circuit board to attach the windings/cap/coax? Just a piece of circuit board glued to the box?

[@evil_lair_electronics]

Had the custom circuit boards manufactured. 2 screws holding them in the enclosure.

[@CriticalThinker-42]

Self proclaimed antenna engineers usually argue among themselves as to why an antenna acts as it does, especially when they see real world differences from their predictions. You need to stop taking them seriously as their fun seems to come from arguing and acting superior. When it comes to antenna efficiency I put more faith in A / B testing than db claims. A / B this antenna against dipoles for each band (as a baseline), verticals (FEB), then against other antennas you think are so inefficient, and show real world on the air results when the bands are so-so. Bottom line, if an antenna isn't putting its signal out where it needs to be, minimal db loss' don't mean squat. More loss with a better pattern will beat it. 73 mike

[@robertvantichelt6448]

Why don't you eliminate the binding post also. In the name of efficiency. If you need a removable antenna just hang a little wire stub out of the box and use the little RC car bullet connectors. Cheap and makes a good electrical connection

[@GoonyMclinux]

The binding post wouldn't be very lossy.

[@thogevoll]

I've been following you for some time now because my son and I are interested in homebrew portable EFHW antennas. Something that I'm curious about and have not found a good explaination for is the capacitor across the primary. What is the purpose of that capacitor? Thanks

[@evil_lair_electronics]

It improves the match, which reduces loss.

[@carlossilva.k2wc.542]

Excellent video, thank you for sharing your experience with us, I just ordered all the parts to build one, quick question, What size of enameled wire did you use for your transformer?,And what is the maximum power to use with core 2661102002? My intention is to use 50 or 25 watts. Thank you in Advance,73

[@evil_lair_electronics]

I used 22ga on this one, but it can take larger wire. It will handle that power level no problem!

[@mabo4848]

Tnx … could you make a vide explain better how to build or wind this ?

[@evil_lair_electronics]

Which part did you need clarification about? The winding is 16 turns, tapped after 2 turns.

[@mabo4848]

@@evil_lair_electronics ok Tnx .. yes i mean the winding

[@kevmscott]

@@evil_lair_electronics How are you tapping the second turn? Soldering a small piece of wire? Are you insulating it in any way (since you have to be removing the coating from the magnetic wire to solder the tap?

[@evil_lair_electronics]

@@kevmscott After I have wound the initial 2 turns onto the ferrite, I scrape off a small area of the wire that would be on the outside and bend it into a little loop, stick a toothpick through the hole, then finish winding the other turns. Then come back with a short section of wire bent into a hook on the end to put through the loop, then solder it. I've seen others not even make the loop and just scrape a straight section of wire, then use the same type of hooked tap underneath it. I don't insulate it, I know some people do and if you just put a little insulating tape on the outside surface of the ferrite there it certainly won't hurt anything. The ferrite isn't very conductive. If you look at data sheets, 43 is 100K resistance per centimeter, 61 is 100M, and 52 is 1 gigaohm. Just don't scuff up the turns next to it and end up with a short between turns.

[@K5azz]

@@evil_lair_electronics , Thank you!

[@brianhall137]

What is the antenna configuration analyzed for this transformer? overall length, geometry, height above ground, counterpoise length if any, etc?

[@DM-fz3ly]

excellent video. Could you share your source for the enclosure box and the binding post? Thanks

[@evil_lair_electronics]

Thank you! Follow the link in the description, there is a link there for the enclosure on Amazon. Also a link for the manufacturer's site of the binding post. I have bought those posts from both Mouser and Digikey.

[@geirha75]

Any experience guys, on 80m with this transformer?

[@evil_lair_electronics]

Too much loss.

[@MeineVideokasetten]

Good morning. Which coax cable (type) do you use here? Tnx dr op. 👋🏻

[@evil_lair_electronics]

LMR-195 timesmicrowave.com/cables/lmr-195-coax-cable/

[@polzovotel]

How do you calculate the right turn number for primary? (I saw you used 2 for 61 mix). Any particular inductance for particular frequency?

[@evil_lair_electronics]

I never go down the path of a bunch of theoretical calculations when it's the real world results I'm after. I just do loss testing with a VNA, looking for what is low loss across the frequencies I want to use it for. When it is ferrite I haven't worked with before like this one, I initially wound them 3T/24T, loss tested, then removed the primary turn on one end and the 8 secondary turns on the other end and re-tested. Do it in that order so you don't have to wind them twice(unless more turns was better, then you're stuck rewinding).

[@polzovotel]

​@@evil_lair_electronicsthank you - waiting for mine to arrive and will start testing !

[@johnbuckley683]

What is the max. tx. power ?

[@evil_lair_electronics]

I really have no idea. 61 mix can take a lot of temperature. It's small and meant for portable use, can certainly take any realistic amount that someone would have when portable.

[@robertvantichelt6448]

Owen Duffy I believe tested the 43 mix version at 20 watts key down. A little bit less efficient but similar core weight to this one. Build one and let us know

[@evil_lair_electronics]

@@robertvantichelt6448 I tested that one in February of 2020: kzbin.info/www/bejne/d5urYpybqKmKgKs It is way smaller, only 18.7% of the mass of this one.

[@robertvantichelt6448]

Ok based on the mass of this core 55g. The ones I got I measured at 58g. I'm guessing 120-140 ssb cw. Maybe more because of the efficiency numbers. Probably 50-55 watt ft8. Now this is only a guess based on core mass and efficiency. Someone needs to test one

[@michaelrichardson4884]

Proper evil review enjoyed that found you probably directed by the youtube algorithm from Colins videos all great content spot on and technical, thanks G7VYH