Ultimate UL Portable Resonant Antenna Build - DIY Micro End-Fed Halfwave Matching Unit

[@djsomers100]

In the middle of a sleepless night, I came up with three ideas that make this build MUCH easier. 1. Instead of trying to solder the twisted tap off the toroid to the center terminal of the BNC (crazy hard), solder a short piece of toroid wire to the center terminal and then when you place the toroid over the BNC, you can solder the short "jumper wire" to the tap instead. Crazy easy. 2. Before soldering the antenna stub wire to the toroid, I thread it down through the center post of the BNC. Way easier than soldering the wire to the toroid and then snaking the antenna stub up through the center post. After you have threaded down, you can strip the end of the wire, and place toroid over the BNC, and solder the antenna stub to the appropriate toroid lead. 3. Use Liquid Electrical tape to provide insulation over your solder points rather than heat shrink tubing. It is much lighter, thinner, pliable and easier to work with than heat shrink. Hope you find these make the construction a LOT easier. Doable even for my 68 year old eyes and fingers.

[@Fluffyshotmephotog]

I would like to see pictures of your construction. I am going to go outside of my comfort zone and try to build this. I guess no better way to learn than to watch others and be ready to make mistakes. LOL - NØLUV

[@RandyBuxton]

Works as described. Much easier way to build these things.

[@techguy9023]

Put the torroid in a small length of pex pipe with caps fed by coax from the BNC with a screw terminal mounted to a brass pex cap. Simpler construction and less likely to break

[@porkyfedwell]

OK, confessional time. I am 61 years old and can see out of one eye. My hands are very, very stable. After working under a high power magnifier I was able to mount the SMD capacitor - no problem. Wound the toroid - no problem! Soldering the primary stub to the center conductor - biiiig problem, but I did it - barely. That's when the trouble began. When I was ready to start adjusting the toroid windings, the primary stub broke free from the center conductor. And then, it did again. Very frustrating! :) THEN, it dawned on me: Why are you doing this, Dumdum? Why am I not just mounting the transformer on a postage-stamp sized PC board, and forget about this design? Do I really care if the thing is as small or as slick as Adam's? No! I refer you once again to the fact that I'm 61 years old. 5 years ago this would have been no issue to build, but 5 years makes a big difference. Time to face reality, dude. I'm 61. Not 25, not 51, not 55... 61. It then dawned on me that the transformer being on a PC board would make it no larger than one of the traps (which are also built on a PC board). The whole thing will still be exceptionally small and light. This confirmed in my mind that I have made the right decision... for me. I will now have an antenna that's not quite as "cool," but very portable and lightweight. And I will happily continue this project with far less frustration and far more enjoyment. Thanks Adam, for this video! It's a great design - for the young. The rest of us will need to engage the gray matter and adapt this to our own diminished capabilities, whatever they may be. Don't laugh at me, it happens to everyone sooner or later. Well OK, maybe I give you permission to laugh a little bit. Chuckle, at least. When I'm not looking. :) lol 73 de KD8ZM

[@alanshapiro6545]

Adam's slick development and presentation of the end fed multiband is great, but for you I would suggest to alter the plan: enclose the toroid and the capacitor in a tiny case, permanently attach a 3-6 ft. length of RG-174 to it going to your transceiver, and finally replace the SMD capacitor with a discrete one. That will give you some space to more easily work with. Also the length of RG-174 will act as a counterpoise which may be beneficial on 40m. I've built my matching device inside a tiny dental floss sample from my dentist. Got that idea from WS0TA/KT5X.

[@K6ARK]

Yes indeed, this is a much simpler method of construction. It's a slightly larger overall package, but for most, that's not going to matter. Unless you're counting grams and measuring in cubic millimeters, it's easy to simplify the design and stick it in a small enclosure.

[@gblan]

There are plenty of people older than 61 who can do this with ease. Age has nothing to do with it.

[@Inkling777]

@@gblan Age does have something to do with this... just not in everyone.

[@genepierson1728]

Lets all slow clap for gblan

[@gruvyalan]

You really break this down. Every QRP operator needs to watch your videos...if for no other reason than to learn what makes for resonant, effective antennas!

[@macgyver5108]

A HUGE "pro tip" for soldering faster and easier is to use additional paste flux/rosin EVEN when using "flux core" solder! It not only cleans up the solder joints better for more solid contacts, but it also conducts HEAT better too, so you don't spend as much time making your connections which saves quite a bit of time too, which seriously helps prevent you from "toasting" heat sensitive components! It's also a good idea to dip your iron tip into the rosin to clean the tip and then brush the tip with a "BRASS" wire brush, not steel which will scratch the "tin" tip on your iron and royally screw it up... Just make sure to blast the rosin off with something like brake/contact cleaner once you're done or else it can make a MESS down the road!

[@JarlSeamus]

As a new HAM but a 35 year Electronics technician, I am very impressed with this design. I could see this as a brilliant commercial product, but also scalable for use in higher output transceivers! Just WOW. 7-3, KD2SML

[@K6ARK]

Thank you Jarl! I initially thought about trying to commercial-ize it, but the construction methods were a bit too finicky for mass-production to be easy. A friend, N7MCB, came up with an improvement on the construction that I'm pursuing that makes it much easier to build. Perhaps I'll at least go down the road of making kits, if not finished products. In the end, I'm most interested in getting others to build, tinker, and have some fun rather than just make a buck.

[@russellwatkinson]

Great tip for using the spool of wire thanks.

[@acestudioscouk-Ace-G0ACE]

Thanks for this, good to see an micro alternative to the usual FT240-43 using configuration.

[@phildurall7466]

Uber impressed with the construction skills Adam! At my age, I don't think I could pull it off. This TRASHES the image of modern Hams as only being appliance operators! Surface mounted components squashed a lot of the fun of building our equipment. This is pure inspiration!

[@edmoreno9308]

Did I mention “You Da Man” again! Thank you from Louisiana. Great project while shut down.

[@edmoreno9308]

How did you make your antenna traps? I could barely see in the video.

[@thuff3207]

Not a bad idea and it was nice you showed us how you make it!

[@ke6mt]

Absolutely incredible. This makes for a really great antenna setup for portable ops. I love using it with my MTR-3B. 73, Rex KE6MT

[@metaller_alex]

Good craft beer is major essential component for this project I beleive ;))

[@miketaylor6700]

That, my friend, was an amazing video. I’m going to watch the whole series of course… and then… omg.. I may order some supplies. Can I do it??? This scares me as much as my first QSO with CW!!!

[@alexwalters1699]

A great design for an ultra-compact EFHW, along with many great tips. I will be making one for my QRP rig. Thank you!

[@hamradiotube]

Now that, my friend, is one sexy looking antenna. Nice tip with the spooling of the wire too. Can’t wait to see the finished product!

[@HAMRADIODUDE]

I worked my first SOTA with this antenna. It worked GREAT. convenient for rapid deployment. Additionally, the Velcro band around the kite winder and a small tree branch, worked excellent. Thanks again.

[@K6ARK]

Yes, I am looking into having them manufactured, probably without a crystal installed for options. I'll be sure to announce it to the community tab on the channel if/when they become available. Kits aren't really an option with the tiny, tightly spaced components.

[@jasonconrad9212]

I just built this antenna, challenging and very rewarding! Thanks for the info!

[@scottlindquist8628]

Absolutely incredible Adam! The ultimate SOTA antenna.

[@Cardassiaprime]

That has to be the most innovative and coolest, Antenna build I have ever seen, I will be building one but not with a surface mount that small.( my soldering aint that good) Thanks for sharing the concept n build. Now I gotta go figure. Barnie M7PBX.

[@dan_nux_vlog]

Just wondering he came out with brilliant idea... Never thought about it before 👍👍👍👍..... Salute.. 🙏🙏🙏🙏

[@neilisawesome]

So I finally go around to building this and the nanoVNA says that it's pretty awesome, although I haven't yet gotten on the air with it. I did want to point out one funny thing that I learned the hard way. You seemed to laugh about your "fancy BNC connector holder," but I'm pretty sure that it's impossible to do without the vise-grips - I melted two BNC connectors (one pretty obviously and one more subtly in a way that I didn't notice until I tried to connect it to something) until I followed your lead and used the vise grip. I think it's a big fat heat sink! Thanks for the build!

[@porkyfedwell]

Same here. Sat the connector in 1/8" of water and soldered the other end, after melting two in a row.

[@K6ARK]

Connecting it to a spare female BNC works like a charm! Give it a try.

[@neilisawesome]

@@K6ARK thanks, Adam. I’ll give that a go next round.

[@gmanshackshack6822]

I wish I could still see well enough to make such dainty connections

[@psjarvin]

You're a wizard. I guess I need one more antenna... At least.

[@olafelsberry9271]

That's gotta be a fancy beer, looks like I'd drink one or twelve.

[@malenve6vid]

Finally got around to try and make one, not so easy as the video shows. All of a sudden I feel old trying to construct it. Adam, you are the master here. Malen VE6VID

[@chuck4050]

Very cool build Adam and great camera work 73!

[@cwguy8960]

I really like your tuning method. My EFHW toroids all seem to work well, but I wonder how much better I could have optimized the match using your technique. It was one of those "Now why didn't I think of that!" moments...! Thank you!!

[@tomon7dc225]

Great video, gave me an idea... not so multimate portable. But is used the tip about the windings to make a 40m efhw. Winding and then unwinding. I did the winding-art without the capacitor and could see multiple dip's in the swr. After connecting the capacitor i did a sweep again, and the SWRdips on the other bands than the 40M where lower then without the capacitor.... another lesson learned why i need to use the capacitor. Thanks for the video.

[@K6ARK]

Yes! The capacitor helps get the resonant multiple higher bands closer to 50 ohms. If you find that their point of resonance is a bit off (for example, 20m is usually a bit above the band when 40m is good) try adding a loading coil 1-2 meters from the feed point, and a bit of extra wire to the end of the antenna to get it back into resonance. The loading coil close to the feed (or the end of the wire) provides more inductive loading on the higher bands than it does on 40m and will bring those bands into resonance when the rest of the wire is tuned to 40m. Good stuff!

[@claudem.p.7969]

very well explained and got very interested in how you tune the toroid. ty

[@gregmihran8616]

Was I the only one getting nervous watching you do that grinding so close to your fingers? Wow Adam, great design and build! You're technique is a pleasure to watch. 73 KJ6ER Silicon Valley

[@K6ARK]

Ha, thanks Greg! FWIW, those diamond blades are abrasive cutters and you can touch your skin lightly with them running and they won't hurt you.

[@tadekboruta328]

Very cool design integrating everything into the connector. Would like to point out though, that the capacitor is only useful for higher frequencies (15m and above). So you can safely skip cutting the BNC.

[@K6ARK]

Yes indeed, that is true. For 17m and below, the capacitor has negligible effect and is not necessary.

[@johnblood4614]

I"d second the request for the supply list for the traps. Looks like more toroids (but which ones??), a small breadboard (where did you source that?) and I'd bet there are some components under the toroid on the breadboard. I'm loving building your antennas. Could you advance a supply list for the traps so I can have everything ordered?? THANKS! Lovely stuff. 73s KD0AXQ

[@ernstmattle1155]

Wonderful work from Innsbruck

[@Hookmodo]

WOW thank you so much for sharing. You are a wizard of HF

[@haramanggapuja]

"Tweezers are huge help." Yeah. So is not having essential tremor. Enjoy your youth, amigo. Steady hands make this kind of project so much easier. Which is why, for me, everything has to be big and ugly and point-to-point thru-hole style. ;-) Nice project.

[@timmcdonough8543]

Excellent project and very good quality video of the details! Might be a bit tiny for my old eyes but the tips on how you tuned it with the spool of wire was worthwhile all on its own. I'm anxious to see the installment where you build the traps. Tim N9PUZ

[@jonathanhaynes9950]

As am I. I looked for the traps video to append this one. Is it forthcoming? Still, an excellent video that yielded an antenna here. W0XO

[@CharlesSmith-dh7gf]

I wish I could get my hands to work to build one

[@taki8592]

DE Z33ST, Hi K6ARK I've constructed efhw antena for 40 meters as you describe on your video with a small variation, i used bnc conector and 10 cm of rg58 the toroid and the capacitor were connected on a small piece of perf board and soldered. Today I had succesfull SOTA activation with my chinese 49 er cw rig, power about 1 watt. Thanks 73 de Z33ST.

[@ve2evn543]

Great build tutorial. Did you make a separate video for the traps? I can't find it.

[@daviddietrich9449]

Adam, I applaud your ability to do SMT. I have two Pico Tuners from SOTABeams. I had to ditch the 100 pf SMT cap for a thru hole one. I'm really good at kit building and soldering, but surface mount is just too small to work with for me.

[@K6ARK]

Yes, it's a challenge, especially with the smaller 0402 components! Hot air and solder paste help a lot.

[@daviddietrich9449]

I will probably have to try it again sometime, but would probably need a good magnifier since my depth perception is a little diminished.

[@nathancross405]

Do you have a video describing the traps construction. I'm eagerly awaiting instruction! Thank you so much for showing off your design.

[@K6ARK]

Not quite yet... I've started filming and should have a trap video out some time soon.

[@moonchild2213]

Excellent build...enjoy all your videos, great information.

[@ol2tmx]

Wow, this is an amazing tiny antenna. I have to test it with my Belka-DX.

[@dickwendell7642]

Brilliant design. We will have to call this the K6ARK antenna. The use of the BNC connetor is the key. The surface mount capacitor creative space saver and the tuning technique simple and effective. I used your BNC technique with a different toroid to complete a similar antenna yesterday. Works great. 2000 mile contacts on 5w and 15w. I only wish I knew about your tuning technique before I epoxied it up. Keep up the great work. It will be interesting to see your traps. Dick K7ULM

[@kennethbell4681]

I'm building one from your parts, tonight, Dick. It's taken me long enough to get started!

[@michaelharriman6080]

awesome video adam. When are we getting part 2???

[@JnJTrueOutdoorAdventures]

Great video Adam!! I guess I will wait now before I build the other antenna until I see this one completed!! Juddie WD8WV

[@K6TJO]

I am having a hard time following what wire ends get soldered where. Do you have a diagram that would show this exactly? Thanks from K6TJO

[@Wayde-VA3NCA]

Hi Adam K6ARK, this is a fun build! I have your version with the tiny, red, round pcb and I'm liking it a lot! I wound that tiny toroid this evening :-) Question about the toroid winding. In the video, you indicate that the twisted stub is the coax center and the short middle stub is ground. I've seen diagrams that indicate the reverse. Have you found that the polarity of the primary matters?

[@ksb2112]

I have built and used this antenna with some remarkable results. Just this past weekend I was able to hit France and Spain from Southern California using 5 watts. The only thing that seems odd about it is that the received signal strength seems low. I'm getting 559 or higher reports from people who are barely showing up on my S-meter. Admittedly my observation is strictly anecdotal. I need to set up a another antenna to get some direct comparisons going. But dang, France and Spain...

[@backcountryamateurradio]

you are an absolute genius. I love this and can't wait to make one. Thanks for showing us how you do it. you're the man!

[@aaronjohnston1584]

Aren't you creating an additional turn or two by passing the antenna lead through the toroid?

[@ut4uum462]

Thanks for Your video. Very nice idea to place the toroid on bnc.

[@HikingWithCam]

This is great. Thank you. For a 20m version, would you do fewer turns?

[@dongelinas5990]

I’d love to build one but I have severe sight problems. 😢

[@prephampaul]

My next project, Thanks Adam!!

[@jeffdyer2393]

Awesome video. I make a portable efhw I use an empty bic lighter to house the transformer. one end the antenna wire comes out and the other I use about 3 feet of rg174. it works great, small, and looks cool. I'm looking forward to the next video. Keep up the good work. Ke4fwe

[@BretChilcott]

Jeff. Do you have photographs of your design? I would like to see it. TNX Bret C / AC0AE

[@jonathanhaynes9950]

@@BretChilcott @jeffdyer2393 I, too, would like to see photos of that design.

[@rfdave3980]

Wound as a auto transformer. Shouldn't the twisted wires go to ground of the BNC, or it doesn't matter?

[@w6mrd900]

Fantastic! Thank you for the great video. So much in such a small package.

[@MiscDotGeek]

Making videos is hard. You did a great job with the video and the build of course. I'll be checking out your other videos as I dive into the EFHW for my own use and on my own blog.

[@marcolauritano1777]

Congratulation, thanks for sharing your knowledge.

[@mariuszstefaniaksq2ode646]

Hello Thanks for the great footage. Tell me if the swr on the antenna changes when changing terrain? Greetings Mariusz SQ2ODE

[@ThatguyFirst]

Is it critical that you have AleSmith on hand, or can you substitute another IPA such as Dogfish Head, Stone, Voodoo Ranger, etc. Also, what about the choice of vessel: aluminum can (conductor) vs. glass bottle (insulator)?

[@K6ARK]

You get at least an extra 3dB out of the antenna if you pour into a frosted glass. 😉 🍻

[@RandyBuxton]

I've constructed a few of these contraptions and have always had to redo after, so it seems, I've put too much epoxy on it. When I tune it (before epoxy) it works as described here. When I put just enough epoxy on the outside (not the sides) of the toroid to hold the wire in place and then re-test it works as described. But when I put epoxy on the sides of and inside the toroid (where the solder joints are) to, conceivably, hold everything solidly in place it where I run into a problem.....testing after this final epoxy application results in the matching unit not resonating on any frequency. As if it has been shorted out. So the moral of the story (as far as I'm concerned) is to only put epoxy on the outside of the toroid to just hold the wires in place. Then use liquid electrical tape for the rest of it. If someone has come across this problem with epoxy as I have I'd be interested to read how you conquered it.

[@joyhamradio]

Cool! I’ll definitely repeat this construction!

[@christopherbenetatos5123]

Great detail. I learned a lot!

[@dongelinas5990]

Wonderful instruction video

[@LevyCarneiro]

Does anyone recommend a good resource (book, site, etc) on how to build this type of antenna for different characteristics? For example, if I want to build one for 40-meter band and takes 100W, what should I change in the materials and turns and dimensions? Thanks.

[@michaelharvie3530]

Hey Adam can you provide a link of where you get those tiny capacitors? I would greatly appreciate it and awesome video. I look forward to building mine soon.

[@michaelfuchs1467]

Great video! 'Fusing' the toroid to the antenna connector is exactly what I've been thinking about TRYING for a while - but probably using two FT-50-43 toroids stacked, using a 49:1 ratio winding and probably a ~1.5kV capacitor for handling 20W in a multi band EFHW for the G90. I'm 'into' digital EMCOMM so it will be close to 100% duty cycle. Have you tried building a 49:1 EFHW this way? 🤔

[@K6ARK]

Yes, I have. Consider a slightly larger toroid. For better power handling, but a couple of stacked 50 size ones should be good at least for 10w.

[@michaelfuchs1467]

@@K6ARK Thank you for your answer! I'm having a hard time finding toroids of right mixture, in right size and for sensible prices here in Scandinavia, at least those made from recognizable material mixtures (43 Nickel-Zinc in this case). I can only find a few Amidon toroids at my local suppliers and also those are being phased out from the stock lists now. I've found a few Ferroxcube as well but not made from 43-equivalent mixtures - and equivalent tables for ferrite materials used by different manufacturers seems non-existent. The toroid sizes available here are 240, 140 and 50 if I remember correctly. Of these only the 50-size would make sense mounting the way we're talking about here - in an ultra portable configuration. I certainly was hoping for a bit more than 10W with two 50-size toroids stacked, and perhaps a bit thicker wire (~0.75 mm I guess would be possible wound on a 50-size toroid - whatever that is in AWG)... Stacking more that two toroids just 'feels' wrong somehow - like as if the physics will be seriously screwed up by the proportions (wire length / turn) . 🤔 I'm definitely on thin ice here and it's probably worth a try since other transformers (like those wound on 'binocular ferries') works well for their intended purposes. Maybe by tweaking the number of turns while keeping the ratio..? Do you know of an impedance transformer calculator (unun) that takes ferrite core geometry as parameter in the calculation? Do you know if it's possible to wind an impedance transformer using a ferrite rod as core? 🤔 That would make another attractive, slim-line 'package option' - if it's possible. (I can't really wrap my brain around what really happens in the toroid windings compared to what would happen in a non-toroidal core. 🙄 Regards from Arctic Norway! 🇳🇴 🗻 ☺️

[@randalltom9750]

Adam... great video... a marvel of miniaturization. I’m into it... QRP kits include the MTR3b (original), and an even older Mountain Topper the dual bander with the Data mode. I follow Gil the ‘Radio Prepper’, and his endeavors towards ultra compact/portable low-draw, survival radios. The Weber designs are amazing rigs. I also have a KX2, but the small CW only radios hold my attention. 72! Hope to see you down the log! KD7UXQ. Rand

[@northwesthamshack9950]

Fantastic video, im going to build this ! Thanks for the video

[@KipIngram]

Geez... I can see my next money sink is going to be an antenna analyzer. :-| That little unit you used 3/4 of the way through seems awfully nice.

[@gilgsn]

Tiny! Great design. The smallest I use is FT-82-43. I always laugh when people tell me anything under a dual-FT-240 isn't efficient. Presumably, twisting the three primary turns is better. I am surprised the ground passing through the toroid isn't a problem. I potted one transformer in epoxy; it no longer worked; did it twice, same result, so caution there. Hot glue has no effect...

[@K6ARK]

I was worried about the ground going through the transformer too. I have found that this design requires 9:1 to 10:1 turns ratio typically, so maybe it has some effect in that respect. I'm certain they're not the most POWER efficient matching units around but they are certainly the most SIZE and WEIGHT efficient 😉. Also, incidentally, I have had no issues with the 5 minute epoxy as potting compound.

[@gilgsn]

It might be the reason for 10:1, who knows.. As long as it works.. I use 24 turns total..

[@K6ARK]

Nice. FWIW, I have found that using two primary turns and 18-22 secondary turns also works.

[@claudem.p.7969]

DO not want to be pushing but what do we need to build the trap. I want to order the parts.

[@DAVIDGREGORYKERR]

Would a 16:1 UNUN hot have had the desired effect or what.

[@javajoe668]

Very cool! Thank you for sharing

[@PghJugrnot]

Update the link for the bnc connectors?

[@jessgypin-ko5ds]

Did you not test the connections before sealing it all up?

[@K6ARK]

It's probably not a bad idea. Look for continuity between the BNC center pin, ground, and the antenna wire.

[@gsansoucie]

Nice video. First thing, wow, that display on the Zoom model, I have the crappy AA-30 base and didn’t realize what I was missing. How much of a difference do you see between your spool out wire near ground trick to an actual antenna suspended from a mast? I’ve always tuned my antennas in their deployed position which takes forever. I like your idea way better. I’d seen photos of one of these matching units on the BNC, but could never figure out how it was done as I only use crimp BNC connectors. Guess I’m ordering some solder BNCs now (and I just placed an order a few weeks ago). Cool, I was supposed to be building traps for my MTR3b for a 20-30-40 EFHW, but got distracted. That is now tomorrow mornings project.

[@K6ARK]

I rough-tune using the spool with the wire close to the ground, then send out a few extra feet and fine tune in the operating position. Great question, and your approach is the way to go.

[@KB1HQS]

I have the same AA-30. Use the AntScope software coupled with the AA-30, much easier to tune traps and this antenna.

[@KB1HQS]

Thanks for sharing. That is some seriously creative antenna building! Subscribed! 73

[@wkjagt]

This is really cool! I want to build an antenna for my QMX (which I should receive in the mail this week) and my rockmite, and this video is a big inspiration. I know this is an old video, so you may not even see this question, but where did you get that box of toroids?

[@K6ARK]

Amidon sells a variety pack that is very useful. I picked up a Plano fishing tackle box with adjustable dividers for storage and organization, then supplemented with additional/other toroids.

[@remstarhe]

Hi Adam. Thanks for your sharing.I love this project. Can I construct this antenna with FT50-43 instead of FT50-61?

[@K6ARK]

Yes, I believe it would work just about as well. Give it a shot and let us know how it turns out.

[@K6ARK]

One note, I have found that the -61 does NOT work as well for the EFHW version. The -43 however, should work fine with this one.

[@PatAutrey]

I’m hoping to create a 2 m Multi element vertical dipole To use as a base station antenna at home I would like for all of the elements to be in phase so that they all radiate at the same time I just don’t know how to create the wiring harness to attach it all to get it to work correctly Any recommendations or advice would be greatly appreciated

[@dombaines]

Nice build video.... 1 question though by adding the 4" piece of antenna wire have you not added a turn back onto the secondary in the transformer?

[@Severris]

Great video, like all your videos. Question...what heat gun is that? I have a compact heat gun about that size, but I really like the nozzle on yours. Thanks.

[@K6ARK]

I have two heat guns. The smaller one is actually a hot air rework station. It's a Chinese model from Amazon but works well. amzn.to/3yL14yi (associate link). Ive had it for about a year and use it for SMD/solder paste board assembly, hot air rework, and shrinking heat shrink tubing.

[@stevek4stb221]

Love your videos Adam. Do you have a place to order your portable keyer that I have seen you use? A friend got a prototype somehow and I loved it!

[@K6ARK]

Steve, send me an email via k6ark.com and I'll get you on the early notification list. I'm building up the first batch now...

[@LeonardoEnergiaSolar]

Eu não tenho um micro transmissor, mais posso usar esta antena em um radio receptor tipo Tecsun PL-600

[@aeromech8563]

Subscribed awesome stuff ✌️😎🇦🇺

[@thejoker-ie1mm]

Great idea for SOTA Adam! 👍 Best 72/73 de IK2RGV Steve

[@mabo4848]

👏🏻👏🏻 Is 10w possible with only one 50-43 ? Did you tried it.?

[@MailmanJustin]

I constructed a 20m version using two stacked torroids. I was able to push 30w digital on FT8 before I saw any noticable heating of the unit. YMMV

[@DonDegidio]

Hi Adam, Just getting around to view this great video. Think I already viewed the trap build video. I know the 5 minute epoxy is easy to use, but have you consider the Bondic UV cured glue? Stay safe. 73 WJ3U

[@robclarke4631]

Hi Adam, I love the video. Very well shot and well explained. I note you connected the autotransformer shared primary / secondary connection to the primary center conductor. Most EFHW transformer designs I've seen have the shared connection connected to ground. Do you see any benefit to the way you have it connected? It obviously tunes well. Regards Rob.

[@K6ARK]

Thanks. I have actually built them both ways and have not found there to be any notable difference. Perhaps a topic for another video?

[@K6TJO]

Hi, I am having significant problems with those special BNC connectors. The center white insulator deformed from the heat of the solder. This occurs on the two or three now that I have destroyed. After all the soldering and deforming of that insulator it won't couple with the female BNC connector. My guess is that the white insulator is not Teflon and is some other type of lower quality plastic. I won't be able to complete this project until I find similar connectors that won't deform under heat.

[@hardywhiteley-boocock5751]

Some can be a real pain, I have the same issue with DIN plugs. Try couple to the female to hold everything together whilst soldering.

[@K6TJO]

@@hardywhiteley-boocock5751 Yes I found it critical to connect an adapter to it before any soldering. The dielectric is likely to deform under the heat and make the entire assembly useless.

[@DAVIDGREGORYKERR]

That end fed antenna might work on the 11Mtr band for those who want it.

[@malenve6vid]

That BNC is sweet. That holds I think the secret to a small transformer. Is it ok to use with a KX3?? Malen VE6VID

[@K6ARK]

Thanks! It would probably be wise to step up the toroid size or stack two if them for better power handling. I have only tested this one to 5W

[@jeffdyer2393]

Love the video I would like to make one for my mountain topper. When are you going to show us the traps. Please. It's been 4 months. Thanks Jeff ke4fwe

[@tiborherman5471]

Hi Adam! Great video, I like how we have similar urge to miniaturize QRP stuff! I just built this and I was wondering why you were using 3:30(1:100 impedance) ratio. I read about the topic and the usual impedance ratios are 1:49 and 1:64. What is your reason for 1:00? I input the antenna to 4nec2 to simulate the impedance and I rarely get to 5k ohms. Wouldn't it decrease the bandwidth of the antenna? Or am I missing something?

[@K6ARK]

The turns ratio difference comes from the way I was winding and attaching these transformers to the BNC, swapping the pos and gnd connections from the usual for this winding style. To put it simply, the first 6 turns (the 3 secondary turns bifilar with the primary and the next 3 secondary turns cancel each other out, so you actually have the equivalent of 24 secondary turns.

[@claudem.p.7969]

SUPER AGAIN. where can we buy the capacitor ? Claude VA2SOB.

[@K6ARK]

DigiKey and Mouser are my usual sources for electronic components. They have a massive selection and and reasonable prices.

[@claudem.p.7969]

@@K6ARK oki the mouser website is giving me a selection of huge ceramic capacitor. may be i should stick to commercial equipment

[@MrLittlmike22]

amazing video! - really useful could I ask where you get that antenna wire? - looking for something sturdy and thin and portable

[@w7mvg-mike39]

How do you determine what power the matching unit can handle? For instance, if I wanted something to work with my 20W g90 what toroid and wire gauge would I need ? Thx

[@daniell8387]

Hey I tried building this tonight. I want to try it out tomorrow but with Easter and all probably won't get the chance however I did have a little more time so I tried upscaling it with a t130-43 toroid, 24 or 22 gauge magnet wire (can't remember which) and a pl-259 connector with a through-hole capacitor. Have you tried it with that config?