I gotta admit that when I saw you doing the SWR on an unconnected toroid / capacitor , I said to myself , "What Magick is This?" , then went to the bench to replicate it! Excellent learning moment - thank you.

I finally built a trapped EFHW for 17/20/30/40, my favorite SOTA bands. Thanks for the great video!

I just sent this to a friend. "Either I'm smarter or this guy is good at explaining". Twenty minutes ago I had no idea how traps were designed or how you'd test them. Tightening/loosening the coils is a great trick. That must increase/decrease capacitance just a hair? I'm definitely going to add traps to my repertoire. Thanks for the great instruction!

Now that you have shown how to calculate how many wraps and the process....I have to build me some traps....another thing on my list to do...great. I blame you for all the things I don't get done. :)

Excellent, I love watching your mini, micro, pico projects!

Thank you. A neat way to tune the traps.

I have been so waiting for this video!

Well done Adam 👍

Adam.... don't ever stop with the build sessions. Awesome!

I always learn so much from your videos. Thank you!

Good timing. This is exactly what I have been doing the past few days.

Incredible amount of information without flooding. Thank you.

Awesome build video Adam , I just may have to try this!

this is just clear as it can be. He makes it seem simple!

You make it look so simple. Looking forward to trying to build one! Thanks

I learned more in 27 minutes than in 20 years of being an amateur, about traps, watching your video. It all makes sense now. I'm going to run out and build myself an end fed antenna. I need a nice antenna analyzer first.

Both the theory and practice are beautifully explained here. Now I feel confident that I will get a good result and will try some. Thanks very much Adam.

Congratulations on the video. Very well explained topic.

Well, one more project for the list. Thanks Adam. Good explanation of how traps work. I'm gonna need some more magnification to add to my bifocals. Great video.

I love your work. Its the perfect combination of science and art.

Oh god it finally makes sense... and testing trap resonance with the analyser is brilliant. I thought you were going to DIP meter it - but it achieves the same thing!

That was one of the best ham radio KZfaq videos I've seen in a long time. Very creative way to make a trap. I've made traps for many year but never gave any thought to making them the way you just showed. and......you taught everybody how to and how easy it is to make the traps. Thanks for sharing, Barry G. Kery, KU3X/QRP

You could teach a lot of people on KZfaq how to make a instructional video, very clear and concise I’m totally new to this subject and have learned more from this and the previous video than I have plowing through several hours/days of other people’s videos, thank you.

Thank you for this. I'm studying for my general class test, and this helps to drive into my memory what a trap is. Cheers.

Thank you for all the information absolutely brilliant.

Thanks for an educational video. I have a 3D printer and seeing these little traps, it gives me ideas for making my own. I might try to build a 100 watt version but still keep portability in mind.

Really helpful videos on half wave antenna matching and traps - thank you so much for making them! Mortimer Rhind-Tutt | UK /G4BSK / QRP Enthusiast

Well put together fella.

Been waiting for awhile to finish the efhw. I can see a Digikey order in my future as well.

Very clever , well done! Awesome videos!

Hi Adam, Excellent video. Found it interesting how you used the RigExpert to check resonance. Stay safe. 73 WJ3U

Great video!!

How’d I miss this? Treasure!

I have to admit I´m becoming a fan of your cool small projects. :) Greetings from Chile. 73s

Awesome. Thank you

Top Job Fella. very good visuals and explanation. Barnie M7PBX.

You should look into buying a Panavise. It makes holding those fiddly little parts stable while soldering and won't damage the parts. Another brilliant design. Thanks! KD2SML. 7-3

Great video

Your videos are the best. Building these is probably a bridge too far for my eyes at this point but who knows...

Excellent ❤

BRILLIANT

de Z33ST, Great explanation as always.

Nicely Done! Especially enjoyed the trap testing with the antenna analyzer. Made it 3/4 through the video thinking he will need need pairs of traps per band (thinking center fed trapped dipole not end fed. Oops!). Headed to the garage to fine the epoxy and the magnet wire. keep them coming. de KB7ZUT

Thanks for this video, very well done. The trap are zn excellent idea. They do get stuck on tred branches, but using a telescopic pole, these are awesome. Thanks again. 👍👍👍 73 Julian oh8stn

Multi-Band single length Antenna! 👍

This is so cooooool.

After building two of these now I can say I am amazed how sensitive the tuning is. The slightest widening or tightening can make the SWR dip drastically off the chart. For me, I started by soldering one of the tails permanently to the capacitor then adjust the windings delicately to where I wanted. Then I soldered the other side permanently and retuned because if would out of tune after the soldering. After, ever so slightly widening or tightening to tune it exactly, I would keep testing to be sure it does not move. Once I am confident it will stay in tune I leave where it is (on the tuning wire still attached to the analyzer) not moving it and then drizzle the epoxy over the outer side of the toroid so wires lock in place. Later I come back with a bit more epoxy as a final coat.

Wow, excellent video! Some questions come to mind. 1. When selecting capacitor and inductor components, how can we make a calculation to determine the maximum power? What factors determine the power handling capability? Is there a voltage or current rating for the capacitor? Is there a voltage or current or inductive value or coil type or coil size that determines the power handling capability? What is the limiting properties of the coil? Does it come down to heat? How can we calculate? Additionally, selecting different wire sizes like 28 AWG seems like it might have some effect on the maximum power handling capability. 2. As we add more traps, inductive loading seems to shorten the overall antenna. What calculations and factors can go into maximizing the bandwidth? If we use really small inductor values and larger capacitor values, will we have more bandwidth in the final product? How can we mathematically determine based on the capacitance and inductance values that we choose how long the final antenna will be? How long each segment will be? How much bandwidth will be lost as we add each trap? I am interested in making a higher-powered version of this multi-band trap EFHW antenna and I'm struggling with trying to determine what the overall antenna length will be, what each segment will be after adding a trap and how to maximize the antenna to keep as much bandwidth as possible as well as keep resonance and reduce losses. It seems like there must be some relationship that we can mathematically determine and use to satisfy requirements or failing that, maybe your experience shows some rules of thumb that can help guide in the right direction? For example, using smaller inductance values and larger capacitance values Versus Using larger inductance values and smaller capacitance values. What do these choices affect on the overall design? 3. Sometimes in videos like yours we hear people talk about antenna efficiency. Can you please describe what efficiency means to you? How can we measure efficiency and do a comparison between various antennas? I am very cognizant of having a resonant antenna, but I don't know what specifically makes an efficient antenna. Thank you very much, I am of course subscribed with notifications turned on and 73. W3GUY

so good

The one question I did not hear you explain about traps is what makes them limited in power. Or how do you build it so more power could be used? Outstanding explanation of how to build the trap!! Looking forward to more great videos!

Hi Adam - many thanks for the video - very interesting to see how you tune the traps, and also impressive to see how small you get them. One question about the toroid you selected - why did you go for material type 2? From my limited understanding, this material type has a frequency range from 240kHz to 10MHz, so it would seem they are not ideal for 20m traps (but ok for 40m). Is my understanding correct, or have I missed something? I would really appreciate a book reference where I can learn more about the principles behind antenna design (including designing transformers and traps). There seem to be many “recipe” books showing different antennas can be built , along with accompanying parts lists, but without detailed explanation about the designs - this isn’t what I am looking for! Could you recommend anything? Many thanks again! Edit: I have found more information, so I will answer my own question in case others come. It seems that the type 2 material has a frequency range to 30MHz, not 10MHz as I wrote above. Both type 2 and type 6 material would be suitable, but the type 2 material has a higher permeability than type 6, so you can achieve the same inductance value with less turns. Clearly when making these microscopic traps, that is an advantage! Hopefully this helps someone!

Awesome video. I really like that you use the perf board for strain relief. I made my traps with the ws0ta PC boards and there is no strain relief except for the heat shrink over the ends. My next build will use the perf board. My experience in using the non-tinned perf board is that it helps to clean the Cu with steel wool or sandpaper for easier soldering. Also tune the antenna with the mast you will be using on the summit. The height of the wire will change resonance somewhat but the mast material will definitely change the resonant point for 40 meters. i.e. carbon fiber versus non conductive. Not by too much but still has an effect. de AI6XG

I do not wish to make a pest of myself but I do not know anyone I trust more for a clear understandable answer than you. My question is that after epoxying a 10 meter trap I find it is resonant at 9,100 when I had thought that it was resonant at 10.0. Since I can not adjust the coil I was wondering if I could just adjust the capacitance to bring the trap into resonance or if this would have some other adverse unintended consequence? Finally I have watched your videos at least 10 times and have not found anyone on youtube that does a better job and explaining things. best wishes Tom

Brilliant!! ...wGOAT

I feel like I learned a lot. Thanks! ~K6TJO

Great ! Tnx !!

This is very helpful. I am curious about the capacitor voltage rating though. The trap represents the end of the antenna for the band, so it would also be at voltage max. Even at QRP, this could overwhelm 50V caps. I'm designing mine with 100pf and 150pf 1kv+ caps and t-67 cores, since that's what I have. The winds are reasonable (18-25 range) at that pf. The inductances are low (.6 to 1.6 for 10 and 14 mHz), and I am unsure if that's a problem.

Very interesting video - thanks. Can you use a nanoNVA in the same way as the Rig Expert for tuning the toriods i.e. looping the test cable through the centre of the toriod ?

The dust from your cutting and sanding of the PC board is bad for your lungs, take it out side next time. You have some really good and fun ideas and I enjoy your videos.

Really enjoyable clear teaching! Learned a lot! Subscribed! 73, John - KK7JBZ

Really impressive. How did you figure this out? Saved this video in my antennas playlist because I’m going to reference it a ton. Thank you for showing how you do it. I need to hang one of these outside a snow cave!

A note on capacitor voltage... The 100v capacitor I used is marginally adequate for 5w. If you plan to run 10 or 15w, consider a 500v or 1kv capacitor to prevent over-voltage and breakdown of the capacitor. With the slightly larger capacitors, consider a T44 or T50 size toroid to ensure there's enough space for the capacitor to fit inside.

Excellent video. Thank you for taking the time to produce and share it. I have one question: at 13m:38s you used your AA-35 to test SWR. Could a NanoVNA act as a drop in replacement to do the same thing? Thanks again, -rob

A trick you could try to widen your bandwidth back out on 40m is use the copper braid of some thin coax like rg-316 or rg-317 or even solder wick braid as your radiating element. The thicker the element diameter the wider your bandwidth is, why antennas like the Bazooka came into existence because cheap coax braid is easy to source.

Hi Adam, greetings from UK! Great ideas you come up. I have this project in mind to use some of your kits and ideas to build a backup antenna (trapped) for 20m and 40m that I could attach to a hiking pole (say at a max height of 1.6m) to be used if mast breaks or main antenna breaks or weather prevents mast deployment for example. Of the three configurations your matching unit kit allows, which would you recommend likely to perform better? I have a manual ATU that I could use with a random wire or to touch up a dipole or end fed halfway. Great to have your thoughts on this. Thanks.

Thanks Adam, and greetings from across the pond. I’ve learned a lot, liked and subscribed. 73 de Steve, G0XAR

I FOUND IT!! haha♡ watching now :) 🤜🏻👍🤛🏻♡♡♡

where in the band are you aiming to tune to? the middle? upper? lower?

I just ordered the parts. A trap dipole will be awesome with my KX-2. One question before I dive down the you tube rabbit hole. Can I use my NANO VNA to do a similar resonance check?

Grate Video! I have a couple of Questions have you tested these at 100 Watts and what is the result. have you considered using 2 traps spaced close together with small offset frequencies to widen the BW of some of the wider bands creating 2 or 3 resonant spots on a single band? thanks

I really admire your micro builds. Your work is well done and the fit and finish is impressive for hand-built equipment. If I want to run my KX3 at 15w, what toroid should I use? Will the T37-2 units be a little too small? Those online calculators are pretty cool, but what if I want to use my hand calculator? Do you know where the calculations are documented? I might even write a program for my HP-41CX. 73 de AG7TX

Thanks for the wonderful trap video. I am novice in the hobby and have stupid question. Can I use air core coil instead of toroid coil which has the same uH value?

Question. I’ve tried building a couple of these but my SWR is sometimes close 1.5 to 2.0 when testing where the circuit resonates. Does a higher swr necessarily mean poorer performance? I find myself trying to spread coils to reach the ideal resonance; then removing a turn; then needing to compress the coils. All of this significantly affects the swr reading of the trap on my rig expert. Has anyone else had this issue?

could you use a multiple capacitors to get the right capacitance, if so are there any limitations? Nice video. 73

It would be nice if you showed the final result on your antenna analyzer. ;)

Before I go crazy and build a trap for every band up to 40m, dare I go 80m? I should ask, how many traps are too many? Currently I've built one for 10m, 15m, 20m, and 30m. I understand that the antenna will be less efficient with the more traps that I add, but I'm thinking of also doing 12m, and 17m. Any advice, or just send it? I am using 24AWG magnet wire and T44-2's with some nice 500V rated mica caps.

Hello Adam, I just found you by accident and I was captivated by how small those traps are. I was wondering, could it be possible to make a 160-10m long wire antenna using as many traps as needed for operating on all bands for permanent installation using maybe some larger ferrite and wires ? Great tutorial 73 André VE2WNF

If you were tuning your trap for the SSB portion of the band, would you still adjust it as low as your showing in the video? Does the amount change for other bands? Thanks for the videos and for all you do to help others.

Very cool. Could I build these while substituting caps that are actually big enough for me to see 👀 🤔?

Hello! Great video! I can’t find the shoppinglist though?

Great video! Question, I have a MFJ-1889t. Could I build a trapped counter poise to use with it?

How can I calculate what tyrods and capacitors, magnet wire I would need for traps to use with 100 watts? Is it even possible?

Excellent! Brilliant! What is the maximum Wattage these traps can operate at? Thanks, George - Alberta Canada

Alright Adam, what runway and airport is your QTH under? I hear a lot of takeoffs going on on this Saturday AM build.... LOL!, but only because my situation is similar, under KVNY 16 Right. Very impressed with how you trust, but verify everything in your antenna builds, for complete optimization of the whole antenna on all bands. What size torroids do you recommend if you want to build an antenna like this for a 15w capable, KX3 or KX2 version? The 50 T2's ?

Excellent instructional video Adam. Thinking about your 100v s.m. capacitors, I assumed they should be good for 25 watts, which is 44dBm or 100v pp into 50 ohms. (Maybe add a safety factor so as to not make thise little guys sweat, and not hit them with more than 10 watts.) For a 100w capable antenna, 50dBm or 200v pp into 50 ohms, you'd want 250 or 500v rated capacitors? Or am I forgetting the impact of the impedance change between the antenna socket at 50r and the feed point impedance of the rig end of the half wave wire, around 2.5kohms? In other words, what's the RF voltage swing across the traps (this has to be known at all frequencies of operation), and how should we use that to size the capacitor voltage rating for various power levels?

I LOVE That I Inhereted BUNCH Of Capacitors, Radio Capacitors and TONN Of Other Radio related Stuff From A KGB Aaggentt, I Have Militatry Grade Stuff That Can Hold 2000Watts And Stuff Like That, HUGE TTorroid Rings, Like, You Can Put Your Hand In it If You Aint Huge ;D So Much Stuff, Caps From 7pf to 450 i saw One so jeah,. variaaty is crazy.

Is it important to use a SMT cap? what kind of thru-hole cap could I use instead?

My 12-year-old daughter is a General, and I got her a 705. I'd like to see if there is a chart somewhere with wire sizes, and torrid sizing with losses etc. I know she will be using JS8Call as well as CW and SSB, she is learning CW now, and my 15 yr daughter is running 15wpm. I was planning on 20w to give a little head room. Does anyone know of a chart or have recommendations? Kids will do all the work on the build.

That is awesome I have learned a lot today. If I want to scale this up to say 800 watts how big does the toroid and capacitor need to be? Thinking this may be good for the qth also. Thanks Jeff ke4fwe

Question - Why two 30m traps? I understand the loading coil is 30m and then you cut wire for 20m and you put the 20m trap there. Cut wire for 30m. But why the 30m trap when the loading coil is 30m? This is something I would like to try but for 40m and 20m

Adam, what's the thinnest wire, I have tried 26awg and works perfect, now I am going to try , Surfstrand Copper Trolling wire, 30lbs, .028 in (0.71 mm) dia. 600ft is $30

Great stuff! What would you recommend for 70cm and 2meter handheld yagi antennas, 10watts?

Should a 20 meter trap be resonant at the low end of 20 meters (14.0) or should it be resonant at the high end of 20 meters (14.350) , thank you Tom, W1TWS

When you set the antenna up with the traps, on the first 20m section that you set up, should you still set up the loading coil on the black tube that came with the kit still?

At 0:45 you mention "...for a little more efficiency...". How do you calculate the efficiency?

An end fed half wave antenna should be capable of multi-band operation without the traps. Certainly a 40/20 meter antenna should work without traps, though it would be optimum for the CW part of 40, and phone part of 20. With a simple antenna tuner you can cover all of both bands. I cut pc board with a jeweler's saw.

excellent tutorial. Question: is it possible to check the resonance of traps without an antenna analyzer?

Great job on the traps, thanks! AA7OY

Your analyzer sweeps very quickly compared to my AA-230 Zoom. Do you know if that is the nature of those analyzers or did you adjust a setting to get it to weep faster?

Excellent build instructions! One question though: Since an EFHW is resonant on harmonics of whatever frequency it is cut for, should it not be possible to do away with the 20m trap and just have one for 30m?