NOTE: DO NOT CUT YOUR ANTENNA WIRE FROM THE END OF THE WIRE. Measure from the auto transformer to the desired length. This is because you may not have exactly 75ft of wire. So if you cut from 75ft to 65 feet, you cut 10 feet. However, since the kit is approximately 75 feet, you may cut short. Makes sense? Cool. email me with questions or concerns. Other mentions regarding the video: LENGTH. I am aware that the calculation for the half wave is L=492VF/F or (492x.97)/F. If F = 7mhz ... L=(492x.97)/7.000 or L= 68.17714285714286FT for the EFHW. Although I recognize this is the correct way of learning. This will be something fun to go test in the future. I have wire with a known velocity factor and we can see how close the numbers are as my EFHW is more towards 64.5-65 feet. I will test this because I am very intrigued with what I have done vs the math that is mathematically accurate. KB6NU has a writeup over here: www.kb6nu.com/dipoles-shorter-half-wavelength/

Thank you for making the print file available. I've just got myself an entry level 3d printer and this will be one of my first prints.

The resistive effect of inductors and capacitors is called reactance. They react to the magnetic or electric fields, and this recatnace is frequency dependant. Inductive reactace is positive on the smith chart, capacitive is negative on the smith chart, hence inductive reactace = 2 * pi * Frequency(Hz) * Inductance (Henry) and capacitive reactance is 10^6 / ( (2 * pi) * Frequency(Hz) * Capacitence (micro Farads)) -- this is 10^6 because of the conversion to microfarads. Regardless you can see this in your nano vna by finding the resonant point on your antenna and tunning slightly above and below it, the reactance+/-johms will flip polarity between inductive and capacitive depending on if you're tuning higher than the resonant point (capacitive) or lower (inductive). You can "tune" any antenna to react at near a 50 ohm load with the right amount of added reactance. This is precisely how an antenna tuner works, but it's far more efficient to do it at the antenna ;)

@HAMRADIODUDE

4 ай бұрын

Thanks.

Well done Sean. K6ARK is 100% correct. His answer is succinct. It is the ground below the radiator that adds capacitance between each end of the EFHW and that effect pulls the resonant frequency away from what the wire is cut for. The PROBLEM is that height above the ground changes for each band, and therefore so does the amount of capacitance between each end as influenced from the ground below. We can NOT use a tuner here because it would likely saturate the UNUN core, so making the wire "resonant" on all bands is the only way to go. 73 & keep up the great work.

This was all new information for me, but you explain it in an easy way. Also, love the shirt!

@HAMRADIODUDE

4 ай бұрын

Awesome! Thank you!

Very nice video; this information is either completely missing or at best just mentioned in passing in most EFHW build instruction! Good job 🙂

@HAMRADIODUDE

4 ай бұрын

Thanks so much! Fun to learn and pass on the info! Cheers!

Great video, thank you. I’m currently making my own EFHW and have this issue and am experimenting with and induction coil.

@HAMRADIODUDE

4 ай бұрын

Good luck!

Excellent. I like that there simple that can make a difference. Just got your antenna kit this week. I'll look to build as soon as I can find an hour or so to get it done. 73, KN4VA

@HAMRADIODUDE

4 ай бұрын

Awesome! Coil is on the way! Simple is key! Thanks again and shoot me an email if you need anything

Thanks for sharing your time with us. I am very new and learning. Have a great day.

@HAMRADIODUDE

4 ай бұрын

So nice of you, have a good one! Enjoy!

@2EOGIY

4 ай бұрын

@@HAMRADIODUDE I have seen a similar solution but with the capacitor on the other side, 6-7 ft from the end of EFHW, so if you cut too short. You could say it was on purpose. :D

@HAMRADIODUDE

4 ай бұрын

Haha.. that's Great idea. Actually I have equipment to make a small pcb

@2EOGIY

4 ай бұрын

@@HAMRADIODUDE, the only issue is that the coil extends the antenna, and the capacitor shortens, so you will need a longer attachment. The positive is that the bandwidth should be wider. I wonder if this is the way to cover 80m, not just the piece of the band.

Hi Sean and thanks for the video! I´m using a coil with 4 loops at a diameter of 5 cm (1,97 inches) about 2 m (6,5 feet) away from the 1:49 transformer and it works perfekt at all of the 4 bands. 73, Bernhard

@HAMRADIODUDE

4 ай бұрын

That's great info. Which toroid do you use? Thanks!

@DC6NS

4 ай бұрын

I´m using 140/43

I’ve got compensation coils on all my EFHW builds to bring in the higher bands…but I just use plastic pipe or conduit and drill it out. That 3D print is awesome….by far the neatest way to do it. 👍

Thanks for the video. My EFHW was put up to be a fast and easy temporary antenna when I first moved into my current home. It has worked so well that it has become a permanent and primary antenna. I'm in no hurry to take it down or replace it. Just a thought...I haven't experimented very much to be able to prove this...but I think if you make the antenna around 135 feet so that it is a half wave for 80 meters then it may bring the resonant points more in line with the higher frequencies. Also, I have cut the wire exactly half way and inserted a capacitor. That seems to help drop the resonant points right close to all the bands 80 - 10 meters.

Thanks for the nice down to earth presentation. I used an inductance and a short piece of wire at the end of my 40m efhw to get into the 80m band. I am lately experimenting with coil/capacitor traps on the efhw. Using a homemade, printed circuit board to mount caps on. Pcb again fits inside a piece of 20mm pvc conduit with the coil wound on the outside.

@HAMRADIODUDE

4 ай бұрын

Id love to see this. Do you have a photo online anywhere

@paulsengupta971

3 ай бұрын

@@HAMRADIODUDE Tim, G5TM, has some videos about using an EFHW with traps.

Great info, Dude. My EFHW looks great on 40 n 20, "too short" on 15 n 10, gonna try this! Cheers, K7KS

@HAMRADIODUDE

4 ай бұрын

Awesome. How long is your wire right now, do you know? I am collecting some data.

@AlanElBee

4 ай бұрын

@@HAMRADIODUDE Probably 64 ft + six inches give or take. Anything longer dropped 40 and 20 resonance too low. It's the TennTennas xformer which works great otherwise. I just noticed the Myantennas EFHW-4010 uses a 63 ft radiator + a coil. Tho using a 56:1 xformer (!!)

10 turns on my coil...and I'm still tuning along...this inverted V will get to me, in the sky, way up high, but I'm singing a happy song.

Thank you for using a VNA display to graphically display the changes to the antenna response to the coil. While the results can be numerically expressed, the graphic display is helpful.

@HAMRADIODUDE

4 ай бұрын

My pleasure. I am trying to incorporate more visuals. Have a good one.

Thanks!

@HAMRADIODUDE

10 күн бұрын

You bet!

I use stainless wire rope and it works well for many years, but it is a little more difficult to tune

Hey Dude, its been a minute. Marconi and Tesla used trapped end feds. As many 7 traps in a single sloper. EFHW is just one section of the OG Trap Antenna. Using the EFHW, make an inverted V, or inverted L. The magic numbers are, 12 and 1/12

@HAMRADIODUDE

4 ай бұрын

Thank You! Hope you're well.

Thanks 👍

@HAMRADIODUDE

4 ай бұрын

Thank you

Hey Sean, great video! My recent problem is with an inverted L random at 84' with a 50' coax using shield for counter. All was good until the LDG 9:1 started giving me intermittent issues with an open circuit. Fast forward to today and it's been a week of grief trying to utilize another 9:1 a guy made for me last year. I've been trying to build my own Unun but parts are scarce like Adam's toroid for the 100w kit. Nothing will tune now and Im physically exhausted from changing out feedline and etc... The strange issue now is that unscrewing the UHF connector from the radio with just the center pin left connected restores the signal. Back to square one and start over I guess. Id like to add you coil but Im using 14 THHN wire. I need to start with a new 9:1 kit and check everthing I suppose. Thanks for the good video. Any suggestions welcomed.

@HAMRADIODUDE

4 ай бұрын

Have you had a chance to short out Counterpoise to Center with 450 ohms of resistors?

I have this efhw 80-10m antenna in average 5 m above the ground with a 110uH coil to make it shorter at 80m. No counterpoise. SWR in average is 1,5-3 and with an atu I get it down to 1,0. What is really strange is when I add the counterpoise. Seems to mess up 17m... atu will not match it. When I remove the counterpoise atu is able to match 17m again.

Great video! Sorry if I missed it, but why 6' from the transformer? I'm unclear on what thought / calculations go into the placement of the coil.

@HAMRADIODUDE

2 күн бұрын

I got you on this one, but it may take me a bit of time to get everything brewed up. Do you have a week or so? Thanks, cheers!

I have always been told the capacitor is for the upper bands on the EFHW with 49:1 UNUN I wonder if anyone has tried an adjustable cap to see if it will tune in the upper bands.

@HAMRADIODUDE

4 ай бұрын

That would be a fun test.

Would the intuition that an inductor will behave as an open circuit from some frequency onwards help? I think after your implicit reference to the inverse relationship between length and frequency, that intuitive analogy might help.

@HAMRADIODUDE

4 ай бұрын

I think it does help, thanks. I think I need to read up on Lenz's law more and incorporate revisit the example.

Did you add extra wire to the antenna to cover the lemgth used in the loop - or did you make the physical lenght slightly shorter after winding a bit on the coil. BTW, the excellent Chameleon LEFS 8010 have about 6 turns on the coil, length of the 40-10 meter part is 63 feet + 67 feet for the 80 m extension

@HAMRADIODUDE

4 ай бұрын

Great question. To answer your question, after tuning for 40 and adding the coil, I did not have to add wire the coil shortens the antenna in that aspect. I did have to add wire initially because I originally cut too short for 40 (mistake on my post part)

Y en que parte del irradiante va la bobina?

@HAMRADIODUDE

19 күн бұрын

La bobina va aproximadamente a 1,8 m del devanado del autotransformador. Aproximadamente 10-12 vueltas. Tener una buena.

@marcelookunz-lu1fk

17 күн бұрын

@@HAMRADIODUDE QSL - 73

How/where did you insert the coil?

@HAMRADIODUDE

4 ай бұрын

Hello, there. Did you purchase a kit from me? If so, shoot me an email. In short, you start rapping about six feet from the actual auto transformer or the toroid. . If not, which toroid, are you using for your efhw

@Doodlez4

4 ай бұрын

@@HAMRADIODUDE i didn't purchase your kit, i apologize 😀. I was thinking of trying this with my setup. 240/140 31 mix torrid at 49:1.

@HAMRADIODUDE

4 ай бұрын

No problem . You may not need a coil. What's your swr look like on the bands as it's is

@HAMRADIODUDE

4 ай бұрын

About 6 feet from the toroid with mine

I run 49:1 on mine

Don't cut too much. Shoot for resonance around 7 mhz.

@HAMRADIODUDE

Ай бұрын

Thanks! Today I am going to jump into 80m. I think the coil will be key to making this work with 80 as well. the 7mhz may be the key factor here (shoot for that to start).

@Philip-KA4KOE

Ай бұрын

​@HAMRADIODUDE another ham puts caps in the middle. Video here on youtube.

I had begun adding a coil to mine when i build them a few months ago. Good to see you share this hwre. N5OBC

@HAMRADIODUDE

4 ай бұрын

Very good! What configuration do you run? 56:1, 49:1, 64:1? Cheers

Great video, 3rd time watched!

@HAMRADIODUDE

2 ай бұрын

Awesome! Thank you! Don't forget to come back for round 4 :D Nice chat this morning.

Thanks!

@HAMRADIODUDE

4 ай бұрын

Thank You!