Fold the end of a Dipole Back - What's Happening?

This took me a few years to work out - folding back the end of a dipole or vertical antenna. But I got there in the end. There is no doubt a formula for this, but this is my practical experience. Here is the link to the Linear Loaded Dipole: • Small Cheap Linear Loa...
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[@KO4TDA]

Has anyone told you Cal you’re brilliant? I’m over here with my head spinning! Keep up the great work!

[@DXCommanderHQ]

Haha.. Thanks!

[@presidentspilot]

Callum,... you sell SUPERB ANTENNAS because you sell yourself, first!! I make it a habit to watch EVERY VIDEO that you produce, as fast as I can get through each one of them. I have learned so much, even at 82 years of age, with my ticket that I got at age 12!! THIS WAS A GREAT VIDEO to put in my bag of tricks!! Kudos, Callum!!...and I THANK YOU, SIR!!...Ron,.. K6PAM

[@DXCommanderHQ]

Wow, thanks! Kerboom!

[@tonyrome5584]

Of course you are 100% correct. I also discovered this effect about 14 years ago putting up a 40 meter dipole. That is also why I understood your design of the fold-over's of your DXCommander vertical. Excellent video!

[@DXCommanderHQ]

Ah! Fascinating!

[@janarets1880]

Great video!! So this is the reason I got problems to tune my inverted V. Thanks again

[@Simon-qn5wm]

Thanks Callum I have now realised why my antenna projects had not given me the results I expected on quite a few occasions. I always thought that folding over insulated wire shortened the element. Glad I watched this video.

[@DXCommanderHQ]

Yes, me too..

[@MisterBigDave]

Just did some of this over the weekend before watching your video. I didn’t come up with any formula but results were similar. Great stuff!

[@DXCommanderHQ]

Ah!!

[@erpece]

Wonderful explanation, Cal - thx!

[@jesselannigan2300]

Well this is a revelation to me. It makes perfect sense though. I'm working on a new 17m rotatable with wire elements. You've given me something to consider while I'm running the tests. Thank you!

[@DXCommanderHQ]

Woo-Hoo! Good thinking.

[@johnsinclair3067]

Inspired by your video on making the loaded dipole, I started running a linear loaded EFHW for 80M. Physical length is right at 93ft versus 131ft for a non-loaded EFHW. Easy to make: two stranded insulated wire cut at 93 feet, solder the pair together at one end, at the opposite end connect one strand to the balun and tune by trimming the other strand. Lots of good DX (Europe and South America) from Kentucky. Thanks for all of the practical science. PAX John (ko4hzh)

[@DXCommanderHQ]

Fabulous!

[@richardwhitcroftkc3rrw63]

Great video! when I built my Pseudo commander classic I had issues with the tune. I had taken the fold over and twisted it around itself.... I did not get the correct tune until I made sure the fold over was the correct length and NOT twisted. It is all about the experiment. Thanks for your wisdom!!

[@DXCommanderHQ]

Thanks for sharing!

[@michaelmohr9700]

This is cool Callum,...very often played at Dipol tuning by adding cuting wiring ! Thank you very match for this video !

[@DXCommanderHQ]

No problem 👍

[@apjbuilder]

Thank you! I was always curious about that !!

[@michaelglauser7877]

Keep these coming my friend! I watch all your videos and appreciate your hard work. I also share what you taught me with others and credit you as source. :-)

[@DXCommanderHQ]

Michael! Trust you OK old friend. Thanks for the encouragement! 73. Cal.

[@adamtaylor31]

You are awesome, Cal! Thank you for these videos, I just subscribed...it would be foolish not to! And thank you for the nudge toward the SWR calculator, i just plopped it right on my desktop. We will be moving out to the country soon and I will be able to flex my antenna wings a bit. Cheers from Maine!

[@DXCommanderHQ]

Welcome aboard Adam!

[@TRIPPLEJAY00]

Perfect timing Callum, because I just made a wire dipole for 10/11m and when I tuned 1:1 without loops at end. Then I made loops and found no difference. But you have confirmed for me what was sitting at the back of my mind. 😆 Thank you always for the free Science lesson's. I appreciate you dearly.

[@DXCommanderHQ]

Perfect!

[@Bond2025]

Forget that, use an end fed half wave antenna. You will be able to use it on multiple bands.

[@houseofhamradio]

Thanks Cal, your timing is impeccable. I just got my Classic setup and have been tuning it using the SWR Calculator and have experienced precisely what you are referring to. Example, I needed to adjust my 40/15M element from 6.98MHz to 7.150MHz which the calculator told me to shorten by 23.76cm. I folded that much back (as well as twisting it) so I didn't cut it and regret it later and it only went to 7.045Mhz which comes out to 38%... pretty darn close to 1/3 which might have been even closer if I hadn't twisted it. Before this video, I searched high and low for the answer as I suspected what you demonstrated. Now I know and can account for it. Thanks and 73s

[@DXCommanderHQ]

Hey good news indeed. Now a LOT of this stuff used to me in the manual but a certain KZbinr thought my senseless descriptions of various physics topics were irrelevant - however I think we need an "advanced user guide" for all these little tricks!

[@houseofhamradio]

@@DXCommanderHQ If I have learned nothing from my electronics days is never let theory get in the way of reality. Reality always wins. The thing that had me questioning this to begin with is how the 40M element folds back down along the mast. If folding back nulled out then you could never get longer than the length of the mast (theory) but we both know that isn't the case since the antenna works (reality)

[@IrishHamRadio]

Very good man… I always wondered about what I would call “folded dipoles” for HF… You’ve given me an experiment idea 💡!

[@DXCommanderHQ]

Go for it!

[@ralphwilmot6351]

3 years ago I did the same thing to an 80m EFHW and at the loop back point which was about 4m high, the last 5m length sloped down to 1.5m high at the end of the aerial which also made it very easy to tune and enabled it to fit my garden. Your video now makes sense to the odd length calculations I found at the time. G4PEY

[@DXCommanderHQ]

I know, I have been baffled by this one for a while!

[@ronwolenski-n8wcr]

I never knew about the foldback at the end of the antenna affects the length. I was taught long ago that it doesn't matter because the antenna would end at the foldback. That must had been for uninsulated wire only! Now it makes sense when I was trying to get a efhw to resonant I had a heck of a time when I had a lot of wire folded back, none of the changes I made made any sense! Thanks for teaching a OM new stuff. Every time I watch your videos I learn something new. I'm definitely saving my pennies for a DX commander!

[@DXCommanderHQ]

Hey Ron! Yes, I was told the same!

[@dsg12345]

@@DXCommanderHQ What about uninsulated wire? Is the same true for that? I wouldn't think so.

[@VK3TWO]

Love it! Thanks.

[@vjdav6872]

👌 - i like practical, most do! Thanks cheers

[@DXCommanderHQ]

You bet!

[@W8VHS]

Thank you Sir. 👍👍

[@DXCommanderHQ]

Welcome 👍

[@edcozart9916]

Another great topic today Callum keep them coming brother I’m feeling wiser everyday sir😎😎😎😎 Ed W9US

[@DXCommanderHQ]

More to come Ed!

[@markramsay6399]

Great video cal. I do a lot of calcs and modelling in my day job. But nothing beats really measurements. Sometimes we do not really know why something works, but know that it does work when checked with measurement. Just like you have done ! Mark, 2E0MSR

[@DXCommanderHQ]

Very true!

[@bodstrup]

Thanks. Some youtuber’s claim that you need some separation between the wires to get the 3:1 efffect - though in context of saving space by folding the dipole. Looks like starting with cheap wire and cutting is the optimum solution. And latest article I read, investigating velocity factor claimed that you need to multiply by a further .95 when using insulated wire. So for uninsulated wire, wave length formula is 0.95 x 300 0 285/frequency (Mhz). For Insulated wire, 0.95 x 0.95 x 300 = 270.75/Frequency (Mhz). I like the practical approach, trial and error !

[@DXCommanderHQ]

Well, I've never seen anyone on KZbin do as many experiments on KZbin as me .. particularly on this subject..! The 3:1 is not constant.. In other words, the ratio is non linear.

[@johnrees44..G4EIJ]

Brilliant, Cal.. This is going to be so useful to so many people..Thank you.. John.. G4EIJ

[@DXCommanderHQ]

Hope so!

[@dklarkinrn]

I have been using your SWR calculator daily as I tune up my new DX Commander. I have added two lines to your calculator for us yanks. In box E7 I added the formula =(E6/2.54) and that converts the centimeter answer in E6 to inches (in decimal). Then in E8 I added =(E7) and in the "Format Cells" menu I changed that box to "Fraction, As eighths". Now when I add the resonant and aimed frequencies I see the result as cm and inches without having to think.

[@DXCommanderHQ]

David, may I ask you to send me that please? qrz at m0mcx.co.uk - sounds great for the 4% of the world who live in 8th :)

[@patrickbuick5459]

Shorted vs capacitance because of the small separation of the fold over legs with dielectric in between (air and insulation).

[@mikemiles3068]

Good video❗️

[@DXCommanderHQ]

Glad you enjoyed!

[@W9HJBill]

As usual, great video Cal. Like you, I prefer applied over theoretical.

[@DXCommanderHQ]

Same :)

[@bradbuck7891]

Nice antenna video- A rare one devoid of “uhs” and “ums”. Pace was such that I didn’t need to speed it up. I sometimes have to play slow talkers at 1.75 x playback speed! Great info in this video, and very listenable

[@DXCommanderHQ]

Yeah, I am same. I run KZbin between about 1.25 and 1.75 myself!

[@mikeerstad3705]

Good to know and it makes sense....all of my di-poles are insulated wire....Thx Cal...

[@DXCommanderHQ]

Ah. Cool.

[@tribulationcoming]

Thanks.

[@DXCommanderHQ]

No worries!

[@Radio_Zombie]

That explains a lot. Got my multiband fan-diple working after a lot of trial and error ... a lot of "no way, this is gonna be way to long/short" for what must have been 100 adjustments... Now I understand why.

[@DXCommanderHQ]

Same!

[@gmrjinx27]

The first antenna I made was based on a folded dipole. Used 300 ohm tv twin lead wire cut for 40m cw. I was using an old all tube radio. Have no idea the swr. The transmitter loaded up just fine. Made a lot of contacts on cw. This was in 1982.

[@DXCommanderHQ]

Fantastic memories, I'm sure!

[@DonzLockz]

Very interesting Callum. I am now smarter than 10:58 min ago. 😁👍

[@DXCommanderHQ]

HAHA Very good! :)

[@bren42069]

I took the end of the wire and wrapped it around itself to shorten it, that worked and it tuned up

[@americaswayout4489]

Cal, finally I have made the deal on relocating and rebuilding my home. I am in a flood zone so it will be built on stilts as much as 8 feet above the ground, plus it will be two-story so I may be as much as 25 feet or more to start, and no metal roof. It will likely be after the first of next year before it will be finished so I will be out of sorts until it is finished, plus I plan to do my open heart operation with weeks in the hospital. By then you will have designed and built something new but anyway when the dust settles I still plan on being a "DX Commander User" !!!

[@DXCommanderHQ]

OK friend.. Good luck fella!

[@americaswayout4489]

With the world economy about to flatten out again and the inflation, maybe I need to resurrect my old blog about economic survival that my user name came from. Things are not as good as they could have been if the Donald was still in office, America blew it giving Biden the chance to destroy everything as he has, but 2 years is not really that far away and folks will be happy to have his harsh treats and cheap gas again by then.

[@temporarilyoffline]

I've been taught (right?/wrong?) that if you fold over and wrap around you're going to gain some capacitance, but cancel out the linear loading effect. That's how I tune all of my antennas, then when I'm happy, I cut off the excess wire (leaving a loop for hanging) and rely on my ATU to do the rest - because no antenna is ever 100%. Would love to get your take on this twist method!

[@DXCommanderHQ]

Hi Steve.. Well after spending hundreds of hours in the field, I still maintain that regardless of capacitance or loading, the 3:1 always seems to hold out for me..

[@temporarilyoffline]

@@DXCommanderHQ ah, Ok. I'm starting to wrap my head around it. Thanks!

[@Graeme_Lastname]

Now for your headache: You need to consider both the capacitve effect and the inductive effects over the length of the folded length + a little bit. What type of ground plane you're using. I've gone through this headache inducing problem once before. Got to consider the dielectric properties of the wire insulation, etc, etc. ad nauseam. Your system system works, thank you, I'll use that. 🙂

[@DXCommanderHQ]

I prefer trial-and-error! LOL :)

[@peterlowrie1216]

Superb. I can see a few 3/4 waves being built for a bit of late summer island hoping de MI5JYK.

[@DXCommanderHQ]

Do it :)

[@Mottersmotters]

Jesus Cal you have just blown my mind. Haven't got a clue what's going on now. Lol Motters M7TRS 73

[@DXCommanderHQ]

HAHA Poor you!

[@philwhoareyou3677]

Great video Callum, as discussed previously i have seen this in action using a VNA and going through this process and whole heartly agree that the ratio changes as you get back closer to the feed point. As for the fact that people think that folding it back would shorten it is interesting basing on the fact the electrical length never changes until you actually cut the wire. The complex maths required to work out whats actually going on is way above my pay grade. But would also be interesting to work out the antenna radiating efficiency of this as in my mind when you think in sine waves and time delays across a peice of wire if you start folding back against yourself the electrical current would get to the point they would start counteracting themselves thus becoming more like an open air dummy load? So many questions! Anyway again cheers and great video.

[@DXCommanderHQ]

It's all about pay-grades - agreed!

[@LouiseBrooksBob]

A VNA should show what is going on in the Smith Chart since there, the region above the x-axis is the inductive impedance and the region below the x-axis is capacitive impedance. One might start with no fold and start folding and examine the changes.

[@davidw460]

Hi - just my simple thought on the impact of folding back on radiation efficiency - for sure the far field is not going to be improved by folding some of the radiator back but it does allow us flexibility to resonate the antenna in a smaller space. If going portable I use fold back, as next time I might need that bit of cable :) .

[@Roddy1965]

My take is that folding back insulated wire shortens the radiating length (because the radiation from the fold-over is 180 out of phase with the non-folded section), but the electrical length is the same.

[@simoncooney9268]

THANKS CAL for an M7 this is great cheers please more stuff for M7 for intermediates licence calculations with calc and how we do it oh im 54 yrs ols lol

[@DXCommanderHQ]

Sure thing! That's all my style :)

[@avaughan585]

Another word I like for practical science is engineering 😉

[@bobmcconomy9961]

Callum, your most recent video showing the installation of a DXCOMMANDER shows you creating a loop in the 40m element below the spreader. What impact does this loop have on the element length?

[@DXCommanderHQ]

Not a lot really.. In isolation, if you just create a small loop, yes you would see a change in element size but for 40m band, it will be negligable.

[@bobmcconomy9961]

Calum, I have a DXCommander classic that I am re-stringing. Your latest DXCommander video shows you installing a 40m element by putting a loop just below the top spreader. How does this loop affect the length?

[@DXCommanderHQ]

Bob, don't worry about it since you will add/subtract at the very end anyway and 100kHz is huge on 40m so you probably won't notice.

[@HamRadio200]

so when we build the dx commander, when adding length, do we add the length to the end, then fold back the regular 6cm, or do we add the wire to the end and not change the position of the original 6cm foldback, essentially creating a longer foldback?

[@DXCommanderHQ]

OK, this is what I do (but not for the user guide!).. Let's say I need to add 1 inch (25mm) to the end of an element.. All I do is graft on TWICE that to the foldback - and it normally works. If in doubt, drop me an email.

[@johngraham5521]

Hi Callum, I got bitten the same way as you, ONLY didn't understand what happened, at the time. I laid out approximatly a half wave of 10 gauge pure aluminium electric fence wire, for 160M. Raised the centre 18 meters high, attached end insulators and rope and pulled the ends out. SWR good at 1.8 Mhz (I wanted 1.850Mhz). I folded back/ twisted around about 1Meter at each end, Perfect at 1.850 Mhz. Ends looked ugly so I cut 500mm off the fold back from each end to make it look tidy. SWR tune went up to 1.9Mhz,????. #@$%&. I lowered the ends and pulled back all the 500mm of fold back, until I had just enough to go through the insulator eyes and got 4 turns around the element at both ends. Luckily tune came back to 1.850Mhz. Contest antenna was saved. . Scarey stuff at the time. Thank you for explanation..... John

[@VE9ASN]

Great video as always. So based on antenna ratio, can we come up with a rough guidelines for 1/4 wave through 3/4 wave?

[@DXCommanderHQ]

Les, drop me an email so I can understand this question better - there might be a video in it..

[@richardcallihan9746]

What if you did the math and cut the wires. Then put some ring lugs on the end of the wires, just bending enough wire so as not to pull back through the lug barrel. Make a few Loops with a suitable suitable tie-rap in between the insulators and ring lugs? Once tuned crimp and solder lugs and replace the tie-raps. A small non-metallic dead-end grip, like are used on utility pole guy cables, would be ideal if exists.

[@n0vty873]

works on efhw's too

[@baslev]

I think it is just how far you fold back the insulated wire. If you fold back a large length it will act as a lineair load. But if you only fold back a tiny bit like 2-5 cm it will certainly affect length. At least that is my experience. Use this method with insulated wire to tune my 4 band square halo which uses full size folded dipoles. The type of antenna could be playing a role? 73, Bas PE4BAS

[@richardcallihan9746]

Does anyone know if a non-metallic dead-end grip exists for small wires? I used the metal ones to guy utility poles and hang stop lights over roadways. Poles were hit occasionally and the cable 3/8" broke before the grip slipped, so easy to install as well. They sort of look like a hairpin and are pre-formed to match a certain dia. cable and you simply twist on the cable w/loop at the end.

[@DXCommanderHQ]

I think I know what you mean.. But I don't know where to get them.

[@klartajanssen4368]

Hi again, second question, if you schorten the wire will de “bending point of the wire” be at the same length from the feed point, or do you move that one too. So the new wire length divided by two which gives us in total a shorter antenna? And if you didn’t do that, why not?🤔

[@DXCommanderHQ]

You can do either.. If you fold the antenna back, the frequency will gradually go up.. Try it! :)

[@daveh9907]

I sure can't get my head around this antenna "stuff" and find it very Interesting. Just reading the Ladder line cancels out electromagnetic waves, isn't that going on here... ? I enjoy listening to you I have no idea what reactance is and will keep looking for a study book for noobs.

[@DXCommanderHQ]

Hey.. I'm the same.. Go one step at a time..

[@dbcustomrc]

KQ4GYT, just got my cert recently and gearing up for general. I’ve been loaned a Kenwood unit that hits 160-10meters. I’m in a budget pinch and can’t afford a lot of fancy kit so I’m looking at building a dipole. I’m limited on available space to mount the dipole and I was curious about this folded design. I’ve been told to run a half wave 80 meter dipole which is going to put me around the 122-125’ mark. Is there a way I can shorten that up using the folded method? Would using inductor coils help?

[@DXCommanderHQ]

OK Daniel, so folding it IS the inductor. If you want 75m, then start with our measurements (ABOUT 25m folding back on itself then trim to suit. So you will need at least 25m of total length. Beware, the harder you load this up, the more losses that will occur and the tighter the SWR curve. I strongly suggest starting with 40m and getting that working. That's what I did. After a few weeks of settling into 40m, you can ADD another set of elements, say for 80m. 40m will also give you 15m band. But to achieve that, you can shorten the 40m element by around 3ft - but ADD 6ft to a foldback. This will bring 15m down. I've done all sorts of videos all about this... If you get stuck, drop me an email.

[@SMShannon55]

I’d be interested in the difference between a simple fold over and a slight wrap of the folded end, say one turn over six inches. It definitely seems to make a difference but I don’t know how to predict the effect.

[@DXCommanderHQ]

Yes.. A small foldover is still about 3:1.. So a 6cm foldback is roughly same as increasing length by 2cm with no foldover.

[@klartajanssen4368]

Hi Cal, Iowa’s wondering about the 3:1 and 5:1. first you shortened the wire 3 x 70, about 2.1 meters. It was too much. Then you tell us about the 5:1 ratio. So 5 times 70 right? But then I would schorten it even more.

[@DXCommanderHQ]

It seems to be MORE loading near the feedpoint, yes.

[@chrisbartlett6022]

When you did "Toms" loaded 80m dipole and cut what you thought was the right amount off, did you then undo the tape and in effect shorten the length of the dipole further by bringing the cut ends back towards the coax. Or did you just trim what you thought was the right amount off, without re folding the full antenna. Just wondering if that made the difference in what you found re effective ratio of cut?

[@DXCommanderHQ]

Chris, I just cut some off the major foldback near the feedpoint.

[@chrisbartlett6022]

@@DXCommanderHQ OK, that is interesting. I am not suggesting you try it, and I have no need for it myself. However if anyone else is going to try this out I wonder how much difference re folding the entire element would make, would it then return to the 1/3 ratio. Idle curiosity I suppose. Probably more curious than normal as I am stuck in the shack mainly with Covid at the moment :-(

[@chrisb3989]

I always fold my antenna wire back to tune it if you closely wind it back it shortens the element as if it’s cut at the fold back……you have to close wind it so it’s touching. I don’t bother measuring specific distances just Chang it “ bit at a time” and measure swr each nibble

[@LouiseBrooksBob]

Folding an insulated wire back on itself must create something with capacitance and maybe even inductance as it will be a loop of sorts. It might be interesting to see this on a nano VNA.

[@DXCommanderHQ]

Yes, that topic needs somoe SCIENCE.. I would love someone to take this on.

[@99corncob]

Callum, I am confused by all the multiples. I have a Rapide that I built with the 40m fold-over. It tunes to about 7.2 now and I need it at 7.1. Your calculator says I should add 13.64 cm. Do you say that I should try adding 3 times this much (~40 cm) to reach my objective? Or 9 times as much?

[@DXCommanderHQ]

OK, so it's NOT a harmonic, just a q/wave.. So in your case, add about 3.5 times as much - then cut back a small amount for final tune..

[@99corncob]

@@DXCommanderHQ Thanks for the reply, Callum. I'm on it.

[@oldfartonabmx2122]

Wonder if I could tune my efhw, by using a pulley on the end and paracord back to the feed end to pull it back and forth ? I'm hoping to (finally!) get it temporarily strung up tomorrow, then eventually get it higher with some poles.

[@DXCommanderHQ]

What an amazing experiment! The further each wire is away from each other, the greater the loading, but it might work :)

[@oldfartonabmx2122]

@@DXCommanderHQ yes, I was thinking it’d have to be a small pulley diameter and maybe some tube to hold the wires close

[@REKlaus]

Makes sense. Now what happens if you fold the end back and then wind it around the main insulated antenna wire?

[@DXCommanderHQ]

Well... sort of the same really

[@eugenecbell]

I have always wondered about folding over the end and never been comfortable with it. I have another question. While studying for my US Extra License Exam, I learned that propagation along an uninsulated wire is practically at the speed of light, but propagation along an insulated wire can be much less, like only 60% of that speed. If this is true I think insulated antenas should need to be significantly longer. Is this the case or have I misunderstood something? Thanks for all the inteligente answers, to follow. Thank you for all your great videos!!!

[@DXCommanderHQ]

Well, I honestly thought it was the other way aroound but DX10 insulated wire (my wire) is around 93%

[@hamtek]

Thanks Cal, very interesting! I am slightly confused though because you say there’s a 5:1 rule when the elements are folded almost entirely in two, and when you initially tried the 3:1 rule, you took too much off. Did you mean not enough off, or do I have something twisted in my mind?

[@DXCommanderHQ]

The 5:1 is when the wire comes right back to the beginning of the feedpoint and 3:1 right at the very end of the element..

[@hamtek]

@@DXCommanderHQ Thanks Cal, that's what I understood, but when you initially followed the 3:1 rule then you would not have taken too much off, and I think you said you initially took too much off before working out it was 5:1.

[@kevinborders4387]

Ive been in ham for about 12 years now, so, still a newbie by comparison to alot of guys. But ine thing ive always said, theres a reason we call it a hobby and not a science. Because all theory in the world doesnt add up to real world application

[@jonthebru]

I watched the video where the expert said folding it back effectively shortened it like cutting. How about twisting the folded wire around the element, I'll have to try that. A 40 meter dipole had the ends going through the insulator and then were soldered, that did the trick unless it needed to be lengthened.

[@DXCommanderHQ]

If you make a loop and then solder it back on itself, the overall length will be to the end of the loop.

[@PatAutrey]

Great "lightbulb" moment - Aha feels good when you finally get it. I wonder if you continue the trend and double back again for another segment on a linear loaded dipole if the next switchback point will then be a 7:1, then 9:1 as you continue the ziz zag pattern on a linear loaded dipole?

[@DXCommanderHQ]

Fascinating!

[@PatAutrey]

@@DXCommanderHQ I was wondering if you might help me with a calculation I'm planning to put up a long wire antenna for field day about-face 250 ft long and use it on 20 m any idea what the impedance would be if it was end fed? I plan to elevate it 5m also what type of gain could be expected

[@bigdaadio.K2WW]

I'm not even going to take the time to look at all the comments, but I hope you guys didn't say that. That's 160 m from side to side because that's what he said about 2 minutes in😊

[@DXCommanderHQ]

Erm.. Not sure which bit you mean - but I definitely said all of that :)

[@brianchandler3346]

I've experienced same with insulated and I got to thinking... when folded over, I'm thinking it would add capacitance and then if twisting part (like I did to hold it in place), that may have added inductance.

[@DXCommanderHQ]

Yes... One or the other!

[@r111k]

So, if I want 16.5 feet on each side of a dipole, but I cut it to 17.5 ft, I would need to fold back 3 feet on each side (so now a length of 14.5 ft) in order to get the equivalent of cutting off a foot on each side? Because the the 3 to 1 factor? By folding back rather than cutting, I can reduce the length of a dipole and get resonance at the same frequency as when I cut to the full length? Today, I put a dipole in my attic at 17.5 feet thinking I can have a little extra to tie the ends and “just in case”. But when I fold the ends, I need to fold a much longer length than just to get the length to 16.5 feet. Maybe you just explained what’s happening, if I understand correctly. Thanks in any case! Great info!

[@DXCommanderHQ]

Basically you have it right.. !

[@r111k]

@@DXCommanderHQ Thanks!

[@billmillar8148]

i have been there two, bits of wire all over the place ,hours and hours up and down a ladder , missed dinners and cold cups of tea ,, the dark are of antenna building lol

[@DXCommanderHQ]

Cold tea.. Yeah, same club!

[@vinniec5286]

This is bothering me a little so I have to ask Cal (or anyone who has done this), when you fold an end back, are you folding it back parallel to the element, or are you twisting it around itself? I would think that twisting it would shorten the electrical length as the twisted back piece would cancel out the forward piece, but that folding back parallel to the element keeps the electrical length. Am I way off? Thoughts?

[@DXCommanderHQ]

OK, so the spacing between the folded-back part and the element is important - but only once it's done. It won't matter (if it's insulated wire). Basically, say you put a 6mm (1/4-inch) gap in the foldback you will end up with slightl more loading than parallel.. Twisted will probably give you a slightly different amount that's all.

[@vinniec5286]

@@DXCommanderHQ Thank you!

[@TangoRomeo121]

What happens if you combine the two methods? Instead of just folding the insulated wire back on itself, what if you first stripped the insulation or jacket off of the part to be folded back? Would that eliminate that length from the equation as you said it did for bare wire?

[@DXCommanderHQ]

Now you are bare copper again, yes.

[@richardneel6953]

Was thinking along these lines. Dipoles in my small space are always inverted v's or sloped somehow which always makes the normal dipole leg length not perfectly come out according to the usual 468/f method. What if we just stripped back an amount of insulation, use the wrap back method (therefore being able to ignore the amount of wrapback) and then just cover it back up with shrink tubing or electrical tape? Viable?

[@iainmeteorscan1555]

@@richardneel6953 Hi Richard. That’s exactly what I do - strip back the insulation at the end of the antenna to bare copper, then tightly wrap back the required amount. The “skin effect” then comes into play (as electrons travel on the outside of the copper wire - not through the core) and linear loading does not become an issue. Thanks for Callum bringing this up in a video, as it must be frustrating to many Hams using insulated wires that their calculations are not working out. I.E. when using insulated wire, and folding back insulated wire, the foldback needs to be approximately triple the calculated length.

[@MattL.-KE0SAW]

So essentially what this boils down to is a 3 to 1 Cut ratio. Where 3 is the bent length and 1/3 Is the actual cut length for desired swr correct?

[@DXCommanderHQ]

Rule of thumb, yes.

[@MattL.-KE0SAW]

@DXCommander excellent, thank you for the clarification! I have an efhw in the attic that I'd rather not cut too short lol!!

[@vicmiller7191]

I must say, your explanations make so much more sense than many text books. Thanks as always. Vic de KE8JWE

[@DXCommanderHQ]

You're very welcome!

[@zeebraeend]

Callum, now you've folded either element once over. But what would the ratios be if you'd fold it in three or four parts? Or haven't you given that any thought yet?

[@DXCommanderHQ]

OK, so more than one fold? I really don't know. You are creating a load, like a coil..

[@zeebraeend]

@@DXCommanderHQ I'm thinking more in a zigzag pattern, not spiral. Or double linear if you will. Now I think of it, that could give an interesting radiation pattern...

[@christher69]

I was subbed before but then i saw no new material so i checked and resubbed, was thinking abt an build idea for u with land and possibilities, maybe you have done this allready, if so appoligies, anyhow, what abt making a wireyagi construction, could it work on poles hammered down say just 1m above ground.

[@DXCommanderHQ]

Wire yagi's don't work at that height.. Same rules apply, at least half a wavelength to be effective. Interesting idea though.

[@Klaatu-ij9uz]

How do you figure all this when your dipole antenna has loading coils in its length??🤔

[@DXCommanderHQ]

In the main, you can IGNORE the loading coils.. Don't adjust them, but the tips should tune on that callculator pretty well.

[@DavidMitchell79]

I would think, with a dipole using insulated wire, you would be increasing the "end effect" as they call it. Folding it back would make a capacitor, the longer the back fold, the more "end effect" one would create. Could this be what is happening when using insulated wire? I am not an electrical engineer, but just read mention of that in my studies for my upgrade to Extra Class.

[@DXCommanderHQ]

I can't remember this video in detail but I know I also touched on foldbacks and coils here: kzbin.info/www/bejne/q3_UcmmarpuWmLs

[@chuckcarter7864]

Calum I can’t understand how linear loading can work due to the phase reversal at the end of the wire which in my understanding cancels the radiation

[@DXCommanderHQ]

CHuck, needs a video - however only balanced feeder cancels.. The linear loading isn't balanced.. Long story but don't worry about it..

[@rambowales5846]

Sooo, if you strip the insulation where the fold is at, effectively grounding/shorting upon itself at the bend/exact length, do you avoid all that crazy math?

[@DXCommanderHQ]

If you strip the end.. then the end of the wire is where the bend is as it starts to come back.. You can't fold a non insulated wire back and expect any loading, correct.

[@ths3900]

FYI - Timeless videos. Thanks.

[@cecilmadden]

My guess is when you fold over an insulated wire you are reducing the length and constructing a linear capacitor on the wire's end. The two pieces of wire make capicitor plates with insulation between them.

[@DXCommanderHQ]

Yes, I think so!

[@soeffner6833]

A bit late to the party. But what would happen if you bared the end of the insulated wire, folded back half the measured amount, then stripped the sheathing of the wire where the end met the main and attached? Wouldn't that provide the ground out needed? That spot could then be resealed.

[@DXCommanderHQ]

I think you are saying what would happen without the plastic sheath.. In which case, you would have a short circuit and the overall length is just that.. The end of the wire is the end.

[@soeffner6833]

@m0mcx Thanks for the reply, I was just curious. And thank you for the videos. You've helped alot with my slow growth as a ham.

[@ElectricityTaster]

Am I right to imagine this as a piano wire that folds back on itself around a very powerful magnet that won't dampen vibrations?

[@DXCommanderHQ]

Well, I suppose so.. We all "see" it differently but I like the idea.

[@JasonPullara]

The dipole foldback needs to be some kind of tiktok dance

[@Bond2025]

Folding an element back on itself is not to be confused with bending an element in a different direction at the end to fit it in to a space! They are two different things.

[@DXCommanderHQ]

I didn't know that was the debate!

[@dodgydd]

Great video. Bet I'm not the first to suggest this, but can you just keep to metric when talking about measurements for antennas which after all are named after 'metres'. Anyone that insists on using inches can just do the conversion themselves. I find it slows up the presentation and flow.

[@DXCommanderHQ]

I know.. However, when I don't swap between the two, I get a thousand comments telling me exactly reverse of what you say.. I can't win.

[@dodgydd]

@@DXCommanderHQ I do laugh out loud when I watch a US ham radio youtuber talk about making an antenna for (say) 2m, then immediately convert 2m into inches and start measuring out, immediately making more work.

[@DavidMitchell79]

I as a US ham, am fonder of the my etric system. It is so much easier in a base 10 number system... I get confused when trying to deal with 12, when I have only 10 fingers. 😂

[@iainmeteorscan1555]

@@dodgydd Hi dodgy. Not only USA Hams, but UK Hams - who should know better! After all, UK has been metric for around 50 years now. It’s so much easier (and precise) to work in millimetres than in feet and inches. Not only that, UK Hams still talk about their Bands in metres, even when Ham Band Plans are now in MHz. I can’t remember the last time I saw a Ham radio transceiver readout in metres! Especially ludicrous it must be to new Hams when 144-146 MHz is described as 2metres! Worse - when 430-450 MHz is referred to as 70cms!

[@colinwise3064]

Hi Calum if you took too much off at 3:1 . At 5:1 your going to take a lot more off . Have i misunderstood something there.

[@DXCommanderHQ]

No.. that its how we discovered the change from about 3:1 to 5:1

[@J123G]

Maybe would make life easier to tune if when constructing each leg the last few feet were uninsulated, then folding it back or extending the length would always be a simple straight 1:1

[@ifpo238]

Lol. That other KZbinr is Dave Casler...

[@DXCommanderHQ]

Erm.. Maybe!

[@JxH]

4:25 "...13cm....which is 7 or 8 inches..." 1) More like 5 inches, and 2) there's a joke in there somewhere. 🙂

[@marccormier2310]

a n a man with your financial resources should not suffer in warm weather

[@DXCommanderHQ]

Log burner and heating off

[@marccormier2310]

@@DXCommanderHQ save the planet my friend lol

[@DXCommanderHQ]

@@marccormier2310 Good thing about slow burning logs is that the carbon released was absorbed in the last 50 years not last 50 million years.

[@timwalsh7410]

I’m a dummy, don’t understand ground plains or what will work, Does it matter if I were to add say 3 more wires to negative (horizontal) and positive vertical ❓ don’t expect to hear from you but your my last chance… Love your vids.. Tim

[@DXCommanderHQ]

No don't a dipole is literally 2 pieces of wire (or other conducting elements). You need nothing more.

[@PatrickKQ4HBD]

I am now more confused than ever.

[@DXCommanderHQ]

Maybe wrong hobby. Read the comments..

[@Massey_Fferguson]

Sponge 🧽 soak it up 🧠

[@Bond2025]

Please only use ONE camera for recording if you are having trouble remembering which one to look at when you are speaking. There is nothing worse that having to watch someones ear or side of their face being filmed as they are talking looking in a completely different direction. This is what news readers used to do on "It will Be Alright On The Night" - the comedy show. They would be talking away looking the wrong way and suddenly realise, then look at the correct camera.

[@DXCommanderHQ]

You keep going on about this,.. You have NO IDEA why I do this, it's to conceal edits. Please stop watching. It's easier for you.

[@sclerismockrey8506]

nothing worse? seriously? then you reaallly ought to stop watching. or maybe try doing it yourself and finding out WHY cuts are necessary and slinking away feeling like the fool you are. good god, if THIS is the kind of thing you find so appalling, you must have a dreadful time living.