Antenna Secrets: The Strange World of Coils and Antennas

[@danlazer8762]

I've learned so much from your videos, Callum. Many thanks for these. I've had my General license here in the US since the mid 80s and have been in and out of the hobby off and on since then. In the last year or so I've come back to it in a big way. Maybe it's just middle age, grown kids that have moved out, or something else, but the way you explain complex information is fantastic. All of this stuff is supposed to be fun and you help make that happen.

[@DXCommanderHQ]

Yes, middle-age is great for ham radio!! LOL

[@mewrongwayKOCXF]

Me Too! Licensed in 1979 in high school then life got busy making a living, then retired a year ago and came back. Went from a Heath HW-16 to a FTDX-10. wow Im having a ball!!! 😋😋

[@G6EJD]

Cal - your actually describing how the Hustler BTV antenna works, they use an LC (trap) circuit at various stages up a pole, what happens is when the LC circuit (they use 4 for various bands) becomes tuned at a given frequency it’s impedance becomes infinite thereby isolating the section above it and effectively reducing the antenna size so that it can tune at a higher frequency and hence achieve your requirement for a single pole with two resonant frequencies. You can also use just a series coil to electrically lengthen a physically short antenna. Example create a dipole of the required length at say 7MHz, then measure its inductance, then eg half the length measure its inductance and then insert a series coil to bring the inductance value back to that required for the full size antenna. You can top load, centre load or bottom load the shorter antenna depending on the desired radiation pattern required. Bottom and centre loaded antennas are the popular in hand held applications.

[@DXCommanderHQ]

OK David.. Remember, in this one, I'm not making a trap - I'm forcing the third harmonic down. In today's test - I got this working and the coil is 5.5m above the feedpoint, so I'm not generating a quarterwave on 20m band..

[@davidc5027]

I love to experiment, and really enjoy watching others do the same. Good luck Calum, hope you discover something new that no one else has thought of before. I guess I'm going to go down to the hardware store, by 50' of wire, and add a coil to my antenna :) and see what happens.

[@DXCommanderHQ]

Yeah, do it :)

[@edwinpd0sot503]

Pure brilliance, rewatching for the 3th time.. Thank you Callum!

[@DXCommanderHQ]

Yeah, I am still wondering myself!

[@edwinpd0sot503]

@@DXCommanderHQ i am convinced, every time you look back on a project and think "how did i ever get to this result, mentally technically or otherwise" you have created something beautiful ! 🤣

[@jps99]

Great lesson on coils here, much food for thought. As a new ham, studying for my General Class license, I find your musings on antennas quite fascinating. Love seeing you go out into your field and setup something new!

[@DXCommanderHQ]

Glad you like them! Yes, I find the whole thing rather fascinating!

[@pc4ad]

Interesting stuff. Came across something like this when experimenting during holiday with the Rapid. Tried to add 60m or 80m just for lols and found some resonant points on places I didn't expect them. This might very well be the reason why. Food for thought for sure!

[@DXCommanderHQ]

Ah. OK Anton. Very interesting, isn't it.. We're not taught this stuff so I'm feeling my way..

[@che59v]

Dear Caliium, Boys and girls, one vertical that is 5/8 of the highest band you are going to work will do all the magic, don't need the height, just above the roof line using the metal roof as radials, all this simplicity is connected directly to rg213 going directly to your antenna tuner and...... AND,,, well, it works like a charm ( on all bands ham or not, lol). It is all about how good is a given radiator ( antenna ) in "putting" the supplied energy around it and at the correct angle ( dx? nvis?) , all this rather than its SWR (let us face it, you might be able to "tune" your old fridge, but does it make it a good radiator? really? will be heavy to put on the roof, lol) ). So,,,,,,, we did a test, putting our idea into real life situation ( we don't trust computer diagrams and nice graphics we found out the hard way, every situation is VERY different) WE made two antennas, the same base used ( change over ) same materials, and connections, one was a "tuned" vertical 40 /15 (SWR 1:1.4 -+) and the same size ( length) antenna being "untuned" was made as "control" , just the same kind of pipe with no coils or balun when that one was attached we were using an antenna tuner ( MFJ 949), the same 50m cable was used for both antennas in this test ( rg213) AND,,,,,,,,,,,,,,,,, well, well, no difference was noted going from antenna A to antenna B on the 40/15 meters ( or nothing that we could see or measure). So, if you want a REAL fully multi-band system you might use two verticals, 10-13m for the low bands ( longer? even better ) and 7 meters for the higher bands, those will be non-resonating antennas, Yes you will use the tuner, but don't think the power loss is a real issue here, it's not. Most important keep having FUN. Remember the issue of SWR was not an issue in the 40s when an open wire was used, and with the invention of coax, thinking has changed, sadly, most that we have been read about SWR and related losses might be wrong and made of assumptions rather than reality.

[@DXCommanderHQ]

All good until you mentioned "tuner".. LOL I enjoy mucking about with matching antennas "on the cheap".

[@LanWolf]

Hi Callum, like,your videos a lot, especially as I like building antennas and experimenting away. What you describe here for 20/40, I built a couple of years ago for my apartment antenna, to get on the air on 20 and 40. I used a 20m band full size dipole, with a coil of about 31uh at each end of each leg (after I unfolded the double folded part what wat used to tune and hang the antenna. The legs alone are now longer than 1/4 wave on 20 ) and then about a meter of wire at the end. That gave me 20 and 40m, although narrow band, but nothing what the atu in the radio couldn’t solve. Biggest problem was hanging it, as the balcony was 7,5m, it was shaped like a inverted U and just 30 cm out of the balcony. As noise levels gone up way high the last couple of years in city I almost never use it anymore, I rather take my Icom 705, a 10m sotabeams mini pole and an endfed antenna to the countryside to make some contacts. I also wonder if the parts for the expedition dx commander would fit the sotabeams 10m mini pole, as it also is 68 cm transport length ?

[@DXCommanderHQ]

Fascinating! Great work too. I think about 31uh is probably cock on..!

[@bergerMeister949]

Your videos are as entertaining as they are informative. I have recommended your channel quite a few times. Thank you for all of your hard work.

[@DXCommanderHQ]

Much appreciated!

[@garryhammond3117]

Thanks for doing such ground breaking research Callum! - I can see a lot of good coming out of this. - Cheers!

[@DXCommanderHQ]

My pleasure!

[@somethingcool7903]

I wish the US would just give it up and go to the metric system like everyone else....it's not hard to convert but it doesn't pop up in your head exactly, especially if you haven't used it in a while. Thanks for sharing appreciate it brother.

[@DXCommanderHQ]

Have a great day and thanks for suggesting.. Write to your government! LOL :)

[@somethingcool7903]

@@DXCommanderHQ Hahaha... write your government. Don't even get me started 😂

[@Trent28888]

I made a centre loaded 80M vertical last year and its 5M wire then a loading coil and then 5M wire so I got 20M and 80M but ive always wondered as the loading coil acts as a trap what effect it would have with say minimum inductance for it to be a trap vs a higher inductance but to answer your question walters and stanton done a vid where he got 20 and 40 on the same wire doing the same thing,btw theres also less capacitance between usin insulated wire and solid copper wire which is what I used

[@MidlifeRenaissanceMan]

I made an end fed vertical for 20m which, where I added a base loaded whip that also tunes 40m. Made a match for it that wasn’t 49/1, much lower fees impedance. Works a treat, especially for portable operations

[@jackK5FIT]

Great video! I had a 40M inverted V with a 20ft high feed point and I needed to get on 80M (around 3860)with it as well. I built two coils out of pvc tubing and I think 78 turns of magnet wire added to the end of the 40M wires. I did it because I didn't have room to add the full wire for 80M. The 40M part was tuned for the digital portion and after much cutting and folding back I was able to get it back where it started and got the 80M part tuned for 3860 with about 2.5 ft of additional antenna wire. It worked great. I took it down when I got my DX Commander Classic and still have it stored. I have no idea of the math. I just know it works. Jack K5FIT

[@DXCommanderHQ]

Hiya Jack. Like you, I can't remember exactly how long or how many turns all my wire antennas had either!

[@petertate3436]

Brilliant work Callam..... My concern with any coil is - when does the ohmic losses and internal coil losses out weigh the benefits the coil brings? Plus there is a change in Q as you move these up and down too. Then we talk constructional weaknesses brought on by the needed tower breaks. For me it's all about constant AM power and 24/7 power on transmission, with highly processed audio. I'd be concerned about burning these coils out and clearly that relates back to constructional issues. I've always understood that the same coil to resonate a short stick gets bigger (more uH) when you move it up. This increases the real world losses (aka that's bad). But in doing so this encourages more current to flow in the vertical element (that's good). I've always use a rule of thumb that the point between (that's good & that's bad) is 45% of the length of your short stick from the base. You won't see any coils in stuff i build any higher than that. In fact I'd rather top load with more wires. But that doesn't help you here. Good work..... I watch with one eye open and the other one watering a bit from being scared.... as I'm from the broadcasting game. 73's as always!

[@Brood_Master]

I would love to hear your experience on antenna building both for home shack and mobile for HF. I'm fairly new to ham radio and I recently built my first antenna. A 3 element horizontal half wave fan dipole with no coils or chokes. Mounted at 26 foot off the ground. It does 40, 20, 15 and about 1/4 of 6 meters without a tuner. I'm very pleased with it especially on 15 meters... I've talked to Japan, Brazil and Puerto Rico with only 20 Watts and get 5-4 to 5-6 signal reports... I want to try a mobile antenna next. Something I can mount on my truck. Any ideas?

[@DXCommanderHQ]

We tested the coil and it doesn't get hot higher up. But I do hear you. It's good fun though.

[@DXCommanderHQ]

James - massive topic.. Stay tuned and maybe cruise the back catalogue of some of my longer presentations. Many deep ideas inside those.

[@petertate3436]

@@DXCommanderHQ is this with 30% or 100% duty cycle there Mr Callum?

[@DXCommanderHQ]

Peter.. I only do 100% duty for testing.. Not like every other manufacturer.. :)

[@kiweekeith]

Thanks a Stack Callum, what a Brilliantly Interesting and Entertaining vidclip.... Much Appreciated .... Very Best to You and Yours from New Zealand .... Keith .... WR 2451

[@DXCommanderHQ]

Ah! Tnx Keith!

[@davidportch8837]

that's brilliant Callum - another great video... when the better weather comes along I think I shall have a go at this...73s KPZ...

[@DXCommanderHQ]

Go for it!

[@JEFF-Elliott]

Hi Callum, the aerial you discuss at the end is very similar to my diamond W710 also W8010, which has two wires in a fan configuration similar to your requirements and I can’t remember how many bands it did but it was said to do five, but I think it will do seven or more.

[@DXCommanderHQ]

Interesting!

[@souta95]

I used some coils like this to give me 80 and 40 on one element of a dipole. 15 also still tunes nicely like a standard 40m dipole, and then I have another pair of wires for 20 meters.

[@ths3900]

Making things simple for the average ham! Thanks

[@jimbronson687]

Well big fellow. I am a physicist and sill cannot follow most of what you are saying or explaining. But I like your channel and have got some answers to important questions. Now I will share with you something i saw in mid 80s. I was an electronics supplier that had 8 TV Stations in my territory. One was Channel 47 in WA State. UHF. It was a slow day and the engineer, and I went to thee transmitter and tower on the local hill a few miles away from the studio. I had seen other TV transmitter antennas but this one was different. It had from the transmitter a wave guide that went to a holllow cylendrical pipe that then had elongated slots in various places on that heavy heavy pipe. I was told that the signal came out of the slots. This cylinder was at the top of the 320' tower and was I assume about 8 feet tall. The reason i saw it was a lightning Stike had damaged it and it was laying on the ground near the tower. They had replaced it under warranty. It did have damage from the lighnig as water due to sideways rain and something plugged up the drain hole. thus when lightning hit it turned the water to stream and blew the thing off the top. I tried to lift one end of it but cid not move at all. It was partly buried from the fall but also just flat out heavy. I later learned they switched to a more conventional antenna but did not find out why as was busy with particles. Neutrinos were the big kahuna at that time. Great channel and great subscribers. You all take care now.

[@DXCommanderHQ]

Hello Jim, you are very kind! The comment on your memory of that strange TV antenna is a LOT of fun...!

[@jimbronson687]

@@DXCommanderHQ I had meant to ask if you folks had ever used or were aware of the strange antenna with holes that are slits or slots? The wave guide is common on UHF ike channels 28 also a customer. but no one I saw used these strange antennas with holes to let the signal out of. It cannot have been yhe only antenna of its kind. No way someone built that heavey turky for just one station. The transmitter was a Motorola Some stations used Harris but motorola was common on UHF. I do not think VHFlow or high would be very usefull to use wave guide. Oh on channel 28 a crack in the wave guide caused the engineers are to heat up. They had to fix that. 28 was licensed for 5000 watts but found 1.25 million did the trick.

[@1000000volts]

i have made a similar vertical antenna , infact i still use it for the motorhome as no radials are needed , use a 12 meter pole make a full size half wave on 20 meters then a small coil to bring the last section to 40 meters , it also tunes up on 11 . No tuner needed , use a 49 to 1 transformer ..

[@mattmcconnell4814]

You mentioned asking ChatGPT about antennas and boy-hell has that sent me down a rabbit hole of interesting takes and explanations about antenna design.

[@DXCommanderHQ]

Yes.. I spent too long.. Don't ask "him" to explain impedance repeat formula. It gets it wrong.

[@mattmcconnell4814]

@@DXCommanderHQ "he" told me a vertically polarized monopole was perfect for NVIS.🙃

[@mattdixon5299]

This is great education! Really enjoy these vids Cal. Clever Chap!

[@DXCommanderHQ]

Matt!! Long time old friend. Come and visit sometime!

[@mattdixon5299]

@@DXCommanderHQ Absolutely, i’d love to. Let’s get that arranged!

[@GhostCallparanormal]

My mind has gone to mush lol. I was never any good with maths so I’m sticking to a dx commander 😂

[@DXCommanderHQ]

You and me both!

[@stargazer7644]

Thanks for making this Callum. It nicely explains what you’ve been working on. Have you ever taken a look at how the driven element of a tribander beam like a Cushcraft A3S works? They get 3 bands out of a single element by putting coils near the end the element.

[@DXCommanderHQ]

Yes, they are traps. I had an A3S once. By the time you get to the 20m band, the traps and coils have reduced the efficience quite a lot unfortunately.

[@acestudioscouk-Ace-G0ACE]

Fascinating stuff and the way you explained it makes sense, although it is way above my learning grade... But you have given me food for thought and I'll be doing some study on it. Sorry I can't give you expert advice but like you, I'll watch the comments to see what responses you get. Best 73, Ace 😁 👍

[@DXCommanderHQ]

Yeah, I'll read the comments too! :)

[@nathanw851]

Very interesting. Cool research, Cal. Wonder if using some foam pipe lagging would suffice for the coil former to reduce weight aloft.

[@g4lmn-ron401]

The foam would have a dielectric impact and change the coil inductance. As an alternative weight saving method take a tube and cut most of it away to make a skeleton former.

[@DXCommanderHQ]

Possibly!

[@mewrongwayKOCXF]

Lets go build that Antenna Callum!! 👍👍

[@benhawke7231]

Now I did learn something about loading coils in the Navy. Where the loading coil on the antenna is placed will determine the angle of the ground plane. Also I do know that your ground plans also affected by the loading coil if you're loading coil for instance is on an antenna that is connected to the side of the house and the loading coil is below the roof line.

[@DXCommanderHQ]

Erm.. If the house isn't conductive it shouldn't matter.. But hey - everything almost works!

[@benhawke7231]

@@DXCommanderHQ I don't know about over there, but over here in the states, if you live in an area that gets a lot of lightning they ground the gutters and run grounding wire/lightning wires along the roof. And aluminum siding doesn't help much either. I do know if you live in an HOA that doesn't like antennas on the roof that a fire stick with the loaded coil on top just peeking over the roof enough to get the coil over the roof line works a bit better than an oil coil or Wilson with the coil below the roof line during skip on 10m, 11m (especially), and 12m.

[@genoa1979]

Fantastic video

[@DXCommanderHQ]

Thanks! 😃

[@JonathanGGMO]

Brilliant explanation, really interesting stuff.👍

[@DXCommanderHQ]

Glad you enjoyed it

[@richardgroves290]

I was with you for a while, but you soon lost me! You're a smart guy and I do enjoy your live performances on a Friday when I get to watch. Studying for my full exam, finding it tough TBH. All the best, 2E0JHW

[@DXCommanderHQ]

Richard, sorry I lost you. But just think about concepts - not the maths or anything. Good luck!

[@alanbond1269]

Hi Callum keep up the videos I have dislexea so I have to look at things differently then most other people. I do things Alan's way that works for me. Maths and spelling don't work well for me. But sometimes just experimenting until it works is fun. Keep up the great education videos. Some parts are beyond me. But alot of your information goes in to my sponge. All the best 73s

[@DXCommanderHQ]

Yes OK Alan, hopefully you can keep up with the concepts.. We all understand stuff a little different don't we. OK. Good luck!

[@electronics.unmessed]

I am using the program NEC quite a bit. Your problem sounds like a classical optimization problem with only 2-6 parameters. In case there is a solution, you can find the optimum by varying these parameters. The other thing I see is, that the folded part at the top of the antenna is pretty close together with the main conductor of the antenna. That gives you kind of a parallel wire waveguide which creates funny resonance effect on its own. I think, it would be better to make the distance between the two wires much bigger, like half a meter or so.

[@DXCommanderHQ]

Well. It does work as the modelling suggested. I made the build video about 1-week after this..

[@electronics.unmessed]

@@DXCommanderHQ OK, I need to check that out.

[@w6dfmp242]

I can’t remember if you had a follow up and worked this out. I’d love to make one for my 6m pole to go with my mountain topper

[@DXCommanderHQ]

I did work it out and I keep meaning to publish results.. The only nuance is getting the placement of the coil is really critical to achieve perfect match on both 40m and 20m.

[@TI2GBB]

Hey cal! Can you make a video explaining how coil works, how to calculate a coil and the turns need it to build it, which instrument its good to use to measure the coils... etc, I think will be great info to teach, specially for the new generations on Ham radio, 73s mi amigo! TI2GBB

[@DXCommanderHQ]

Coils.. Well, I am more of a suck-and-see type of guy BUT yes, there are resources. I'll add it to the list!

[@NickFrom1228]

Realllly enjoyed this one Calum. If I can scratch up some bread I'm going to have to ping you for some antenna wire and do some experimenting. On a side note, I've also got the wild hair to experiment with dipoles made from tent poles. You can buy the tubing and insert pretty cheap and they are already perfect for take down so I'm going to give it a go and even try it for a sota activation. Fingers crossed.

[@DXCommanderHQ]

Do it!

[@Bro-f3h]

Another good one thanks Cal

[@DXCommanderHQ]

Glad you enjoyed it!

[@brianfields4479]

Very good. I wonder if the top hat ant design came about because of the same type of thinking or is that something totally different.

[@DXCommanderHQ]

Well, who knows.. But good thinking.

[@iz2mgn]

Thanks Cal, vy interesting. Playing with pieces of wire and Rf it’s awesome. 73,Mauri Iz2mgn

[@DXCommanderHQ]

It sure is!

[@M0BPQ]

Its a long time since I owned a Sandpiper vertical, but i think they worked along a similar principle? They were not trap antennas. As you do your tests, have a look at the useable bandwidth too I would anticipate the low Q of the coil built as described to reduce the 2:1 SWR bandwidth.

[@DXCommanderHQ]

Indeed, we'll look at that. Good point.

[@jluke6861]

Thank you for the great Video.

[@DXCommanderHQ]

You bet!

[@stirlingpark6145]

Callum, two questions please, firstly, what would happen/the effect be, if you connected the centre of the coax to the ground and the shield of the coax to the vertical? I guess that theoretically/practically nothing would change? Secondly, does the radiation pattern change if the VSWR is not 1:1 or "low"? I am wondering if a VSWR of say 5:1 might possibly create advantageous lobes so long as you could increase the output power to compensate? I am thinking of fixed wire antennas in particular. Thanks in advance.

[@DXCommanderHQ]

All good questions.. Actually, I once did Q1 and other than getting a really hot (buning microphone!) it still worked.. Q2 Actually SWR does nothing to the pattern other than obey the laws of length (in other words, you can change the length and lobes appear and disappear according to the principles of element length. I must say, very good questions!

[@kenluning909]

A very interesting video. Thanks for sharing this. W5KAL

[@DXCommanderHQ]

Many thanks!

[@andrewwhittaker6622]

Hi So the 12.4m has end effect fold back ends I wonder what changes that would make to your dipole harmonic resonances Cheers Cal

[@DXCommanderHQ]

Well... ALL wire antennas have end-effect.. But we do small changes to the final tune on the foldback instead of the coil - it's easier.

[@davidsheedy5793]

So, the DX Commander line of antennas do not require guy wires for support or am I not paying attention? By the way, love your video, great job...

[@DXCommanderHQ]

OK, for the Signature 9, you don't need guys. The remainder do.

[@jaredringenberg]

Awesome, thanks for the info!

[@DXCommanderHQ]

Any time!

[@bassangler73]

Above my head...lol...You got a new notepad I noticed...ha ha....I would love to hear your band play, do you have any jam session videos?

[@DXCommanderHQ]

Erm.. Not really. We're still a bit rought around the edges. And bass guitar clipping. Need to make a change next Thursday.

[@bassangler73]

@@DXCommanderHQ I understand...live recording is tough, especially when you got a guitar player like me who likes to run an EVH 5150 amp wide open...lol

[@DXCommanderHQ]

OK.. just for you.. This was only a rehearsal.. Don't judge! kzbin.info/www/bejne/eqHMn3eXi5KKd9E

[@bassangler73]

@DXCommander you guys are pretty tight, sounds great!! Thanks for sharing!

[@gfodale]

I've always preferred brandy for 'loaded' antennas. Your way sounds more predictable though so I'll give it a try. As an added bonus, I won't have to wait for an 18 year old antenna.... 😁

[@T.M.G2014]

Would you consider making some of these 2 band wires with your products be great to have a few in a grab bag, and pole for complete novices

[@DXCommanderHQ]

Erm.. Yes, that's the idea.. Let me practice first :)

[@T.M.G2014]

@DXCommander sorry for the slow uptake my adhd don't allow me to pick up on things that's right in front of me at times , now I just look stupid Anyway I'll look forward to these being in stock

[@daveg8htfadlibaudio250]

Hi Cal, do you think it would be easier to perfect the dimensions and the coil inductance values if you did the experiments at say 5 or 10 times the frequency and used the good old antenna analyser to test it all out and then re calculate it back down in frequency ***** just a thought, as of course the whole thing would be easier to handle as it wouldn't be that tall. Regards Dave.

[@paaao]

The issue with that is, as you go up in freq and your wavelength gets smaller, your antenna also becomes far less affected by the earth. Because it's more than a wavelength up in the air. Most HF antennas are never used even half a wavelength above ground, and this has a large effect on the swr/resonant point and the radiation pattern.

[@DXCommanderHQ]

Hiya Dave.. as the other commented suggested, the earth changes.. But maybe on a vertical it might not matter too much. Yes - you COULD what you suggest but since I'm only faffing around with a 7m pole, it should be pretty easy. Good idea though.

[@sauroiu5asa696]

I did It. 20 and 40 on the same element with also a Surprise ...

[@DXCommanderHQ]

Ah! Very good. Write to my email. I am initerested!

[@Hydrostream1972]

Good stuff like always 👍 😊😊😊😊😊

[@lc79tourer26]

why don't you have a look at a W3DZZ? I use one set up as an inverted V fed with 50 ohm coax and a balun and it works on the pre wark79 HF bands quite well.

[@DXCommanderHQ]

Well, I don't know why I want to look at that. I'm very interested in these harmonics.. Sorry if I didn't explain myself better.

[@forgediron]

​@@DXCommanderHQ Hi Callum! The W3DZZ is a multiband dipole that works on 5 HF bands with only one LC trap tuned to 7.05MHz. As you said half a dipole on end is a vertical. I know you like MMANA. For questions like this 4Nec2 (Free to download) is a great tool due to the optimization sweeps that it can do. It can put a load like a coil in the element and then move that load along the element looking for the lowest SWR automatically until it finds the best solution. Its a bit more complicated to use, but you are very good with MMANA so 4Nec2 shouldn't give you too much trouble. I know you don't want an LC trap in your design, 4Nec2 can help you find the best position for the coil. It can also do calculations changing the inductance of the coil to find the lowest SWR. MMANA is a great tool for simpler questions, 4Nec2 can tackle more complicated questions like this one. 73'

[@penrox0]

Interesting stuff Callum… but in the back of my mind I am also thinking of the Vertical Trap, which also gives 20 and 40 on one element.. I would need to understand (electronically) the difference between what you are experimenting with and a trap. Then consider the EIRP of both…. Is the trap more efficient? You do realise I will be thinking of this all day 😂😂😂😂 Cheers .. Andy G0NKK

[@DXCommanderHQ]

I know.. They MIGHT be very similar..! I was hoping the moment method MAY produce a better pattern though for the 3rd harmonic. Software doesn't think so. WOuld atrtap reduce performance of a 40m element more than the shortened coil up high? That's the other consideration. The only other advantage to this system is if someone specifically needed a smaller element. Lot's of fun!

[@OhmSteader]

Perhaps your the one to ask this most difficult question. I have yet to get a straight answer. How are the Smith graph radiation patterns produced. Is it conjecture or something that can actually be seen with some kind of instrument or device? I have been able to see the static charge patter on a charged pvc pipe using ashes sprinkled about the pipe and saw the ghost. It was a series of torroids up and down the pipe which can be discharged like individual cells by putting a light bulb or my finger near each one and hear the click as they are discharged. People think I am crazy and asking too many questions which will not even be on the extra exam anyway. I have to wonder if dusting ashes over my antenna array would show me the pattern which I am wanting to see. Please sir, give me some insight. I know you know. Thanks

[@DXCommanderHQ]

Smiths charts.. It's like a 3d puzzle. Frankly, I'm not the one to ask for the best answer. Maybe Mike M0MSN might help. Ask on his channel..?

[@mikeerstad3705]

What about MOVING INDUCTANCE COIL .....If you wound a coil and had it mounted on an antenna wire without any electrical connectivity....but on a pulley system, that slid it up or down an antenna wire... Just a thought....

[@DXCommanderHQ]

Try it..!

[@m7trsradio]

Hello callum. Great video. I built the 40/20m antenna vertical for your antenna ecoms comp. I did a pole version and a string in a tree. It works well. I didn't win 😭 but I will trade you for a expedition 😁😉😉 Motters M7TRS 73 👍🏻

[@DXCommanderHQ]

HAHA!

[@m7trsradio]

​@@DXCommanderHQ 😁 if I can help in anyway let me know. I can not remember what I put in the pdf I sent you now. It had pictures of the things I use. I haven't use it since I took all the pictures and write up. Motters M7TRS 73

[@donstor1]

I suppose that you can have several antennas if you have the room and switch to the one closest to the frequency you are working for the best signal. If you have the room for it. I am lucky that I don’t play with DX because I have a huge cluster of 2 meter and 440 repeaters in my area and I spend most of my radio time talking endlessly with them. Something to think about though if I get interested in DX.

[@chrisgarry8456]

what way do you twist the coil clockwise or anticlockwise??

[@DXCommanderHQ]

Depends on the anti-matter within the magnetronic chambers. Seriously, as you probably know - it doesn't matter..

[@chrisgarry8456]

@@DXCommanderHQ thank you 😁

[@somethingcool7903]

Man that antenna is sweet (the DX)I haven't dare to even look to see how much they run.....don't want to risk the heart break😁

[@DXCommanderHQ]

Not expensive!

[@somethingcool7903]

@@DXCommanderHQ Really. I was thinking of getting one of those fishing poles but for 40-50 but I'd pay up for the DX better quality last longer and I'd rather support you then the alternative no offense.

[@timg5tm941]

Different animal but the shortened end fed Halfwave has a 34uH coil at 10m from the 49:1 to act as a choke and loading coil for 40m, with about 1.85m of wire the other side of the coil. Total length 11.85m. Provides 40,20 and 10 (10 as a full wave). 73

[@donalfinn4205]

Have one!

[@baslev]

Have one as well 🙂

[@tennesseered586]

Bottom line on all of these shortened antennas is: How well do they radiate compared to full, 1/4 wave, resonant verticals? The only way for amateurs to know is to use them.

[@DXCommanderHQ]

If you are not a regular you won't know that we used this not last Friday Live Stream but the one before. Couldn't tell the difference!

[@JayN4GO]

Cal, why do you only sell verticals? You have the name and fame now. Why not sell sky loops , half squares , doublets etc ?

[@DXCommanderHQ]

I could do more but there's only Loki, Wendy and I.. And we're already flat out. It would be fun to find someone who could work part time (reliably!) making up elements, loops, dipoles etc with that Kevlar wire. There's a market for that. But there is never enough time..

[@DonzLockz]

​@@DXCommanderHQ I would love to do that part time reliably but daily travel from VK stops that. :( I'll have to pop in when I visit the UK. 🍻🤠

[@db3mi]

11:15 Cal, are you sure that the antenna is resonant on these frequencies? Or just have a good SWR? I'm sure the antenna will work, but resonance means no capacitive or inductive reactance but just ohmic resistance. A end half wave - as an example - is resonant but has a bad SWR because of it's high impedance (which is basically ohmic resistance). The question is no offense, i'm really interested and you propably know I'm your follower, fan and customer. Maybe i'm a too theoretical idiot (without understanding the theory ;) ). To understand whats happening, i think we should think of the antenna being a resonant circuit which we are able to tune with capacitors and coils in series or in parallel to tune frequencies which also does a tuning/matching in impedance. And you can think of antenna wire being a transmission line for another part of the antenna. Transmission lines transform impedances too. A good thing to understand what's happening is a smith diagram. Greatly explained by w2aew. 73

[@DXCommanderHQ]

Yes, I am sure it's getting out very well and let me explain why.. The 30m coild on the 80m element works "too good". I would expect to see a tail off in performance but everyone reporting an excellent result on 30m. I think we need to test it hard and work out the results. PS - Far field plot seems to show we're moving RF in the right direction too. Very good question!

[@peterlowrie1216]

If you can get 80/30 you should also in theory get 10 as a 3 half-wave dipole using the 30m section without the need for separate element for 10.

[@DXCommanderHQ]

But it's not the 30m "section". The harmonic has moved again due to the coil not being a trap.

[@peterlowrie1216]

@@DXCommanderHQ true, oops forgot that

[@mm3nrx]

Very interesting experiment and results. Mmmmm an AI designed antenna...now we are speaking...but alas it may put you out of a job Cal :D

[@DXCommanderHQ]

Oh yes! Woops :)

[@DonzLockz]

You are more OCD than me, haha! When the bills stop coming, I'll buy a HF radio, put on my lab coat and experiment.🥼 I retired early so I have plenty of time.👍

[@DXCommanderHQ]

Do it!