How to Shorten Wire Antennas with Loading Coils

[@RicksHamShack]

Moving a fixed inductor up or down to change the antenna frequency of resonance-that's some great information. Thanks Callum.

[@rickvia8435]

Loading coils have always been my worst fear when designing a shortened antenna, so I stopped even attempting it many years ago. Thanks, Friend.

[@DXCommanderHQ]

Yeah OK!

[@robertmeyer4744]

That was real good. Placement of the coil is key as well. I did notice with base loading on vertable ground mount antenna . the diameter of the coil makes the Q of antenna band with of tune point change. shows up on VNA doing SWR sweep of band. large diameter coil increases the band with of the tune a tad and small diameter makes the band with of the tune smaller . higher Q . also the more inductance needed the tighter the Q is. more loading the tighter the tune and smaller band with. also the spacing of turns on coil changes tune as well. lot to keep track of when making a coil. Cheers !

[@DXCommanderHQ]

Yes.. I didn't cover that..

[@jackK5FIT]

My 2nd antenna build was a 40m inverted V. Later I needed to add 80m but didn't have the room. I found a video by Dave Tadlock on youtube (2011 video) showing how to build loading coils for he ends of the 40m elements with an additional 4 or 5 ft of wire to get 80m. I built 2 and used them successfully for a year or so. It's 78 turns of 18ga magnet wire around a 50mm (1&1/2in pvc) core. 80 m was very narrow banded but all I wanted was one frequency anyway so it worked like a charm. I still have that antenna in storage.

[@caerffili_callin]

Than you so much for this. I just made a top loaded 1/4 wave vertical for 10m in my loft and there is not enough room for the full height so made a top loading coil and it has been working remarkably well. Used the calculators and coincidentally ie totally by accident my coil is of the correct inductance value, so confirmed I do not have to change anything.

[@DXCommanderHQ]

Brilliant!

[@B_MAD_24]

I spent a long time on that website designing my loading coil for the 630 meter band.

[@IrishHamRadio]

This loaded 20/40 antenna is exactly what I want for SOTA…. Very interesting on the detail and online calculators as loading coils still somewhat of a mystery to me. Between watching this and what Tim has been doing with coils also, building one has definitely moved up my priority list!

[@DXCommanderHQ]

OK.. I will make a dedicated video about this shortly..

[@IrishHamRadio]

@@DXCommanderHQnice one Callum 😊

[@patrickhooper1757]

The coil works great for the 40 meter element on the rapids mast. Colin actually told me the number of turns, worked great.

[@FatJoey-k9m]

I love this dude- Your channel is OUTSTANDING. 😂 Love it!

[@DXCommanderHQ]

Glad you enjoy it!

[@EmJayArr]

Well that's a coincidence. Just this week I started thinking about how to do exactly that: making a 20m & 40m vertical with maybe a loading coil or hat. I hadn't gotten very far yet, but it's good to know it works and to get some hints!

[@DXCommanderHQ]

Cool!

[@alanslade2319]

Great stuff again and I'm always looking for my glasses, and most of the time they on the top of my head, take care Callum and see you soon.💯👍

[@DXCommanderHQ]

Thanks, you too!

[@matthewduhon]

Great video, I plan on trying to build a dipole 2 element yagi like your new videos. Using a loading coil and the Rapide poles for each leg for 40m

[@DXCommanderHQ]

Yes you can do that.. The only issue really is height.. Ideally, you need more height.

[@matthewduhon]

@DXCommanderHQ it would be added to my current tower and multi band yagi master at 60ft

[@Jiminico]

Would like to calculate how much inductance is needed for a coil for an EFHW and how far from the unun so all the harmonics are tuned better. Not really trying to shorten the wire length as much as just trying to keep the higher harmonics better in tune as the fundamental frequency was tuned for.

[@DXCommanderHQ]

I think Tim G5TM has been working on same.. Try his channel.

[@Jiminico]

@@DXCommanderHQ Thanks, I’ll check out his channel.

[@mewrongwayKOCXF]

Awesome Callum! Antenna's are so much fun!!

[@M7BVV-Phil]

Great to see you back on my screen Callum, as always some dam good information! P.S. I haven't seen your specs, I generally find mine down the side of my chair,hihi.

[@DXCommanderHQ]

Cool, thanks!

[@BrokenSignal]

Those links are handy, bookmarking them now. Thanks Callum!

[@DXCommanderHQ]

Yes.. Very good..

[@49MoFo51SoB]

Perhaps I am mistaken, but at minutes 1:19 and 3:01, you enter the value '2' in the calculator under the line 'diameter of the conductor in inches,' which means 50 mm, the diameter of the coil's core. This seems too large for the diameter of the wire being used. Is this correct?

[@DXCommanderHQ]

I do indeed put in "2 inches" (50mm)

[@49MoFo51SoB]

​@@DXCommanderHQ Thank you for your response. To fully understand how to use the calculator for finding the required impedance, the '"diameter of the conductor in inches" field should be filled in with the outer diameter of the coil's core, not, as it might seem at first glance, the diameter of the wire used to construct the coil. Apologies in advance if I’m becoming a bit persistent.

[@thomasperina2990]

Welcome Back Lord Callum: I definitely missed your humor as well as your antenna wisdom. The nice loading you made is terrific but how much power can you run into it or calculate, please advise sir. Maybe you could make a video on this as I'm certain it could become complicated. God Bless you sir & my best to Wendy and the dogs. TMP, Unit 22 from N.J

[@DXCommanderHQ]

Power.. The only way is brute force test. But folks get paranoid.. frankly I would surprised if this even got hot on SSB at 1,500W.

[@darrellh3769]

Awesome stuff Callum!!👍👍👍

[@WR3ND]

I'm trying to make an HT quad-band (6m, 2m, 1.25m ,70cm) antenna wrapping wires around a bit of rubber tubing, which is going great so far. But, I was thinking I could just cut the 4 wires to full wavelengths and coil them up adjacent to each other around the tubing, making the total antenna length about 132cm. Unfortunately, I'm not sure how to calculate the effects of inductance and choking at the different frequencies, turns, and lengths. I don't have an unlimited amount of wire to experiment on to find out.

[@WR3ND]

The calculator is telling me it should be 0.0 microhenries. 🤔

[@WR3ND]

Maybe I could double the overall length and have ground leads of equal lengths between the positive element leads. 🤨

[@DXCommanderHQ]

OK, I really like the idea of the 4 wires actually! However, I don't know either!

[@WR3ND]

@@DXCommanderHQ Thanks, yeah, I'll just have to get some more wire to mess with. Cheers.

[@johnhess351]

Where should I put a loading coil in a full wave 80 meter horizontal loop to make it 160m? At low current point or high current point?

[@DXCommanderHQ]

The high current will give you max loading. But I was taught that if it was square, do the 4 corners (assuming it was fed in the middle of one line. If I had to do it again, I would just do it at the feedpoint. Beware though, loading up a loop to half frequency is very inefficient..

[@philwhoareyou3677]

Hey Cal, great video. I have been playing with shortened verticals using loading coils. Reading up on them the position of the coil relative to the feed point, the lower you go also drops the coil impedance but also the efficiency of the antenna. So me being a smarty pants thought why not go higher and get as much omph as you can get. Well... so you end up with quite the coil at about 75% point. I was wondering if we swap out the wire wound coil for a ferrite wound inductor what happens, as this would take up less space and leave you with more wire for the given height that radiates but how does this effect the bandwidth with a higher Q inductor in place?. Any one tried this? We are in Winter down here in ZL so I haven't pursued this much further. I am using 4x40mm conduit as its relatively cheap and stays vertical. Anyway thought I just chuck that question out to see if any one has. End goal was a trapped vertical with loading coils.

[@DXCommanderHQ]

Good question.. I don't know..!

[@philipchandler330]

So I've made a 64:1 balun are the antenna lengths that apply to a 49:1 still apply?

[@DXCommanderHQ]

Yep

[@philipchandler330]

@@DXCommanderHQ Thanks DX Commander appreciate you greatly from YCARS in SC

[@joffa5555]

The gauge of wire doesn’t affect these values? Or is this predetermined on the website?

[@DXCommanderHQ]

Use it as a guide.

[@joffa5555]

@@DXCommanderHQ Thanks for replying. I appreciate your videos. There always easy to follow and fun.

[@Pu1sjl]

LlGuys, good morning. Is it possible to create a 49:1 balun with the T200-2 toroid? 73 of PU1SJL.

[@DXCommanderHQ]

Honestly, I really don't know.. Probably.

[@williambouchard4480]

Okay, so I have a meter that will check micro farads and pico farads, but how do I check micro henries? Thanks.

[@williambouchard4480]

Just did some research and learned about LCR meters. With that meter I should be able to check inductance. I learn something new everyday!

[@DXCommanderHQ]

Looks like you nailed it.

[@paulsengupta971]

@@williambouchard4480 I bought an LCR meter from AliExpress. It wasn't expensive.

[@Chris_KI4WCO]

Question for my antenna Elmer....how would a coil affect a delta loop? Could you use 3 coils be used to shrink the total size?

[@DXCommanderHQ]

You can make it shorter.. Of course.. Erm.. OK this is a huge subject actually. Try it.. thats how I used to do stuff.

[@johnrees44..G4EIJ]

Thanks Callum..Excellent, informative video...as always..73..John

[@stevet7522]

Anyone have a calculator for a coil loaded halfwave?

[@DXCommanderHQ]

Try Tim G5TM and go to his channel..

[@vinniec5286]

Thank you for the video. I have to ask, though, about the "diameter of the conductor in inches". You had it as 2. I would think it would be like .2 inches. Did that affect the math?

[@DXCommanderHQ]

About 2 inches / 50mm. Yes diameter affects the inductance.

[@vinniec5286]

@@DXCommanderHQ ok thank you

[@dheller777]

You ought to build these for your DX Commander series like the classic so you could do 80 meters. I think you woulsd sell a bunch of them for sure!

[@DXCommanderHQ]

But so easy to make :)

[@FromthehamshackwithNJ4Z]

Brilliant Stuff!!!! great explanation!

[@DXCommanderHQ]

Thank you kindly!

[@rjollis]

This is confusing. I pumped through the dimensions of the 80m coil and antenna element from my DXC Sig 12.4 and it doesn't work out. Not even close.

[@DXCommanderHQ]

Trial and error.. I never used that calculator for the 12.4.. Interesting..

[@ChaplainDaveSparks]

Very useful. Now if I can figure out to homebrew a _”Ham Stick”_ - IOW, a helical antenna … Or even calculate the frequency of a pre-made helix, like a _Slinky™,_ when it’s stretched to various lengths. *73 de AF6AS*

[@paulswift700]

Hi Callum. That's ver interesting. Over here in Thailand is very difficult to import antennas of any kind. Therefore I have to make my own. I can't see your information on the coil calculation program. Can you please give me the information. If coil size I normally use the coil 34 program. But if it comes with your one I can use that instead. Many thank. Paul. De​HS0ZLQ, G0MIH.

[@DXCommanderHQ]

Please either search for the titles - or see the description. The links are there..

[@fm71450]

Thank you!

[@DXCommanderHQ]

You're welcome!

[@SnowLynxPreparedness]

Thank You for the video - however there is a simple method to calculate the parameters of the coil without guessing - I asked "Copilot" AI that question "I have 2 inch pipe and 4mm diameter of wire and I need to create an air coil of 0.9 microhenries - how many turns of wire I need to place on the pipe ?" and it gave me the answer Certainly! To calculate the number of turns for your air-core inductor, we can use the following formula: [ L = \frac{{d^2 n^2}}{{18d + 40l}} ] Where: (L) represents the inductance in microhenries (µH). (d) is the diameter of the coil from one wire center to another wire center (specified in inches). (l) is the length of the coil (also specified in inches). (n) is the number of turns. Given your parameters: Diameter of the coil ((d)): 2 inches Length of the coil ((l)): 1.25 inches (approximately 0.4 times the diameter) Desired inductance ((L)): 0.9 µH Let’s solve for the number of turns ((n)): [ n = \sqrt{\frac{{L \cdot 18d \cdot 40l}}{d}} ] Substituting the values: [ n = \sqrt{\frac{{0.9 \cdot 18 \cdot 2 \cdot 40 \cdot 1.25}}{{2}}} ] Calculating: [ n \approx 26 ] Therefore, you’ll need approximately 26 turns of wire on your 2-inch pipe to achieve an inductance of 0.9 µH. Remember to wind the coil tightly and apply epoxy for mechanical support after winding Thank you again for the video.

[@BrokenSignal]

I use AI a lot with HAM as well. It's great but always double check the results. Modern AI will guess when it doesn't know the answer.

[@DXCommanderHQ]

Watch out with ChatGPT.. "he" got something wrong with me..

[@justawfulgamer7738]

How is this different than an ugly balun?

[@DXCommanderHQ]

Ugly balun works on unbalanced coax. This is a wire element. Good question.

[@gfodale]

Not sure I would want an 'un-holely' coil on my antenna. Just doesn't seem right..... :P 😝

[@2140BlackCreek]

Can't find your glasses? Oh, Callum, that's the third thing that starts to happen in "old" age. I forgot what the other two are supposed to be. 73 AA7MO

[@rkirke1]

My GF in the background while I'm watching this: "Who the f*** is Henry and why's he so small?!"

[@DXCommanderHQ]

HAHAHA