How To Make A Simple Small Space Ham Radio Antenna For 40 Metres (Plus 2 Other Bands!)

[@IrishHamRadio]

Ah wonderful Tim!! I’m now definitely more enlightened and getting closer to having a go at one of these choked/loaded antennas with my own coil…. I understand now how you make and measure the coils, but silly question however…. How do you know how many uH you need?? I know I should probably know this!! 😅

[@timg5tm941]

As a ROUGH idea. Look at the 1/2 wave on feet on the band you wish to choke and that gives you a good idea of the uH needed. So for 20m 33uH and 10m about 16uH seem to do the trick Dave.

[@IrishHamRadio]

@@timg5tm941 ah ok class! Got it 👌🏻 thank you 😊

[@GM5DDX]

Could you make one for 10, 15 and 20?

[@timg5tm941]

I have done - check out a video I did a month or so ago, using traps.

[@kevinnicholls1017]

Another helpful video. I cannibalised exactly this antenna just last weekend. I had built it as a shortened EFHW for SOTA and holiday locations where space is limited. I deployed it as an inverted V and found it very sensitive to the height of the loading coil and unpredictable in different settings so I abandoned the idea. All that I needed to do was to watch your video. Setting it up as a vertical gives a predictable height for the loading coil and repeatable antenna! Good work. Thanks MW0KXN

[@timg5tm941]

Glad it worked for you Kevin!

[@mareksp9tkw908]

TIM this antenna as vertical works well on 20 and 40, 10 on another hand is poor. Much better to set it up as inv-L with transformer 2mtr of the ground apex at 7mtr and rest on antenna as horizontal as possible. When you model it you will see that 10m give a quite a good performance.

[@timg5tm941]

Fully aware of that difference. Of course it’s main benefit as a vertical is enabling 40m without any radials. For 10m it’s 3dBi down compared to a 1/2 wave mounted at the same height at a 5 degree elevation angle. Not a huge game changer and still capable of DX. I’d classify poor as being 2-3 S points down. On 10m this antenna isn’t that bad. 73

[@MikeN2MAK]

I see an LCR meter in my future.

[@johnsonstechworld]

Currently I have squeezed in 40/10m inverted V fan dipole into my small space. When the solar cycle 25 starts going down and 10m goes down, I will try to use coil loaded dipole for 80m. Or should I convert a 40 to 10 m EFHW which I purchased and currently in my shelf, with a coil to work for 80m as well? I presume that 20m long wire will be too short to make it work on 160m as well? 73 de Jon, VU2JO

[@timg5tm941]

Any of those would work. A 20m long wire is pretty short though for 160

[@johnsonstechworld]

@@timg5tm941 Thank you. 73

[@OlivierGindensperger]

Hi Tim! I constructed a 49 to 1 auto transfo with 3 stacked FT240/43 tores and 1.5 mm² enameled copper wire. Not really optimal (as colin, MM0OPX reported). I mounted your designed EFHW antenna on a 14m spiderbeam pole and I can not get the 40m tuned. 20m and 10m are quite good but with 1.8 meters wire above the self (37uH designed with Coil32/64 program) I cannot get a tune. This evening I retried to get a tune with 3.4 m wire shortened to 2m but all the time I only get resonance between 6,6 and 6.7MHz and something with an SWR of 5:1 to 3:1 at 11 Mhz. That's why I tried this evening with a longer wire. til now, no Tune on the 40m band. Why? Mistery. Hi! ❌ - 1 - 9/11/24 9:48 PM Coil64 v2.2.33 - One layer close-winding coil  Input: Inductance L: 37 microH Frequency f: 14.175 MHz Former diameter D: 50 mm Wire diameter d: 1.38 mm Wire diameter with insulation k: 2.8 mm Wire material Mt: Copper Result: Number of turns of the coil N = 44.916 Length of wire without leads lw = 7.452 m Length of winding l = 128.564 mm Weight of wire m = 99.862 g DC resistance of the coil Rdc = 0.086 Ohm Reactance of the coil X = 3,295.374 Ohm Self capacitance Cs = 2.266 pF Coil self-resonance frequency Fsr = 22.75 MHz Coil constructive Q-factor Q = 251 Loss resistance ESR = 7.894 Ohm Additional results for parallel LC circuit at the working frequency: => Circuit capacitance: Ck = 1.141 pF => Characteristic impedance: ρ = 3,295 Ohm => Equivalent resistance: Re = 661.182 kOhm => Bandwidth: 3dBΔf = 70.649 kHz Input data for LTSpice: Inductance: 37.001μ Series resistance: 85.893m Parallel resistance: 497.326k Parallel capacitance: 2.266p If I try with 35uH: I have to short the coil from 2.5 turns. Will try tomorrow if the weather keeps dry... ❌ - 1 - 9/11/24 9:51 PM Coil64 v2.2.33 - One layer close-winding coil  Input: Inductance L: 35 microH Frequency f: 14.175 MHz Former diameter D: 50 mm Wire diameter d: 1.38 mm Wire diameter with insulation k: 2.8 mm Wire material Mt: Copper Result: Number of turns of the coil N = 42.498 Length of wire without leads lw = 7.05 m Length of winding l = 121.794 mm Weight of wire m = 94.486 g DC resistance of the coil Rdc = 0.081 Ohm Reactance of the coil X = 3,117.245 Ohm Self capacitance Cs = 2.2 pF Coil self-resonance frequency Fsr = 23.53 MHz Coil constructive Q-factor Q = 277 Loss resistance ESR = 6.994 Ohm Additional results for parallel LC circuit at the working frequency: => Circuit capacitance: Ck = 1.402 pF => Characteristic impedance: ρ = 3,117 Ohm => Equivalent resistance: Re = 676.176 kOhm => Bandwidth: 3dBΔf = 65.348 kHz Input data for LTSpice: Inductance: 35.000μ Series resistance: 81.269m Parallel resistance: 536.671k Parallel capacitance: 2.200p 73 de F8BOE ...-.-

[@timg5tm941]

How long is the wire below the coil for 20 and 10?

[@OlivierGindensperger]

@@timg5tm941 Hello again Tim. Good question! As I saw that my coil on a 50 mm form was too heavy (260 g) and made my spiderbeam pole bend too much, so I decided to make a lightweight version on a 25mm form and 1mm enamelled copper wire. Ad so I got a 78 g coil. I made all the measurement with my MiniVNA Tiny and had the same values than with the bigger coil. After watching closer to your VNA graphs, I saw that your 10m band results were not so far away from mine, on 20m I had now a better SWR. Shortening further to get resonance on the 40 meter band let me cut the higher portion down to 1,10 meter, real shortened one!!! In the end I have similar results than You have... Varying the forms calibre brings the advantage that you can play with the length of wire needed for the top section of the antenna. I'm considering now to eventually add the 80 meter band. 73 de F8BOE ...-.-

[@johnnorth9355]

I am going to take down my EFHW and my Vertical and use the bits to make something a bit different . The goal is to get away from the local QRM of Solar and other electronic device noise. Desperate times call for desperate measures . Quite what I am going to do I am still working on . Oh er ! 73 M7BLC.

[@timg5tm941]

Good project!

[@brianfields4479]

Personally I would leave the vert up , and work on a rx ant. 73 zl3xdj.

[@johnnorth9355]

@@brianfields4479 I am intrigued by the idea of a loop on the ground around the outside of my garage for rx but have yet to work out how I can automatically switch antennas for rx and tx. I am a limited knowledge late life M7 after all 🙂.

[@brianfields4479]

@@johnnorth9355 there are tx/rx auto switches on the market. I myself made a ant auto switch using a switch output from my rig. I use a resonant vertical for 40m and one on 20m, fed with one coax, and on rx I use a low to the ground dipole on rx, but loops on the ground work very well. 73 zl3xdj

[@genoa1979]

This antenna for portalble in 40 meter have good angle for dx?

[@thesisdavid]

Hi Tim, What is the lowest radiation angle we can get on this antenna for DX?

[@timg5tm941]

Hi there - at 5 degrees elevation its best band is 20m, about the same as any half-wave vertical. On 10 and 40 its around 3dB down on a similar style antenna.

[@M0JSX]

Excellent video Tim. I wonder what the radiation pattern looks like on 10m? I know on a “standard” 40m EFHW, the pattern is a little erratic up on 10m (while it does technically work).

[@timg5tm941]

It’s slightly down on the 1/2 wave as full waves exhibit higher lobes (-3dBi at 5 degrees take off). The earlier video I referred to towards the beginning of this one (link on the screen) covers the modelling. 73!

[@M0JSX]

@@timg5tm941 thanks Tim. I did watch that video too! I'll blame the early hour!

[@timg5tm941]

@@M0JSX no worries mate!

[@spython1553]

Tim, another great video! How do you calculate the lengths of the radiators and the required inductance of the coil for the bands you want?

[@timg5tm941]

Hi there. The radiator lengths: cut 10m initially for the lower longer part - this is a 1/2 wave on 20 and full wave on 10m. It is important to also attach the coil but not yet the top shorter wire, Trim the lower wire until you get a good match on 20 and 10. Then attach the top wire (initially about 1.8m) and then cautiously trim that for best tune on 40m The lower longer wire is barely affected. As for the coil, the 35uH inductance is important in that it provides enough impedance to choke off 20 and 10 and present enough loading to make 40 usable and fit on to a 12m support such as a fiberglass pole. 73

[@spython1553]

@@timg5tm941 thanks for the detailed reply!

[@chazwozza67]

Where all ya CB videos gone?

[@timg5tm941]

Into the mists of time!

[@siddharth4662]

can you show the working of this antenna please if possible!

[@siddharth4662]

got it! :-) thank you very much... i owe you a beer if I ever come back to England again! :-)

[@timg5tm941]

You're on!

[@9bar7and9bar8]

Hi Tim, same as the Hyendfed antenna which I think you have ?? I wonder have you compared the 2. After seeing a previous video of yours with the 12m pole and the hyendfed I bought the same and it seems to work well. Great to have a go at building one, good work !! Just need this weather to improve so we all can get out a bit more. 73 Sid MI5UTC

[@timg5tm941]

Hi Sid! Yes its the same design and I am glad to say that this design replicates it. They are very well made antennas aren't they? I would say there is no difference between the two antennas. Great to hear from you. 73

[@HamRadioQso]

How well will that work at let’s say at a 45 degree angle?

[@timg5tm941]

You mean as a sloper? It’ll be fine .. often used that way

[@HamRadioQso]

@@timg5tm941 I thought it would be. Thanks for the reply

[@32_bits]

Its possible to measure inductance and capacitance with your Rig Expert, check the device menu.

[@timg5tm941]

Nice! I will

[@R50_J0]

I have three of the Atlas meters. Kind of non-traditional looking but they’re accurate and excellent quality.

[@timg5tm941]

Indeed they are!

[@M7BXR]

Have you had a trip back to Wales Tim? Sounds like youve had an accent top up! 🙂

[@timg5tm941]

I spotted that too! I usually get more Welsh if I get tired or speak with family/friends from back home. I think I was tired this day! 73

[@davidbridge3542]

Sounds like one to make. If i found the details for my coil based upon my size of wire and pipe dia, could i make the antenna in one continuous length ? It was only your testing explanation at the end that gave me any doubts??

[@timg5tm941]

Yes you can do this although bear in mind that if it is short then it becomes more of a headache to add wire. I like to keep my coil detachable as I have other plans for it for other antennas. 73

[@markramsay6399]

Great video Tim, Thanks. Mark, 2E0MSR

[@timg5tm941]

Thanks Mark!

[@M7BCN]

Great work buddy, looking forward to the next one. Thanks Tim.

[@timg5tm941]

Thanks Brian!

[@mrkopecky]

I guess I could use same theory to make a “sporty 40” coil. Thanks Tim.

[@timg5tm941]

Absolutely. You can load the top of a 5m Q wave and add about 1.5m of wire to have a 20/40 ground mounted vertical with ground radials using the same coil.

[@brianfields4479]

Interesting ant Tim, would the ant gain anything if radials were added do you think. 73

[@timg5tm941]

Not as it’s a Halfwave no

[@daveengstrom9250]

Sorcery!

[@timg5tm941]

Indeed!

[@paulsengupta971]

I've got a coil ready to put up a 40/20/15/10 EFHW and have it work on (at least a bit of) 80m as well. The plan is to run it over my house roof and down the garden. I appreciate it might not work properly in the rain! :-)

[@timg5tm941]

Give it a go Paul!

[@johnsonstechworld]

Oh! I see that somebody is already about to try my plan for 80m when the solar cycle 25 goes down! 73 de Jon, VU2JO.

[@paulsengupta971]

@@johnsonstechworld You can get commercial coils to do this, I've actually bought one second hand, but I'm going to create my own for another antenna.

[@johnsonstechworld]

@@paulsengupta971 It is not that easy to locate one in this region. May be I will try to make one. I was wondering whether I can use 1 sq mm insulated electrical wire from local electrical shop? It is there just across my home. The coil might turn out to be quite bulky and heavy. For the regular enamelled copper wire, I have to hunt in the city with hardly any parking space near such shops over here!

[@paulsengupta971]

@@johnsonstechworld I have made ununs and coils with solid core mains electrical wire, they work fine.