HAM RADIO: The 64:1 EFHW Transformer build. 49:1 and 64:1 UnUn builds

[@JxH]

For those confused why 8:1 turns ratio becomes a "64:1" transformer, it's because the voltage ratio is in proportion to the turns ratio, and the current ratio is in inverse relation to the turns ratio, so the IMPEDANCE ratio is in proportion to the turns ratio SQUARED. In this example, the voltage on the secondary will be 8x higher, and *thus* (conservation of power, sort-of) the current will have to be 8x less (as power is conserved, ignoring losses), so the impedance at the secondary Z = E/I = 8x / (1/8x) = 8x8 or 8^2 = 64x. So 50-ohms nominal would become 3200-ohms. Thus approximating the characteristic impedance of a half-wave antenna over real ground.

[@smokeweedeveryday9099]

Thank you for this comment. Been trying to wrap my head around this for a couple days now. You just made it clear.

[@RC-Heli835]

@@smokeweedeveryday9099 Glad you got it! I'm really confused now!😀

[@Welshwizzard1]

Would ,like to see a sweep with a VNA .

[@danielhorvat4340]

Have you checked the coverage and insertion loss above 14MHz, the 3 turns/24 turns on two 240-43 cores are good only for 160-30m.

[@JxH]

0:27 "...three primary followed by 21 secondary..."

[@woodskid4ever]

I have the same question. I’ve seen the bifilar windings considered primary only, followed by secondary windings with single wire to complete the ratio of bifilar/ primary : single/secondary. I hope someone answers this.

[@clems6989]

Its an autotransformer by definition so primary turns are part of secondary turns...

[@JxH]

@@clems6989 No. An autotransformer is a *single* winding with a tap partway along. This is not that. This is two windings, with the secondary continuing after the primary stops. Cheers. 🙂

[@clems6989]

@@JxH Yes, Many people build it as you describe. And just tap the 2nd winding...

[@MrLittlmike22]

amazing video - soso helpful! i am intrigues to see finally what the difference between 3 to 24 turn VS 2 to 16 turn is ! thank you for doing this - this is GREAT Clear, detailed amazing

[@Soupie62]

The 3 turns make an inductor, in series with the source impedance (typically 50 ohms). Reactance = inductance × frequencies × 2 × pi. When reactance equals impedance, you have reached a -3dB cut-off point. A high pass filter. Having 3 turns instead of 2 gives higher inductance, the unun is more efficient at lower frequencies. 80 metre band, maybe even 160 metre.

[@Mark300win]

​@@Soupie62i lost you at the very end, so are you saying that 2 turn is preffered for lower bands(80m) and 3 primary turns is more efficient for higher band like 40m and up? Thanks

[@Soupie62]

@@Mark300win Generally, inductance is proportional to N^2 (square of the number of turns). If a single turn has inductance X, 2-turns will be 4X, and 3-turns will be 9X. 9/4 = 2.25, so a 3-turn coil will be about 2.25 the inductance of a 2-turn coil. If a 2-turn coil is 1 uH (micro Henry), its reactance at 3.5MHz (80m band) is about 22 ohms. In series with a 50 ohm source, coil signal is about -5dB. A 3-turn versiion is 2.25x this, or 2.25 uH. Reactance st 3.5MHz is about 49 ohms. Coils signal is now about -3dB. Conclusion: more turns is better for low frequencies. Maximum useable frequency is a different topic, where the core material in the transformer becomes significant.

[@Mark300win]

@@Soupie62 awesome! Thank you

[@alexdokic5567]

Hello Mike, enjoyed winding this Transformer this morning and getting tangled up in wire and twine! Measure twice cut three times haha! I used 2mm wire but forgot that twisting the wire shortens it a bit, third time success. That’s a great way to twist the wire with a drill. 2mm wire is the absolute max to use although winding it wasn’t too difficult. Thanks for your videos on previous projects. 73 Alex M0KVA

[@seanwood8043]

Excellent craftsmanship as always Mike ! Keep the videos going they are worth waiting for .

[@mike-M0MSN]

Many thanks Sean, finding time for the hobby is difficult at this time.

[@seanwood8043]

Well and your videos are technically more substantial than a bloody random review of whatever gear some one sent someone to review( Pander) or doing unboxing's lol. Baby's want milk, men want meat , you got lot meat on the bone information and skill wise and I for one appreciate that time you take . Can't tell you how much I have learned last couple years watching you and Calums's videos, and a few good laughs thanks again and keep doing what you do !

[@M0PQA]

Excellent video. Very educational. Please do the LED version.

[@randalweil8762]

Thank you You where very clear, Concise, explained the calculation formula well

[@ranchosinnombreannjimmy8427]

Nice Transformer! 1.8mm is 15 gauge wire. Murica just use 14ga.

[@seanking7221]

Thanks for this video and detailed explanation of how everything connects.

[@Joe-KN4IFI]

Nice job Mike. I sure do like the clear top case. Every time I go out and check my EFHW I have to take the cover off. The clear top case would make checking my EFHW so much easier. 73 Joe

[@mike-M0MSN]

Yes a very good point Joe, thanks 😊

[@buddyhoover57]

Excellent work!!

[@garyh8315]

Great vid Mike, I have been looking at building a 49:1 for /p on holiday. This looks really nice though in the clear lid box.

[@mike-M0MSN]

Thanks

[@M7BXR]

Wouldn't a neon indicator give a nicer glow and less chance of it upsetting something? Reminds me of those SWR upsetting things we had in the late 80s for mobile CB antenna 😆

[@mike-M0MSN]

Yes I remember them, glowing on top of my car antenna…😂

[@EA8CVZ]

Gracias por el vídeo. Un like para tí.

[@andrewhill4226]

Winding toroids is an art and I find put the radio on with music and make sure your on your own, etc. Try to keep calm and take your time. I have some wound and never tested ! Now I see your clip, I will give them a go. I have only made them for around 150 watts and test them to 100 watts, no big issue being an M6, you have to test them and may as well do it on air rather than a dummy load. Thanks for your construction video, you will inspire folk to make one and try. Andy M6APJ.

[@mike-M0MSN]

Cheers Andy. 👍

[@azarellediaz4892]

How do you determine the wattage one of these will work with and how do you go about creating one for a higher power transmitter? Thanks 73

[@JayN4GO]

Did you notice how much db of loss is between the 49:1 and 64:1 on 80 and 40m bands. These are the only 2 bands that interest me at the moment but im not sure which to build. I have built the 3 core on 52 mix 14.2 with this heavy enamel wire. I’m thinking I should have went with the 64:1. Close spaced turns by the way.

[@randalweil8762]

This video builder shows the video in his playlist. Which one is better? 64:1 or 49:1 and he shows a print out screenshot of his findings on the SWR on at different frequencies. In my personal opinion, based on that and what he did 2 turn 2 core. 49:1 seems to fit the bill across the board

[@davidschwartz9636]

Hi Mike. Thank you for this video. At the moment I've got a 49:1 I made to use with an EFHW, after watching this, I'm going to try out a 64:1. Think I'll try and source a box with a clear lid like you've used, it's good to be able to see the thing working and to be able to check it's ok, without the need to open it up. Regards David (M0XQZ)

[@Caniculus100]

How about testing the balun with a resistor to see how it transforms the impedance. We need to see how many bands is fairly resonant.

[@eliekadi_OD5KU_KU5OD]

thank you for your educating videaos,..super glue between the toroids would be helpful

[@MrCapuletty]

Произведение исскуства!

[@robertbird7297]

Thank you Mike for filling in the details of the finer points. What size wire would you suggest to use with the toroids (1500w)?

[@stargazer7644]

You'll likely need more toroids for 1500W. Once you saturate the toroids your SWR will go nuts. And they'll get very hot.

[@DonDegidio]

Hi Mike, Excellent job winding the toroid with the enameled wire. Didn't notice if the box has a seal for the lid. If it doesn't, wrap the seam with electrical tape. You and the family stay safe. 73 WJ3U

[@mike-M0MSN]

Hi Don, good to hear from you, yep there is a gasket so water tight 🤔🍌🍌

[@JBud1911]

NICE JOB KR6BJ , John

[@2e0txe]

Fantastic build! Looking forward to the testing before I wrestle with the wire hahaha!

[@mike-M0MSN]

Yes next video, what is better a 64:1 or a 64:1 or a 49:1.???

[@Rubedo777]

I followed the engineering but I don’t follow the electrical applications because I’m not the brightest bulb in the box . The build qualify is exceptional something I’d be proud of doing. You’re a good builder Mike and easy to follow along even if I don’t understand some of it… it was stumping me about why some of the wire was twisted… the primary’s. And I was confusing transformers with baluns… similar but different. I’m thinking of building a radio from a kit… I can follow drawing and plans even if I don’t understand the theory’s if you follow my meaning. 🫥 Best wishes to all. 73.

[@stargazer7644]

All baluns are transformers, but not all transformers are baluns. The difference is how they're wound. A proper 4:1 balun (for example) actually has two devices in it - a 4:1 transformer, and a 1:1 balun. TRXLab did a wonderful series on how they work and how to make them: kzbin.info/www/bejne/oX7PfJl-fbdrfLs

[@Rubedo777]

@@stargazer7644 Thanks… and I really liked his German accent. I think I should leave this clever stuff to others and just buy my things from the retailers… but thanks for your advice. I’m watching more of the posts… it’ll probably fuse my brains though. 🤪

[@brentjohnson6654]

I have ordered the EFHW 8010 kit from HF kits via ARRL. I have been interested in the EFHW for portable work as it can be resident on all the bands. I will need to make decisions on the low bands (SSB or CW) because of the high Q factor. Nice build

[@jeansalomon371]

Great !!!

[@ranchosinnombreannjimmy8427]

Besides the inductance values in the primary winding (where they're twisted together), what is different were I to use coated wire(household) instead of magnet wire???

[@mike-M0MSN]

I guess it is that you can get magnet wire closer to the core, (better coupling) but I bet you would not see much difference....

[@Capt_Duffy]

What a beautiful piece of work... 👍👌

[@mike-M0MSN]

Many thanks 🍌🍌

[@bitemykrank1970]

The wire gauge is simple...it's 1.8mm. Hence the label..........also known as 15 SWG, 15 BSG or 13 AWG. So as to be not at all confusing in anyway. And if your going to add LED's, go the WHOLE HOG and add WiFi, Bluetooth and a coffee percolator aswell...for those LONG nights DX'ing

[@mike-M0MSN]

I do like the idea of the coffee plug in…😂

[@azarellediaz4892]

I can’t find a table of the different measurement standards for wires, can you provide a link to your given data?

[@azarellediaz4892]

Great video, thanks for the education. One thing, the idea shared at the end is awesome, how would you go about putting the led(s) in that would light up when you transmit? Also, how do I know if I need a 9:1, 49:1, or a 64:1 unun?

[@mike-M0MSN]

I have not worked out the fine details yet on the LED's, 9:1 for a random length of wire (non resident on any of the HAM frequencies) --- 49:1 halfwave length 80M - 10M. ---- 64:1 = halfwave length 160M to 40M

[@williamgrocott8925]

Nice video Mike. But help me understand why 64:1 when 49:1 works..? It would be nice to see a VSWR comparison between the two. Thanks 73 de Will, M0LGW 👍🏻😊

[@mike-M0MSN]

Well that’s a go question, the short answer is that they both work well. A 49:1 transforms from 2450 Ohms down to 50 Ohms and the 64:1 from 3200 Ohms to 50 Ohms both the 2450 and the 3200 ohms are present at the end of a length of wire depending on the length of counter poise and radiating wire and ground conditions. I choose the 64:1 as I have found that it is the most suitable for me having built both.

[@jonpg1jsf118]

That there is a work of art ! Not sure a light show is necessary though :)

[@mike-M0MSN]

You are probably right.

[@HooPhartd]

Did you account for the length loss of your twisted pair. After twisting mine, it did not make the trip. Oh well, it will get used in a future project.

[@TeamYankee2]

Nice job on this.. about to make one... so what type of toroids do I need ?

[@mike-M0MSN]

43mix 240 size

[@Silverscott]

Hi Mike, excellent video !! Can you tell me where did you find your waterproof outside box please ? It seems very good quality. Thanks for your answer :)

[@mike-M0MSN]

eBay

[@vicmiller7191]

i have a additional question about the enclosure, Who is the manufacturer of this little box? I have been looking to purchase just the enclosure but my big box stores do not carry anything like the one used. I like the way it looks and how the box appears to seperate the mounting screw area from the internals of the box. this appears like a better moisture seal when the cover is in place. preventing water from entering the enclosure from the screw holes. Thanks and 73 Vic de KE8JWE

[@azarellediaz4892]

Exactly my thoughts.

[@trevwaters1]

Would have help novice if you mentioned size of bolts and size of wire used. Maybe you mentioned halfway through video but I switched off because it seemed to general.

[@stargazer7644]

He did say the size of the wire - 1.8mm or approx 14 AWG. The size of the bolts doesn't really matter just so long as they're at least as big as the wire.

[@TimRedman]

For us Yanks, the 1.8mm wire should be equivalent to about 14-16AWG.

[@TimRedman]

Also, if you can find a reamer like what you would use to prep copper pipe, the kind with the swivel tip, they work fantastic on plastics like PVC, to clean up drilled holes.

[@RechargeableLithium]

According to Eland Cables, 1.83 mm diameter is 13 AWG. 73

[@mike-M0MSN]

Cheers Chaps..

[@MakeDoAndMend1]

Confused. I thought the start of both primary and secondary. Twisted wires was centre of coax connector. George

[@mike-M0MSN]

Both will work, voltage or current is the difference..

[@michealbell5042]

Can you do a 12 to 1 please Mike

[@eoinm0nvk110]

Mike, do you not put a small hole for condensation?

[@mike-M0MSN]

That is a good point, sometimes I do however with a clear case I can see if I need to add one later or not.

[@W6IWN_Radio]

Beautiful work!

[@wifiwizard]

VERY professional job with the prolject. I thouroughly enjoyed watching the video and I will attempt to construct one that works and looks GREAT! '73 K5ZF

[@mike-M0MSN]

Many thanks..

[@johnblake4503]

So if a 49:1 is usually constructed with a ratio of 2:14 turns why is a 64:1 a ratio of 3:24 turns, could it also be a 2:16 ratio ? 16/2 = 8 as does 24/3. 8 x 8 = 64 etc ?

[@lovelycollection100]

Is the ratio 7x7 49 8x8 64

[@stargazer7644]

Yes, both transformers will have an impedance RATIO of 64:1, but the actual measured impedance of the primary on a 16:2 and a 24:3 will be different. You want the coax side to be close to 50 ohms for a good match with the transmitter. Ideally you want 50:3200 ohms, not 25:1600 ohms (as an example) at the design frequency even though both of these are 64:1.

[@benalamon4699]

How much power can this 64:1 UnUn Balun handle? CW? Digital Transmission? USB?

[@mike-M0MSN]

400 Watts SSB ish.

[@GastoNet]

How much power can handle using 2 toroids? I'm wondering if I need 2 or 3 for 1.5 kw. Many thanks for the video.

[@justmejonboy]

When would you choose a 64:1 over a 49:1 or is it just experimental to see what gives a better match ?

[@mike-M0MSN]

Yep experimental

[@justmejonboy]

@@mike-M0MSN I built a 64:1 over the weekend, was great on 40m but not great on 20 15 or 10. I also tried different capacitor values from 100 to 300 pF. In the end I converted it to a 49:1. Best results were without the capacitor.

[@stargazer7644]

It depends on the impedance of the antenna you're trying to match. If it is closer to 2450 ohms you use the 49:1. If it is closer to 3200 ohms you use the 64:1. If you don't have any way of measuring the antenna impedance you use the one that works better :)

[@azarellediaz4892]

⁠@@stargazer7644I’m totally new to this, what are you referring to 2450Ω or 3200Ω and how do I find out what I have?

[@stargazer7644]

@@azarellediaz4892 It is the impedance of the antenna you're trying to match your 50 ohm radio to. Just try both and use the one that gives the best SWR.

[@jorgerodriguez-wp6en]

Hello there sir. Excellent your video of Un-Un 49:1 A question. I have very small Amidon 50-43 toroids. They are really small. I want them only for a Un-Un receiving antenna (SWL). Do I have to put the capacitor 100pf too? .. Thanks for reply. 73 George

[@PaulaBean]

LEDs or neon lights could be nice! However xmas is half a year away.... ;)

[@Oregun]

Nice job!

[@mike-M0MSN]

Thank you

[@SeppaFrattini]

Hello Mike, did you spot any difference winding the turns in this particular direction instead the opposite one? The windings we usually see on the internet have the twisted section on the right. And also is there a real benefit using 3 + 21 (or 3 + 18 for 49:1) instead the (would say) classic configuration 2+16 (or 2+12)? Thank you, best 73 IV3IAA

[@mike-M0MSN]

I have returned to the simple 2 + 14 as there was no real benefit to the 3 + 21 so the classic wins....

[@azarellediaz4892]

@@mike-M0MSNif going to the 64:1 unun is not worth it, why not share that as a pinned comment so others don’t waste time in a futile project?

[@acestudioscouk-Ace-G0ACE]

A very neat job and well described. As for the last comment about LEDs lighting up on transmit...must be a throwback to your CB days and the Wally light on the end of your antenna! 🤣

[@RC-Heli835]

Mike do you just order all the stuff you need instead of buying a kit?

[@mike-M0MSN]

Yep I tend to have stuff lying around and then build from it....

[@DonzLockz]

that should take alot of power. Was there a heat and weatherproof rating on that case?

[@x_CrossHair_x]

I know this is all about Ham Radio.. I only SWL.. Messing around as I don't have the knowledge to calculate my own balun / unun currently using a 49:1 best up to now for me.. (Will try a 64:1) for sure.. (Thing is) would love to RX from 30KHz to 30MHz.. the 49:1 gives me 500KHz to 25MHz (At best but very weak) above that. (I guess not possible to get 30KHz o 30MHz) with a balun ?? anyway thanks for the 64:1 tutorial will try it..

[@mike-M0MSN]

I guess it depends on the length of wire. but 64:1 may be better??

[@x_CrossHair_x]

Thanks for your Reply to my UNUN Problem 49:1 or 64:1 I don't think is the Problem in my case.. The length of the (Long wire) would be better if I could have a longer run.. However I have maxed out the length restrictions of my property.. so perhaps a new style / type of antenna would be required for the lower frequency.. (Tunable Loop antenna) is what I am considering to Rcv 30 khz to 500 khz.. then for frequencies (above 25 MHz) just use my Discone antenna for that, and above... 73s@@stargazer7644

[@stargazer7644]

@@x_CrossHair_x Just keep in mind that discone antennas work equally poorly across a large range of frequencies. Band specific antenna perform far better. 30-500 khz requires very special antennas because resonance at the freqs require truly huge antennas - so all practical antennas are low efficiency at those freqs.

[@x_CrossHair_x]

Thanks again for your input.. and band specific is my dilemma.. So.. I'm working on it. With hopes of constructing a Tunable (Box Frame Loop) if that is a good enough visual description.. Not sure if you can call it a Magnetic loop.. but close to that. in appearance. (Long main loop / with an induction loop. tuned with a old school open air Adjustable Capacitor.. in the picofarad tuning Range).. all I can do is cross my fingers that when built.. Will Work 🤞🤞.@@stargazer7644

[@paulkazjack]

Where did you get the torroids from? And what value are they? Thanks.

[@mike-M0MSN]

eBay and 240/43 mix.. :)

[@ukm6yik69]

U have to put led in Mike he awesome

[@mike-M0MSN]

Cheers

[@1shARyn3]

Couldn't you do 300W on 1.0mm wire?

[@mike-M0MSN]

Yes, however I’m unsure of the key down time as heat is a factor…

[@mikemiles3068]

No just watching little Green spots on Radar.

[@MrLittlmike22]

also - a reevant question if oone were to use stranded wire - seems to me that the whole process would be faster ? can one use standed wire??? (asked around - opinions differ....) anyone tried stranded wire?

[@paulkazjack]

Yes you van do that.

[@stargazer7644]

You can use stranded wire, but it has more loss at RF and will get hotter.

[@vicmiller7191]

I love the LED idea. That would be neat to see in action. Nice build for sure. Thanks for sharing... Vic DE KE8JWE

[@mike-M0MSN]

Searching eBay as we speak for some…

[@75ohmHAM]

QRO wire meet QRP connector 😅

[@mike-M0MSN]

in the UK, everything is QRP

[@lllJuanlllCarloslll]

No test 🙊🙉🙈

[@azarellediaz4892]

You use metric measurement wire, in the USA we use wire gage, and when I look up magnet wire on Amazon the metric measurement wire gives the “internal” measurement… how do I know which one matches to your design requirements?

[@mike-M0MSN]

internal?? use google! 1.5mm = 15 gauge

[@jimlosh3305]

Very Nice build Mike. Just be careful of the Leds. They can add noise on the transmit signal. KC2DEQ. Jim

[@mike-M0MSN]

Thanks for the tip Jim.

[@michaelm1keyhardy865]

Always a pleasure watching other people knowing what they are doing, i'd rather buy one my days of building stuff is over ive got Essential Tremours now but great work Mike. de MIKE M1KEY M0FCG

[@azarellediaz4892]

Sad you have that terrible condition and can’t enjoy tinkering any longer. This means now you can spend the time teaching the new generation of upcoming Hams.