Build you own 4:1 BALUN with coax (045)

[@robertw1719]

I just stumbled onto your channel and have watched a few videos. Very impressive and informative! As an RF engineer just getting back into Amateur radio I am sure many of your videos will be helpful. And, by the way, your drawings and video editing are top notch! 73s and God bless!

[@eie_for_you]

Thank you for the great encouragement! Welcome back to the hobby! 🙂 Now that your getting back into amateur radio, my next video (which I am currently in the process of editing) might be of interest for you: "HF Operations for You" The whole point is bringing folks who are either new to ham radio or who have been away from it for a while up to speed on equipment, operating dos and don'ts, frequencies and their use and more. My plan is to have it out next Wednesday. My next *planned* video after that is a folded dipole for 2M & (possible) 70cm.

[@TheGeorge1952]

This is the best explanation of this much misunderstood balun that I have seen. Thank you!

[@eie_for_you]

You are very welcome! 🙂

[@W1RMD]

First of all, Liked and subscribed! This is the best explanation I've heard on this subject. The ARRL Handbooks and Antenna books don't explain this well at all in their hundreds of pages. I never understood why my beam never worked right until now. The pigtail length works the OPPOSITE of the stub section. I have to wrap my head around the fact that longer pigtails RAISES the frequency. I did see that number three of your tests worked the best because the 50 ohm coax likes a connection closer to ground and the half of the stub that hooks to the 200 ohm impedance likes the lager gap between the center conductor and ground. Thanks for saving me a ton of time and slobber (solder)! Excellent job on the audio and video quality! 73's

[@eie_for_you]

You are very welcome, Ryan! Rule of thumb ... R.F. is just magic! LOL 🙂

[@paulkf5pv]

Thank you, Sir. You and your experience have solved my issue with changing my old circular cross polarized sat beam into a vertical or horizontally polarized antenna. ❤

[@eie_for_you]

Wow! You are very welcome! I am so glad I could be a help! 🙂

[@paulkf5pv]

@@eie_for_you also, I could see the love in your eyes for your fine specimen of feedline with that molded BNC connector. 🙂 I've done all my homework and took notes. I'm going to get started on it right now.

[@paulkf5pv]

1st one completed.1.2:1 at 146.000 Mhz. I had to trim twice. I did at the 8% to the length and still had to take off 1" of the pig tails. I am going to try adding 10% to the next one instead of 8%. I am using RG8X here and taking an educated guess of the velocity being .79. when you said it was narrow banded, you were not kidding. now onto the one for the horizontal side of the beam.

[@eie_for_you]

@@paulkf5pv Woohoo! 🙂

[@eie_for_you]

@@paulkf5pv If you are doing the trimming and all connected to the antenna, then you are probably also seeing the narrow banded aspect of the the antenna as well. I looked at the velocity factor for RG8X. I got varying reports from 0.78 to 0.82 depending on the construction of the particular brand. I was very surprised that Pasternack's datasheet and webpage did not show a VF for the coax. I'm glad to hear that it is working for you! 🙂

[@terrybailey2769]

A nice well paced explanation, thank you. I have used these before and never understood how they worked, I now do.

[@eie_for_you]

Glad it turned on the light bulb for you! :-) It was amazing how many places I had to look before putting this puzzle together.

[@moosehead4497]

You are awesome! Love to see someone build a balun based on FIRST PRINCIPLES and not just following someone elses design they read on the internet

[@eie_for_you]

Thanks, man!😁

[@Sky1]

I feel like I am back in college but I can understand this instructor

[@eie_for_you]

Thanks, man! 🙂

[@masuka666]

I wish I had youtube and your channel when i was young 😃

[@eie_for_you]

Thanks, man! 🙂

[@iamhe999]

Great explainer...Kudos... Well Done... we need to hear more from you..

[@eie_for_you]

Thank, man! I'll keep 'em rolling out! 🙂

[@zachscott4867]

This was great and very informative. Thank you for sharing!

[@eie_for_you]

I am so glad that you found it helpful! You are very welcome! 🙂

[@BarefootBeekeeper]

Excellent explanation, thank you.

[@eie_for_you]

You are welcome! 🙂

[@tomtwist1081]

Nice presentation. What you really want is to make the pigtails 200 Ω. Then you can use any length. You can do this by stripping the jacket and braid at both ends of the stub, making the pigtails the desired lengths. When close together, they are 205 Ω. You have a much higher impedance, by separating them. Then you strip off 3 mm of dielectric, to connect the center of the feed line. The braids connects the same way as before. In engineering, we only use m and mm, cm is used in everyday language. And specifying a length 0f 4.445 cm is 2 digits too much. You won't be able to cut them to 0.1 mm precision.

[@eie_for_you]

Interesting thought. 🙂

[@grumpy_ken]

I watched a couple of your videos and they have been really good, especially this topic. I'm new to amateur radio and I am building a lot of dipoles. subbed- on my way to the video about band rejection just using coax 👍

[@eie_for_you]

Thanks so much for the encouragement! I am glad that you are finding them helpful. 🙂

[@grumpy_ken]

@@eie_for_you I just made a small folded dipole for 1090MHz ADSB and was using 75 ohm RG6 to connect it to an SDR as it is what I had. I went back to this vid as a reference and made a matching transformer from a half wavelength stub. I know the math is solid but I was still pleasantly surprised to see such a simple solution actually work in a real life application. very cool!

[@eie_for_you]

@@grumpy_ken WOW! That's really cool! 🙂

[@antenaseinterfacescb]

Great explanation about 4:1 coax. I will try this fer 11 meters band to use a Delta Loop. Tks fer nice video. 7351.

[@eie_for_you]

You are very welcome! Let me know how this works for your project.

[@antenaseinterfacescb]

@@eie_for_you I will. 7351.

[@margaqrt]

A coax stub matching transformer is an interesting video topic. However, at HF the physical length of the 1/2 wavelength section could be quite long. Also, at 2 meter operation I'd be more inclined to employ a resonant dipole or j-pole. Nonetheless, a very detailed presentation including the math to back up the theory. Very few amateur radio KZbin authors delve into the math. Thank you.

[@eie_for_you]

Thank you for the encouragement! 🙂 Surprisingly, the ARRL antenna handbook had nothing in the way of explanation. 😞 I have a few videos on coax stub matching. It is in the "Stub Match" playlist, among others. Here is one application for this BALUN ... I built a folded dipole tuned to the 2m band and fed it with this kind of BALUN. Because 70 cm is 3x the frequency of 2m, the antenna works well on both bands. It now hangs in my attic as my indoor antenna for bad weather.

[@W1RMD]

@@eie_for_you Good to know!

[@Duke-William]

@@eie_for_you Excuse me, this should work for 70cm associated frequency when added to 2m dipole, but what other frequency (band) should it work for? 🤔 Adding 70cm+200cm should affect the 2m halfwave your dipole was originally designed for.

[@eie_for_you]

@@Duke-William Well, this is a complicated question kind of. Antennas generally will work on every odd harmonic (1, 3, 5, 7...) So an antenna cut for 148 MHz should be reasonably functional on 444 MHz. With that said, in my practical experience, they do not work as well on the 3rd and even less on the 5th and so on. The 4:1 coaxial balun should work on every harmonic as it is based on being 1/2 wavelength long. But, again, in practical terms, it doesn't work as well on harmonic multiples as it does at its design frequency. So, my folded dipole that I create in this video kzbin.info/www/bejne/l6XReoCtgtd_ppI works great on 2m and OK on 70 cm at the top of the band. Hope this helps 🙂

[@Duke-William]

@@eie_for_you Thank you , for the explanation. Love this channel!!!

[@nova5t872]

Thank you

[@eie_for_you]

You are very welcome! :-)

[@Timberfist]

What a wonderful video and what a wonderful channel. This is the first of your videos that I’ve seen and it’s an instant subscribe for me.

[@eie_for_you]

Thanks! I am so glad that you found this video helpful! Welcome to the "family". 🙂

[@dennisqwertyuiop]

great video,hanks for sharing

[@eie_for_you]

Thanks, Dennis! BTW, I discovered the mic issue. Check out the community tab for my channel. Mind blowing discovery.

[@ChellathuraiKuttralingam]

Superb

[@eie_for_you]

Thank you! 🙂

[@arconeagain]

I used this on my 11m J Pole and it was most effective at removing the CMC issue I had.

[@eie_for_you]

Now *that's* cool! I've never heard of a balun used with a J-pole.:-)

[@arconeagain]

@@eie_for_you in my opinion, there's no better use for this balun... apart from a folded dipole. J Poles are shocking for CMC, and I was having trouble with the SWR, or SWR readings going up when I elevated it. I employed the half wave coaxial balun, and it completely stabilised it. These antennas are supposed to trail behind a Zeppelin. I even used a quarter wave radial to decouple the pole, the antenna was not insulated from the pole for static discharge. This radial or stub runs parallel with the pole, fixed a quarter wave down from the bottom of the antenna/tuning section. It was the most effective vertical I ever ran.

[@eie_for_you]

@@arconeagain I just learned something! I *never* knew that about the ubiquitous J-pole! Thank you! That was soooo cool! 😀

[@ericpilboue3276]

Thanks a lot, sure i will be indicatived soon.

[@eie_for_you]

You are welcome! 🙂

[@murpheyslaw]

John 3:16 - love it, and the video was pretty good too- blessings

[@eie_for_you]

Thanks, man! 🙂 God is good!

[@acestudioscouk-Ace-G0ACE]

I revisited this video and was grateful for the explanation behind the "how to". Knowing why we need to do something helps me learn and retain much more easily. Thank-you. 73 G0ACE

[@eie_for_you]

I'm in the same boat as you! I *need* to know the "why" behind things. Without that it is impossible to extrapolate what I am learning to new applications. 🙂

[@ButcherRobert]

I would like to see you build one for CB frequency with coax using a dipole antenna

[@eie_for_you]

Well ... these sorts of BALUNs are really only convenient at the higher frequencies. The CB band is starting to get really cumbersome because 1/2 wavelength is somewhere around 18 feet (5-1/2 meters) long. The other thing is that you wouldn't need one for a regular dipole because its impedance is 50 to 75 Ohms. A 4:1 BALUN would have in input impedance of 10-12 Ohms, no match for any normal transmitter.

[@izzzzzz6]

I'm thinking this is better than a transforming balun regarding heat loss and performance on fixed bands. I would be tempted to use a common mode choke at the feedpoint such as ferrite beads or ugly choke and perform the bal to unbal or whichever type of transforming with coax matching / transforming. I'm guessing this is a similar approach to when you want to add or subtract a piece of extra coax when you want to slew an antenna array. In a simple co-phase array you can delay slightly the signal at one antenna or the other to steer the radiation angle left or right. Using a short version of this transformer (or a combo of a slightly shorter and a slightly longer 1/2 wave coax transformers) could achieve this. if your array also has reflectors and directors you can also switch in and out small inductor windings on the reflectors and directors to switch their roles, With the combination of both you have front to back and left to right options. Just one question. Is this actually a balun, an un-un or both? It would also have been nice to hear pros and cons between this technique compared to ferrite transformers with a touch of info on choking common mode across the two options. I would love to see a discussion or talk regarding adding a coax transformer like this at the tuner when using open wire rather than fitting a regular 4:1 ferrite balun at or in the tuner. There is so much work that can be done on the feedline, adding bandpass stubs, changing coax lengths depending on frequencies used and different ratio transforming. It would be nice to see you go deeper into this, for example how would you create a 2:1 or a 49:1 with coax why is there usually such a big jump to these higher ratios when choosing baluns etc. Is it possible to get more than one band by adding another coax loop in parallel or different lengths back from the feedpoint, how would you combine the two of them (or more coax baluns) to find the correct lengths for each and positioning along the feedline. The visual on the vna makes experimenting possible without trying to get into complicated math, if you play for a few weeks with a few hundred meters of coax you can literally see what is happening on the vna, either way, can be quite mind numbing work. It would be nice to see some standards for options all printed up tried in practice and back-checked by the community. One thing i would like to see more of on youtube is good real world comparisons vs different methods or with and without. Often it is hard to tell what works well in practice vs what doesn't when side by side comparisons are not always captured on film. PS. If your up-cycling moulded connectors you never know if there is some sort of matching / filtering or transforming built into that moulded connector!

[@eie_for_you]

To answer your question ... yes, it is actually a BALUN as the grounded/return portion of the coax never actually connects to anything but itself. These sorts of BALUNs are practical for VHF and above, but get real cumbersome real fast as we descend in frequency. Conversely, the typical BALUN we see in use for HF won't work for beans at the higher frequencies.

[@NandangRochendi-e1g]

Thank

[@eie_for_you]

You are very welcome!😀

[@mctoddhikvision6189]

great video

[@eie_for_you]

Thanks! 🙂

[@cerberus333dog]

good info presented very well!

[@eie_for_you]

Thanks! 🙂

[@stanholmes4293]

Thanks for your interesting videos. With the coax balun is it possible to design a 49:1 balun?

[@eie_for_you]

You are welcome! 🙂 No, this style of BALUN is strictly going to be a 4:1 BALUN because of the principle behind it.

[@victoryfirst2878]

I am wondering how you could make a BALUN for TV antennas Ralph ??

[@eie_for_you]

Well...it depends on the antenna. If of the folded variety, then this one would work for a particular band of TV frequencies. These are pretty spread out so this frequency-sensitive 4:1 BALUN wouldn't give you all of them done well. If you are talking about a YAGI (beam)-type, the impedance is generally around 30 Ohms and the input impedance of most TV antenna inputs are 75 Ohms. There are various forms of impedance matching schemes you can use. One simple one is to simply connect the feedline further out on the driven element. This is a *BIG* subject in its greater context. 🙂

[@victoryfirst2878]

SO antanas of different type have different Ohms value that are used in TV reception ?? Would you tell me where I can look to read up on the subject matter ?? Thanks much for helping me understand Sir. Peace. vf @@eie_for_you

[@eie_for_you]

@@victoryfirst2878 An antenna is an antenna, regardless of what you are receiving. The same principles apply to all antennas. One does not need a special antenna for digital signals that is different from analog signals. At that level, all of the signals are analog in their electromagnetic nature. The impedance of the antenna depends on the style/configuration of the antenna. All antennas need to be *physically* tuned for the specific frequencies they are supposed to operate on. The commercially manufactured TV antennas actually have more than one section in order to cover the very divergent frequency bands used for TV transmission (VHF LOW 54-88 MHz, VHF HIGH 174-216 MHz, UHF 470-806 MHz). The whole topic of antennas is a HUGE topic and there are MANY texts on the subject. Here is a good reference for you: www.amazon.com/ARRL-Antenna-Book-Radio-Communications-dp-1625951116/dp/1625951116/ref=dp_ob_title_bk Yes, it is aimed at amateur radio antennas, but, like I said, an antenna is an antenna and all the same principles apply. I did an Internet search for "building a TV antenna" and found several articles. How good they actually are .... I cannot speak to that.🙂

[@victoryfirst2878]

Thanks for the information Raleph. Much appreciated Sir. @@eie_for_you

[@dannywhittle4245]

Think Ill just buy one :D

[@eie_for_you]

Be careful, my friend! Pay attention to the frequency range. For HF and the like, purchased ones are probably the way to go. For VHF and above ... You *COULD* do the same thing with a stub match as I demonstrate in this video: kzbin.info/www/bejne/goqXeKyprbh4l5I

[@cesarastiz9691]

Hi Ralph, this is the first video I watched from you and founded very instructive. I just wonder if the pigtails lenth will be as critical on the HF as it is on VHF. Although the balun line may be too long for low band, I prefer this balun to a wide band coiled 4:1 balun for my center fed 5/8 vertical 15m antenna.

[@eie_for_you]

As frequency increases, all measurements get more critical because they are based on the wavelength of the frequencies involve. So, at lower frequencies things get a LOT easier, but a lot bigger, too. :-)

[@salahjuma]

Thank you for a great i built 4-1 coaxial balun for a Yagi Antenna the swr 1.0x across the board from below 144mhz to 150 mhz. I have 2 questions i could use a hand with. 1- after building the balun and add 2 pieces of wire to use for trimming, now the question in the video you have mentioned by trimming you pulled the sweet point down from 150 to 146mhz, what i understood from building antennas and have been doing it for over 30 years , if you shortened the length the sweet point moves up not the other way. On the dr element that is. Now with coax balun is the other way around i just need to reconfirm the point on the video shorter pulls the sweet point to lower frequency? 2- when using a yagi with a loop dr element full wave, does the balun calculation works the same? Thank you by the way it is my first time using coaxial balun, normally just use a gamma match or coils balun. Best regards Salah 9K2SJ

[@eie_for_you]

Wow! I'm so glad that this worked for you! You ask two good questions ... 1. Making the BALUN coax *longer* lowers the sweet spot. But making the pigtails longer raises it. Counter intuitive, isn't it. Conversely, shortening the pigtail length drops the sweet spot frequency (in a non-linear fashion). Two things change at the junction between the end of the coax and the pigtails: [1] The velocity factor of the medium and [2] The characteristic impedance of the medium. These two factors along with the length of the pigtails and the impedance transformation in the BALUN coax work together to create our counterintuitive experience. Almost makes me want to break out my Smith chart! 2. If you need a 4:1 BALUN to match to an antenna of any configuration, the BALUN calculations should remain the same. I do not know why they wouldn't.🙂

[@stephennelson-smith3312]

This was brilliant - I really enjoyed your presentation style and from first principles approach, thank you! It always makes me chuckle to see "imperial" measurements decimalised... 0.021 of an inch? If you're going to do that, why not just use metric measurements in the first place? A more serious point/question concerns the accuracy of measurements/cutting. You measured using a tape measure, marked in 1/8th increments... yet your target length was at a target accuracy of about 1/50th of an inch. Whenever I try to measure and cut coax (or any wire for antennas) I find that my accuracy is also thrown off by the fact that the wire doesn't sit dead straight (nor did yours in the video). All of this makes we wonder why we're using the speed of light to more than ten significant figures. Seems to me like your inaccuracies in cutting and measuring are going to huge compared to the accuracies of the initial calculation, right? I wonder whether we can be a lot more "rule of thumb"? Given you can maybe eyeball a millimetre... half a mm is getting close to your ability to cut that accuracy, and given the comparatively huge margin for error with the initial measurements of the coax, I wonder how far off you'd be with a more finger in the air starting point, since you're going to adjust with the pig tails anyway? Thanks for a great video, liked, and subscribed, and I look forward to watching more of your content.

[@eie_for_you]

First, I have been burned (badly) in the past by rounding off too early in my calculations, so I always carry a lot of decimal places right up to the end, then round the final result. It is amazing how quickly early rounding can magnify into major differences in results. As far as inches vs mm ... well, I am much more comfortable with inches. I agree, the metric system is so very much superior, but I grew up in the Imperial world. I have learned to use my "calibrated eyeball" to accommodate. Then, in the end, knowing that no matter how accurate my calculations or my ability to precisely cut wire and coax, nothing *ever* comes out perfectly. The old adage of "cut long and trim to tune" comes into play. I can always make it shorter, I cannot make it longer.

[@stephennelson-smith3312]

@@eie_for_you I agree; Today I did some sample calculations with early rounding, and it's surprising how quickly the inaccuracies multiply. Thanks - I learned from this conversation. I'm going to watch your ones about measuring velocity factor now, as I have a need to do this! You may well see me pop up in the comments to those videos too!

[@eie_for_you]

@@stephennelson-smith3312 Enjoy enjoy! 🙂

[@thomasfink2385]

Fantastic! Exemplary!

[@eie_for_you]

Thank you! 🙂

[@digyourrig3800]

Now this is the way to explain what your doing.. Way to many idiots out in the ether making something with NO explanation... Outstanding Video.

[@eie_for_you]

Thank you so much for the encouragement! Thanks! 🙂

[@terryboyle]

This was perfect for the way I look at the process. We are doing a group build in our club for dipoles for 4 or 5 members. You mentioned testing the the velocity factor of the specific cable you were working with and we will definitely need to do that. What tool did you use to do this?

[@eie_for_you]

Thanks for the encouragement! Measure Velocity Factor? Well ... you can do this any one of several ways. You can use the venerable nanoVNA or an Antenna Analyzer or use the TDR method which requires a scope and a signal generator. I prefer to use the VNA, myself. I outline all of these methods in my various videos on the subject. Check out my "Velocity Factor" playlist. 🙂

[@qutips33]

can you make a 4:1 unun on a ferrite ring?? otherwise a good video

[@eie_for_you]

You *might* be able to. They make 4:1 BALUNs that way. But I honestly cannot say for sure. Never did it myself. 🙂

[@hennero.3826]

Thank you for the video. 🙂 I am just starting with Amateur radio and hear people talking about these balun/unun things in their videos while I do not understand much of it yet. Maybe many of the experienced OMs know what's the math behind it, but I don't, and this is the first video that shows something about that background. However, I am apparently missing some basics regarding this. Do you have a video online that explains more about these basics? If so, could you tell me which one it is? Thanks in advance, and God bless you, brother (I conclude that someone who has John 3,16 in the background is a brother🙂). Rev 22.12a. 🙂

[@eie_for_you]

You are very welcome for the video. 🙂 Which "basics" are you unclear on so I can point you in the right direction? Yes, I am a born again believer in Jesus Christ ... and AMEN on Rev 22:12a ... soon! 🙂 You can look me up on QRZ.com ... WA2PUX. My email is there.

[@aarongriffin81]

Can you make a 2:1 balun using this method? If so, where can I find instructions?

[@eie_for_you]

Sorry .. this method will only provide a 4:1 BALUN. Thanks for asking! 🙂

[@washingtonstatepicker3460]

How did you strip the shielding

[@eie_for_you]

I'm assuming you are referring to how I removed the excess shielding. I have a really good pair of *sharp* side cutters that are primarily used as flush cut for component leads on the bottom of PC boards. Something like these: www.digikey.com/en/products/detail/american-hakko-products-inc/CHP-170/6228793 🙂

[@peterfardell9267]

But if that is only for one frequency (half wavelength) this must be of very little use. I need to tune a G5RV antenna with a 300 ohm balanced feeder into the usual 50 ohm unbalanced feed to my transceiver. The antenna covers all hf bands and needs a regular atu but must incorporate a balun. Would your coax valin help me here?

[@eie_for_you]

It should work for all frequencies in which the balun coax is some multiple of 1/2 wavelength long. So, if it were cut for 3.5 MHz, then it would (should) also work for 7.0, 10.5, 14 and so on. With that said, a balun of this sort to be used on HF frequencies would require a LONG piece of coax. If it were cut for 3.5 MHz, the the balun coax would be somewhere around 93 feet long (assuming 0.66 velocity factor). This type of balun is far better suited for maybe 6m and above.

[@Duke-William]

This is excellent! I am planning to use this for decoupling my antenna for analog UHF TV receiving (if possible today). It is a DIY antenna that I made myself. V-shaped straight dipole elements and the plane of the V are aligned horizontally to the ground. Element material is 0.5 cm diameter aluminium tubes. And length of each element is around 30cm (which I made for around 500-600mhz average frequency capture) The antenna is mounted around 8m above ground (in a wood pole, so is not grounded). The receiver cable (in to signal booster) impedance is 75 ohms. I don't know the impedance of the antenna and have no tools or knowledge to calculate impedance either. Can it be a 300-ohms antenna? I just want to know if this balun is suitable for that? I am grateful for an answer. Thanks.

[@eie_for_you]

What you describe here sounds like a “Yagi”-style antenna. I cannot speak to its impedance explicitly, but a lot of yagi antennas have an impedance in the 30 ohm range. You could model the antenna in the FREE 4NEC2 antenna modeling program and it will give you an idea what it’s actual impedance might be. I have a series of videos on the topic to give you a leg up on how to do this. Hope this helps. 😀

[@la6yja]

John 3:16. I love it :-)

[@eie_for_you]

Praise Him for His grace and love!

[@la6yja]

@@eie_for_you Amen!

[@StreakyP]

question... if you have a quarter wave vertical connected to the co-ax (no balun) the braid MUST be connected to ground or radials or groundplane directly at the antenna. When you see the diagrams of this balun it always shows a true ground being provided to the antenna triple braid connection point. Generally when we amateurs sling this outside up at the antenna there isn't any true ground to be found up there so the "triple screen" point just gets left "floating". How does this work?. The signal travelling up the central core of the co-ax has somewhere to go but the ground return path is disconnected. Modelling this as a 100ohm resistor going to true deck from each side of the balun o/p (ie total 200 ohms ) that means the return path is not back down the coax but along the external ground and back into the rig at the rig's ground point (or worse still if it was a portable rig via the capacitance from the floating rig chassis to deck in which case you are going to have an "rf hot" rig with rf on the chassis). An open circuit screen at the antenna wouldn't work for a monopole. Why does it work here?

[@eie_for_you]

Good question! I am on the road at the moment. I plan on getting back to you when I get home and have access to all of my "stuff." A reply to this will act as a reminder to me. 🙂

[@StreakyP]

@@eie_for_you thanks for looking into this. I have asked the same question to Fez. I had been about to build one but it just struck me "But where is the return path ".. I have some type 61 ferrite cores on order so I'm currently just going to make a conventional balun instead for portable use. I was just worried that without the availability of an antenna end earth we are not using the main co-ax properly as a transmission line but using it just as a shielded wire where its length will be a factor.

[@eie_for_you]

@@StreakyP A little misconception here...when I said that the "coax" was a circuit "component", I was referring to the BALUN coax, not the feedline. Yes, the feedline does change the composition of the impedance (all feedline, everywhere, at any frequency) so the actual impedance as seen at the end of the feedline will change with length. With that said, the SWR will remain the same because the composition changes is such a way that the SWR is the same, but the values of the real and reactive parts of the impedance itself changes (see the Smith Chart). 🙂

[@eie_for_you]

@@StreakyP The return path comes by way of the BALUN coax which is part of the entire system. The shield/screen of the feedline is, indeed, connected to something: the shield/screen of the BALUN coax. "By what method?", you might ask? The center conductor IS connected to the shield via the capacitance between the center conductor and the shield. There is inductance from end-to-end. In its simplest, non-lossy form, it is modeled as a series of infinitesimally short sections consisting of a series inductor and parallel capacitor. Thus, the characteristic impedance of the coax. While we might not be able to physically see it connected to anything, it is connected to something. This style of BALUN does indeed work and has been used for many years by many people to accomplish this task. Furthermore, it operates perfectly well regardless of the length of the coaxial feedline coming from the transmitter. Hope this helps to dispel the mystery. 🙂

[@TheMrDrMs]

If I'm not mistaken this is a voltage balun, not a current balun, which is fine for VHF, but might not hold up so well on higher duty cycle modes on HF if someone were considering that.

[@eie_for_you]

Yup, you have that 100% correct. 🙂

[@clauslauridsen4373]

many baluns if you want 160m to 10m ?

[@eie_for_you]

Well, this is a frequency dependent BALUN as it relies on the electrical length of the "loop" of coax. If you want a broadband HF BALUN as you describe, then you will require a more traditional BALUN which sports a TORIOD or ROD ferrite. 🙂

[@W1RMD]

Okay, another question. Did you settle for feeding the folded dipole with 50 ohms and 200 ohms out of the stub and it was "good enough" being 100 ohms off, or did you use 75 ohm coax to try to get it right? I tried using my MFJ 259b analyzer with 75 ohm coax and a 300 ohm resistor and I got results not usable for any accurate testing purposes. I don't know how good the MFJ analyzers are with 75 ohm systems and dealing with complex impedance as they're based on a 50 ohm system. Might be okay for dipoles fed with 75 ohm coax but gets too confusing for it when dealing with multiple impedances, especially at vhf. Thanks.

[@eie_for_you]

You already know that a dipole *in free space* has an impedance around 75 Ohms. But, when mounted "near" the ground, its impedance drops approximating 50 Ohms. Thus, the ubiquitous 50 Ohm systems for antennas. The same sort of thing applies to a folded dipole. The exact impedance of the folded dipole will depend on environment it finds itself in. So, my folded dipole may very well be closer to 200 Ohms if it finds itself near grounded stuff, like a mast. Because my coax feed was to be 50 Ohms, I used 200 Ohms. You can see the folded dipole that I intended this 4:1 BALUN for in this video: kzbin.info/www/bejne/l6XReoCtgtd_ppI The results are pretty good overall. One last note on the MFJ-259B which I have significant experience with (the club owns a B and I have the C). It is just "OK" for a relatively narrow band of applications. Measuring impedance is NOT in that small subset of applications. I compare the results of a nanoVNA to the MFJ-259 here in this video: kzbin.info/www/bejne/hqXMaXiorMR-ock For the convenience, the MFJ-259 is easy and fast. If you want real truth, then the nanoVNA or similar is the way to go. With the nanoVNA you can actually calibrate it with a 75 Ohm standard and use it to measure a 75 Ohm system even though it is technically a 50 Ohm device!

[@W1RMD]

@@eie_for_you Thanks. I would imagine that mounting the folded dipole as a driven element to a vhf beam would also lower the impedance. Yes a Nano vna and Tiny sa are on my Christmas list. I appreciate all of the help. 73's!

[@PaulaBean]

17:12 Are you sure? Those old telephone wires might be worn out by the millions of telephone calls they have carried 🤪🤪🤪

[@eie_for_you]

LOL

[@NVRMTmotion]

The balun length is cut to exact length and then the ends are stripped, right?

[@eie_for_you]

That is what I showed in the video. Because we are allowing for sweet spot adjustment by pigtail trimming, the measurement isn't super critical ... as long as they are all the same.🙂

[@NVRMTmotion]

@@eie_for_you That's fantastic, thank you!

[@eie_for_you]

@@NVRMTmotion 🙂

[@sarandeepsingh921]

hi man i want to make log periodic dipole antenna which can work on 3g,4g and 5g bands frequency from 600-6000mhz so can you help something about it ? I have made once Logperiodic dipole antenna which works on 698-2700mhz very good

[@eie_for_you]

Well ... I can truthfully say that I know nothing of designing log-periodic antennas. Sorry, no help here. 😞

[@daveengstrom9250]

I can understand the need for a 4:1 balun. I don' t understand the need for a 1:1 balun. Can you explain?

[@eie_for_you]

Good question! BALUN stands for BALanced to UNbalanced. While, yes, a BALUN can be used for impedance transformation like the 4:1 BALUN, its primary purpose in life is to take the unbalanced feed (coax) and turn it into a balanced feed (antenna). Antennas like to be driven with a balanced feed, which means that one side is driven high while the other is driven low. Coaxial feed is unbalanced. The braid/shield/screen is ground. It, for the most part, isn't moving in potential. The center is changing in voltage level. With all of this said, the braid likes to see the same impedance as the center conductor, thus we can feed a dipole or inverted vee directly with coax. The load is balanced, but the feed method is not. A secondary benefit to using a BALUN is a reduction in common mode currents coming back at the operating station. Not all BALUNs are good at this; some are better than others. A Current BALUN is great for driving antennas with somewhat unsymmetrical impedances. That is to say, the environment of one leg of an antenna is different than the other, so its impedance is going to be different. A Current BALUN is designed to drive the same amount of current into each side of the antenna irrespective of its impedance. A Voltage BALUN is designed to apply the same amount of voltage to each side irrespective of impedance. Hope all of this helps. 🙂

[@daveengstrom9250]

@@eie_for_you Thank you. I was unaware there were different types of baluns (current and voltage).

[@eie_for_you]

@@daveengstrom9250You are welcome! 🙂

[@davidpanetta5492]

just one question, what antenna did you use that needed a 4:1 banun at two meters 146MHz?

[@eie_for_you]

I was planning on my video for the folded dipole antenna for 2 Meters (see the video: kzbin.info/www/bejne/l6XReoCtgtd_ppI) which has a characteristic impedance of 200-300 Ohms. I knew I'd need a 4:1 BALUN for it, so this video was born. 🙂

[@djkevy2006]

Hi I've tried making one of these 3 or 4 times and can't get any sort of match? I must be doing something wrong? What am I looking to measure on the nano is it impedance / swr or both ? What would your final calculated length of the balun be for 101.4mhz and the length of the tails ? I must be calculating wrong Thanks

[@eie_for_you]

As shown in the video, I am looking at SWR. An important question ... Are you testing the BALUN with a fixed, metal film, 200 Ohm resistor or connected to the antenna? If connected to the antenna, are you *sure* that the antenna is, indeed, properly tuned to the target frequency? What is the characteristic impedance of the antenna by itself? You can measure this with your nanoVNA (kzbin.info/www/bejne/mpinhGeon8dgfbc). Regarding the length BALUN coax...the final calculated length would depend on the velocity factor of the coax that you are using for the "BALUN Coax." If the VF of the coax is 0.66, then the BALUN coax should be on the order of 41.48 Inches or 105.37 cm long according to my calculations. This is using the 8% longer to accommodate for the pigtails and a frequency of 101.4MHz. Hope this helps. 🙂

[@djkevy2006]

Hi thanks for the fast reply. Yes I was using a fixed metal film 200ohm resistor. Ok, so if I cut my coax to 41.48 inches then add my tales around 3inch ish ? then i should trim them back down to get the lowest swr ? I'll give it ago and post my results Thanks again Kev

[@eie_for_you]

@@djkevy2006 I will look forward to seeing how it goes for you. Again...assuming a velocity factor of 0.66. 🙂

[@NamasenITN]

Is it 4:1 or 3:16??

[@eie_for_you]

It is a 4:1 balun. The "John 3:16" is the reference to a Bible verse which is the wallpaper on my computer.

[@cybersean3000]

So with this 4:1 balun I can build antennas for 2m with 300 ohm TV twin lead.

[@eie_for_you]

Yes, you can. 🙂

[@reubengeorge220]

Need to explain what the length. Equally what a wave length in measurement is

[@eie_for_you]

The length of the BALUN coax has to be 1/2 wavelength long, electrically. RF travels more slowly through coax than it does in free space, so a piece of 1/2 wavelength coax is going to be shorter than a 1/2 wavelength in free space. Here is a brief explanation ... The wavelength of a given frequency in free space is the speed of light divided by the frequency {Wavelength = (speed of light)/(Frequency)}. Now, when we are talking about coax, or any transmission line for that matter, the Velocity Factor is how many times the RF slows down when traveling through it. So, for RG58 with a velocity factor of 0.66, the RF travels down the coax at 0.66 * the speed of light. So, a wavelength long piece of this coax is {0.66* speed of light/frequency}. I explain all of this in detail in my introductory video on Velocity factor which you will find here: kzbin.info/www/bejne/fancoql-p7lpo6c I hope this helps. 🙂

[@cyrilpontilla5769]

Very nice explanation, but how about if 144MHZ , so what is cutting of Balum

[@eie_for_you]

The procedure is the same. Instead of using 146 MHz as the frequency in the calculations, you use 144 MHz, which will mean the BALUN coax would be about 1.4% longer. 🙂

[@cyrilpontilla5769]

@@eie_for_you what is the 1.4% ? Im planing to make a 7 element 2 stock yagi antiina with Balon , Can you give me also the Diagram of 7 element @ 144MHZ ?

[@eie_for_you]

@@cyrilpontilla5769For the YAGI diagram, I will point you to the same place that I would have to go: the A.R.R.L. Antenna Book. As far as the BALUN is concerned, it is dependent on the velocity factor of your coax and other factors as I laid out in the video. So, no, I cannot give you the dimensions for your BALUN. You will just have to follow the directions that I have provided in this video and determine them for yourself. 🙂

[@vicsorianochannel4278]

Good day sir I'm from Philippines I have a project for my 13 elements I want to know how to do making a balun for my 13 elements for 145.000MHz thank you in advance for your reply sir God bless

[@eie_for_you]

I am assuming that you are talking about a 13 element YAGI antenna. If this is the case, then a BALUN probably isn't what you are looking for. The feed impedance for a YAGI antenna is generally lower than 50 Ohms, in the vicinity of 30 Ohms. There are a number of methods that are used to connect your feeline to this antenna. Our first thought is to connect our feedline at the very inside end of the driven element. The simplest way to choose a feedpoint where the impedance is higher is to move this point of feedline attachment out a little ways on the driven element on both sides. The further out you go, the higher the feedpoint impedance, as I understand it. I am no expert on yagi antennas. I hope this little bit of help is useful.

[@vicsorianochannel4278]

The antenna build was the 13b2 of cushcraft sir I don't know how they make balun for there 13b2 they gave the lenght of elements but I have no idea how to make balun actually I made balun like yours bu I can reach swr to 1:1.1

[@eie_for_you]

@@vicsorianochannel4278 If you purchased the Cushcraft 13b2, 13 element yagi antenna, it comes with its own "UltraMatch BALUN." Adding anything beyond that is unnecessary. The feedline connects directly to the supplied matching box.

[@ornithopterindia]

👍

[@needhelp2453]

Why did you need a 4:1 balun for 2 meters?

[@eie_for_you]

Well, suppose I were to build/create a folded dipole antenna for two meters. These would be those "bow tie" looking antennas that you see. These have 200 to 300 Ohm impedance depending on thier environment. Then you would need some fashion of a 4:1 BALUN to use it with a standard transceiver. In fact, I created one such antenna with a 4:1 BALUN like this one which I use all of the time. Because the 440 band (70cm) is 3x the frequency of the 2M band, this antenna works well for both.

[@WT2D-Michel]

To match a 200 ohms impedance to a 50 ohms so the SWR will be 1:1 ratio. N2MTM

[@BrianReneChristiansen]

in video 14:30 you write 28,79 inches = 78,13 CM my calculator says 28,79×2,54=73,1266

[@eie_for_you]

WOW!!!! You are soooo right! Now THAT's a real oopsie! I cannot fix the video itself without permanently deleting it, but I can add a note in the comments correcting that problem. Thank you so much for pointing that out.

[@eie_for_you]

Note added to the description. Thanks again for the sanity check! 🙂

[@peterfardell9267]

The main function of a balun is to prevent or reduce common mode currents in the feeder. Impedance matching is of secondary importance.

[@eie_for_you]

Aaaah, then a common mode choke would be a better choice. See my videos on the subject. There is one specifically on common mode chokes (kzbin.info/www/bejne/qZCteYN6dpyea7s)

[@arconeagain]

This worked very well for CMC for me. I read an explanation as to why on Ham Stack Exchange.

[@jerryKB2GCG]

yikes, 1/2 wavelength at 40M…about 60 feet!

[@eie_for_you]

Well ... yes...and...no. Yes, it is long. But, the velocity factor of the coax (e.g. 0.66) will reduce the overall length significantly. A quick calculation puts the average coax at about 45.4 feet for the center of the 40 meter band. Obviously, this is still way long and that is why these types of 4:1 BALUNs are generally used at much higher frequencies, though there is no reason you couldn't use one on 40 meters if you don;t mind the huge length of coax to do so.

[@PaulaBean]

@@eie_for_you Could you roll up those 45ft coax baluns? Or would that introduce unwanted capacitive effects?

[@eie_for_you]

@@PaulaBean While "what happens inside coax stays inside coax" on a theoretic level, if it were me I'd roll it that way I want to roll it and then remeasure the electrical length. Rolling changes the physical parameters of coax to some degree in the practical world.

[@PaulaBean]

@@eie_for_you Yeah that would be an interesting experiment: 16 ft of coax stretched out, measuring its capacitance, then rolling it up, and measure the capacitance again. If the braid is part of the system, the two measurements might differ. But how much?

[@eie_for_you]

@@PaulaBean But...for this 4:1 Balun, we are not talking capacitance. We are talking electrical length. Different animals.

[@russc788]

Thank you but this is far too technical for beginnings. I can see from the comments its a good video for more advanced techies.

[@eie_for_you]

The point of all of my videos is not just the "how to" but the "why" behind it all. I appreciate your point of view on this ... and, yes, I can see your point. However, the point of my channel is for those who want to know more, understand the why, be able to extrapolate past the "how-to" to their own application. This requires more information which I provide. 🙂

[@russc788]

@ You certainly do 😀

[@eie_for_you]

@@russc788 Thanks! 🙂

[@williamna5800]

wait, wait, wait. A YT video of soldering with an iron that doesn't have 2 years of crust, mouse bones and cat hair all over the tip?? I'm surprised they even let you post this. I thought YT was only allowing soldering videos with nasty and filth tips!

[@eie_for_you]

LOL! I knew I was violating community standards, but I am rebellious like that! 😂

[@XwpisONOMA]

Unnecessarily long video 😕👎

[@eie_for_you]

I am sorry that you feel that way. I have a particular philosophy regarding the production of my videos. I do not assume that my viewers have know this or that. I try to supply *all* of the answers so that even the neophyte can have success. This makes my videos longer, but very much complete. I got tired of videos that assumed that I know things & then jump over needed facts assuming knowledge on the part of the viewers that they do not necessarily have. As a result, my videos are longer, but I attempt to be complete with everything even the total neophyte might need.