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

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!

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

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

great video,hanks for sharing

Excellent explanation, thank you.

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

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

Superb

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 RU-vid authors delve into the math. Thank you.

Think Ill just buy one :D

good info presented very well!

Thank you

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.

Thanks a lot, sure i will be indicatived soon.

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

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

Thank

Fantastic! Exemplary!

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!

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

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?

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

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.

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

John 3:16. I love it :-)

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.

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

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

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.

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.

👍

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.

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?

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

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

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

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

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

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

many baluns if you want 160m to 10m ?

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

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

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

Is it 4:1 or 3:16??

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

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

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

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

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

Unnecessarily long video 😕👎