Balun Chokes - How do they work?
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- čas přidán 8. 07. 2024
- In this video, we take a look at a toroidal core wound for a CMC Balun Choke for Ham Radio Antennas. We will look at how this core attenuates unbalanced current while passing balanced current.
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Check out my Chokes, Baluns and Ununs Playlist: czcams.com/play/PLm8ROkpFeqoqkGQtBYfcT9Y-2GCKxBuuk.html
Thanks for the post.
Let me explain a bit in detail.
Differential mode currents flow with equal magnitude but in opposite directions.
Hence, the magnetic field created by one winding carrying current in one direction cancels out the magnetic field created by the current in the other winding at any given instant time.
But the CMC (common mode current) or vertical current or simply antenna current that tends to flow from the feed point to the shack on the outer surface of the outer shield braid will encounter a huge inductive reactance. The inductance is about 50 microHenry (in your demonstration) and the inductive reactance calculated by the formula 2pifL in ohms.
The bifillar winding may be avoided because the characteristic impedance of the line is around 100 ohms.
The CMC choke must be made using specific core materials of specific size for the specific power levels and specific Teflon coaxial cables for the specific bands of interest.
For 160-40 meter bands, #31 or 43 would be fine.
For 20 meter and upwards 43 or #52 will do.
There are inductive, resistive and capacitive parts.
G3TXQ and other sources like K9YC ferrite cook book may be consulted for a deeper understanding.
De VU2RZA
Thanks for the detail SR 👍
@@TheSmokinApe you are welcome ape
De VU2RZA
Amazing video.
Glad you enjoyed it!
Thanks Ape , another informative video!
Thanks for checking it out Chuck 👍
So glad TheSmokinApe is around to splain this stuff for us! Thanks for all the effort you put in to educate the ham community.
Lol, thanks Bob 👍
Great video!
Thanks James, glad you liked it 👍
Another Great Video. Thanks Man
Thanks HRC 👍
Much appreciated.
Thanks for checking it out David 👍
First good explanation I've seen about use of toe-roids for chokes. Thanks Ape
Thanks for checking it out Dennis 👍
That's top notch learnin material right there
lol, thanks Andy 👍
Great explanation of the common mode choke process. 73
Thanks KS0JD, glad you liked it 👍
👍Thank you sir.
Thanks for checking it out 👍
We appreciates you, too, Ape.
Awe shucks, thanks Lee 👍
Very interesting. I'm thinking of getting a ham ticket and because of my *_VERY_* limited back yard area I'll have to do a lot of work to get antennas running properly. So many thanks for the info.
🙂
Good luck with it, I am sure you will figure something out!
@@TheSmokinApe🤔
By my calculations, son, the impedance of 3uH is somewhere around 68ohms reactive at 80 meters, so you're going to see almost a 50% loss of signal to the feedpoint when you consider the series reactive offset on that band. That is since it appeared that you hooked it up in series. 67 ohms reactive is assuming you have a ~50 ohm resonant antenna. If the feedpoint is 67 ohms capacitive, urine luck. I have not looked at other bands. They would need to be looked at individually.
I wouldn’t put much credence into it, son. While I’m sure you are a wizard with the maths, I believe these measurements were taken with the janky leads….
Is it same as used in Smps filters circuits??
Sorry, I’m not experienced enough with smps to answer
When running this type of choke, does qro and the thickness of the cores matter like they do in a transformer?
It does matter but to a less extent as the main reason for larger cores is heat dissipation which is less of a problem in chokes.
Cool. What happens when you vary the number of turns? How does an air choke compare? (How would you measure an air choke on a vna)
The number of windings does make a difference but when you get about ~11 the impact is greatly reduced. The magnetic properties of the core is the magic in a choke which is missing in an air wound choke, the work but need to be accurately tuned, which is difficult, and are very narrow in bandwidth making them limited for effective use. You can measure then with a VNA.
Just finished building one using RG174 (for QRP use) on a small type 31 material. Once fully assembled, I ran an insertion loss test and it's very flat from 3 - 50MHz. Very low insertion loss! I'm of the impression that type 43 would be better used as a transformer in the same frequency range. Type 31 for chokes; type 43 for transformers (1:1, 2:1. 4:1, 9:1, etc). The material in 31 opposes fields in the HF range while 43 being of a [slightly] different composition aids in impedance transformation. For folks who don't have VNA's but might have access to an analyzer, put a 50Ω non-inductive resistor on the output of the choke, and test for SWR across HF. If the reading is high, then it's a bad design, but if it's low and almost flat, you have a
usable choke. Just pay attention to the power handling capacity of the unit.
#43ferrite (ui=850) is Ni-Zn and #31 is Mn-Zn (ui=>1000) ferrites.
Any ferrite being ferromagnetic, can be used as a transformer or as a CMC choke for a particular frequency range.
#73,75,77 are all Mn-Zn ferrites with ui=>2000 or more and can be used as transformer cores for the lower most end of the HF and the MW frequency band; they can very well be used as CMC chokes too.
De VU2RZA
Hey oob, I typically use 31 for broad band chokes. That said this particular core FT114-43 is commonly used by dipole antenna manufacturers which is why I was testing it in the first place. That said, I felt it was an adequate example for this demonstration. Thanks for the comment!
@@TheSmokinApe you are right, ape.
De VU2RZA
I've tried all sorts for chokes and transformers even junk from hamfests which ultimately end on power cords. Yes, there is some cross-pollination between the various types but as each type has its unique specs, they also act as either a choke or a transformer in different parts of the spectrum, hence the different types. Were they completely interchangeable there'd be no need for the various types. This past Hamvention I attended a presentation Friday evening at a dinner where this very topic was discussed and led by Bob Brehm, AK6R, Chief Engineer of Palomar Engineers. He has a plethora of information on their site including the above presentation. I was able to speak with him separately about this and broader "core" topics. The nice thing about Palomar Engineers is you can buy a complete unit or you can buy whatever parts you need and roll your own. I've bought cores from eBay and Amazon but never sure if the item is what it's advertised as. Buying from Bob I never have to worry. I have bought complete units and parts to make my own. I'm very pleased with the products and tech support he provides. I'd rather source my information and parts from a reputable company. I also consider the "Ape" a reputable source. That's why I subscribe to his channel.
@@oobihdahboobeeboppah Thanks for the details and for the vote of confidence 👍
Could you explain balun vs unun? I recently bought the LDG RU-1:1 unun as it appeared to advertise as use as a choke. (Appears to be working preventing my computer usb from disconnecting while transmitting ft-8). I’m using a buddiestick pro (balanced antenna?), so thought I should be using a balun but it seems most of those I could find came with posts to attach directly to a dipole or similar. Sorry for my ignorance but am I way off on this?
Hi, the buddy stick pro is essentially an unbalanced vertical antenna with a counterpoise (elevated ground radial)
You are using the UnUn to curtail the CMC that tries to disconnect the USB when you operate FT8 mode.
A bifillar wound or a coaxial cable wound cmc choke can be used as a BalUn or UnUn depending upon where you put it.
When placed at the feed point of a center fed 1/2 lambda dipole it is called a BalUn; ie, looking from the antenna side, and the dipole being a balanced device.
From the coaxial cable (an inherently unbalanced device) it may be called an UnBal, though the terminology is not in vogue.
A UnUn is a device connecting two Unbalanced ports together on either side.
The impedance transformation achieved can be simply a 1:1 or other ratio as well.
The bifillar wound or coaxial cable wound choke when used on a coaxial cable feeder before it enters the shack end of the coaxial cable it is called a UnUn (because both coaxial cables are Unbalanced devices)
A UnUn can be used at the feed point of OCF dipole (Windom etc) , the slimjim, J pole and the EFHWA etc.
So, the UnUn, what you are using is correct in your buddy stick pro antenna.
De VU2RZA
@@subramanianr7206 thank you!
There are combined designs balun choke and transformer. Two toroids. Any comments on those?
I think they are handy, I always use chokes with transformers. Thanks for the comment 👍
I need some help on this question, I have spent hours searching for the answer. Does it matter what direction or if you use a crossover technique to wrap the toroid. I see a ton of fancy CMC windings online but when I test a toroid (like Ape does in the video) I just throw wraps around it and get good inductance readings from nanovna. Thank you for any help, from my QTH in Texas, '73
The orientation of the wraps isn’t that important. If it tests out OK, use it and see how you do. Thanks for watching TB 👍
@@TheSmokinApe Thanks Ape!
What do you consider an excessive amount of insertion loss for a 1:1 choke? I am getting about -1.5 on a homebrew. Does that seem excessive?
I’d say that’s getting there, I’d definitely want less than a dB
I would becareful with that lc meter,mine worked alrite for what it is,ive hardly used it and now its a paper weight
Thanks for the heads up Trent
I've been watching various videos and playlists as you suggested (and will continue to do so), but it seems as though you use the terms balun and choke interchangeably from time to time. My purchased antenna (FD40-3 from Radiowavz via HRO) has a 1:1 balun already, but it seems as though you've said that to combat/eliminate CMC that I need _another_ choke immediately after the antenna on the feed line, and even again down at the radio, and further mid-way depending on feed line length.
If balun and choke are interchangeable, then it seems like I don't need _another_ one at the beginning of the feed line???
In one of your videos, you mentioned "stacking" them? What does this look like???
And how do I determine which wrapping method is appropriate? Number of turns and/or wrapping up one side and then coming back down and up the other side the other way...
If you have an antenna with a Balun or a Choke you do not need a second one at the feedpoint. Both Baluns and chokes balance current and reduce CMC and both terms are used interchangeably for both devices, often you will hear the term "balun choke". There are a few ways to make both, so pick a design you like and try it, measure with a nanoVNA and pick what works best for your situation. Hope that helps 👍
@TheSmokinApe It does, and I have a Nano on the way, once it arrives (yet another learning curve), I'll investigate.
I'm getting what I believe to be interference from either my antenna and/or my feed line turning on a couple of "capacitive touch" lamps and the garage door opener lights in my house. That doesn't bother me except for whatever affect I'm having on my neighbors, so I'm trying to clean up radiation.
How does a ferrite core compare to a coax air core?
What mix for a 10m choke?
Can I replace the coax air choke for a ferrite one on a 10m flower pot antenna and get a better result. Ie lower insertion loss than ~4.3m of coax and decent common mode rejection.
An air core Balun or ugly (not exactly though) BalUn is not broadbanded and might vary well become a wave trap for a particular frequency band with the right amount of inductive and capacitive reactance.
Ferrite loaded BalUn can be compact and offer the right amount of resistivity for the CMC that tends to flow on the outer side of the coaxial cable shield.
I believe, by flowerpot antenna, you mean for the 2 meter band and you can very well use 2-3 turns of the coaxial cable feeder on the 1" long #61 ferrite cylinder sleeve core.
And the 2 meter band calls for 144-148 mhz only and hence an air core ugly BalUn will serve the purpose well.
De VU2RZA
@@subramanianr7206 Thanks I have an 2m flowerpot already. Was planing a 10m (28mhz) one and it calls for 4.3 metres of coax air choke. The lower section is ~2.5m of coax to mid point where the centre coax then joins to the ~2.5m wire going up for the upper section. So from input to the choke to the actual mid point real feed point is already 6.8m of rg58. Then I have the coax run back to the rig which could be rg213. Just trying to cut down the coax loss in the 4.3 meters in the air choke
@@moozoowizard hi, that is fine.
A flowerpot antenna (for the 10 meter band, 2.5 meter on either side) is, for convenience and polarization, essentially a center fed dipole in vertical orientation.
For this band, 4.3 meter RG58 coaxial cable wound as an ugly BalUn is the easiest way and its bandwidth is adequate.
A CMC choke wound on a #52 (ui=250) or #61(ui=125) ferrite core (either a torus or a sleeve cylinder) to bring about an impedance of 500 ohms or more is warranted here. Use the formula 2pifL to calculate the reactance in ohms.
Instead of RG58, you can use RG316, Teflon coaxial cable for a much smaller bending radius; it is good to handle more than 100 watts.
De VU2RZA
@@subramanianr7206 Thanks. Very Good info 👍. I'll do that. VK6MIK
@@moozoowizard thanks and you are welcome 👍
De VU2RZA
Always Be Choking
You damn right! Thanks for watching Mike 👍
Can we do this again for 2200m and 630m? 😁Thanks Ape.
That’s the next one 👍
Helps stop bleed over .
You need to set up your own toe-roid, choke, balun and unun shop... "Ape's Toe's and Roid's"👌😄
Haha, thanks Don
Ferrite beads....put them on your mic or coax.
Yep, that's always a good idea 👍
No Iron core, a steel nut will be a good substitute for this,
I am sure that will work to some extent but the magnetic properties of ferrite are greater. Thank for the comment Manual.
Hi, maybe you are joking, or mistaken.
Ferrites are iron oxide plus other metal elements containing ceramic materials interspersed with nonconducting glue material, synthesized as in the pottery making for specific magnetic properties and purposes.
Steel or soft iron are good for DC and low frequency AC.
De VU2RZA