#66: Toroidal Core Winding Results

[@subdynoman]

I'm learning how to make SWPS for car audio...attempting real high power values. This is great info, and yes the fact that any medium has an effect on the reading is both surprising and expected. Audio has led me to concepts in physics and understanding the nature of light and waves, it's no surprise that at high frequency, there appears to be a sensitivity to matter.

[@jamesmcintyre9985]

This is a very interesting discussion. I'd like to have seem the comparisons done after adjusting the number of turns to get roughly the same inductance, though.

[@hankhamner3671]

This is probably the most informative video or article on toroid winding I have ever seen. This has really cleared up many questions I have had about cores and windings. I have a question about common mode chokes. Assume I want to wind for 40 meters (7.2 MHz approximate center frequency), is high impedance the most critical factor? Does the SWR of a choke matter if you have high impedance? Thanks and please keep up these very informative videos.

[@w0qe]

Hank, There are two properties at play here: Differential impedance and Common Mode impedance. Winding turns of a transmission line thru a core increases the common mode impedance but does not change the differential impedance. If you have a 50 ohm circuit with 50 transmission line and you use some of the existing transmission line to wind around a core the differential impedance and SWR do not change even though the common mode impedance increases. If you add some transmission line length for the core then the SWR does not change even though the differential impedance does change (assuming the SWR was not 1:1). The previous statements assumed the transmission line is lossless. Does this make sense? Larry, W0QE

[@JustinMuir-rh2ph]

Great video! It really helped me grasp the basics of toroids and windings. A must see for anyone building their own baluns and ununs!! Thank you Larry!!

[@crazyDIYguy]

Your work and videos are very unique and enlightening to say the least, it's very difficult to find information on this subject matter. Much much appreciated 😎👍🙏 thanks a million for taking the time.

[@w0qe]

Glad you are enjoying the videos. Larry, W0QE

[@PixelSchnitzel]

That is *immensely* helpful. Thanks for going through that effort. I marked this in KZbin for future reference.

[@w0qe]

Glad you found the video helpful. Larry

[@eie_for_you]

I have been investigating winding toroid inductors. I start with a T50-2 core from Amidon. 1 turn, 2, 3, 4, 5, 6, ... 15 turns of #24 insulated wire. I repeated the same experiment with a T50-6 core with very similar results. I am winding them at 100%. I am measuring the impedance using a Tektronix TTR503A VNA properly calibrated at the end of the clips where the toroid is connected. I consistently get more inductance than the equations from Amidon would tell me that I would have. This increase is generally on the order of what would be expected with 1 additional turn on the core. Based on this video here, it seems that this is not unusual and that the calculated inductance from the official formula is more of a minimum value than it is an actual expected value. Maybe you can help me understand this a bit. Thanks.

[@w0qe]

I have mentioned this previously and it is pretty obvious. If the core has a "high" permeability virtually all the flux from each turn is captured by all the other turns resulting in an effective inductance that increase as the square of the turns. At the other extreme if a core has a "very low" permeability or maybe even an air core a fraction of the flux from each turn is captured by the other turns causing the inductance to increase linearly with the number of turns. The classic "Wheeler" formula for inductance shows this linear increase for single layer solenoid type windings with an air core. Now a core material such as #2 which has a permeability of 10 which kind of in the middle. The Amidon formula assumes you are winding with a higher permeability material. If we assume that nearby turns couple better than turns which are farther away you generally see the inductance rise as sort of a square of the number of turns and gradually changing to a linear increase of the number of turns. Does this make sense? Larry, W0QE

[@eie_for_you]

@@w0qe Got it. Ya know ... there is a LOT of magic in RF and, to some degree, there is more magic with inductors than in some of the other things (it seems). I appreciate the fact that you answered. Thank you. 🙂

[@thormusique]

I just came across this video. Excellent presentation, thanks for sharing! There's a lot of information to consider here but it's well worth the effort. I truly appreciate your in-depth analysis, and I look forward to watching more of your videos. Cheers!

[@harry4516]

very nice video, thank you ! I knew that moving the windings changes inductance, but seeing the changes in self resonant frequency was very interesting. Do you have a video showing the performance of a ferrite toroidal transformer using different winding technics (i.e. twisted, parallel ...) ?

[@w0qe]

I do not have such a video but it would definitely be an interesting topic. I will keep it in mind and thanks for the suggestion. Larry

[@epleace]

Thanks for all the time, work and experience that has gone into this. Very helpful for me - I'm about to wind a balun and an RF choke (or 2) for an antenna in my attic. One day I'd like to be that fluent with the topic. 73, KO4ZSD

[@bobkozlarekwa2sqq59]

I wanted to thank you for the videos you produce - it’s helped to demystify the Smith chart topic in general which has always confused me. Got a question - I made inductor to eliminate some RF that was getting into my phone lines. I used a 2” core (mix 43) and wrapped about 8 turns (4 turns in one direction and 4 reversed) using 4 conductor telco wire. Worked great! Now, I want to make it smaller. If I were to take three lengths of thin “Kynar” wire (used in wire wrapping), twist them together, than wire them in series. If I create a smaller version of the original choke, would the three-conductor wired in series have any advantage? Or, would it be better to have three parallel windings and wire those in series?

[@samuellourenco1050]

Nice video. I've learned something today, besides the reason why one shouldn't do a UnUn using 26 core material (fell into that trap, although for LF and MF is fine with a pretty good efficiency). However, mind that the toroid is shielded, but you add tiny capacitors between the coils when you put your finger there. That is why your resonant frequency drops and Q is destroyed (it is further from being a pure inductor that it was).

[@msaradio7455]

Glad I found these videos, and the channel in my search for info on Toroids, thank you! VERY HELPFUL!

[@w0qe]

Justin, Take a look also at videos #64 ans #65 which also deal with toroids. Larry

[@countryside8122]

Is it possible to make a speaker transformer out of one of these for 8 ohms for tube radio?

[@w0qe]

These transformers do not have a high enough permeability for use at audio frequencies.

[@singlehanded12]

Awesome information, better understanding of the dark arts of RF.

[@acestudioscouk-Ace-G0ACE]

Thanks very much for this, a lot of work for you and good that you should share the information. This is the first of your videos I have come across as a returning ham operator. I've liked and subscribed and will now look at your other work. Thanks again.

[@w0qe]

"Ace", Glad that you found the information useful. Enjoy the videos. Larry, W0QE

[@briand9513]

This video answers many questions that I had about toroids and windings. Thank you very much for all your effort.

[@w0qe]

Glad I could help. Larry

[@y_x2]

Impedance is not so important in an absorber. Because these tores are in serie with what appear as an antenna in some case it can deteriorate the filtration that you try to achieve you need resistance.

[@ziadkhatib3712]

Hi I need to make a balloon for 40m band and I have toroid 50mm*30mm*20 mm how many turn should make pls answer me

[@w0qe]

Ziad, I can not answer your question for a couple of reasons. Knowing the size of the toroid without knowing the magnetic material and knowing what power level and number of turns you might need does not allow me to give you an answer. What is a "balloon for 40m"? Is this an end fed half wave antenna that is supported by a balloon or is it something else? Larry, W0QE

[@acestudioscouk-Ace-G0ACE]

@@w0qe I think he may mean balun.

[@SunilAruldas]

Lots of learning!

[@kuldeepjayaswal9933]

i need to design 280uH inductor for dc todc converter. pls help i calculate as I need 20SWG wire toroid core with 55 turns. pls comment

[@w0qe]

Kuldeep, A T-200-26 with 55 turns is 280uH. #26 material is good for DC supplies and 55 turns of #20 wire would easily fit. Larry

[@kuldeepjayaswal9933]

W0QE thanks today i will do in lab

[@RealRobotZer0]

Are these "materials" standard across manufacturers ?

[@w0qe]

RobotZer0, I don't think there are any real standards about materials for powdered iron and ferrite materials. Every manufacturer has similar ingredients but slightly different amounts and processes in the cooking of the core. Not all manufacturers use the same numbering for materials. TDK has a completely different numbering for core materials. Also from a single supplier there is a fairly wide tolerance for permeability (+/-10% or 15%). This probably is not what you want to hear but don't be deterred. Many designs do not need a precise inductance value and usually construction techniques matter more than who made a particular core. Larry, W0QE

[@nlo114]

Hi Larry, I find your videos very useful! (My college qualifications have evaporated after 40+ years). If I wound an 'octofilar' auto transformer of 8x6 turns for a 64:1 balun, would it work, or should I just copy everyone else's trifilar 8x3 baluns on youtube? (I have a 140-43 + 26AWG silver plated PTFE at my disposal), Cheers, Nick

[@w0qe]

Nick, I really can't answer your question definitively but multi-filar windings couple better but have more interwinding capacitance. These 2 effects kind of offset each other. Sorry that this might not be the answer you were hoping for. Larry, W0QE

[@exwaized523]

Can you share the equation of inductor toroid design?

[@w0qe]

The equation was in the video. What exactly are you looking for? Larry

[@exwaized523]

@@w0qe the equation to define the wire length and the number of turns for toroid core

[@w0qe]

@@exwaized523 There are several approximate formulas I use. There is an old program called "Mini ring core calculator" by DL5SWB that is pretty good. It is free and the latest version is 1.2. Just do a search for it. I also have some local data from cores I have wound in the past. The company Amidon (www.amidoncorp.com) who sells toroids has a free flyer and other data to calculate what you want. Larry, W0QE

[@exwaized523]

Got it. Thank you so much, Sir.

[@Redled_Original]

Thank you for this Video and greetings from Germany. Very helpful!

[@w0qe]

Hi "Redled" You are welcome! Larry

[@ziadkhatib3712]

Or for multi bands

[@davidw460]

Absolutely Awsome :)

[@ErnestGWilsonII]

I'm going to have to watch every video on your channel! 73 W3GUY

[@w0qe]

Ernest, Thanks! I am glad your are enjoying the videos and are finding them useful. Larry, W0QE

[@falconhawker]

T106 2 Iron powder cores T106-2 OD*ID*HT 27*14*11.5mm 13.5nH/N2 10uoIron dust core Ferrite Toroid Core Coating Red gray

[@gajendrapawar6473]

Hi