Sunday, August 11, 2013

When I first started kit building some years ago it was the dreaded toroid winding that I never looked forward too. After winding and rewinding over time it has not become a dark task, it has taken some time to get the hang of it but I can say that I  no longer get uptight about the process. I have learned some tricks and some never ever skip steps when it comes to toroids. 
I am in the process of building my second K2 rig from Elecraft and there are lots of toroids to be wound. Now having said that if you want you can order per-wound toroids from the toroid guy. If you do order toroids that are per-wound I would encourage you to try to wind your own as well. What I have found is it's only practice that is needed to get the hang of the winding thing. In the past I have built many Elecraft kits were toroids have been involved, I have learned as I said some tricks, some must do stuff and things to stay away from when it comes to this art. 

My advice when winding single conductor toroid....
1. Most if not all the time you have more wire than you need so when told to cut a conductor to lets say 12 inches I give myself around 13-14 inches. A wise person told me "it's better to have and not need than to need and not have" 

2. If you are winding a toroid that has lets say 20 turns when you hit 19  I stop and count the turns just to make sure I am not at 20 or that I lost count and am only at 18!  I have had both happen.... it's better to check rather than cutting the excess wire and finding out you need to somehow add 2 more turns. 

3.Once the toroid is wound check the turns to see if they are more or less equally spaced. Take your time and move the windings around the core. Use a plastic tool or wooden tool for this a metal tool (screw driver) may remove the paint on the wire and cause a potential short.

4. Take the new toroid and see how it fits on the board. Sometimes you may have to squeeze the turns or open them up a bit for the toroid to fit properly. 

5. Once the turns are good and the fit is good you can trim off the extra wire. When I do this I always make on leg shorter than the other. I find you can place the toroid on the board with less effort by having the lead staggered in lenght. This is very evedent when you have a toroid with more than one winding..

6. Now that the toroid has the right amount of turns, it is spaced correctly, fits nicely and the leads are cut one longer than the other....its time to remove the enamel coating off the wire. There are some various
 ways to to this........ 
Getting ready for solder blob
A. Use a lighter to burn off the coating
B. Use sand paper.
C. The solder blob method.
D. Use a razor knife to scape the coating off.
E. I have heard some dipping the wire in var-sol....would not recommend it.

I use the solder blob method and I have tried the sandpaper (find it just to rough for the delicate work that is needed) I have tried the lighter method but found on the smaller toroids I am not able to control the heat and end up burning off to much insulation. The razor blade scraping I have not tried and really don't want a razor knife that close to my fingers.'s the solder blob for me!! I find if I put the toroid in an alligator clip to hold it I can in a very controlled fashion remove the right amount of enamel from the toroid.
I change the tip on my Weller soldering iron to a larger tip and use a .030 diameter solder. Most of my board work is done with a .020 diameter solder.

7. Once the toroid wire has been stripped I use my DMM to check to make sure the coating has been removed and there is good continuity. Oh and for toroids that have more that one winding I check to make sure there is not shorts between the windings as well.

8. It's now time to solder the toroid in place and I find once the toroid is soldered in place before the leads are trimmed you can heat each solder blob up again and give each lead a LIGHT pull with a pair of pliers. This will allow the toroid to sit firmly on the board.

Some tips
1. Practice practice's like CW it's an art and over time you will get the idea and look forward to it.
2. Some toroids have nice rounded edges but be aware of those with sharp 90 degrees edges. These toroids can if your not careful remove the insulating coating from your wire and potentiality cause a short.

Using a paper and pencil to count
3. When  you have a toroid with 20 turns or more you can go buggy trying to check the turn count. What I do is lay the toroid on a sheet of paper and pencil make on the paper each turn. I then count the pencil marks and sometimes ticking them off as being counted.

4. Use two sizes of soldering tip's one (I use the Weller ETC 1/8 tip) for the solder blob used to melt the insulation off the wire. Then a thinner tip (I use the Weller ETR 1/16 tip) for soldering the toroid to the board.
ETR and ETC tips

Coming soon how to wind the bi-filar toroid and transformer toroid.


  1. Mike, you were right about your site being helpful. I have been both excited and fearful about winding toroids.
    Thanks for the tips on technique and especially which method you prefer for removing the insulated bit at the ends.
    I appreciate you introducing me to your site. I will be coming back a lot!

    1. Nice to hear from you I was just reading your blog and thought this site may be of some help to you. If you do have any questions please feel free to email me at I will do the best I can to help out. The toroid can be a bit intimidating but in time it becomes no big deal. It's like riding a bike just takes practice.

  2. Hi Mike,

    Very interesting about the toroid winding etc., and this is very useful as I have never wind any toroids, and soon I will have to. Have bought me a little kit and it has some toroids.
    And now the stupid question: how does that solder blob method work ? What are the steps to take ?
    Anyway, maybe I am going to love winding toroids, who knows ;-)
    This will be a plus if I ever going to build my own K2 :-)

    73 Patrick ON4CDJ

    1. Good morning Patrick, thanks for stopping by the blog and taking the time to comment. I wanted to send out a response as soon as possible. I have been working very long hours these past few weeks which leaves me very little time for radio and the blogs. I wanted to let you know that I will post an answer to your question on Saturday when I am off and at home. I wanted to take time to answer your question. I did not want to rush an answer off to you and probably make good old toroid winding more confusing. Sorry for having you wait until Saturday but things have been very busy here and I don’t want to give you a rushed answer.

    2. No worries Mike, you are very helpful, as always.
      We all have busy lives to live and plenty things to do. Fortunately I am having holidays now, so I have time to wait ;-)
      Thank you for your time and the reply, and I'll check these pages in the next days.
      You enjoy your weekend Mike !

      Patrick ON4CDJ