Re: Toroid Ferrite Loop Stick

Everett N4CY

You do not need to glue, or space the toroids, I have tried it both ways. Just get a 1" dia dowel rod and cut it just slightly shorter than the total length of the 18 stacked toroids. Then use wood, or plastic disk the ends of the dowel rod to hold and compress the toroids (The disk can be screwed on). 

Based on my experiments it appeared that, by doing the above, that the combined toroids looked as though they were one solid rod. I base this assumption on looking at the induction readings of a coil being moved from one end of the rod to the other. The induction is less on each end and higher in the middle of the rod, which is the same thing that I saw on a solid bar. 

When you wind the 3 coils, you will need to use less turns on the middle coil in order to try to keep the inductance the same for each coil. 

Everett N4CY

On Nov 9, 2015, at 2:58 AM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:


I couldn't help myself and ordered 8 more toroids. My plan is to have 3 coils wound which will have a total uH in series for AM. I think those windings will cover 2 toroids, but 3 would be fine too. Those sets of 2 or 3 toroids I'll glue or tape together, and then use most of the rest as spacers which can be arranged in different patterns. For example, in one of Everetts tests he found a 5-6 inch spacing between coils worked best on a FSL. So I could slide one coil set on the core, then 3 spacer toroids, then the second coil the other side 'up' so the turns go in the opposite direction, then 3 more spacers and then the 3rd coil and finally one toroid with a pick up coil at the end. If all 18 toroids work very well together, that is fine. If the extra length is not that big an advantage, I could make a smaller version with a single coil out of the extras. It will be quite a while before I can get this all done. I like the fact it will be a test bed whi ch can be modified easily by just rearranging the coils and spacers on a 1 inch rod.  - FARMERIK

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