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Author Topic: Which 1:4 balun for unbalanced tuner operation?  (Read 6339 times)
N1LO
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« Reply #15 on: October 08, 2008, 10:21:57 AM »

Hello Jan,

Sometimes that happens here on EHAM.

I don't have enough knowledge and experience to predict if you can substitute an iron powder toroid for a ferrite one.

What I usually do is study the manufacturer's application recommendations. My understanding is that for transforming baluns, you choose a material that is not lossy at the desired frequencies. If you know that this material is suitable, of if it is used successfully in other BALUN/UNUN projects, than it's a good bet that it will be fine.

It seems to me that no single mixture is good for 160-10m: It takes a higher permeability to be suitable for 160m, but then it becomes too lossy at 12-10m. A mix good for 80-10m does not have sufficient permeability for 160m.

I included the permeability on the plan so that builders could make substitutions among alternate ferrites available to them.

As for the number of turns, I don't know how to predict that. For my balun project, I now recommend 10 turns instead of 9, which, by experimentation and testing, moves a minor impedance bump out of the 17m band.

If you find another material, size, turns and wire gage combination that works, please send me the information and I'll add that to the plan as alternate construction.

GL,

--...MARK_N1LO...--
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GOUDURIX
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« Reply #16 on: October 08, 2008, 11:21:27 AM »

Hi Mark,

how have you been testing for impedance?
I do not have the equipment (other than 2 SWR/power meters) & dummy loads to test baluns (VSWR over the whole freq spectrum).

As for toroid choice, Sevick prescribes iron-powder core for a 1:4 Ruthroff (voltage type) for use in a tuner balun - Amidon T300-2 with 17 turns or Amidon T-400A2 core with 21 turns. Those have a permeability of 10, and should be more linear and rugged than ferrites. Permeability 10 proved to be better than other permeability P-I cores.
So I will use 17 bifillar tunrs on each toroid.

Jan
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