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Old 01-27-2010, 04:03 PM   #1
CROSSBOLT
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Saw an "unun" on the DXnet or something that showed a 9:1 unun with 5 turns on the primary and 15 turns on the secondary on a "Type 75" toroid. I do not know what this kind of a toroid is. My e-mail to the guy is yet unanswered. I will show my ignorance by relating a T-68 is a toroid of .675" OD while a T-25 has an OD of .250" and so on. Does not seem to be a T-75 anywhere. Am I looking in the wrong place?

Karl
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Old 01-27-2010, 09:10 PM   #2
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Maybe this article will help.....http://www.k0bg.com/unun.html

or this http://www.bobsamerica.com/9-1balun.html

Ken
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Old 01-28-2010, 08:50 AM   #3
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The specifics of the torroridal core do not affect impedeance transformation but will affect frequency and power levels (Different cores work better at different frequency ranges, and at different power levels)

How a substitution will affect the result I'd have to do some serious research to find out

But if you have the spec sheets for the cores in front of you,,, It should be easy to figure it out for any ham General or higher.
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Old 02-05-2010, 02:34 PM   #4
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Ken, your second link is the one I saw for this unun gizmo. down next to the bottom picture is reference to a type 75 core which I cannot find on the 'net nor in Mouser. I could substitute another core if I could identify a type 75.

Thanks for the links!

Karl
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Old 02-14-2010, 12:03 PM   #5
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Here is what I have figured out regarding the unun that Ken has linked: Type 75 refers to core material. This may be a slam dunk for you guys with more experience but it was a learning experience for me! I also did some measuring from the pictures on the link and determined the core was over 2" in diameter. Now I think I have enough info to try and fabricate one of these "ununs" for myself.
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Old 02-16-2011, 11:35 AM   #6
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Have done some more studying: a 2" core of Type 75 material would be designated T2-75/K or thereabouts. Type 75 material and type K are interchangable.

Karl
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