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Old 10th Jun 2021, 10:20 pm   #1
mole42uk
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Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
Default Modifying an inductor?

I am trying to make a pi filter for 1MHz and a known 10µH ferrite cored inductor resonates at about 850kHz. Two of the 10µH inductors in parallel offer about 1.3MHz so I conclude that the impedance I'm after is in the region of maybe 12.7µH.

I have these two inductors in my RF bits box. On one is the inscription 10.1619, the other reads 10.1691. They look similar but one has a slug and the other doesn't. Having tested these in my filter, they both offer a resonance at about 1.4MHz. My question is this: can anyone guide me how to modify the coils to gve me a resonance at 1MHz, and I'd prefer to use the one with the slug because I can tune that a bit. Each has ~40 turns, I wonder if I need to rewind at say 30 turns, or is that too simplistic?
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