Sleeve balun ferrite materials

Discussion in 'General Electronics Chat' started by wpri268, Jan 1, 2014.

  1. wpri268

    Thread Starter New Member

    Feb 18, 2012
    23
    0
    I want to add a balun to my pennant antenna feedline to further decouple it from the antenna itself. Instead of breaking the coax to insert a balun which will only create additional loss my intent is to use ferrite beads over the coax as a sleeve balun. Research I have done about line isolating baluns says that they work because of choking action. This of course implies inductance. Many designs involve using high permeability materials like Fair-Rite #77. I find this a problem because of the complex permeability of high perm materials. Most appear resistive and not inductive at frequencies > 2MHz which makes sense since they are meant for RFI suppression.
    I have a bunch of Steward/Laird LF beads that would be perfect for my balun but this material peaks as resistive at around 4 MHz.
    Would I be wasting my time trying to use these beads?
     
  2. wpri268

    Thread Starter New Member

    Feb 18, 2012
    23
    0
    This link is the answer to my question. LW and MW baluns must be inductive:
    http://www2.fhi.nl/hf/archief/2012/images/1.emctorfid.pdf
    The presentation does a good job of explaining how the complex permeability u' and u" of a ferrite interact as frequency changes and what they mean to selecting a proper core material. I wish I knew this before.
     
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