On Mon, 8 Jan 2007 23:41:46 -0500, Jeff Maass wrote:
>My concern is the +12Vdc on the feedline to a preamplifier, which
>will pass through a choke of 8 turns of RG-8X through four #31
>2.4-inch toroids. The current is low.
You have two very good reasons NOT to worry. First, the toroids see
only the DIFFERENCE between the current on the shield and the
current in the center conductor, which is zero. Second, the current
is low, but it could be large and not affect operation of the
ferrites.
Fair-Rite publishes extensive data for their materials and products,
including data for changes in permeability with temperature and DC
bias.
If you haven't done so already, take at look at
http://audiosystemsgroup.com/RFI-Ham.pdf
which includes a long discussion about how ferrites work. I may need
to expand it a bit to address questions like yours. I covered it in
a piece that I wrote for the pro audio world.
Jim Brown K9YC
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