The question remains, what is the best material (among those
available) and how many single turn toroid forms should I
plan to incorporate to effectively suppress this noise?
Maybe there is a better way? I'm all ears...>>>
I already tried to answer you. All you can do is pick the
core with the highest impedance at the problem frequency.
Everyone knows, and I already pointed out, you cannot use
multiple turns in vehicle wiring.
As I pointed out, the best core will almost certainly be 33
material, which will be a bit better than the 43 you have.
You won't find much better because the best cores are not
available in large diameter or thick walls because of
problems when more effective materials are made too large.
73 or 77 would be ideal, but the size is limited.
61, as suggested to you, is NO GOOD. It is a VHF suppression
material. Anyone suggesting 61 plainly doesn't know core
materials. It is about ten-fold LESS impedance for a given
core dimension at HF than 44. They probably think the
material numbers are in order of permeability, they are NOT.
The material numbers are not in any particular order related
to impedance or frequency.
Your best bet is adding some grounding straps and bypass
capacitors, because according to numbers cores have a
limited effectiveness.
I have one other suggestion. Listen to the AM radio for
ignition noise. If it has it, COMPLAIN to the dealer. Don't
tell them you are installing a two-way radio.
73 Tom
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