On 7/17/2024 12:16 PM, Dave (NK7Z) wrote:
If you are trying to suppress 14 MHz and lower I would use mix31, if
above 14, mix43.
Fair-Rite #43 is NEVER a good choice below 30 MHz. Mix #31 is the only
good choice for 160M through 10M, and slightly better than #43 for 6M.
Place about 7 to 10 wraps of cable on a ferrite. Each pass through
center counts as a turn...
Number of turns needed depends strongly on the core. For most #31
clamp-ons, 2 turns is about right for 6M, 3 for 10M, 5 for 40-10M.
It is CRITICAL that turns are sequential around the center of the core.
Out of sequence turns cancel. I ran into this with the year-plus of lab
research that produced the latest (2018) Cookbook. It can be difficult
to get 5 turns in sequence through a clamp-on and have them stay that
way, although cable-ties can help. Depending on the o.d. of the cable
and the i.d. of the core, even 4 turns can be difficult. There are a
couple of photos showing this on page 22 of my latest update of my
original RFI tutorial.
http://k9yc.com/RFI-Ham.pdf
73, Jim K9YC
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