On 3/18/2014 8:49 AM, Gary Smith wrote:
I'm going to try the 10 rolls of coax again, this time alone.
Contrary to popular mythology, a coil of coax is NOT an effective common
mode choke, because it is inductive. An effective common mode choke must
have a large value of resistance at the frequency of interest. Only a
multiple turns wound through suitable ferrite cores to form a low Q
parallel resonant circuit are effective, and a LARGE value of parallel
resistance is needed both for power handling and for noise suppression.
See the "Cookbook" in k9yc.com/RFI-Ham.pdf for specific bands and
combinations of bands. 4-5 turns of RG-213-size coax through 5 #31 or
#43 Fair-Rite cores covers 20-10M effectively.
73, Jim K9YC
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