[Amps] Triband balun

[Jim Brown]

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