[RFI] Common Mode In-Shack Choke

[Jim Brown]

On 4/7/2021 1:29 PM, Tony wrote:
> I'd like to cover all HF bands if possible and wondered if using two 
> chokes in line  i.e., one with mix 31 and the other with mix 43 would do 
> the trick?

No, #43 is NOT suitable for use at HF, due to production tolerances and 
the relatively high Q of #43 compared to #31. But multiple #31 chokes in 
series, wound with RG400, or pairs of PTFE #12 or white/black stripped 
from Romex ARE a good solution. See my choke cookbook. One choke would 
be wound for the lower bands, another for higher bands. The cookbook 
includes such recommendations.

http://k9yc.com/2018Cookbook.pdf

However -- if a choke on the shack end of feedlines reduces common mode 
noise, the shack very likely has problems with bonding and grounding. 
Study N0AX's ARRL book on the topic, or my slideshow pdf for talks I've 
done at Visalia, Pacificon, and for several ham clubs.

http://k9yc.com/GroundingAndAudio.pdf

73, Jim K9YC