Topband: Elimination of Treadmill RFI on 160 meters

[Jim Brown]

On Fri,1/30/2015 2:49 PM, Jim Garland wrote:
> But, like I said, maybe I'm not following something.

Right -- you are not. First, you don't understand what common mode is. 
Second, you don't understand the choke. A ferrite common mode choke 
STARTS OUT as a lossy inductor, but one with shunt capacitance. This 
forms a very low Q resonant circuit (typically 0.4), and thus a very 
broad resonant peak. It is the resistance around resonance that forms an 
effective common mode choke.

I've discussed this in considerable detail in tutorial form in 
k9yc.com/RFI-Ham.pdf  and some of that material has been added to the 
ARRL Handbook. There's also a pdf of the slides that go with an RFI 
tutorial that I've done for several ham clubs. It's on my website -- 
k9yc.com/publish.htm  I suggest that you study these two pieces. It's 
far too much work (and probably boring for many readers of this list) 
for me to post it here.

73, Jim K9YC