[Elecraft] OT: K3 vs an RFI noisy furnace

[Jim Brown]

On 11/10/2010 10:20 AM, Don Ehrlich wrote:
> I tried a quick and dirty fix which consisted of wiring a pair
> of two microfarad/400 volt mylar film capacitors directly to an AC plug (one
> capacitor from each line to the ground pin) and then plugging it into the
> same outlet as the treadmill.

This is unsafe and illegal, because it creates large leakage currents on 
the green wire.  The maximum permitted leakage current on green is 5 mA.

One proper way to filter the AC line is with a filter that includes 
series inductance (usually a common mode choke) and much smaller shunt 
capacitors.  Common mode current on the AC line can also be suppressed 
using multi-turn ferrite chokes wound on the mains power cable.

See http://audiosystemsgroup.com/RFI-Ham.pdf

73, Jim K9YC