[Elecraft] RFI With KPA500 Full Output on 40m

[Jim Brown]

On 3/18/2012 7:05 AM, Jim Sheldon wrote:
> I trip every GFI outlet in the house.  I haven't found enough big snap-on ferrites to hit all the romex coming out of the panel, but when I do, I'll certainly put 'em on.  A really big one that would snap around the incoming line at the panel would be nice, but so far I haven't found a source of snap on's that I can afford.  Not sure either on what material would be best for that.

As was noted in another post, the ones that trip are defective (poor 
design). The solution is to replace them with GOOD ones.

As K2VCO noted, ferrite beads clamped onto a wire are next to USELESS 
for HF RFI.  Ferrite chokes work by adding a parallel resonance in 
series with the wire that they surround, and a single bead or clamp-on 
is resonant around 150 MHz. To make it useful at HF we must move the 
resonance down to the HF bands by winding multiple turns through it.

Study http://audiosystemsgroup.com/RFI-Ham.pdf  for a detailed 
explanation and lots of detailed advice.

73, Jim Brown K9YC