On Mon,8/15/2016 5:39 PM, KD7JYK DM09 wrote:
The results were disastrous! Massive amounts of RFI blasted from every inch
of the cord and most of the wiring in the shop where none had existed before
regardless of the filters used. I asked on this list how this could be. No
response.
I missed that post, but I'll respond now. The reason is VERY simple. The
noise is NOT a differential signal, so filters don't work to kill it. It
is a COMMON MODE signal, which causes common mode current on the AC
line, so you need a COMMON MODE CHOKE to kill the current. The current
makes the power cable as a transmitting antenna. I just posted that in
a response to Doug, which I don't think he understood. I posted a link
to a tutorial that includes specific recommendations for winding turns
around a #31 ferrite core to form the common mode choke. I also posted
a link to a slide show that includes a photo of a suitable choke. I
suggest that you take a look at that email and both links.
73, Jim K9YC
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|