[RFI] Sling Link RFI

Jim Brown jim at audiosystemsgroup.com
Wed Jul 11 10:37:02 PDT 2012

On 7/11/2012 10:17 AM, Scott Yost wrote:
> Anywhere there is AC wiring it is hot.  So I have it radiating from my own home wiring as well as theirs.

That suggests that both your own home and theirs might not be well 
grounded at the service entrance. The AC mains coming into most homes is 
a twisted triplet (hot, neutral, hot), so from an RF point of view are 
tightly coupled together. Neutral MUST be bonded to ground, and ground 
must be carried with hot and neutral to every outlet.  The ground 
connection at the service entrance SHOULD serve as part of a low pass 
filter for the common mode signal (and there should be another one at 
HIS service entrance).  The characteristics of that filter will depend 
on the length of the ground wire, and on the quality of the ground 

Grounding in homes is often screwed up by careless electricians. For 
example, in the home I bought here in CA, neutral WAS properly bonded to 
the enclosure at the service entrance, but the "ground" connection was a 
50 ft long #12 that was clamped to a spigot for a garden hose, and the 
spigot went to PVC pipe.  So there was NO earth connection at all, and 
when I added earth electrodes (rods) for my ham station, all the power 
line noise went to ground through the power wiring to my ham gear.

I strongly agree with the suggestion that you buy him a wireless router 
and whatever other gear he needs to make all his computers work with 
it.  And if you do, be sure to add multi-turn ferrite chokes to both 
power wiring and the wired connection to his internet modem.

73, Jim K9YC

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