[RFI] Internet Switch RFI

Jim Brown jim at audiosystemsgroup.com
Sat Nov 21 19:50:43 EST 2020

Hi Jim,

POE may very well be the problem, in which case I'd choke the hell out 
of the cable carrying the POE, and/or replace it with a shielded CATn. 
That, of course, requires that the equipment on both ends terminates the 
shield properly. :) A good first move is to inspect the ethernet 
connectors to see if there is a shield contact.

If there's an SMPS, either internal or external to the main unit, the 
easiest solution, if you can pull it off,is to simply replace it with a 
linear supply. The methods I've used are in this NCJ piece (pp7-8) and 
more descriptively in the slide deck from Visalia (starting on slide 137).


If some component of the noise is differential mode, radiation can be 
reduced by using a good twisted pair. The four pairs that make up 
CAT5/6/7 are usually very high quality.

73, Jim K9YC

  On 11/21/2020 3:15 PM, Jim McCook wrote:
> I know internet switches have been discussed a couple of years back, but 
> I found no help in the archives.
> A new S-9 RFI noise just appeared on 3.513 KHz as the center frequency. 
> It's a hump about 14 KHz wide.  I tracked it to a neighbor's house 180ft 
> away.  It's a new internet switch that she just bought from Amazon: 
> Aumox SG518P 18 port Gigabit Network Unmanaged Switch, 16 Port POE with 
> 2 Uplink Gigabit Ports, 250w. It also generates signals from 160 through 
> 40m at 143 KHz intervals, but the only one that concerns me is the one 
> centered at 3.513.  She uses 13 of the ports for many different 
> functions around her house.  It does NOT have a separate power supply! 
> It is unrealistic to think of putting toroids on all those cables and 
> the AC line.  Her cables are too short to do that without splicing new 
> sections with toroids on each one.  I know NOTHING about these 
> switches.  Does anyone have experience with one using this many ports 
> that either has a separate power supply or does not generate RFI?  This 
> is a very nice neighbor and I will not just tell her to fix it.  I'd 
> hope she can return it and get one that is RFI proof.  Covid access is a 
> problem.  73, Jim W6YA
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi

More information about the RFI mailing list