[RFI] Internet Switch RFI
jim at audiosystemsgroup.com
Sat Nov 21 19:50:43 EST 2020
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
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