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).
http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/KillingRXNoiseVisalia.pdf
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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