How to keep cat5e cables from picking up RFI?

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Last winter I did some in-wall cat5e wiring from my router to my
computer.  It's probably about a 50' run, maybe a bit more.  I then
got some new nice speakers for my computer.  At some point since then
I've found that the speakers are picking up some talk radio station.

I've narrowed down the source of the interference to the network
wiring.  If I pull the cable the radio station goes away.  Plug it in
and it returns.  I tried pulling the cablemodem cable from the router
and the interference persists.  I've tried various patch cables from
the wall to computer with no change.

The wire I used was UTP cat5e.  Nothing special...it was bulk from the
local home store.  Would shielded cable fix the problem?  I'd hate to
rewire, but if it would fix the problem then I would.  If so, does any
shielded cat5e do the job?  What about the jack?  Does it have to
change?  And I guess the patch needs to be shielded as well?

thanks!
fg

Re: How to keep cat5e cables from picking up RFI?
benjunk@pookmail.com wrote in part:
Quoted text here. Click to load it

This is odd.  Even split pairs (which you don't have with
color-coded jacks) wouldn't explain pulling in AM onto speakers.

However, the unused conductors in the Cat5 can certainly
act as an antenna which could pull AM onto the mobo,
especially if the PSU/mobo grounding is poor.

Check your grounding (wallplug and case).  Also route
your audio & speaker wires well away from the Cat5.
The audio patch cable should be shielded or it will
pick up all sorts of noise.


-- Robert


Re: How to keep cat5e cables from picking up RFI?
On Tue, 2 Dec 2008 10:24:57 -0800 (PST), benjunk@pookmail.com wrote:

Quoted text here. Click to load it

This is common mode interference and it should be easy to get rid of.
Have you tried ferrite beads on the Cat5 cable? Loop it several times
through the bead and your RF should just be tiny amount of waste heat.
Not enough to measure.

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