Tony,
My experience has been that long CAT5/6 cables do radiate and cause
RFI. Mostly it is carriers on numerous HF and VHF frequencies. Any
broadband noise has generally turned out to be a "bad" power supply
or specific device such as a router or access point.
In order to minimize the problem I keep my modem and router/in-house
access point at the same location, connecting them with a one foot
CAT5 cable. I do, however, have one 225 foot run of CAT6 going up a
tower right into the midst of my antenna farm! It is for a tower
mounted access point for a 5.8 mile link to a repeater site. This
cable was a major problem. It now has multiple common mode chokes at
both ends - some optimized for VHF, some for upper HF, some or lower
HF. All other cables (power, internet, etc.) connected to the
network are similarly fitted with chokes. This does not completely
eliminate the problem but brings it down to a level I can live with
considering the benefit of the extended LAN link to my repeater
site. I got rid of all the switch mode wall warts that came with
network devices. The modem, router, and passive PoE injector for the
tower mounted access point are all fed 13.8VDC from an Astron linear
supply.
73, Paul
On 06/01/2015 12:53 AM, Tony wrote:
All:
I'm about to relocate the wireless router in my home which currently
sits next to my internet modem connected with a short run of CAT5.
Relocating the router will lengthen the CAT cable by 40 feet so I'm a
bit concerned about RFI birdies, noise etc.
That said, I was wondering if it's better to relocate both cable modem
and the router to the same location to keep the CAT cable short. I would
then have to lengthen the coax cable for the modem instead of the CAT
cable.
The question is: which setup has more potential for RFI?
Thanks
73, Tony
--
Paul Kelley, N1BUG
RFI Committee chair,
Piscataquis Amateur Radio Club
http://www.k1pq.org
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