Topband: 2Wire, Inc. 3800HGV-B Gateway. RFI --Problem fixed for now..

Jim Brown jim at
Sat Feb 4 10:38:58 PST 2012

On 2/4/2012 8:13 AM, ZR wrote:
> Im running 250' of shielded CAT5 from house to equipment trailer where the
> router resides and then another 120' up the tower to the 5.8GHz link.

The issues, Carl, are not with CAT5, shielded or unshielded, but rather 
with the equipment on either end, which can generate RF trash or be 
susceptible to RF trash. Some commonly used Ethernet products produce 
birdies on the HF bands (a couple of frequencies on 30M, around 14,030, 
21,052, the low end of 10M, the low end of 6M are places I hear them, 
and there are others). Some digital equipment produces loud broadband 
hash. I've seen some POE stuff used with data links at tower sites that 
were quite noisy on the MF and HF bands. This trash gets radiated 
several ways -- usually most strongly from common mode current on the 
Ethernet and power supply cables (or coax if it's used), and often 
directly from wiring internal to unshielded boxes.

Ferrite chokes can greatly attenuate the common mode part of that.  
Using shielded CAT5/6/7 can help if, and only if, the shield is 
optimally terminated at both ends (both ends are likely generators of 
digital trash). That usually means bonding to the shielding enclosure at 
both ends.

73, Jim Brown K9YC

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