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Re: [TowerTalk] OT: Exterior Ethernet Cable

To: "Tower Talk List" <>
Subject: Re: [TowerTalk] OT: Exterior Ethernet Cable
From: "Jim Brown" <>
Date: Mon, 11 Aug 2008 11:46:09 -0700
List-post: <">>
On Mon, 11 Aug 2008 14:19:21 -0400, Roger (K8RI) wrote:

>I have one run that is 133' and parallels the cables to the tower from 
>the shack. It actually runs with them for about 10' as well as another 6 
>to 8' in the ham shack where the modem, router, and switch are located. 

Proximity to coaxial cables doesn't matter for differential mode coupling, 
only for common mode coupling of common mode current on those other cables. 

>About 40' (between the garage and shop) of that run is directly under 
>one of the 40 meter sloping dipoles. 

That part of the run matters -- it is coupling between the ANTENNA and the 
cable. But that is primarily COMMON MODE coupling. A common mode choke 
fixes that problem. 

>It also runs within 10' of the tower base. 

Doesn't matter, except to the extent that it gets close to a beam on that 
tower! Again, common mode is the potential problem. 

>In the shop the computers are setting within 2 to 3' of 
>the rigs, which run the legal limit.  

Doesn't matter. Virtually all rigs are shielded, and SHIELDED EQUIPMENT 


Jim K9YC


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