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Re: [TowerTalk] Wireless ISP on Ham tower

To: "Tower Talk List" <>
Subject: Re: [TowerTalk] Wireless ISP on Ham tower
From: "Jim Brown" <>
Date: Tue, 30 May 2006 22:06:47 -0700
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On Tue, 30 May 2006 15:53:10 -0500, Chuck Sudds wrote:

>I have unshielded CAP-5 wire running from the 
>tower to the house, approximately 125ft away, to my router

>I have never experienced any interference from the ISP setup to any ham 
>frequencies that I operate (HF, 6M & 2M) BUT I occasionally interfere 
>the ISP dish.

I have identified SEVERE RFI from the Ethernet wiring and hardware to HF 
at a site in CA. I have identified at least two culprits (and there may 
be more), and they all boil down to LOUSY suppression from cheap network 

I would be VERY surprised if you don't have birdies from the Ethernet 
cables on 14,030, 10,121, 21,052, and around 28,016. These are the ones I 
often encounter on CW, and I'm sure there are others in the phone and 
digital sub-bands and on the low end of 50 MHz. This is radiated common 
mode by the cable, and can be fairly well suppressed by ferrite chokes. 
See the tutorial on my website for details.

Using shielded CAT5 will probably not help (where are you going to tie 
the shield?), but putting it in electrically continuous grounded metal 
conduit will. 

There is also direct radiation from unshielded network equipment. This 
stuff is broadband noise. The only solution I know of is to shield it, 
which can be a non-trivial project.  :) 

Jim K9YC


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