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Re: [TowerTalk] OT: Exterior Ethernet Cable

To: "Tower Talk List" <towertalk@contesting.com>
Subject: Re: [TowerTalk] OT: Exterior Ethernet Cable
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 12 Aug 2008 00:59:01 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Roger said:

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

I replied:

> Doesn't matter. Virtually all rigs are shielded, and SHIELDED 
EQUIPMENT 
> DOESN'T RADIATE OR RECEIVE. ANTENNAS DO! 

>But again I was pointing out that 
>being close to RF normally has little effect.

Being close to a rig does NOT make you close to RF. RF field strength 
is generated by RF current flowing in an unshielded wire. It does not 
leak out of a well shielded box (or at least very little). The RF is 
out surrounding the antenna, not next to the rig. 

A ham shack is hot with RF only when RF current is flowing through the 
shack -- for example, when common mode current is flowing on the 
transmission line. I had a lot of RF in my shack in Chicago when I 
loaded a long wire (on 80 and 160) that ended at the antenna tuner in 
my shack, or a 30M vertical that was 10 ft away out the window. The 
shack was hot with RF because it was close to the antenna, not close to 
the transmitter. 

73,

Jim K9YC




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