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Re: [TenTec] RF Ground

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] RF Ground
From: Jim Brown <k9yc@audiosystemsgroup.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 05 Apr 2009 12:01:49 -0700
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Gary Hoffman wrote:
> My point is different.
> I don't care if the coax radiates.  In fact I accept that it will in 
> virtually all cases, at least to a degree.
I do, for three reasons. RF in the shack, RF in my living room and my 
neighbor's living room, and, VERY important, noise coupled from 
reception on the coax to the antenna to the RX. 
> I was referring to the effect at the input to the radio.
IF the coax is connected to the CHASSIS of the radio, no shield current 
(common mode) enters the radio. If, however, the shield is connected to 
some point INSIDE the radio (by definition, a pin 1 problem), shield 
current (common mode current) WILL enter the radio.
> If we shunt the current away from the radio....to ground... at that point, 
> then it will not flow into the radio.
This doesn't matter if there's no pin 1 problem (that is, if the shield 
goes straight to the chassis).
> I was trying to keep noise out of the radio, for the purposes of addressing 
> the original "buzz" problem.
> Of course many posters here don't agree that ground has anything to do with 
> it, and some focus on "pin 1" and others have their pet causes.  I was 
> addressing one item that had a theoretical solution.
I'm simply cutting straight to the physics of what's happening. As EMC 
guru Henry Ott says, we must keep track of where the current is flowing. 
Henry talks about the hidden schematic concealed behind the "ground" 
symbol. As Bob, K4TAX, observes, those points labeled "ground" are not a 
single point, they are wires with inductance and resistance. If current 
flows on them, they will radiate. Any radio wave that hits it will 
induce voltage and current. And any current will produce an IZ drop.

If you guys went to study my tutorials on the pin 1 problem, you 
wouldn't be arguing with me!  :) 

Jim Brown K9YC
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