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Re: [RFI] computer shut down

To: rfi@contesting.com
Subject: Re: [RFI] computer shut down
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Wed, 30 Dec 2015 09:40:18 -0800
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Tue,12/29/2015 1:33 PM, W9RPM wrote:
Hi, I recently started having a problem on 30 meters with one computer with Multiple Monitors jumping everything around on different screens, and another computer shutting down. I have a couple of other computers in the shack that are not affected.

Several thoughts, John. First, STUDY my tutorial on Power, Grounding, and Bonding, and carefully implement every part of it. http://k9yc.com/GroundingAndAudio.pdf Some of the advice you have received from others is quite good, most notably to study the position of your antennas with respect to your station.

Other advice has been quite bad - here's the right way.

1) ALL of the equipment that is part of your station should be powered from the same AC outlet box, or from outlets whose grounds (the green wires) have been bonded together at the outlet. Equipment, like computers, that are NOT connected to your station can be fed from different outlets.

2) ALL of the equipment that is part of your station should be bonded chassis-to-chassis with short, fat copper. Bonding should follow the paths of the interconnections, NOT to some common point, because that common point makes the bonding path longer. For example, bond your computer chassis to your rig. If there's an accessory box connected to your rig, bond it to the rig. If it goes to the computer, bond it to the computer. For laptops, you can usually find a chassis connection at a DB-connector.

3) Bond ONE of those chassis points to your station ground (usually the rig) to all other grounds in your home -- ground rod(s) where antennas enter your shack, the main AC power system ground, CATV ground, Telco ground, etc., and make sure that all of those grounds are bonded together.

4) Add multi-turn ferrite chokes to every cable that is connected to the computer(s) with RFI issues. Start with the power supply and video cable (if there is one), USB and RS232 cables, audio connections to your rig, etc.

5) AC line filters are rarely of much value. If you do use one, make sure that it is bonded to your station ground with short fat copper.

Yes, some of this differs from long-standing myths about "ground loops" perpetuated by the ham community for decades. The tutorial clearly shows why those myths are wrong. N0AX, who edits the ARRL Handbook and ARRL Antenna Book, and who writes a column in QST adapted many of my recommendations for his columns on grounding and bonding. HE "gets it."

73, Jim K9YC
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