[TowerTalk] Back of desk grounding buss

[Stan Labinsky Jr.]

To all;

A long, long time ago, I sat through a "grounding and shielding" course 
provided by my employer by a company involved in making sure that the guy in 
the black van in the parking lot couldn't see what was on your computer's 
monitor screen because it and its connecting cables were radiating the 
display data.  The big word used at the time was Tempest.

One point the instructor made was to look at your whole system setup from a 
top down attitude (like you were the ceiling) and make sure that all of the 
interconnections came from a common hub, like an old wagon wheel.  But, 
there should ONLY be spokes... NO WHEEL-RIM.  No cross connections from one 
spoke to another which would create a magnetic loop capable of coupling both 
in and out.

How's this work?  Well, the HF rig connects to the amplifier and then to the 
tuner and then to the entrance panel.  The VHF rig the same way.  But NO 
connections between either radio unless that lead ran from the HF rig to the 
entrance panel and then back out to the VHF rig, like fingers of a hand. 
That means that all the line power line cords and any chassis bonding follow 
that same path as well.

Could it become clumsy?  Sure, but you have no loops.

Years later I was involved in building a piece of factory semi-conductor 
manufacturing equipment.  I rigorously followed that overall scheme in the 
electronic/electrical design.

It paid off big time when the output of the 20 meter (actually 13.56MHz.) 
15kW RF generator was left unconnected by the maintenance guy, the coax 
cable center pin laying against the tool's frame.  All seemed to go well, 
except that the glow in the chamber didn't come on.  It was a plasma 
deposition tool.

The generator had reached an output of 4,500 watts before one of the control 
computers forgot what it was supposed to do.

Was this post a bit long winded?  Yes!  But, does the scheme work?  I guess 
it does.

Stan


-----Original Message----- 
From: Ian White
Sent: Sunday, March 23, 2014 6:34 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Back of desk grounding buss

Jim K9YC wrote:
>
>Those interconnections, especially analog audio, is one big reason why
>chassis-to-chassis bonding is far better than running individual wires
>to a common point (or bus bar).
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