Re: Amoskeag Lightning Arrestor Questions

On Wed, 18 Jan 2006 07:18:57 -0800, Dan Richardson <> wrote:

>>The Astron RS-35 power supply connects utility power neutral to the
>>case. It also connects the 13.8 volt return to the case. [This is
>>commercial common practice but is prohibited in Military Systems
>>design.]
>
>You've tweaked my curiosity what does the military do?

Hi Dan,

They use ground as a shield, not a current carrier. This is also
suppose to be code for commercial and retail electronics devices.
Connecting the metal cabinet to neutral was supposed to have slipped
into La Brea tarpits with the dinosaurs. Back before polarized plugs,
you could electrocute yourself by guessing wrong, touching the metal
surface and also being grounded. The bridging between toasters and
water taps (or stove tops or fridges) come to mind.

Also common, but nearly as fatal, was the practice of putting two,
series capacitors across the AC line into receivers to cut down on
noise from the lines. They would also take the tap of the two caps
and tie that to the chassis, thus insuring half the line potential was
always on its surface, unless you provided a ground connection. This
was one of those suicide connections where if you were holding the
chassis and pulled the ground lead, you automatically became a fried
line fuse. Members of our hobby have preserved this suicide
connection by grounding their remote antenna (or equipment) through
the coax shield instead of through a separate ground wire (this is why
we have codes).

GFI breakers sense the common mode current (that current that has
escaped the neutral/hot loop) on the shield path (although it is
called a safety ground for 60Hz service).

73's
Richard Clark, KB7QHC
.

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