[TowerTalk] Shack ground

[Jim Brown]

On Wed, 16 Jun 2010 16:44:31 -0400, Pete Smith wrote:

>but the new thing I found was his bonding of the electrical outlet 
>grounds in his shack to the shack's single point ground. 

OF COURSE there must be a bond between the green wire at the outlet 
and the shack ground. This so-called single point ground concept is 
badly misunderstood. Fundamentally, ALL grounds MUST be bonded 
together. Bonded means ROBUST and LOW IMPEDANCE. Robust means BEEFY 
and physically solid -- it can carry a lot of current and it won't 
break. Low impedance means LOW INDUCTANCE, which means SHORT. It 
should be obvious that if equipment is connected ONLY to a star 
point, the length (and thus the resistance and inductance) of the 
connection between them will be equal to twice that of the distance 
to the center of the star. If that star happens to be ten feet away, 
that's too much R and L. Better to bond them all together following 
the shortest practical path, AND to some local star point, then take 
that to the more distant star point. 

The other grounds that MUST be bonded together for lighting safety 
include metallic plumbing, building structure (steel, if there is 
any), CATV, MATV, telephone, the power system ground at the service 
entrance, your station ground(s), and any lightning rods. It also 
turns out that proper bonding reduces hum, buzz, and RFI in systems. 

ALL of the above is covered by the National Electric Code, which is 
a model building code written by a consortium of EEs, and which has 
been adopted by most local building departments. Grounding is 
covered in Article 250. It is a VERY good code. The only thing I 
would take issue with are a few provisions in Article 810 governing 
the size and type of antenna wires, which I find un-necessarily 
restrictive. 

73, Jim K9YC