[TowerTalk] [RFI] Back of desk grounding buss

[Jim Brown]

On 3/21/2014 9:02 AM, Jim Lux wrote:
> So, maybe we should be focusing more on 60 Hz bonding and whether it 
> can take the fault current from a MV distribution line that contacts 
> your antenna. 

Hi Jim,

I think most would agree that we should prevent that possibility by how 
we locate antennas.

With respect to your earlier post, "short, fat" to me means the braid 
stripped from TX coax, which is roughly equivalent #10, or #12 stranded. 
Yes indeed, at the frequencies of lightning, inductance dominates. But 
the emphasis on low resistance is for bonding to minimize potential 
differences between equipment with unbalanced connections for baseband 
signals (audio, control, data) that are the result of mains power 
leakage currents. When you do this bonding, and do it well (short, fat) 
you completely eliminate the need for transformers to kill power line 
"buzz."

Yes, magnetic coupling can induce voltage and current into loops, BUT -- 
when we run a separate chassis bonding wire to some common point, and 
then add a low voltage connection from one chassis to another (coax, 
audio cable, control cable, etc.) we have formed a loop, and it's a big 
one. And since magnetic coupling is proportional to the loop area, big 
is bad.

It is a REALLY bad idea to tie each piece of gear separately to a single 
ground rod -- that creates a really big loop when that equipment has 
cables running between them. Those who advise against "daisy-chain" 
bonding are missing this.

73, Jim K9YC