[RFI] Daisy chain vs Common Ground in Shack

[Ward Silver]

Thought I'd chime in here - my ears were burning

Jim and I see eye-to-eye on equipment bonding.  Among other things, he 
recommends a direct connection between all equipment enclosures with a 
heavy bonding conductor (wire or strap) - this works.  It requires a lot 
of equipment-to-equipment connections but if you're willing to do that, 
it will work fine.  There must be a ground conductor from the enclosures 
to the ac safety and lightning protection ground system.  Jim makes 
things a lot easier by using Powerpole connectors in each conductor (he 
uses green insulated wire and green Powerpoles so the purpose is clear) 
to ease connection/disconnection.  It also helps a lot if you can easily 
get to the back of the equipment.

My recommendation is close - use a heavy RF bonding bus (pipe, strap, 
bus bar, etc) immediately in back of the equipment with short, heavy 
jumpers to each enclosure.  If you can't easily get to the back of the 
equipment, this method is somewhat easier to work with.  The end result 
is pretty much the same with a little bit longer connection between each 
piece of equipment.  There are photos of each method in the book and 
some on the book's website at 
www.arrl.org/grounding-and-bonding-for-the-amateur.

K8RI also brings up a good suggestion - if you want to use the braid 
from old coax, fine, just don't remove it from the old coax :-)  Leave 
it in the jacket and treat it as a really large-diameter wire.  That 
would certainly work.  It's not cheaper than a spool of good old #12 or 
wire stripped from scraps of Romex, but if it's on-hand and you want to 
use it, fine.  Just don't put it where water can get to it - just like 
for RF connections.  I'd peel back about 3/4" of jacket, trim off the 
center conductor and insulator, twist the braid into a pigtail and 
solder it (not crimp) into a crimp terminal.  Maybe dab on some sealant 
to keep water out of the end.  But that seems like a lot of trouble 
compared to using heavy wire.  There is nothing magic about braid - it's 
just trying to be a flexible equivalent to wire and because it's on coax 
we tend to attribute special RF properties to it.  Whatever...

The goal of bonding, however it's done, is to eliminate any voltage that 
exists between pieces of equipment (primarily caused by ac power 
currents and harmonics, lightning-driven transients, and common-mode RF) 
with sturdy connections between them.  This is compatible with all of 
the ARRL's recommendations on grounding, as well, so it's more of a 
clarification than a change in recommendation.  The book goes on to 
illustrate additional techniques for managing RF in the shack, power 
distribution, establishing lightning protection, etc but that's beyond 
the scope of this discussion.

73, Ward N0AX