[RFI] Long distance grounding

Tom Rauch w8ji at contesting.com
Mon Jun 11 21:22:54 EDT 2007


> Something that has worked for me and a few other hams in 
> the past is to
> take a length of old RG-8/RG-213 NON FOAM type
> coax and hook the center conductor on one end to ground 
> rod and
> center conductor other end to rig area common ground point
> then take a .001 uF Ceramic Disk Cap and connect from
> center conductor to ground at each end ( 2 caps needed )
> ( Foam coax would probably work but I generally avoid 
> using
> it unless I need low loss in a system - it has a bad habit
> of wicking up moisture if not sealed properly or 
> gravitaing the
> center conductor towards the shield in a tight bend !)
> Maybe some one on the reflector will let us know why it 
> works
> most times.

Oh boy! One of my favorites! :-)

The center conductor does nothing at all Dennis. You can 
throw it away. Same for the capacitors. Skin effect keeps 
all the current on the outside of the shield. Since you 
don't have any differential currents and there isn't any way 
to create them, you can't force any current inside the 
hollow cylinder called the shield.

So what you really have is a round braid that is much larger 
diameter than a thin wire, so better than a thin wire, but 
nowhere near as good as a wide flashing would be.

As a matter of fact if you could pull the guts out of the 
cable and throw them away without having the cable collapse 
it would work the same.

The rest is pure fantasy as Faraday, Lentz, Maxwell, and 
others would tell you if they were still alive.

73 Tom 




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