[TowerTalk] Coax Grounding

[jeff millar]

Hi Tim...

I'll take a shot at this.

   - Ground rods are a standard practice but they don't really do much when
   typical lighting current hits 1 to 100 KiloAmps
      - 1 ohm ground rod and 1 KA is still 1000V...and real ground rods are
      not that good
      - Mountain top installation use a ground grid with many ground rods,
      but they still mount the equipment on a wooden platform to prevent arcing
      to the concrete
   - The real trick is to bond the coax shields, AC power ground, and any
   phone or internet to a common ground plate
      - Mountain top installation use a large copper plate with all the AC
      outlets, Modems, Coax feedthru, etc on the plate
      - They also wrap the room near the floor and ceiling with a ring of
      copper bus to keep everything a the same potential
      - The idea is to admit that the shack will jump to 10 KV above ground
      on a strike, but to ensure it all jumps together
      - Keep that in mind as you sit at the radio with your feet on the
      floor and headphones on your head
   - For an amateur installation, run the coax to a common bus bar and
   connect that bus to the Rig ground stud with wide flat cable
   - The flash tube lighting arrestor is good for dipoles that do not have
   a good DC connection from center conductor to ground
      - I recall seeing sparks jump to the concrete floor from the center
      pin of a PL-259. It was connected to an 80M dipole.  The sparks jumped
      about every second.
      - For many beams, the center conductor is a good DC ground for the
      KHz and low MHz lighting frequencies
   - There are two types of lightning in the shack to worry about
      - 1) Comes in the tower and goes out to the ground, water pipe, well,
      power ground, etc.
      - 2) Comes in via the power line, cable line, water pipe, etc.  and
      then goes out through the feedlines and tower
         - The tower is a good radiator for fast rise time energy entering
         the house
         - I lost a bunch of stuff when the house down the street was hit.
          (chimney, blew the clean-out door across the room)
         - Anything with a long wire connected to the power failed: Radios,
         telephone, door bell transformer, garage door opener,
thermostat transformer
         - Also a 8 inch diameter plasma burn on the outside of the house,
         opposite where romex was coiled for spare circuit

jeff, wa1hco

On Mon, May 9, 2016 at 5:29 PM, Timothy A. Holmes <taholmes160 at gmail.com>
wrote:

> As I am rebuilding the tower, I want to install proper (or at least
> reasonably proper) lightning grounding on my coax lines.
>
> My impression of what I have read over the years is that I need a ground
> stake near the enterence to the shack with gas discharge tubes on it for
> each line of coax.  Right? wrong? totally out to sea?
>
> Is there something else I can / should be doing without totally breaking
> the bank? (Yes, I know whatever it is is cheaper than replacing the house,
> but im talking REASONABLE risk (The tower will be shorter than the
> surrounding trees))
>
> Also, what type / brand of discharge tubes should I use, I notice a
> disparity in price -- Again, I want to be reasonable -- As noted, I am near
> DXE and would prefer to use their stuff as I can pick it up and save
> shipping
>
>
> Thanks
> TIM
> W8TAH
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