[TowerTalk] Lightning Protection

[Jim Lux]

On 7/8/13 7:18 AM, john at kk9a.com wrote:
> I also have a shack on the 2nd floor and I also disconnect all cables
> going to the tower. I only use the station for major contests so doing
> this is not really inconvenient. Disconnecting however is not a reliable
> means of protection as the energy can be induced into anything nearby. I
> am not sure if there is any way to stop this from occurring. Even if you
> disconnect it is a good practice to have multiple lines of ground rods a
> single point ground and MOVs or GDTs on every rotator and relay.
>
> John KK9A
>


I'm not sure about the value of the multiple lines of ground rods *from 
the entrance panel*.  I just don't see the physics of what it's doing 
there.  The goal at an entrance panel is to have everything tied to one 
reference voltage, and let that go up and down.

For fast transients, the inductance of the wiring to the ground is going 
to be dominant impedance, not the resistance to "earth".

Consider that lots of communications installations are on the top floor 
of a tall building, and have essentially NO direct connection to ground. 
  (for instance, the TV transmitters in the Empire State Building, where 
the antennas have been hit countless times.. so often that lightning 
researchers hooked up stroke recorders to them)


Transient suppression devices to suppress differential mode, most 
definitely. But to "chassis"?  I'm not so sure it's useful.