[TowerTalk] Ground Rods

[Jim Lux]

At 08:07 AM 5/4/2004 -0700, Bill Turner wrote:
>On Mon, 3 May 2004 18:38:26 -0600, Grillo's wrote:
>
> >One of the calculations I was looking at can drop impedance from 300 
> down to 5 ohms with using only 4 of these rods.
>
>_________________________________________________________
>



>This reminds me of the school of thought that says the connection to
>your ground rods must be tight.  As if lightning, having traveled
>thousands of feet through the air, is going to be stopped by a gap of a
>few thousands of an inch.

I suspect that this is for dissipating an induced voltage (not a direct 
strike).  As a practical matter, there are probably more "nearby" strokes 
that cause problems than direct hits.

Direct hits are more rare (difference between being the bullseye and 
hitting the target anywhere)

With a direct hit, as you say, the lightning finds a path to ground, and if 
your equipment gets damaged, it's probably not a little damage, but a 
significant "exploded front end" kind of damage.

With an adjacent hit, where you just got a few kV (or even a few hundred V) 
transient on the antenna connector.. enough to cook the input mixer, 
perhaps partially, or to partially cook something else.

The advice to ground the radio input when not in use comes more from the 
"protect the delicate receiver from middling transients" than the "protect 
the rig from exploding in a direct hit".