Topband: Vertical Lightning Protection

Donald Chester k4kyv at
Wed Jan 5 19:07:05 EST 2005

> > I have had a large
> > vacuum variable capacitor
> > in place to do the job for several years, but lightning took its
> > toll
> > last spring. I thought I had
> > ample protection...a 350uh choke across the base insulators to drain
> > off static build-up,

It's not static build-up that causes the damage from a  lightning surge.  It 
is the electromagnetic pulse radiated directly from the lightning discharge. 
  We once had a near hit, and it magnetised my computer screen so badly that 
I could see large bright yellow, violet and green spots all over the 
display, although it otherwise worked ok.

Most significantly, the computer and phone line modem were all completely 
disconnected from the power and telephone lines at the time.

When there is even a remote liklihood of thunderstorm activity and I leave 
my antenna system unattended, I disconnect everything using large knife 
switches, and ground to the radial system.  I also have a heavy duty spark 
gap across the base insulator, and a static discharge rf choke is in place 
whenever the system is in use.  In over 20 years, my most serious lightning 
damage was a burnt-out carbon resistor in my receiver's outboard rf 


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