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Re: antenna rig and Lightning



Demos,

I agree to a point.  I have all my coax cables going into the shack and
routed to Alpha Delta coax switches with gas discharge units.  All
pieces of equipment are grounded to a common point with same length
cable, and this point is routed to a three point ground system in the
ground outside the shack.  

I prefer DC grounded antennas if they are in the clear.

Remember that lightning comes from the ground up.  Streamers of
electrons rise towards the clouds, and a bolt follows this trail as a
return stroke.  Any free standing piece of metal will develop a
potential, and send streamers towards the clouds.  A long piece of wire,
insulated from ground will develop a tremendous potential.  If you bleed
off these excess electrons, you dramatically reduce your risk of being
struck.

A dipole, disconnected from the equipment, and coax thrown on the floor,
will arc across the connector, if the coax shield is grounded.  I used
to have a long wire terminated in a length of coax.  I disconnected it
from the rig when not in use.  The radio was in my bedroom.  One early
morning, while the wind blew, and a storm brewed, I kept hearing a snap
and seeing a blue light.  Once I came to my senses and saw what was
happening, I ran to the kitchen and grabbed a hunk of aluminum foil.  I
jammed it into the connector to force the center conductor to ground,
and eliminate the building potential.  It takes electricity 10,000 volts
to jump a 1/8" gap through air.  I think I came very close to blowing
the back wall out of my house that day.

Every person who has ever been hit by lightning talks of their hair
standing up immediately before being struck.  They were actually sending
a stream of electrons towards the clouds, and were struck by a return
stroke.

73, Mike


Demos Doulou wrote:
> 
> Hmm,  I have never disconnected anything for over 20 years and have never
> had a lightning induced problem from either the antenna,power or phone
> lines.  Of course everything has the best surge protectors and ups system I
> can afford and all are hooked to a central common point ground.
> 
> My opinion is if you have everything connected to surge protectors and
> grounded CORRECTLY, you will not have any problems  except from maybe a
> direct strike and even with everything disconnected you may lose equipment
> from that.
> 
> 73
> 
> Demos KR4US
> Tampa Bay Florida, Lightning Capital of the States
> 
> -----Original Message-----
> From: Roy Welch <rdwelch@swbell.net>
> To: amsat-bb@AMSAT.Org <amsat-bb@AMSAT.Org>
> Date: Thursday, May 27, 1999 3:23 PM
> Subject: Re: [amsat-bb] antenna rig and Lightning
> 
> >My two cents worth.
> >
> >I have a fused disconnect box on my operating desk which opens everything
> >from the power mains with one throw of the knife switches.  I disconnect
> >all coax leads during bad weather.  I disconnect my modem (internal) from
> >the phone line and I unplug the PC at the wall socket.  HOWEVER, I forgot
> -bb" to Majordomo@amsat.org
> 
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> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

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