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[TowerTalk] static drainage

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Subject: [TowerTalk] static drainage
From: (Tom Anderson)
Date: Mon Jan 27 12:02:03 2003
Jon, Pete:

If you're disconnecting the coax outside, don't forget about the equipment
grounds.  Several years ago a friend of mine in Arlington TX had all of his coax
disconnected when lightning hit the top of his 60 ft. tower.  The surge came 
the tower and into the ground underneath his house and came back up his 
ground located on the opposite side of the house from the tower.  It fried
everything he had common point "grounded" in the shack, including his Icom 751A.

Tom, WW5L
Colleyville TX

Jon Ogden wrote:

> Pete,
> There's been HUGE discussions on the danger of disconnecting for lightning
> protection.  A pulse on your feedline could literally jump through the air
> in your shack looking for that lowest resistance path to ground.  And if you
> disconnect via relay or switch, I doubt you get much protection there.  The
> pulse would probably arc over your relay or switch and go right through your
> equipment.
> You want to do all you can to prevent the lightning from entering your house
> or shack.  Relays, filters, chokes, etc. inside the shack just aren't safe.
> If your RF safety choke in your PA takes a strike, it will probably blow the
> heck out of that choke and possibly a good part of your amp.  If I remember
> correctly, those chokes are pretty high inductances.  Lighting doesn't like
> high inductance and may not even take that path.
> Unless you disconnect outside your house/shack and physically remove the
> cables, then I'd be very concerned.
> Additionally, with the disconnect method, you either have to unhook all your
> cables every time you leave the shack or risk having a storm/strike sometime
> when you are not home, etc.
> Even if you still chose to disconnect, having surge protectors outside the
> shack at the tower base or at the place where you have your SPG is a MUCH
> safer idea.
> 73,
> Jon
> NA9D
> on 1/27/03 10:01 AM, Pete Smith at wrote:
> > At 09:00 AM 1/27/03 -0600, Jon Ogden wrote:
> >> Agreed.  With such protectors (ICE and Polyphaser both have DC grounded
> >> models) there is no need for any other form of static drain.  Plus, I've
> >> been told that with continuous static drain, it makes your receive quieter
> >> as you aren't hearing any noise from static build up.
> >
> >
> > On the other hand, I have consciously opted for the "disconnect everything"
> > method of lightning protection.  Given that, couldn't I simply shunt an RF
> > choke to ground inside the relay box at its output jack, so that any time
> > an antenna is connected by relay, any static goes immediately to ground
> > before it gets upstream to the radio?  For that matter, as long as I am
> > using my amplifier, which has an RF safety choke to ground, don't I get
> > equivalent protection?
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
> Citizen of the People's Democratic Republik of Illinois
> Life Member: ARRL, NRA
> Member:  AMSAT, DXCC
>   <- Updated on 1/22/03!!!
> "A life lived in fear is a life half lived."
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> TowerTalk mailing list

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