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[TowerTalk] Sparky Pays a Visit

To: <>
Subject: [TowerTalk] Sparky Pays a Visit
From: "Gedas" <>
Date: Mon, 1 Aug 2005 20:12:31 -0500
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Hi everyone.  I wanted to share with you a lightning strike incident which 
occurred to me last week Tue afternoon.  I thought I had done a pretty good job 
protecting against lightning so this came as quite a surprise.  I'll try to 
give you a run down of the antennas and shack as it pertains to grounding.

I have 3 towers up, one at 80', one at 50' and one at 70'.  Each is a Universal 
Aluminum self supporting tower which I have supplemented with a single set of 
3/16" steel guy wires about 2/3 of the way up.  Each tower leg has it's own 10' 
ground rod connected with a 3' length of #0 wire.  The towers are each 
separated by 130' and are in a straight line configuration.  The 80' tower has 
a short 40m rotatable dipole at 90'.  At the 80' level I have suspended an 
inverted vee for 75m.  Each of these was fed with not quite 300' of 9913F type 
coax.  The cables were currently lying on top of the grass as I had just 
installed them 2 weeks earlier. I was just starting to play on HF after many 
years on VHF SSB and MS.  The 70' tower has a new X7 at 75' and the 50' tower 
has a pair of 17B2 on Az/El for moonbounce.

All rotor cables and coax from all towers terminate to a 18"x18"x1/8" Aluminum 
panel I have in place of one of my basement windows.  The panel is at around 
ground level and uses N-type feedthrus. The panel has 2 mechanical connections 
for ground.  Each one has attached a 3'-4' length of #6 wire that goes to 2 10' 
long, 3/4" copper pipes.  The panel thus has 4 ground rods.  When I am not 
using the shack all cables and coax are physically disconnected from the panel 
(from the inside) and separated from the panel by a foot or so. For almost 10 
years this setup has seemed to serve me well and I recall riding out some 
terrible storms with tons of hits all around the QTH with no misfortune.  All 
equipment was connected to AC power but not turned on.

This last Tue afternoon a fast moving storm with a large amount of 
cloud-to-ground strikes moved directly over the QTH and the 80' tower took a 
hit.  My wife said it sounded like a grenade went off inside the house.  She 
made her way downstairs only to find the entire basement 100% filled with thick 
smoke. Visibility was VERY poor. She was afraid the house was on fire. Once I 
got home I looked things over and discovered that I overlooked a small folded 
dipole made of TV twinlead that I had tucked into the blinds just above the 
panel.  The dipole was purely indoors and was not touching the panel.  My guess 
is that it was several inches away.  The panel became highly charged and arced 
over to the dipole.  The dipole was NOT terminated but ran close to my Aluminum 
radio shack speaker for the FT-990. The speaker wire conducted the arc into the 
rig.  Half of the dipole is missing. Half of the speaker wire is also missing. 
The connector on the back of the FT-990 got blown out and t
 he back of the rig looks like it was hit with a flame thrower for about 10 
seconds.  The rig is dead.  Of course the AL-1200 was next because it was 
connected to the FT-990. Once it got into the 220 mains it found the Commander 
II VHF amplifier.  The tailtwister rotor is shot as are the coaxial cables from 
that tower. Some additional items such as 2 routers, PC interfaces, ATV 
transceiver etc are also DOA.

This has taught me that my towers are not very well grounded nor is my entrance 
panel.  It also has shown me that anything located near the panel is vulnerable 
to flash over.

I take this opportunity to share this with you in the hopes that you can learn 
something from my experience and keep yourself and your equipment safe.


online gallery
web page

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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