[Elecraft] Lightning Strike - Metal Roof attracts?

Wed Sep 14 20:00:39 EDT 2011

An alternative to unplugging everything -- create a system where 
everything will be at the same potential through a surge event and you 
will have no damage.

Run a #4 (or larger) perimeter wire around your house (and any other 
buildings) with a ground rod at each point where it changes direction, 
connect it with #4 wire to everything metallic in your house structure 
or outbuildings, and then connect it to the 3 or 4  #4 wires radiating 
from each of your towers or masts - those radial wires should have 
ground rods connected at intervals not exceeding twice the length of the 
ground rods.  (8 foot rods spaced every 16 feet, or 4 ft rods spaced at 
8 foot intervals, etc.).  The length of the radial rods should be at 
least as long as the tower or mast is tall.  Oh yes, all these grounds 
must connect to the utility ground rod(s) for the house.  Anything 
metallic in the house (including the roof if metal) should connect to 
this ground system).  Install a "whole house" surge protection device at 
the electrical panel. and put surge suppression devices on incoming TV 
antenna, cable TV/internet lines, telco lines, etc.

In addition, all lines coming into the station should enter through a 
"grounding window" (a copper or aluminum panel) where your coax 
lightning protection devices are mounted, the station power comes 
through this panel too with a surge protection device (do not skimp on 
the quality), all telco and ethernet, rotator cables, remote antenna 
switch wires, (everything entering the station). also come through this 
panel and each conductor is equipped with an MOV or similar protective 
device.  The panel is connected to one or more ground rods (also 
connected to the perimeter wire and the utility ground point) with good 
low impedance ground strap (only gentle turns).  In other words, 
*everything* within the station has its connectivity routed through that 
grounding window, and every piece of equipment in the station and within 
reaching distance of the operating position is tightly bonded to that 
grounding window, and all the ground wires and rods are connected to 
each other.

If you do all those things, you may not have to disconnect everything 
from your transceiver during a lightning storm.  As an added benefit, 
you may eliminate many hum sources in your station's audio system, and 
the locally generated noise may be reduced.

I know all of that is not practical for some existing structures, but 
take the recommendations as intended, and know where your deficiencies 
are, then do what you must to protect your home and equipment.  I have 
some of that system in place or in-plan for the near future, but I still 
do not operate during a lightning event. Each transceiver is connected 
to a dummy load automatically when I remove power from the antenna relay 
system for additional protection.

A bit of planning will provide you with some protection, but whatever 
you install, do not depend on it with your life - there will most always 
be some deficiency, so do take reasonable precautions during an 
electrical storm (stay away from the operating position).

Look at the Safety section of the newer ARRL Handbooks, and review the 
information on station protection at the Polyphaser website for more 
detailed information.  Ron Block has provided some good information 
regarding these practices in QST several years ago, sorry but I cannot 
recall the year, but it was a 3 part article.

73,
Don W3FPR

On 9/14/2011 7:03 PM, Sam Morgan wrote:
> just curious
> how many things (actual number please)
> do you unplug from both your K3 and the computer/router?
>
> I know my K3 has 14 or more cables to it
> and the radio computer has to have at least that many again
> the firewall computer in the other room has 6
> and the router has 3
> then there is the other computers
> and the hub......
>
> not saying it's not a good idea
> just wondering if I should some how simplify my life?
>
> GB&  73
> K5OAI
> Sam Morgan
>
> On 9/14/2011 5:17 PM, drewko wrote:
>> I think i've posted this before: During lightning season I disconnect
>> everything from my K3 when it is not in use, including headphones and
>> key. Same goes for my PC and router. I leave no cables connected to
>> any of these boxes. It is a bit annoying, especially at the start of
>> the season when I have to get used to the disconnect/reconnect routine
>> all over again. But the alternative is as you have found: the rare
>> close strike probably means everything that is connected will get
>> taken out.
>>
>> We also experienced a lighting storm Sun night, here 150 miles to your
>> east. Maybe it was just the awareness of the dreadful anniversary but
>> I remember thinking that it sure was some unusual sounding thunder:
>> the rumbles were long and building rather than quick and decaying.
>>
>> 73,
>> Drew
>> AF2Z
>>
>>
>>
>>
>> On Wed, 14 Sep 2011 15:55:31 -0400, Alan wrote:
>>
>>> Hello,
>>> Unusual electrical storms here on top of hill on Sunday evening (9/11).
>>> On Saturday, the roofing contractor finished putting half of metal roof
>>> on house. Received lightning strike to roof (I think), but saw flash
>>> onto front walkway. Heard explosion right at my wall. Couldn't find
>>> point of hit though. Roof was finished Monday.
>>>
>>> Is that new metal roof a target for the next storm? Never had a
>>> lightning strike near here before this.
>>>
>>> For the curious: Damage was everything connected to my LAN ... Apple
>>> MBPro, Mac Mini, MacPro I/O, router, hub, soundcard connected to K3 on
>>> old Windows PC. The K3 ant and power were disconnected (but two audio
>>> cables from old PC were connected to K3): my K3 is shot and on its way
>>> to Elecraft. A Comcast TV box was shot, and the tel and Internet all
>>> needed reset from Comcast. Still finding problems ...
>>>
>>> Limping along with old Win-2000 PC.
>>>
>>> Cheers, Alan
>>>
>>> Alan D. Wilcox, W3DVX (K2-5373, K3-40)
>>> 570-321-1516
>>> http://WilcoxEngineering.com
>>> http://eBookEditor.net
>>> Williamsport, PA 17701
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