[time-nuts] Thoughts on lightning protection measures....

[Bob Camp]

Hi

The lightning hit is both a great big voltage and a wallop of current. The
voltage is the thing many people get worried about. Almost all of the damage
I've had has come from current induced into near by conductors and similar
magnetic field issues.

That said, the voltage spike has likely jumped several hundred feet to get
into the vicinity of your house. Hopping from this to that while trying to
run through the house is trivial compared to the distance it's already
traveled. 

There are indeed ways to take care of this stuff. Some systems are set up
for a "how many strikes per hour" type of operation. They do indeed run
properly in a high hit rate environment. You do *not* want to foot the cost
for an installation like that. Having the (insured) house burn down is much
cheaper ....

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of MailLists
Sent: Thursday, April 12, 2012 11:22 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thoughts on lightning protection measures....

You're right, but it's highly depending on the used construction 
materials... The building I live in, is quite like a Faraday cage - 
reinforced concrete. Even higher frequency radio signals have a tough 
time entering, mostly through the windows.
What I wanted to underline is that, even if the house would be build 
like a Faraday cage, any conductor from the outside represents a 
potential dangerous ingress path.

Of course, the generated fields would affect any sensitive equipment, 
but with the low impedance path of an antenna cable, even the less 
sensitive ones could suffer catastrophic failure. Not to neglect are all 
the other conductors entering from the outside - power lines, metallic 
pipes, etc.
"Full protection" is quite difficult, almost impossible, to obtain, but 
an antenna cable is the preferred path.


On 4/12/2012 6:02 PM, Attila Kinali wrote:
> On Thu, 12 Apr 2012 17:39:57 +0300
> MailLists<lists at medesign.ro>  wrote:
>
>> Regarding the TBs, even if they are the only ones directly connected to
>> the antenna, the cable is already punching through the house Faraday
>> cage, and chances are quite high that the lightning discharge won't stop
>> at them.
>
> A house isnt a faraday cage. Not by far. Unless you live in a box made out
> of solid 5mm steal plates.
>
> If a lightning hits your house directly and is going down the lightning
> rod down into earth there is a good chance that the electric and magnetic
> fields you have in the house will fry sensitive electronic equipment....
>
>
> 			Attila Kinali

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