[TowerTalk] Fwd: Shielded shack

Sat Sep 28 13:27:51 EDT 2013

The idea is not to let any current through the aluminum foil. ALL connections to the foil is in ONE point, the point there everything is entering the shack. I do not believe tht the foil would protect the shack from a direct lightning strike. What is the possibility that will happened anyhow with a 85 foot tower next to it. OK, never say never!

My idea is to protect the gears inside the shack when lightning strikes the tower. I don't believe the current going through the foil will be that high. It is determined by the capacitance between the shack and the ground, and the rise time of the voltage, right.

Presently, I have an aluminum plate under my radio equipment to which everything is grounded. The plate acts like a "half" Faraday shield, and I believe that arrangement saved me a couple of times. (I have had three (3) know direct strikes in my house and have learned the hard way how to protect electronics; telephones, stereos, etc.) I have not lost any ham equipment yet.

Grounding of the foil will be via a conductor connected to the tower. Hope that is not against any code.

73 de,

Hans - N2JFS

-----Original Message-----
From: Roger (K8RI) on TT <K8RI-on-TowerTalk at tm.net>
To: towertalk <towertalk at contesting.com>
Sent: Sat, Sep 28, 2013 11:56 am
Subject: Re: [TowerTalk] Shielded shack

On 9/28/2013 1:51 AM, Grant Saviers wrote:
> If it is lightning protection and not RFI shielding that is desired, 
> then what is done for explosive magazines ought to be enough!
> http://www.seftim.fr/publications/DDESB/17-3-LIGHTNING_PROTECTION_FOR_CRITICAL_EXPLOSIVES_OPERATIONS.pdf 

> has many references, but there are older documents I've seen in prior 
> google searches.  e.g. http://www.apd.army.mil/pdffiles/p385_64.pdf  
> Or standards for protection of petroleum storage facilities.
>

Remember you are building a cube and all 6 sides need to be covered.

IE:  It's just a stick built room covered with a grid created out of 
rerod for lightening protection and a LOT CHEAPER than using copper 
unless you don't have a welder and have to hire that done.  That is a 
lot of rerod.<:-))

I'd pitch the foil idea.  Hard to bond reliably, fragile, and very 
little current capacity before vaporizing and setting the "shack" on fire.

I would add, that if the tower or shack ever takes a direct hit, your 
ears will likely ring for an hour or so.  Course, good insulation is 
also good sound proofing.

73

Roger (K8R)

> I would also think that foil is a bad choice as a conductor should you 
> have a strike when #2 or larger is what is commonly used in large 
> structures frequently hit.
>
> On 9/27/2013 8:05 PM, Hans Hammarquist wrote:
>> Gentlemen,
>>
>>
>> I am on the process to build myself a (small) free-standing shack 
>> next to my tower. I am thinking (which usually is dangerous) that I 
>> should "dress" my shack in aluminum foil, making it into a large 
>> Faraday Cage/shielded room.
>>
>>
>> By connecting the foil to the tower and make sure all wires entering 
>> my shack enters through a (relatively) small window I should be able 
>> to make the ultimate lightning protection.
>>
>>
>> What can go wrong with this? The foil will be connected through-out, 
>> walls, floor, ceiling. All the feed-through connectors, surge 
>> protectors etc will also the connect to the foil. I will using a wide 
>> aluminum strip to connect the tower to the foil. Yes, the tower has 
>> nine (9) gounding rods, so I believe that is OK.
>>
>>
>> Any feedback?
>>
>>
>> 73 de,
>>
>>
>> Hans - N2JFS
>> _______________________________________________
>>
>>
>>
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