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.
Although I guess you could call it a Faraday Cage, these really are not
effective at the frequencies operated (160through UHF), but I'd think a
fairly effective lightening protection protection cage could be built
using #3 rerod (about 5/16ths) with the rods laid out using 6" to 12"
spacing, (my personal preference = 6")vertical and horizontal with each
crossing junction welded. I'd make the door the same way with it bonded
on the hinge side using copper braid with the other side camming tight
against a conductive vertical member The whole thing could be covered
with aluminum window screen (on the inside of the rerod) to create a
real Faraday cage although I don't see any advantage in doing so.. I'd
cover the outside with Vinyl siding for appearance. Finish off the
inside like normal construction. You are probably looking at $300 +/-
for rerod and welding every junction is a lot of welding although each
weld is small.
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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