Faraday Cages

[KG7ENF - Mike]

Great subject last night on the net regarding building Faraday Cages, lots of good information shared.  Great for me as it was my first net as I am a new member.

A question I brought up was how do we know, after building one, if it really works.  So I agreed to do some testing and report the results.

I spent a lot of time with my friend Google after the net and found some interesting, builds and a method to test your build.  The basic test is to put a FM radio on a stong channel, place in the Cage and close it up and see if you hear the radio, simple.  Need to know if others have other methods of testing your final build.

So next was to build one and the more I researched how to build one, I realized I already had a great Faraday Cage in my garage.  I use a gun safe to store my "stuff".  So I put an FM radio in the safe and closed it up.  It cut the signal off completely.  The safe is also bolted to concrete floor, so has a pretty good ground.

So you may have a Faraday Cage you can use now to store radios etc.

Lets keep the conversation going.

Ken thanks for hosting the net last night!

Mike Vonada
KG7ENF

[TWP]

Mike,

First, welcome to the forum and thanks for your input.

Re your gun safe, please be aware that there is a "crack" at the door seal, all the way around the door.  This is where the EMP will gain access to the content.

It can be sealed by several means, all of which require that a metal to metal contact be made all the way around the gap.

Some options are copper or aluminum foil.  There is a lot of information online about this.  It applies to any Faraday cage which has a door, lid or other access port.  For example, ammo cases, garbage cans, safes, etc.

A warning, if there is a non-conductive seal (a rubber bumper or water proofing for example) around the door, this is a "hole" in the EM barrier and should be either removed and replaced or covered with a conductive (metal) lining.

If you will recall from the 'net discussion, earth grounding is less of a factor in EMP shielding.  Grounding offers a current path, useful for diverting the electron current of lightening strikes, but an EMP is a field (Electric and Magnetic) which induces current directly in conductive objects, even very small items, such as semiconductors and the associated wires around them.   That induced current will heat (possibly melt) wires and semiconductor crystal structures. It doesn't need a complete circuit to flow.

An example of how this works is electromagnetic heaters used in medicine to warm the human body.  There is no current path, but just repeated EM pulses which move electrons back and forth.  An induced EMP (either nuclear triggered or by CME) is one, very strong, pulse which pushes and pulls electrons in a conductor.  That very high momentary current, back and forth, heats the conductor.

[KG7ENF - Mike]

Good stuff, and thanks for the replied.  Work in progress, right now.

[Ken K7KBJ]

Wednesday's session of the Northern Nevada Preppers Group Net has been posted.
We talked about the prepper's Faraday Cage.
Here's your link:   http://nnpg.net/022217_radio.shtml

Here's the Chat Room transcript:

NNPG - The Northern Nevada Preppers Group Chat

7:43:01 PM
Ken K7KBJ joined the channel
7:52:00 PM
Ken K7KBJ
Tonight's topic is The Faraday Cage
7:56:22 PM
TWP joined the channel
7:56:29 PM
TWP
Hi Ken
7:56:32 PM
Ken K7KBJ
Hi TWP
Tonight's topic is The Faraday Cage
Practicing my typing
7:57:07 PM
TWP
Thanks, I got the notice too.
7:57:35 PM
Ken K7KBJ
I know. I emailed it :-)
7:58:08 PM
TWP
That would be why your name was on it! <g>
7:58:26 PM
Ken K7KBJ
Dang! So much for OPSEC
hahahahahahaha
7:58:53 PM
TWP
Next time, remember to use your secret identity...
about one minute?
7:59:50 PM
Ken K7KBJ
10 sec
8:00:16 PM
TWP
Light the fuse.
8:01:31 PM
N7SAX joined the channel
8:01:43 PM
TWP
Hi SAX
Ken, REOC???
8:04:01 PM
N7SAX
Sorry I checked in early again I'm in as an administrator
8:04:30 PM
TWP
No problem, you're just 'special' <g>
8:04:32 PM
N7SAX
I tried logging off and it doesn't change anything
LOL
8:05:28 PM
TWP
I logged in before you, so that isn't the cause.
8:06:22 PM
N7SAX
Any suggestion(s)?
8:06:59 PM
TWP
Re being admin? Nope, just wield power wisely....
8:07:18 PM
N7SAX
LOL
'been talking to Jerry and learning a fair amount about Faraday Cages
8:08:48 PM
TWP
He is the "source" for just about everything prepper.
8:09:22 PM
N7SAX
Yes indeed
8:09:36 PM
kb6dkv joined the channel
8:09:46 PM
Ken K7KBJ
Hi DKV !!
Tonight's topic is The Faraday Cage
8:09:59 PM
N7SAX
Hi Ken
8:10:04 PM
Ken K7KBJ
Hi SAX
8:10:51 PM
TWP
Hi DKV
Jerry sounds kind of "stuffed up"
8:12:36 PM
Ken K7KBJ
He has the flu
8:13:07 PM
TWP
Got that, It's going around...
I mean "understood" not that I have it too.
My one Faraday cage is a cardboard box, 12in x 12in. covered in Aluminum foil. Inside I put my spare power supplies, modems and computer wires (adapter cords, power cords, etc.).
Each item is in a plastic bag which is also wrapped n Aluminum foil. This is a double conductive layer with no holes larger than the width of a human hair.
Sorry, no pictures
8:22:01 PM
Ken K7KBJ
I'm wondering if a Faraday cage can offer some protection from a nearby lightning strike
8:24:37 PM
TWP
Ken, Yes, it would, however a direct hit on the cage would melt the conductive shield. The magnetic field around the lightning bolt would be shielded from the cage content.
8:25:07 PM
Ken K7KBJ
that seems reasonable
8:25:23 PM
TWP
This is where the question of grounding is a big factor.
If the cage is grounded, it will attract a nearby strike.
8:27:53 PM
Ken K7KBJ
here's a cool link for some copper gasketing......
https://leadertechinc.com/products/enclosure-products/beryllium-copper-fingerstock/?gclid=CjwKEAiAirXFBRCQyvL279Tnx1ESJAB-G-Qv8SzcXh84lVdE-0ARFgZ_jeinNiALYRfhG1h9BGoVqxoCbeTw_wcB
beryllium is very tough and like a spring
8:29:27 PM
N7SAX
This is from Jerry:
http://hollandshielding.com/Section-13-Foam%20rubber%20sheets
Also:
https://www.twpinc.com/wire-mesh-material
We should have a Faraday Cage workshop
I have learned a lot recently
8:32:13 PM
Ken K7KBJ
absolutely !!
8:32:19 PM
TWP
SAX, yes, good idea
8:33:20 PM
kb6dkv left the channel (timeout)
kb6dkv joined the channel
8:35:43 PM
N7SAX
Lead acid auto battery vulnerability is controversial, some say they need to be "dry" or buried 5' deep or more a CERTAIN authority states that lead acid batteries are not vulnerable to an EMP/HEMP
8:36:50 PM
TWP
Depends on whether the batteries are in circuit. Stored unconnected, they are relatively immune.
The problem is induced current in conducters.
8:38:14 PM
kb6dkv left the channel (quit)
kb6dkv joined the channel
8:39:44 PM
N7SAX
We need to develop a curriculum from which we all can learn the fundamental physics involved that will render us with the elusive understanding that must be fundamental once principally understood. Sorry for the verbosity...
8:40:20 PM
TWP
We are learned here, message received...<g>
Jerry has a lot of written material which would answer most questions on this subject
8:44:41 PM
Ken K7KBJ
Jerry Be Da Man !!!
8:45:13 PM
N7SAX
Our community (in my opinion) needs a Primer that simplifies the energy behavior of an EMP/HEMP so those of us who are not can come to understand and visualize EMP/HEMP energy "waves" such as we understand and visualize aquatic waves...
8:45:24 PM
Ken K7KBJ
If you don't know, he has an incredible number of books he has written. Really fun reading! Google him. Jerry D Young.
8:46:23 PM
N7SAX
sorry for the typos
8:46:59 PM
Ken K7KBJ
We are very informal here !
The education flows from Jerry like that lava hose in Hawaii !!!!
Hot, awe inspiring and never ending !!!
8:48:58 PM
TWP
SAX. the "primer" would be Physics 201, It could be done in a classroom situation, but harder to pick up from just the book.
8:49:35 PM
N7SAX
I only did 101
and few people have got that far
8:50:48 PM
TWP
Listening to Jerry right now and you get some idea of how and what needs to be in said primer. Jerry has some relatively low level documents about this whole subject
8:52:53 PM
SpeyPage joined the channel
8:53:19 PM
Ken K7KBJ
Hi SpeyPage !
That's an odd name.
hahahahaha
8:53:38 PM
SpeyPage left the channel (quit)
8:53:47 PM
Ken K7KBJ
By SpeyPage
8:53:51 PM
TWP
Hi SpeyPage Bye SpeyPage
8:53:54 PM
Ken K7KBJ
It was fun while it lasted
Guess we scared it off
8:54:08 PM
TWP
Was it something I said?
8:54:25 PM
Ken K7KBJ
Maybe I need to shower more often
8:54:47 PM
TWP
Change soap?
8:55:01 PM
Ken K7KBJ
Or just use some
8:55:46 PM
TWP
But that's the prepper way....
9:00:08 PM
N7SAX
Perfect example GPS
9:00:53 PM
TWP
If the GPS satellites survive an EMP or CME event
The mapping units have internal memory files and don't need the satellites
9:02:49 PM
kb6dkv left the channel (quit)
9:03:04 PM
N7SAX
As long as the handheld units are not fried
Thanks everyone, Jerry, Get Well Soon, please let me know if you need any assistance...
so long, 73
9:06:30 PM
Ken K7KBJ
Good Night !!!!
9:07:47 PM
Ken K7KBJ left the channel
9:06:43 PM
TWP
Good net Ken, thanks

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[Jerry D Young]

Finally able to get out and get on the internet for a bit. Attached are some of my thoughts on EMP and Faraday cages. Some of it is rather jumbled, being a collection of short to long posts on various forums in response to questions asked.

Here are some links that did not make it into the .pdf

If you are contemplating doing a full room, or even a whole house, this double sided foil, if installed correctly, creating a full 6-sided bonded box, properly grounded, could be used:
http://dennywholesale.com/245-denny-foil-double-sided-vapor-barrier-pallet-pricing.html

One source for the recommended 20opi copper mesh:
https://www.twpinc.com/wire-mesh-material/copper


http://www.majr.com/
http://www.lessemf.com/mag-shld.html


Everything is just my opinion.