Another Faraday Cage

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Re: Another Faraday Cage

Postby kmussack » 03 Oct 2016 15:04

I decided to apply my idea and build a FC for my laptop computer.
Using a 20mm ammo can it fits like a glove.
Image
Image
Last edited by kmussack on 13 Jul 2017 13:13, edited 2 times in total.
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Re: Another Faraday Cage

Postby Joe » 05 Oct 2016 08:37

Excellent.
I will be doing the same soon.
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Re: Another Faraday Cage

Postby kmussack » 11 Oct 2016 13:50

It seems this topic was touched on over on survivalblog.com, J.W. Rawles' site.
The following is fully attributed to that site;

Letter Re: How to Convert an Ammo Can into a Faraday Cage
By James Wesley Rawles | August 13, 2013 | Print This Post | Email This Post |
Sir:
I have some of the larger military surplus ammo cans and would like to build my own Faraday cages to store my spare electronics [to protect them from EMP or a severe solar storm]. Do you have any sources to guide me?

OBTW, I just finished reading your novel “Patriots”. That was a great read and I could not put it down. Regards,- J.L. (Former NYPD Officer)

JWR Replies: What you plan to do is is pretty simple, since the can and lid are already great Faraday shields. The only issue is the gap where they join. That joint needs to be conductive, in order to create a fully protective cage. I recommend that you:

1.) Remove the can’s rubber gasket. (Save it, in case you decide to restore the can to water-tightness, at a later date.)

2.) Wearing eye protection, use some coarse sandpaper or a rotary wire brush to remove the paint on at least a 3-inch section of both the top lip of the can and underneath the lid where the gasket was attached. This bare metal will provide a good electrical contact between the lid and body of the can.

3.) Replace the gasket with a continuous thick “fuzz” of stainless steel wool that will just barely allow the lid to to be clamped shut. (Selecting the correct thickness to use takes a bit of experimentation.) The steel wool can be glued in place so long as you do not insulate the short section(s) where you sanded off the paint.

Store items inside wrapped in plastic bags or in heavy duty cling wrap, to insulate them from the can. Use additional padding (bubble pack or gray foam) inside if the cans will be transported loaded with fragile gear.

Do not add an external grounding strap.


I forwarded a link to this thread to survivalblog.com as a contribution.
We'll see if they find any value in it.

NOTE:
Simplicity is the ultimate sophistication.

Clare Boothe Luce

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Re: Another Faraday Cage

Postby kmussack » 15 Jan 2017 07:12

I continue to experiment and build Faraday Cages (FC) to protect my electronic gear.
I've owned an old USGI surplus strong box for years and since getting vaults I haven't had much use for it. It occurred to me that, it being made of steel, it might serve as a FC. There were two holes in the bottom that would have to be plugged so I thought I could do that with nuts and bolts. So while I was at it I bolted this strong box to a two-drawer file cabinet in the "Man-Cave".
Image
Continuity is not essential but the reduction of gaps is the key to resisting the penetration of RF energy. So with flat washers I tightened this interface so as to minimize any gaps. This attachment also keeps the strong box in place.
Then I used paint stripper and steel wool to bare the metal of the strong box all around the opening.
Image
Next I fabricated an overlapping cover for the strong box opening using that same copper sheet plastic laminate material I used for the other FC builds.
Image
Since the width of the strong box exceeded the width of the copper sheet plastic laminate I was forced to join two pieces of the laminate with aluminum tape. Using a multi-meter I learned that the adhesive of this tape is NOT conductive. So again I was relying on gap reduction to exclude RF.
Testing showed the strong box to be RF tight with the overlapping cover in place even before the strong box lid was closed and snapped down.
This FC is handy because it is off the floor, within arm's reach of my radio bench and is large enough to contain all of my first line gear.
Last edited by kmussack on 17 Jul 2017 06:14, edited 1 time in total.
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Re: Another Faraday Cage

Postby kmussack » 30 Jun 2017 04:04

Right now over on Survivalblog.com there is a four part series about how to convert a 20mm ammo can into a Faraday cage.
I imitation is the sincerest form of flattery I'm very flattered, but not cited.
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Re: Another Faraday Cage

Postby mosby's men » 14 Aug 2017 18:17

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Re: Another Faraday Cage

Postby mosby's men » 14 Aug 2017 18:20

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Re: Another Faraday Cage

Postby kmussack » 16 Oct 2017 07:44

UPDATE;

I have discovered through use that the folded copper sheet should be applied to the opening before attaching the lid during each opening/closing cycle.

If you leave the sheet formed to the lid as shown in the preceding images it will eventually get fouled during closing and the copper sheet will be bent improperly leaving an RF gap.

This will also agravate any O.C. issues you might have.
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Re: Another Faraday Cage

Postby whls4legs » 16 Oct 2017 13:13

Used your idea w/40mm cans. The fact they latch from both sides caused me to do just that to get a decent seal. I did not remove the rubber seal, bared the steel edge of the can, (padded can), laid copper over opening, evenly attached lid. Copper contact seems complete. I don't open these once filled and stacked. I have also, on some, removed the lid seals and fixed the flashing to the lid. Can't see much difference. Unless I'm missing something. The rubber seal may even encourage good copper to steel contact.

These hold replacement alt/gens and starters for tractors, electronic set for 1998 Jeep Cherokee. Sealed first, like everything else, in Digi-Key Dri-Shield 3400 20x20 antistatic bags.

Anyway, thanks. Pretty good idea.
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