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Author Topic: Faraday Cage  (Read 2609 times)
KD9FRQ
Member

Posts: 175




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« on: March 17, 2017, 04:23:13 AM »

Just thinking about protecting some portable gear that would not be used all the time............

First, Would storing a modern HT in a surplus ammo can be a reasonable Faraday cage?

Second, would lining the walls of the shack with copper sheets also be a good Faraday cage?
I have access to copper rolls from a local roofer.

No, I am do not think the Russians are going to attack. Just thinking about long term
storage and protecting the gear and an exercise in understanding the practical application
behind a Faraday cage.

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K1HMS
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Posts: 463




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« Reply #1 on: March 17, 2017, 06:38:06 AM »

There is no real advantage to a faraday cage provided the antenna is disconnected. Store it in a water tight container with a couple of little bags of dissicant to keep it dry. Some of the better kitchen storage containers are very air tight. You will need to charge the battery once in a while Or it will die, every 2-3 months should do it.

A Faraday cage shields against RF. It would take a good size nuc at close range to produce enough RF to blow the first stage assuming the antenna is connected.

The larger problems are flash x-ray, Gama, heavy particles, and electromagnetic pulse. Thin copper will help a little but not enough. You would need Pb or Ta.

Store the water tight container low and against the basement wall so that it is shadowed by the dirt outside the wall. Unless the threat is overhead, in which case it doesn't matter, the radio should fine.  You will have larger problems.

A Faraday cage need not be solid provided the openings are less that .1 wavelengths at the highest freq of interest. Many testing labs use copper window screen to build walk in size cages.
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ND6M
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Posts: 553




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« Reply #2 on: March 17, 2017, 08:30:47 AM »

just put the HT in a microwave,..................... YMMV
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K8AXW
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Posts: 6312




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« Reply #3 on: March 17, 2017, 08:40:49 AM »

6M:  Simple problem with a simple solution!  Very good.

An ammo can is a good storage container.  (Ammo has been stored in these containers for decades!) Moisture absorbent packs are also a good idea. 

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W1VT
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Posts: 2489




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« Reply #4 on: March 17, 2017, 09:51:02 AM »

just put the HT in a microwave,..................... YMMV
Won't work.  Microwaves have door seals using frequency sensitive quarter wave RF choke flanges.
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WB6BYU
Member

Posts: 17061




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« Reply #5 on: March 17, 2017, 11:51:26 AM »

Quote from: K8AXW

An ammo can is a good storage container.



A good container for a lot of things, but not necessarily RF-tight.  There is a rubber seal around the lid
that prevents good metal contact.  Yes, the top may be electrically connected to the case through
the hinge (depending on the amount of rust and/or grease there) but the gap is large enough to let
RF through - at least over some range of frequencies.

I can tell you from experience that they are not smoke-proof, either.  A short on the battery wires
inside the can contained much of the smoke, but certainly not all of it.
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KD0REQ
Member

Posts: 2018




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« Reply #6 on: March 17, 2017, 12:06:49 PM »

wrap it in foil.  if there is a large enough EMP to get through the foil, then you are not going to be in a position to use the equipment, being goo or ashes.

and notice I did not dredge up and polish the old "let Faraday out" joke.  that's got to be good for at least One Genuine Internet Point.
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KA4DPO
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Posts: 780




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« Reply #7 on: March 17, 2017, 12:12:39 PM »

wrap it in foil.  if there is a large enough EMP to get through the foil, then you are not going to be in a position to use the equipment, being goo or ashes.

and notice I did not dredge up and polish the old "let Faraday out" joke.  that's got to be good for at least One Genuine Internet Point.

Do you have Faraday in a cage? Grin
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KD9FRQ
Member

Posts: 175




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« Reply #8 on: March 17, 2017, 03:30:18 PM »

Thank you.  Just wondering out load as they say.............

I am not really worried about an EMP but I thought if I can help protect my gear, I would.
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K9MHZ
Member

Posts: 1440




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« Reply #9 on: March 17, 2017, 03:44:31 PM »

Not a thing wrong with making one.  You can do some very good receiver testing among other things.  The ARRL testing lab (as is the case with most good labs) is one big Faraday Cage.
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W4AMP
Member

Posts: 24




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« Reply #10 on: March 18, 2017, 05:11:10 AM »

A metal trash can will work in a emergency. But you would have to know the pulse was coming. Shocked
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K8AXW
Member

Posts: 6312




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« Reply #11 on: March 18, 2017, 09:13:01 AM »

Didn't know that Zack.  I have always thought the black panel around the inside of the door was a 'seal' that prevented microwaves from escaping from the oven.

TY for the info!

As for the ammo cans, the lid overlaps the can and the rubber seal becomes somewhat meaningless.  IMHO.  However, if the original poster is this concerned about radiation ruining his gear, then the only option is to build a copper lined box for his gear. 

It would be a nice gift for any survivors assuming they knew how to work it an had someone to talk to.  BTW, when putting your gear in the box, include the operating manual. 
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KD9FRQ
Member

Posts: 175




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« Reply #12 on: March 19, 2017, 05:26:05 PM »

However, if the original poster is this concerned about radiation ruining his gear, then the only option is to build a copper lined box for his gear. 

This is more thinking out loud about protecting one piece of equipment for storage because it may not get used that much. I had the parts on hand, so I built it.
Again, thinking out loud.......I thought hmm...if I can store it long term, how about upgrading the level of protection at minimal costs since I have access to the
copper sheeting.

I am more worried about the New Madrid fault under the Mississippi Rive south of St. Louis cutting off many of the communications cable that go under the river,
a run-way barge takign otu the I-24 bring over Ohio river at Paducah, KY and general grid failure due to out-right attacks on sub stations that will not get repaired
soon or just plain failure due to lack of maintenance.  In my town, several of the substations are not well protected. A drunk driver or medical emergency driver
could easily hit one and the resulting failure could cascade across town and take months to repair.
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K7KBN
Member

Posts: 3473




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« Reply #13 on: March 19, 2017, 08:30:37 PM »

wrap it in foil.  if there is a large enough EMP to get through the foil, then you are not going to be in a position to use the equipment, being goo or ashes.

and notice I did not dredge up and polish the old "let Faraday out" joke.  that's got to be good for at least One Genuine Internet Point.

Do you have Faraday in a cage? Grin

Yes.

How long has he been in there?

Faraday, day 'n a half...
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73
Pat K7KBN
CWO4 USNR Ret.
N6YFM
Member

Posts: 502




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« Reply #14 on: March 20, 2017, 04:58:26 PM »

Wow.   Just when I thought I had seen everything.....

You don't need cans, containers, tin foil, foam rubber, voodoo dolls, or dancing medicine men to protect your HT.
My Yaesu FT-470 has been going strong for ~30 years, across many moves, and being tossed about in several garages.   
It does not sit in a case. Never has. And if something as big as a house fire or Nuke happens, I've got much larger problems
than an HT lost :-)

Another reason you really should not protect your HT so well;   If it never gets abused/broken, you are never going
to have an excuse to buy the super duper next year model.

Cheers


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