# Faraday Cage



## YuccaFlatsRanch (May 3, 2004)

If I was going to be building a small bldg for a storage room, what would I have to do to the structure to make it into a Faraday Cage?? Lets assume the building was 8 by 12.

Would a grounded 8 x 20 foot MilVan Container act as a faraday cage??


----------



## longrider (Jun 16, 2005)

Yes it would, provided there are no holes like where the rubber seals are. just a simple ground on one side will do.


----------



## WolfWalksSoftly (Aug 13, 2004)

You could line the walls and ceiling with chicken wire making sure all are connected to each other good and then run wire to grounding rods. Then you could put up plywood walls or whatever.
This would be a good one for Radiofish to chime in on.


----------



## Explorer (Dec 2, 2003)

Any metal container that is protected on all four sides and top with a sturdy ground will work. A sturdy ground consists of a heavy ground rod driven into the ground with a heavy connector wire to the building, triple ought should work.


----------



## radiofish (Mar 30, 2007)

WolfWalksSoftly said:


> You could line the walls and ceiling with chicken wire making sure all are connected to each other good and then run wire to grounding rods. Then you could put up plywood walls or whatever.
> This would be a good one for Radiofish to chime in on.



WWS - how did I know that you would bring up my name??????

Well yes it probally would - providing 'In My Opinion' if the following were done. 

Take and make some ground straps (I use the copper outer braid from RG-8 large diameter coaxial cable with the ends soldered to round crimp-on connectors) and then ground each piece of metal where there is a joint to the piece adjacent using metal screws and "star" washers. I did that to all of my vehicles to 'electrically bond' all body components togeather including the doors, hood, and exhaust systems. 

Is the trailer floor metal plated, or is it just made of wood?? If it is a wooden floor - Then the chicken wire/ rabbit wire mesh inside layer that is electrically bonded, then covered over would be a prudent investment.

You want a "continous/ solid" metal shield to make an effective "Faraday Cage" That means all six sides, top, bottom, and the other four sides... Do not forget the bottom of the 'Faraday Cage'!!!!

Then take and have a large copper braid attached mechanically (wire is too small in diameter/ for the skin effect) from the outer metal shell (two would be better - 1 at each end), and run as short a piece of grounding braid as possible, to at least an 8 ft. ground rod. What is the conductivity of the earth/ soil, where the grounding rod is placed at???

Of course, if the doors are left open when an electronic pulse in who knows how many volts (not microvolts) per squared meter occurs (E per M2/ Hard to do scientific notation here. Where is my paper and pencil at??..) - then all bets are off....

You also need to see what the mechanical clearance of the metal doors to the metal frame are.. Rubber gaskets filling a large gap in the door frame, will not stop any electromagnetic fields (E.M.F.)...

Just my thoughts on the subject...... de KK6ZY


----------



## palani (Jun 12, 2005)

radiofish said:


> You also need to see what the mechanical clearance of the metal doors to the metal frame are.. Rubber gaskets filling a large gap in the door frame, will not stop any electromagnetic fields (E.M.F.)...
> 
> Just my thoughts on the subject...... de KK6ZY


EMP being a short duration pulse of really large amplitude means energy distributed into the gigahertz region. Any small gaps would end up allowing energy to penetrate the interior.

On a small scale a sealed tin can could possibly protect small electronics. Would not even have to be grounded as the electric field could not penetrate. Even this would not stop the magnetic field from going whereever it wanted.

About twenty years ago the plant I worked at was concerned because 15 watt vhf radios on the forktrucks were transmitting next to some sensitve machine tools. We shorted out the velocity command signal to one servo drive on one of these machines and found that the closer we were the faster the axis we had disabled would drift off position. These servo drives were in NEMA 12 industrial boxes. We used a 5 watt Motorola MX radio for these tests at 155 mhz. Just by way of illustrating that even small openings and low power will allow RF energy to penetrate. We did reduce the intensity of this effect by using conductive rubber gaskets but never eliminated it completely.


----------



## iLori (Feb 1, 2009)

RE: Grounding rods... Is this something you buy? Can you make them? Do they have to be driven into the ground? As in, if I make a faraday cage for a loptop, ipod.... just a few little things, I'd rather put it on a shelf or something rather than storing it outside with a grounding rod shoved in the dirt.... obviously


----------



## radiofish (Mar 30, 2007)

duplicate post - something had a hic-cup!!


----------



## radiofish (Mar 30, 2007)

iLori said:


> RE: Grounding rods... Is this something you buy? Can you make them? Do they have to be driven into the ground? As in, if I make a faraday cage for a loptop, ipod.... just a few little things, I'd rather put it on a shelf or something rather than storing it outside with a grounding rod shoved in the dirt.... obviously


Ground rods are a piece of metal usually copper coated/ clad - that are 4 to 8 feet long. Used to be able to get them at Radio Shack.. They are driven down into the ground with a sledge hammer, and a conductor is run from being attached mechanically from the rod, to inside a house, etc..

I have 2 seperate ground rods driven 8 feet apart, with some copper "buss bar" buried underground also, in order to ensure a good ground system, for my ham radio equipment. The gear is located inside the house, and is not buried in the ground!!

Some radio installations even use the older metal or copper (non PVC/ plastic piping) "cold water pipes" found in houses/ apartment buildings, for a makeshift ground rod system. Or even a rod/ metal pipe that is driven into the earth for grounding electrical meters and breaker boxes.

Palini - good point!!! I did not want to get into the physical wavelenghts of the EMF frequencies. A signal in the GigaHertz or above range is in the centimeter/ millimeter wavelenght range. That is a very small opening folks!! Another reason why I fully shield the final amplifer tank circuit sections, of my HF transmitters and linear amplifers..... Just think what 1.5 Kilowatts at 146 Mhz/ or even at 445 MHz would have done to the logic controllers for that servo drive!!!


----------



## Gary in ohio (May 11, 2002)

rose2005 said:


> Interesting...
> 
> Our whole house generator is inside a metal casing which is grounded. Does this mean that it is protected too, or am I over-simplifying things?
> 
> Rose


NO because it has wires comes outside and thats where the EMP will come in.


----------



## Gary in ohio (May 11, 2002)

YOU should have MANY ground rods driven into the ground, YOu should have wire on the inside and outside all tied to the ground rods.


----------



## snakeshooter1 (Mar 8, 2009)

longrider said:


> Yes it would, provided there are no holes like where the rubber seals are. just a simple ground on one side will do.


I have seen the cages made out of chain link fence so how does that work then?


----------



## radiofish (Mar 30, 2007)

snakeshooter1 said:


> I have seen the cages made out of chain link fence so how does that work then?



Well the cages made out of chain link fence keep those critters locked up, so nobody gets a MegaHertz..

I need a better description than what you gave.. 
Was it inside of a metal building?? 
Out in the open??
In a movie??

Even having been inside several Anechoic Chambers used for antenna testing, that those are not a chain link cage.. Neat pictures of some Anechoic Chambers here..

http://www.globalemc.co.uk/anechoic.html

Here is some EMI/ EMF sheilding for you. Rated for Embassy Use.... 
If you are really paranoid/ I mean worried - I would recommend purchasing the Hyper-Shield set-up!!!!

http://www.globalemc.co.uk/shielding.html

Nor do I think this contraption is made out of chain link fencing..

Mobile sound and light resistant electromagnetic isolation chamber
USPTO Application #: 20090146862
Title: Mobile sound and light resistant electromagnetic isolation chamber

Abstract: A device enclosing a volume shielded from certain levels of sound, light and electromagnetic radiation, such device that prevents electromagnetic communications and recording devices from transmitting and receiving communications from outside of the devices protected environment while remaining mobile and ungrounded. (end of abstract)

Need more info, to answer your question.....


----------



## WayneR (Mar 26, 2007)

Could non working microwave ovens be used for storing small items. As it is a shielded container to prevent the escape of high frequency RF energy, it should prevent the same from entering. Ground the container as previously discussed. 

This would provide easily accessable protection for small items such as radios, automotive electronics and laptop computers.


----------



## GoldenCityMuse (Apr 15, 2009)

Grounding rods are available at your friendly building supply big box, in the electrical section. If you have alot of rock, you can lie them sideways in a trench, but it does not work as well. Buy several. Also, if you live in a dry climate, the soil can dry out VERY deeply, so water where your ground rod is during the drought.

Another thought, when you build your next storage building, pour your cement slab around a couple [or 4/6] ground rods. Then you can build metal shelves to hold your metal boxes that hold you laptop, etc. Using the correct grounding cables/ clamps, etc.

Have I done it yet, sad to say no, I still have a lot of work to do just preparing for the higher percentage disasters. Got to get my water supply upgraded.


----------



## Jim-mi (May 15, 2002)

A inexpensive cage can be rigged up using a old refrigerator. Add enough sheet metal to cover the door gasket gaps. Add hefty wire to run to the ground rod.

Grounding in dry soil areas can get complicated.
I wont get into it but ground rods and brine/salt are used.
Big TV/Radio station antennae towers do this . .of course depending on local soil conditions.........

When you've got a 1000 foot stick poking up into the sky you get REAL serious about the grounding aspect. 

For the 120' wind turbine towers I've installed, on some I have coupled two 8' ground rods together ( 16' )to get that much deeper to moist soil.

Good grounding is a serious thing......


----------



## tab (Aug 20, 2002)

If one doesn't want to line a building with chicken wire, how would you ground the (new)foundation? I know there is another thread somewhere that details how to ground a new metal building but this doors are a new thought (probably didn't "absorb that part).


----------



## ET1 SS (Oct 22, 2005)

We have four grounding rods on our house, just in case.


----------

