Do It Yourself Faraday Cages
 

It appears building a Faraday cage isn't as tough as you might have thought. In fact, you may already have one. The point of a Faraday is to use a highly conductive metal to box in your devices. A grounded metal toolshed may in fact function as a Faraday, at least to some degree. Here are a few increasingly reliable approaches:

Building small Faraday cages for household devices: http://www.endtimesreport.com/faraday_cages.html

"Faraday cage material: Electric fields are best conducted by materials that conduct electric current the best – silver is #1 and copper is #2. Aluminum is ~60% of copper. Iron/steel is farther down the scale. Aluminum is a good poor man’s foil against EMP; double wrap it to be safe. I prefer copper foil."

With radio's and smaller appliances, a Faraday cage can be built by using two cardboard boxes: one should fit tightly inside the other, and the item to be covered should itself fit reasonably well inside the smaller box. That is about the most work involved--finding the right size boxes! The outer box is then covered with aluminum foil or Mylar, as from a cheap "space blanket." A grounding wire is then taped to the foil. I then cover the foil with black 6 mil plastic, taped securely in place, to protect the foil from ripping. At the end of the ground wire I attach a cheap small alligator clip from Radio Shack. The item to be protected is placed inside the inner box, which acts as insulation from the outer box, and any EMP hitting the foil and is bled away by the ground wire.

http://www.endtimesreport.com/pictur...day_cages2.jpg

Some medium sized electrical equipment can also easily fit into boxes covered with foil for EMP protection. My laptop computer, for example, fits easily into a Faraday box made from a box that held reams of paper: the entire lid is removable, allowing easy access to the laptop in its case, but is safely stored when not in use.

For larger items which cannot be boxed, such as living room TV sets, etc, I tape a Mylar space blanket to a piece of 6 mil black plastic sheet, using double-sticky tape every foot or so to make sure the Mylar stays in place (it is slippery). I leave a 2 inch edge of black plastic showing all around the space blanket, and while taping down the edges I put on a short lead of ground wire. When it appears that EMP or CME's are on the way, the blanket can be draped over the appliance, the alligator clip attached to a small, unobtrusive ground wire behind the cabinet, and any electromagnetic radiation will be diverted to the ground wire. Very cheap, simple, and once done, items can be "draped" for protection very quickly indeed. The "EMP Blankets" roll up for storage, but can be unrolled and thrown over a TV/VCR setup, a computer/monitor combo, etc. As EMP comes from altitude and is line of sight, it's OK that the bottom isn't covered, as the bottom of the units sit on non conductive wood.

For full rooms, bug out shelters, and garages: http://www.hollandshielding.com/faraday/faradaycage.php

Mu-Copper foil has high damping properties in the electrical field (up to 120dB) as well as in the magnetic field (see table). It is easy to apply, like wallpaper, with a special adhesive for walls, ceilings and floors. This makes it possible to create a Faraday Cage with high shielding performance yourself in an economic way.

http://www.hollandshielding.com/fara...entilation.JPG

Depending on the quality of the doors, vent panels, filters and windows it is possible to realise a damping up to 60-80 dB in the E-field in an existing room without loss of space in just a few days.

The standard width is 1000 mm and the foil can be delivered on rolls or prefabricated sheets. For the joints you can use a 50 mm overlap,seaming tape or copper tape with a conductive self-adhesive

Personal observation: This sure is bullish on silver and copper, as they are the two most recommended metals for the creation of a Faraday cage.

Re: Do It Yourself Faraday Cages
 

Nice article.

I'm wondering if the wire mesh used on the inside and outside of a straw bale house to help the earthen plaster stick could be used as a Faraday cage if grounded? You would have to do the roof as well.

Anybody know the size of the spacing in the wire cage that will still stop EMP and other types of radiation?

Re: Do It Yourself Faraday Cages
 

yes, that wire mesh certainly could be used. it depends a little on how the wires are joined where they cross. if they are galvanized so that they are electrically connected, this is better for shielding than just having woven wires.

to evaluate an existing structure, you would need an RF source (on one side of the house) and an RF sensor (e.g. spectrum analyzer) on the other side.


the rule of thumb for electronic packaging is that any aperture in the electronic enclosure should be 1/4 wavelength or smaller.

so then you have to look up the frequency, use the formula
Velocity = frequency x wavelength ... where velocity = speed of light ... and do the calcs.

it's been a while. one reference - the door on your microwave oven. the small holes stop microwave frequencies but allow the passage of higher frequencies (e.g., visible light).

EMP is much more complex. an EMP consists of a huge amplitude, broad spectrum of frequencies.

when you work on military stuff, you worry about conducted AND radiated susceptibility. the 1/4 wavelength guideline we engineers use is for radiated energy.

for conducted energy - e.g. energy that couples from the EMP event to the cable & connector on EVERYTHING - it's like designing for transients (lightning being one example).

so, typically, you will use a connector that has bandpass filters that allow desired frequencies to pass - but stops other frequencies.

you can even get paid for designing stuff like this. :23_31_2:

once i bought a Max IIcx that had been either prepared for classified work - or EMP - or both. the mouse and keyboard and video connectors had massive filters on them.

of course, the thing with EMP is - it's very hard to absorb all that energy.

Re: Do It Yourself Faraday Cages
 

How well would a metal shipping container work if insulated inside and grounded outside?

Re: Do It Yourself Faraday Cages
 

Metal window screen.......

Re: Do It Yourself Faraday Cages
 

i am in a box with foil coving it as i type this

Re: Do It Yourself Faraday Cages
 

How about a used nonfuctional microwave oven?

Re: Do It Yourself Faraday Cages
 

it would work great for protecting electronics that is not plugged in.

i don't know if they're steel or aluminum or a clad combination.

steel is good because it catches low frequency EM radiation like 20 kHz.

let's say there are holes drilled in the wall to allow signal and power lines through. then the EMP can induce a voltage on the signal & power lines.

one work around - fiber optics.

EMP will not alter fiber optic transmissions - unless it blows up the cable or the equipment it's attached to.

so yeah you could build a Faraday Cage lab/office/workshop that used fiber-optics for signal (all Internet) and some other clever invention that doesn't involve a cable to get power in.

then you just need some breathing holes, and a few fans to make sure the occupant has decent air, and you have an EMP proof and fairly classified compliant workspace.

the expensive rooms that are used for EMI at companies like TRW & Northrop Grumman tend to have copper. e.g. rooms for classified meetings - copper wallpaper. personally, i like it.

in that case they're not using the copper for EMP, they're making sure that nobody sitting in the street with some good antennas and the appropriate recording equipment can spy on America's (and Israel's) Military Industrial complex, e.g. a meeting going on in the copper wallpaper room.

they also have labs for doing measurements that have copper walls. e.g. so they're not affected by outside radiation.

one place i worked at was developing an instrument that was severely interfered with by the local FM radio station. they chose a core system frequency that happened to be real close to the radio station's frequency - accidentally. they were a definite customer for an EMI room or the low-cost approach, a metal shipping container.

the EMI rooms that defense contractors buy (for classified work and for EMI measurements) are expensive. the contractors charge big $$ for what is physically very similar to a metal shipping container.

Re: Do It Yourself Faraday Cages
 

how about a school bus?
Mobile Faraday cage.

Re: Do It Yourself Faraday Cages
 

Yeah, I was actually going to ask if anyone has done a van, bus, etc.

Re: Do It Yourself Faraday Cages
 

Finally a use for all those copper pennies.....

:biggrin:

Re: Do It Yourself Faraday Cages
 

This is actually more reason to consider an old vehicle. The engines and electrical are almost fully enclosed within the steel body. Today's are fiberglass.

Re: Do It Yourself Faraday Cages
 

yeah, good point.

i think EMI and EMP is fascinating. it's fun to work on if you design something for EMI/ EMP & then someone else pays to fab. the parts.

but as far as preps, i think the destructive influences on the ground, e.g. on 2 legs, are worthy of real concern.

if you're prepared for everything but EMP, you're prepared.

Re: Do It Yourself Faraday Cages
 

I'm not sure I see the point of shielding from EMI, for most home-consumer electronics. That's more of a health-quackery sort of subject. Unless you live right under some high-voltage wires or light your home with Tesla coils, it's not really a concern. The EMI given off by 110V-220V wall current isn't worth worrying about.

-----

I'm not sure that EMP is really worth worrying about either. If you're close enough to a nuclear blast that you receive the EMP damage, you've got much bigger problems than the fact that your Game-boy doesn't work anymore.

A steel 6-side box grounded at all four corners would work pretty well, at least against the EMP. You'd want shielding with a lot of iron in it, and steel is mostly iron.

-----

The military/government is said to be working on microwave devices that will disable vehicles. I doubt you could "harden" a car against something like this without switching the car's ignition system over to a dynamo or generator. Every alternator in every car you see uses a semiconductor regulator susceptible to microwave damage.


-end-

Re: Do It Yourself Faraday Cages
 

That paragraph shows that the Faraday cage proposed by the author will not work well. A Faraday cage needs to be grounded at the frequencies of interest, not just at DC. So while a small-gauge wire with an alligator clip is fine for DC, it is a big inductor (reactive element) at high frequencies. As frequency increases, radio frequency energy uses less of the conductor to move the electrons. Basically, the electrons all stay on the surface and the impedance of the connection increases with frequency. This is called the skin effect. What it means the cage is not well-grounded and is essentially worthless.

A better means of grounding the cage is to use a single wide, flat copper braid attached to the cage. The end attached to the cage should be attached across as much of the width of the braid as possible. The other end's entire circumference (wrap it around the rod) should be attached to a ground rod driven well into the earth.

Gaps in the cage material itself also lessen its effectiveness as a slot antenna is the net result. This can actually increase the power transmitted into the device intended to be shielded.

Re: Do It Yourself Faraday Cages
 

Great braid can be had by stripping old rg-8 comes to
mind.

Strip the braid off in one piece and flatten it.

Great ground cable!

Re: Do It Yourself Faraday Cages
 

I actually did that back in the late 1980s with waveguide beyond cutoff and fiber optic transceivers mounted in steel boxes. Basically each end had a connection for two fibers, one for transmit and one for receive. Here is a good link to an Intel document on the issues.

http://www.formfactors.org/developer...erview_098.pdf

Re: Do It Yourself Faraday Cages
 

I understand that with todays technology, the law enforcement people can look straight through walls and essentially spy on people.

Would a copper clad room stop this? Or how would you stop someone from looking into your house, from say across the street?

Re: Do It Yourself Faraday Cages
 

yes. the copper (or aluminum) will block all but low frequency RF. it will also provide a very bland image for any thermal instrument.

they (person trying to surveil you) would need to escalate to (for example) X-Ray equipment. which is not very portable.

if you are serious about this, i suggest the thicker cooking aluminum foil sold at some restaurant supplies. a lot cheaper than copper, and, since you're talking about basically using it as wallpaper, just, easier to work with than really thin alum. foil - which rips too easy if you're taping it or something.

Re: Do It Yourself Faraday Cages
 

I am serious, and will be building a new house in the next 18-24 months. The intent is to incorporate it in the building and not just the internal room surfaces. I also have a good source of woven 314 stainless steel fabric which has an un-uniform weave from 3-5 mm, and I was thinking of using this as well to knockout differing wave lengths.

Not sure about the aluminium, for health concerns. Any other options?

Does the room lining have to be a solid surface, or can it be a mesh as well?

Re: Do It Yourself Faraday Cages
 

As for ways to test the finished box, will this block radio waves ?

Re: Do It Yourself Faraday Cages
 

Grounding is for lightning rods. It has nothing to do with shielding.

The Faraday shield depends on conductivity all the way around. A car body is no good because it doesn't go all the way around anything. A file cabinet is no good because there is no conductivity between the parts. A microwave oven is no good because the door is not actually connected to the rest of the box. (It uses a trick to shield at the frequency of operation only.)

Aluminum is a good conductor but aluminum oxide is not, and it oxidizes easily. Copper is a good conductor but if it's not welded or soldered it can become a lousy conductor. The wires in a window screen only touch where they cross, so after a while they lose conductivity. You can correct that failure by soldering them together. A trash can is a good start, but the conductivity to the lid is uncertain. It needs to be soldered shut.

As for EMP, you are most likely to get one from a lightning strike. Boaters quite often lose their compass because of a lightning strike. So you can get some tested practical advice from boating suppliers. They mostly talk about grounding. You need to remember: grounding is for lightning rods. It has nothing to do with shields.

Re: Do It Yourself Faraday Cages
 

You could use radiant barrier foil.

It is relatively inexpensive, and helps keep the house a more even temperature.

Re: Do It Yourself Faraday Cages
 

you mentioned copper originally. it looks nice, and it can be soldered.

another option is tin, or zinc. depends on your budget, and the amount of shielding you need.

what frequencies are you trying to block ? DC to daylight ?


agreed - you do need to be concerned about contact between layers of metal. using metals that can be soldered makes a great way to create a shield that envelopes an entire room.

my background is with EMI shielding for electronics, working with electrical engineers. in 24 years, every single EMI shield i worked on was tied to circuit ground.

that may or may not apply to what boston is trying to do.


one other factor that needs to be considered - presumably you want the EMI shield to work as well at time t= 10 years as at time t=0.

therefore, the galvanic potential & compatibility of different metals needs to be considered. dis-similar metals can get pretty damn crusty, corrode, and lose contact.

one fun way to understand shielding better is to take apart old electronic instruments, and to look at the shielding techniques used - ground straps, beryllium copper gaskets, etc.

since this sounds like a "serious project" (we're talking about a house), at some point measuring EMI shield performance is in-order. for this you need a signal generator and an antenna (on one side), and a spectrum analyzer and an antenna (on the other side).

Re: Do It Yourself Faraday Cages
 

See embedded above.

Re: Do It Yourself Faraday Cages
 

Perforated metal sheet (small holes) gets around the wire-to-wire connection/conductivity issues of screen or mesh and still allows for ventilation.

Larger openings/slots or conductor pass-thru's in the shielding will compromise the barrier's effectiveness depending on the frequencies to be blocked, and may act as waveguides at some frequencies, feeding energy into the interior, which could even act as a resonant chamber.

R.

Re: Do It Yourself Faraday Cages
 

I've been told a microwave oven, grounded, makes good storage for a AM/FM tuner and a couple of hand helds.
Save the HDTV? The laptop? .... **** that. You can have em.... anytime I'm without access to that useless crap, life seems to improve. Not sure why that is.

Re: Do It Yourself Faraday Cages
 

Well, it doesn't. The door is NOT connected to the rest of the box. It uses a trick called "reflected short", which only works at one frequency. For any other frequency it is an open box.

And I repeat, grounding has nothing to do with shielding. Grounding is important for a lot of reasons, but shielding is not one of them.

Re: Do It Yourself Faraday Cages
 

To be honest I have no idea what frequencies I should be trying to block.

My only concern is that I have no wish to be invaded by prying eyes, and with the way technology is, alot of people could have the same technology as an over the counter item in years to come.

Call me a cynic, if you will, but I also believe that the law enforcement forces will be used to monitor people, just like GIM members, who are somewhat different from the masses. And I want to protect myself and family from this type of scrutiny.

Re: Do It Yourself Faraday Cages
 

rule #1 - do not use a wireless network. even an encrypted one.

i've met too many good engineers, electrical & otherwise. there are engineers out there who can hack into your encrypted wireless network. some of them already work for the government; others just like money and are willing to do contract surveillance work.

rule #2 - follow security guidelines of a mega-security geek. this is the guy i trust -
http://www.mechBgon.com/

he has a link, "security guidelines". he's a hyper-experienced computer tech that put this together probably because he got tired of explaining it over and over.


if you're following good computer security procedures and avoiding wireless networks, it would take a real pro to hack into your computer. it would probably take a little social engineering, e.g. finding out what your interests are, then posting an innocuous link here that takes you to a custom-designed website that molests your computer.

i think the greater danger is physical security. the one person i know who has had documents stolen ... the surveillance person broke into the residence.

so for that, it's not copper wallpaper you need, it's old-fashioned neighbors who are nice enough to keep an eye on your place, along with all the physical security things people talk about (locks, guns, dogs, well-trained children, etc.).

Re: Do It Yourself Faraday Cages
 

Thats good to know.

No I Love Lucy reruns for me.

Re: Do It Yourself Faraday Cages
 

That's true with the old WEP encryption. There's even a utility you can download that will crack WEP in a few seconds to a few minutes.

WPA and WPA2 changes the broadcast key with every packet, so if you put a 30+ character password with symbols, caps, ascii, etc... it would probably take 20+ years to crack the key. Something like this (below) copy and paste to a memory key...(ascii uses alt-then a number (0-255) i.e. alt 178= ▓

;)

zC╗h╝f╞}x╟c1☻Θ░ag.n~(j;&:6D▒rfE7!n♥t��╝╟╞─d[B☺5v^▒}m@╚hJ_?♣�kKe╝h#C_~�░g╔2w▓CPD:6>sX

Re: Do It Yourself Faraday Cages
 

I must admit that I am not overly concerned with computer hackers, and I do not live in a country where guns are prelevant.

Whilst physical harm is a concern, it is not something that I dwell on, on a daily basis.

My real concern, strange as it may sound, is the government and I would like to minimise any contact with them as possible. Unfortunately, this may not be possible, but the less they know about me, and the less they can find out about me, the better I feel.

You see, like many, I am a real threat to them in that I question their motives and my lost freedoms. I am not an extremist in the accepted sense of the word, I do not protest in marches or parades, I do not have a gun or aspirations of violence, I am just an ordinary person, which is a greater threat for their existence and one world government serfdom.