Faraday Cage - Page 2
Firearm & Gun Forum - FireArmsTalk.com > General Discussion Forums > Survival & Sustenance Living Forum > Faraday Cage

Reply
 
LinkBack Thread Tools Display Modes
Old 09-29-2012, 01:00 PM   #11
Feedback Score: 0 reviews
 
clr8ter's Avatar
 
Join Date: Jan 2011
Location: South Central NH
Posts: 3,557
Liked 1104 Times on 734 Posts
Likes Given: 733

Default

True, it might be hard finding a 5 story grounding rod, LOL. If that were the case, I don't know what I'd do.....I guess I'd have to trust the building's wiring........

__________________
clr8ter is offline  
 
Reply With Quote
Old 09-30-2012, 03:43 PM   #12
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
Join Date: May 2012
Posts: 256
Liked 81 Times on 54 Posts
Likes Given: 15

Default

Quote:
Originally Posted by ellis36 View Post
I'm not sure about that. Check out
http://www.endtimesreport.com/faraday_cages.html

As for the question…it would depend on the integrity of the ground wires from the outlet back through the main breaker box out to the power company ground. Some unknowns there but a possible solution. The thing is, shielding for RF is an iffy thing. Because of the short wavelength a ground wire can actually act as an antenna under the right conditions. The ground needs to be as large, as short and as direct as possible.
Google 'Faraday Cages.' There is lots of info there about this subject.
It is the conduction path, not the grounding that create a Faraday cage. For example, (non-convertable) cars and flying airplanes pass lightning, protecting the contents (people) ... they are not grounded. Some newer airplanes are made with composite materials ... they explode when hit by lightning, so NASA (and others) developed and tested a copper mesh to embed in the composite skin to provide a discharge path to keep that from happening (it also provides a ground plane for the radios).

If you watch Mythbusters, they had a cage at the top of a Van De Graaf generator used to demonstrate lightning ... the cage was not grounded, if it was the "lightning" wouldn't have been attracted to the test objects.
Touching the inside surface of the cage has no effect, and presents no danger for the same reason ... the cage is a better, less resistive path than the objects contained within.

I'm not saying you shouldn't ground them, I'm just saying that 99.9% of the time, it's not needed. Adding a ground would basically control where the charges are drained. If the grounding system is insufficient or inefficient (there's more to it then slamming a rod into the ground and screwing a wire to it), chances are you'd cause more problems than you think you're solving.

Wikipedia has a pretty good explanation: http://en.wikipedia.org/wiki/Faraday_cage

Another thing to consider is that a true pulse is made up of an infinite number of third-order harmonics, meaning that given a sufficiently strong pulse, some energy will penetrate a mesh of any dimension (smaller = less, solid = total).
__________________
scottmac is offline  
 
Reply With Quote
Old 09-30-2012, 04:38 PM   #13
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
ellis36's Avatar
 
Join Date: Sep 2011
Location: Batesville,Mississippi
Posts: 946
Liked 796 Times on 371 Posts
Likes Given: 458

Default

Quote:
Originally Posted by scottmac View Post
It is the conduction path, not the grounding that create a Faraday cage. For example, (non-convertable) cars and flying airplanes pass lightning, protecting the contents (people) ... they are not grounded. Some newer airplanes are made with composite materials ... they explode when hit by lightning, so NASA (and others) developed and tested a copper mesh to embed in the composite skin to provide a discharge path to keep that from happening (it also provides a ground plane for the radios).

If you watch Mythbusters, they had a cage at the top of a Van De Graaf generator used to demonstrate lightning ... the cage was not grounded, if it was the "lightning" wouldn't have been attracted to the test objects.
Touching the inside surface of the cage has no effect, and presents no danger for the same reason ... the cage is a better, less resistive path than the objects contained within.

I'm not saying you shouldn't ground them, I'm just saying that 99.9% of the time, it's not needed. Adding a ground would basically control where the charges are drained. If the grounding system is insufficient or inefficient (there's more to it then slamming a rod into the ground and screwing a wire to it), chances are you'd cause more problems than you think you're solving.

Wikipedia has a pretty good explanation: http://en.wikipedia.org/wiki/Faraday_cage

Another thing to consider is that a true pulse is made up of an infinite number of third-order harmonics, meaning that given a sufficiently strong pulse, some energy will penetrate a mesh of any dimension (smaller = less, solid = total).
Good post with good info. As with a lot of situations, nothing is as simple as it might appear.
__________________
ellis36 is offline  
 
Reply With Quote
Old 10-01-2012, 01:31 PM   #14
Big TOW
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
WebleyFosbery38's Avatar
 
Join Date: May 2012
Location: Irish Settlement CNY
Posts: 6,169
Liked 6895 Times on 3465 Posts
Likes Given: 7484

Default

SM explained it well, my experience with Faraday Cages has been purely scientific, the signals and pulses we are trying to eliminate are so small that they could not possibly damage Electronics equipment but they would provide false data in Bio Research Labs. Never considered EMP protection for survival as is being talked about here and we never had any drills or skills in Anti Armor to deal with it although we always knew it was likely if there was a nuke detonation danger close or further. Im not exactly sure what the primary shock frequencies are for a bomb of that magnitude, the Third and Fourth order harmonics are truly incalculable at the JQ Public level and I leave those calculations to the PHD's, I just build what they describe, twice if they are wrong the first time! My head hurts just thinking about the calculations but the pressure behind them is seismic.

What he said about the density of the mesh is a real factor in effectiveness, thats why we use woven copper cloth, its nearly impervious to any frequency and the edges solder well for a closed loop on the shield. Grounding isnt important so much in an aircraft thats potential resistance is in the Millions of Meg-ohms impedance wise in a pathway to ground. As a cage sitting near ground yet not earth grounded solidly, the potential for inducement grows larger.

__________________
WebleyFosbery38 is offline  
 
Reply With Quote
Old 10-01-2012, 10:29 PM   #15
Feedback Score: 0 reviews
 
clr8ter's Avatar
 
Join Date: Jan 2011
Location: South Central NH
Posts: 3,557
Liked 1104 Times on 734 Posts
Likes Given: 733

Default

At what point did this forum switch languages? LOL

__________________
clr8ter is offline  
 
Reply With Quote
Old 10-02-2012, 11:03 AM   #16
Big TOW
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
WebleyFosbery38's Avatar
 
Join Date: May 2012
Location: Irish Settlement CNY
Posts: 6,169
Liked 6895 Times on 3465 Posts
Likes Given: 7484

Default

Quote:
Originally Posted by clr8ter View Post
At what point did this forum switch languages? LOL
Das Copperscplinger und der groundenkafish ist guflickin in der feiselpunkt, ist Kaput!

Defined means, if your anywhere near an atomic detonation, bend over and kiss your arse goodbye!
__________________
WebleyFosbery38 is offline  
 
Reply With Quote
Old 10-04-2012, 11:18 AM   #17
Feedback Score: 0 reviews
 
clr8ter's Avatar
 
Join Date: Jan 2011
Location: South Central NH
Posts: 3,557
Liked 1104 Times on 734 Posts
Likes Given: 733

Default

I also meant to ask, and this may be stating the obvious, if smaller mesh size copper is better, and sealing up the seams completely is better, does it follow that a box made from solid copper sheet welded at the seams would be the best? (Yes, you can WELD copper.)

__________________
clr8ter is offline  
 
Reply With Quote
Old 10-04-2012, 11:53 AM   #18
Big TOW
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
WebleyFosbery38's Avatar
 
Join Date: May 2012
Location: Irish Settlement CNY
Posts: 6,169
Liked 6895 Times on 3465 Posts
Likes Given: 7484

Default

Quote:
Originally Posted by clr8ter View Post
I also meant to ask, and this may be stating the obvious, if smaller mesh size copper is better, and sealing up the seams completely is better, does it follow that a box made from solid copper sheet welded at the seams would be the best? (Yes, you can WELD copper.)
Absolutely, solid is much better than any mesh but you might not wanna know how much thats gonna cost (unless your making a shoe box)! The real world application of shielding from Nuke radiation/ EMF is in every XRay room in the nation, Lead! It blocks almost everything you can throw at it, the very old houses like I own actually have shown less RF passthrough than new ones and thats been attributed in large part to layers of Lead paint that limit penetration naturally. Lead sheets are much cheaper than Copper and pound for pound, less penetrable than nearly any other material but certainly is not the safest substance to have a ton of in close proximity to your family.
__________________
WebleyFosbery38 is offline  
 
Reply With Quote
Old 10-04-2012, 01:56 PM   #19
FTF_SUPPORTER.png
Feedback Score: 0 reviews
 
Join Date: May 2012
Posts: 256
Liked 81 Times on 54 Posts
Likes Given: 15

Default

Quote:
Originally Posted by clr8ter View Post
I also meant to ask, and this may be stating the obvious, if smaller mesh size copper is better, and sealing up the seams completely is better, does it follow that a box made from solid copper sheet welded at the seams would be the best? (Yes, you can WELD copper.)
Solid is "best." However, you'll have to judge whether the cost differential is worth the marginally better performance.

For a pure Faraday effect, conductivity king. If you are also looking to block radiation (all with a single layer of some metal), then you'll need to weigh one thing (conductivity) versus another (radiation shield) according to your needs.

There's a lot of talk here about using copper or aluminum, but mu-metal is actually better for most magnetic / EMI / RFI shielding applications (http://en.wikipedia.org/wiki/Mu-metal ). It's still electrically conductive for the Faraday effect, but is more effective against most types of magnetic fields.


We used this to shield rooms used for electron-microscopy; the 'scopes imaging ability is sensitive to stray magnetic fields.
__________________
scottmac is offline  
 
Reply With Quote
Old 10-04-2012, 04:08 PM   #20
Feedback Score: 0 reviews
 
Join Date: Jun 2011
Location: Mississippi
Posts: 134
Liked 3 Times on 2 Posts
Likes Given: 16

Default

I like this disscussion. There are some gaps in explainations, but overall good info.

There are many factors in and emp event, weither CME or bomb supplied. There are ground effects as the currents are top to bottom and bottom to top. EI: E1 and E3 currents. For me I have only nested faraday cages. Grounding may actually cause you more problems from E3 currents. Do lots of more study before making any solid plans.

For some good reading and a lot of it, here is some from ORNL. About 14 MB of it...

http://www.ornl.gov/sci/ees/etsd/pes/pubs/ferc_Meta-R-319.pdf

Jimmy

__________________

Make sure your not someone's PITA....

Hope for better, prepared for worst...


Last edited by Jimmy; 10-04-2012 at 04:10 PM.
Jimmy is offline  
 
Reply With Quote
Reply

Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Firearms Forum Replies Last Post
American cage fighter 'rips out still-beating heart of training partner towboater The Club House 8 06-03-2012 07:48 AM
I want to see (blank) locked in a cage with (blank) skullcrusher The Club House 54 12-20-2010 08:16 PM