Faraday Cage

**DaveK** · 11-18-2013, 01:31 AM

I am new to the forum and I hope my question is not asking for trouble.

Can anyone direct me to information, either here on the board or elsewhere, on the construction of a Faraday Cage?

**crashdive123** · 11-18-2013, 08:03 AM

Try this one for starters. http://www.wilderness-survival.net/f....php?20974-Emp

**DaveK** · 11-18-2013, 01:21 PM

Excellent information. Thanks!

**DaveK** · 11-26-2013, 06:52 PM

Crashdive123

It took a while to digest all of the information from cwi555. It sure shows how complicated things are. Many thanks!

One of the reasons I requested information on Faraday Box construction (and EMPs) is the need for a speaker on the subject. Our Ham radio group does a weekly net on a variety of topics and there have been several requests for a discussion on this one. With the benefit of IRLP (Internet Radio Linking Project) we can link Hams from almost anywhere, as long as certain connections exist. Any thoughts or any Hams out there who can help?

Thanks!!

**crashdive123** · 11-27-2013, 07:44 AM

Sorry - I'm not involved withe ham operators (the radio types, not the food) so really can't offer any advice there.

**Wildthang** · 12-03-2013, 02:54 PM

Well, I do know one thing, during a significant EMP, you better have the ham unit disconnected from the antenna and power source. If modular power supplies are used that also need to be disconnected and kept in the faraday cage with the transceiver. As long as the antenna is disconnected, and the ham transceiver is enclosed in a grounded metal enclosure, it should survive the EMP. Even a metal trash barrel with a lid could be used for a faraday cage as long as it is grounded to earth ground.

**RandyRhoads** · 12-03-2013, 03:06 PM

I thought only things connected to the power grid or antenna are in danger from an EMP.

**crashdive123** · 12-03-2013, 04:34 PM

Not true. This is a fairly good explanation.

First, the electromagnetic shock can disrupt electrical devices. The second effect is similar to lightning—a power surge that would burn circuits and immobilize electronic components and systems. The third is a pulse effect that flows through electricity trans*mission lines, damaging distribution centers and fusing power lines. Any of these can cause irreversible damage to an electronic system.

Source: http://www.heritage.org/research/rep...-awareness-day

**RandyRhoads** · 12-03-2013, 04:37 PM

I just read an article saying they could only pick up the pulse if they had several feet of wire such as an antenna or power grid. Not true? It said even items left on, batteries in, were fine, as long as they didn't have the feet of cord in them.

**Wildthang** · 12-04-2013, 06:34 AM

IC chips work on very low voltages somewhere around 3.6 volts dc, and if they are exposed to an induced pulse value more than 3.6 volts, it would render them inoperable. In an extreme EMP voltage pulses can be induced through air and not just wires and transmission lines. Wires and transmission lines will attract the higher voltages but it does no stop there!

**crashdive123** · 12-04-2013, 07:11 AM

Originally Posted by RandyRhoads

I just read an article saying they could only pick up the pulse if they had several feet of wire such as an antenna or power grid. Not true? It said even items left on, batteries in, were fine, as long as they didn't have the feet of cord in them.

Just like a lightning strike nearby can fry electronics that are not on or plugged in, so to can an emp. How and what it affects is determined by the amplitude and wavelength of the pulse.

**Rick** · 12-04-2013, 10:15 AM

Randy, current can be induced into anything if the source voltage is high enough, source voltage is close enough and there is a difference in potential between the two materials. Even insulators will conduct voltage under the right circumstances. Here's an interesting video of high line work. Watch closely at the 1:03 mark as the lineman intentionally balances the potential between the helicopter and the high line and again at the 2:50 mark.

You can see the voltage jump from the high line across a span of a foot or so. I have no idea what the voltage is that the high line carries but I would guess in the 300 Kv range. Now think about that in the millions of volts that an EMP could deliver. It's not apples to apples but it does serve as an analogy to help understand that an EMP can induce voltage into any conductor whether it has an antenna or not or whether it is connected to the power grid or not. Hope that helps.

**RandyRhoads** · 12-04-2013, 01:06 PM

Cool thanks.

The article said most peppers waste time with faraday cages and emp protection when it was as simple as unplugging. I wondered why so many people went through so much if that was true.

**Wildthang** · 12-04-2013, 01:52 PM

Cutting through all of the extreme hooplah of the EMP theories, if you have a sheet metal building, and the sheet metal is grounded to earth ground using a ground rod that is solidly grounded to the sheet metal roof and siding, that will protect almost anything inside the building. Of course the electrical service to the building would need to be disconnected for full protection.
This would protect most normal equipment from all but the most extreme EMP.

**hunter63** · 12-04-2013, 02:54 PM

Originally Posted by Wildthang

.................................................. ...This would protect most normal equipment from all but the most extreme EMP.

I'm think that if this happened, you wouldn't have to worry about it much anyway......

I good part or the population was gonna be helpless as soon as their phones and interweb die.....