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#201102 - 04/28/10 03:48 AM Protecting against EMP
marduk Offline

Registered: 01/25/04
Posts: 160
Loc: Mid-Missouri
I've been thinking (my DW and kids would suggest that now is a good time to run for cover).

With the potential for EMP damage Impending solar storms , and based upon the effects of EMP, that is known Carringtton Event & Starfish Prime , would the following idea have merit. I am not and don't play one on TV – an Electrical Engineer.

Would my metal sided outbuilding function as a Faraday Cage? It has sheet steel sides and roof. Would I need to bond the roof and sides, the doors (walkthru and vehicle) to the building. Would the rebar and rewire in the floor be enough, would I need to bond this to the walls. What size bonding conductors and how many would be needed? Realistically what current flux would I need to consider in the calculations?

Thoughts? Shared knowledge. As the kids say: “skool me”

"Sometimes, it's better to be lucky than skillfull"

#201112 - 04/28/10 11:51 AM Re: Protecting against EMP [Re: marduk]
Am_Fear_Liath_Mor Offline
Carpal Tunnel

Registered: 08/03/07
Posts: 3078

An insulated metal box within another metal box which is properly earthed should be fine to protect sensitive electronic equipment against most forms of naturally occurring EMP. i.e. say a laptop needs protecting then a aluminium laptop case inside a aluminium storage chest inside your earthed metal shed should work out fine to protect the laptop against EMP. If this doesn't work against a very specific man made EMP scenario then chances are your not gonna be around within the next 10-15 minutes for find out if it didn't work anyway... wink

#201119 - 04/28/10 04:31 PM Re: Protecting against EMP [Re: Am_Fear_Liath_Mor]
ILBob Offline
Old Hand

Registered: 02/05/10
Posts: 776
Loc: Northern IL
There are a lot of myths and just plain bad information out there about EMP and its potential effects.

Most modern electronic equipment is a lot more resistant to the effects of EMP than you might think. Its not a 100% thing though. Some equipment will survive and others not, with no discernible reason why.

Grounding has no effect whatsoever on the protection a Faraday cage provides, nor does it provide any additional protection against EMP.

EMP is as much an antenna issue as anything else. If your equipment is not connected to a long wire, its probably reasonably safe.

Any metal enclosure such as a car body, an aluminum case, or a metal building can provide some protection, but it is not a proper Faraday cage, because it does not completely enclose anything. There are plenty of places for leakage.

Unfortunately, much of the literature on the Internet about EMP is oriented toward military applications where they consider any degradation due to the effects of EMP as undesirable, so they go to extreme lengths to prevent it. This makes it appear as if EMP is some kind of monster that will destroy everything electrical in its path, which is far from the truth.
Warning - I am not an expert on anything having to do with this forum, but that won't stop me from saying what I think. smile


#201124 - 04/28/10 05:26 PM Re: Protecting against EMP [Re: marduk]
philip Offline

Registered: 09/19/05
Posts: 639
Loc: San Francisco Bay Area
I'm not sure EMP protection is worth whatever it costs. I think the likelihood is remote, asymptotic to zero. And having your personal Faraday cage isn't going to save you from whatever effects befall the rest of the world if an EMP happens.

If the rest of the world or the US is pretty much wiped out electronically, what will you have in your shed that will save your family and you from those effects?

#201127 - 04/28/10 06:50 PM Re: Protecting against EMP [Re: marduk]
Arney Offline

Registered: 09/15/05
Posts: 2485
Loc: California
Originally Posted By: marduk
With the potential for EMP damage Impending solar storms...

Are solar storms much of a direct threat to personal gear? I've really only heard of the greater power infrastructure being at risk, like generating facilities, the largest transformers, etc.

#201257 - 05/01/10 04:34 PM Re: Protecting against EMP [Re: Arney]
Susan Offline

Registered: 01/21/04
Posts: 5163
Loc: W. WA
"Are solar storms much of a direct threat to personal gear? I've really only heard of the greater power infrastructure being at risk, like generating facilities, the largest transformers, etc."

If/when we have a good one, we shall find out what worked and what didn't. Nothing beats experience, right?


#201265 - 05/01/10 07:22 PM Re: Protecting against EMP [Re: marduk]
Brangdon Offline

Registered: 12/12/04
Posts: 1204
Loc: Nottingham, UK
Originally Posted By: marduk
Would my metal sided outbuilding function as a Faraday Cage? It has sheet steel sides and roof. Would I need to bond the roof and sides, the doors (walkthru and vehicle) to the building. Would the rebar and rewire in the floor be enough, would I need to bond this to the walls. What size bonding conductors and how many would be needed? Realistically what current flux would I need to consider in the calculations
An EMP has an associated wavelength. Actually it will have a bunch of them, and it's the shortest that matters. The holes in your Faraday Cage need to be smaller than whatever that wavelength is. I'd expect a building to have holes that were too big, but you can't do much meaningful design without knowing the kind of EMP you are defending against.

It's probably easiest to get a smaller Cage and keep backup equipment in that. A microwave oven would probably do in a pinch, as they are well-sealed against microwave radiation. A simple metal box with a tight-fitting lid (metal-to-metal, not a water-proof rubber seal) would be good too.
Quality is addictive.

#201298 - 05/03/10 01:23 AM Re: Protecting against EMP [Re: Brangdon]
Tirec Offline

Registered: 08/24/07
Posts: 52
Loc: Rocky Mountain West
I've been doing research on EMP of late, and While I don't consider myself an expert, I think I've learned enough to make a educated assessment for my personal risk assessment.

My summary: In an emergency, needing to rely on electrical equipment could be risky, such as resupply of batteries, requiring a generator, water damage, etc. If your start your preparations on the foundation of working without electrical equipment, then each and every piece which does work is added convenience and comfort for your situation.

Here's a part of how I came to my assessment.

I found this in “Nuclear Weapons Effects Technology” , http://www.fas.org/threat/mct198-2/p2sec06.pd

The effects (of Transient Radiation Effects on Electronics (TREE) and Systems-Generated Electromagnetic Pulse (SGEMP)) depend not merely on total dose but also on dose rate. Naturally occurring effects include total dose from electrons and protons trapped in the Van Allen belts and single-event upset (SEU) or even single-event burnout. SEU results when enough ionization charge is deposited by a high-energy particle (natural or man-produced) in a device to change the state of the circuit—for example, flipping a bit from zero to one. The effect on a power transistor can be so severe that the device burns out permanently.

Delayed gammas in a 1–10 microsecond period at the same dose rate can cause latchup and burnout of devices. Latchup is the initiation of a high-current, low-voltage path within the integrated circuit and causes the circuit to malfunction or burnout by joule heating.

Total ionization greater than 5,000 rads in silicon delivered over seconds to minutes will degrade semiconductors for long periods. As device sizes decrease, the threshold for damage may go down.

It is inherently difficult to predict the effects of TREE and SGEMP from first principles. Because components, circuit boards, cases, connectors, and everything else within a system can be arranged in many ways, and because radiation can come from any direction, only a detailed simulation can do the job. The task of prediction is made more complex because the effects of the radiation pulse can depend on the operating state of the system at the moment the radiation passes through it.

Other good information is available from Nuclear Contamination and Avoidance FM 3-3-1 Appendix C - Nuclear Burst Effects on Electronics http://www.globalsecurity.org/wmd/library/policy/army/fm/3-3-1_2/Appc.htm

Note: This figure outlines the likely vulnerabilities of categories of equipment. Individual items within each category can vary considerably in their vulnerability to EMP. Any equipment attached to a collector or antenna has increased vulnerability.

Low-power, high-speed digital computer, either transistorized or vacuum tube (operational upset)
Systems employing transistors or semiconductor rectifiers:
Computers and power supplies
Semiconductor components terminating long cable runs, especially between sites
Alarm systems
Intercom systems
Life-support systems
Some telephone equipment that is partially transistorized
Transistorized receivers and transmitters
Transistorized 60-to-400Hz converters
Transistorized process control systems
Power system controls and communication links

Vacuum tube equipment that does not include semiconductor rectifiers:
Alarm Systems
Intercom Systems
Teletypes & telephones
Power supplies
Equipment employing low-current switches, relays, meters:
Life-support systems
Power systems control panels
Panel indicators and status boards
Process controls
Hazardous equipment containing:
Pyrotechnical devices
Explosive mixtures
Rocket fuels
Long power cable runs employing dielectric insulation
Equipment associated with high-energy storage capacitors

High-voltage equipment:
Transformers, motors
Lamps (filament)
Air-insulated power cable runs
Rotary converters
Heavy-duty relays, circuit breakers.

EMP can cause two types of damage, functional damage and operational upset. Functional damage is physical damage to the equipment which requires replacement or repair of components. Operational upset does not show any physical damage but interferes with the operation of the equipment by erasing data from a computer memory or by causing a computer device to send an erroneous signal to the piece of equipment it controls. Operational upset can occur at EMP energy levels that are 1% to 10% of those required to inflict functional damage.

Humans can be directly injured by EMP only if they are physically touching metallic collectors (cables, railroad lines, etc.) at the moment of the tremendous EMP surge. EMP hazards may exist from indirect or secondary EMP effects. For example, damaged electronic equipment may catch fire if relays are switched to the wrong positions. Also, those using digital instruments, such as for navigation or health care, may receive incorrect information from those instruments that have been upset by EMP.

SCADA (Supervisory Control and Data Acquisition) systems collect data from various sensors in a factory, plant or other remote locations and transmit the data to a central system to then manage and control the systems for which the data was collected. Some examples of SCADA use include control of sensors, relays, pumps and conveyors in manufacturing and distribution systems, remote monitoring of systems in hazardous environments, facilities requiring precise climate control, mining plants, water and electrical utility installations, oil and gas refineries, pipelines, nuclear power plants and mass transit systems. According to the Critical National Infrastructure Report (http://www.empcommission.org/docs/A2473-EMP_Commission-7MB.pdf), released April 2008, general-purpose desktop computers and SCADA remote and master terminal units were the most susceptible to damage or upset of all items tested. The result of EMP interrupting these systems, even temporarily, would cause a catastrophic failure of the systems, and in the case of transportation systems, an immediate risk of a significant loss of life.

In 1986 the American Radio Relay League's (ARRL) QST Magazine presented a 4 part series titled "Electromagnetic Pulse and the Radio Amateur". This series was condensed from a US Federal government National Communications System report "Electromagnetic Pulse/Transient Threat Testing of Protection Devices for Amateur/Military Affiliate Radio System Equipment".
Part 1 appears in QST August 1986, pp. 15-20, 36 (http://www.arrl.org/tis/info/pdf/88615.pdf)
Part 2 appears in QST September 1986, pp. 22-26 (http://www.arrl.org/tis/info/pdf/98622.pdf)
Part 3 appears in QST October 1986, pp. 38-41 (http://www.arrl.org/tis/info/pdf/108638.pdf)
Part 4 appears in QST November 1986, pp. 30-34 (http://www.arrl.org/tis/info/pdf/118630.pdf)
You may be able to access the articles through ARRL if you're a member, but they're currently available at http://www.qsl.net/w3bmd/emp.html

Some liken EMP to lightning. Unlike lightning, EMP works on all phased angles, vertical and horizontal combined. Because lightning is phased one direction only, when a charge reaches a 90° it will be stopped. Being both vertically and horizontally polarized, EMP will go around 90° angles. (www.aussurvivalist.com/nuclear.empprotection.htm)

Lightning pulse rise time is a few millionths of a second, lasting hundreds of milliseconds at lower frequencies than EMP. Field Strength is a few thousand volts per meter (highest at 50-100yds ~< EMP). EMP pulse rise time is a few billionths of a second, lasting less than a thousandth of a second in <100MHz frequency range (esp. 100kHz - 10MHz). Field strength can be 50,000 volts per meter. While 99% of HEMP energy is at frequencies below 100mHz, most HEMP occurs in the frequency ranges between 100kHz and 10mHz.

Cresson Kearney recommends the following steps be taken to protect radios from EMP in the book Nuclear War Survival Skills published by the Oak Ridge National Laboratory, 1979 edition, page 19:
- Use only the built-in antenna on AM radios. The built-in antennas of small portable radios are too short for EMP to induce damaging surges of current in them.
- Keep antennas of FM, CB and amateur radios as short as practical, preferably less than 10 inches. When threatened by EMP, do not add a wire antenna or connect a short radio antenna to a pipe. The surge current resulting form EMP can damage diodes and transistors, ending a radio’s usefulness or reducing its range of reception.
- Keep all unshielded radios at least six feet away from any long piece of metal, such as pipes, metal ducts, or wires found in many basements and other shelters. Long metal conductors can pick up and carry large EMP surges, causing induced current to surge in nearby radios and damage them.
- Shield each radio against EMP when not in use by completely surrounding it with conducting metal if it is kept within six feet of a long conductor through which powerful currents produced by EMP might surge. A radio may be shielded against EMP by placing it inside a metal cake box or metal storage can, or by completely surrounding it with aluminum foil or a metallic window screen. Old microwave ovens with the cord removed will also provide protection.
- Disconnect the antenna cable from your car radio at the receiver – or at least ground the antenna when not in use by connecting it with a wire to the car frame. Use tape or clothespins to assure good metal-to-metal contact. The metal of an outside mirror is a convenient grounding point. Park your car as near to shelter as practical, so that after fallout has decayed sufficiently you may be able to use the car radio to get distant stations that are still broadcasting.

The key principles to remember when dealing with shields and shelters are the requirements for a continuous shield made of metal. Shields are continuous when they have no breaks or openings. Once the shielding metal is at least a few millimeters thick, having a continuous shield with no breaks is more important than adding more layers of shielding metal.

In some situations, power sources may be more vulnerable to EMP than the devices being driven. While generating equipment may be fairly resistant to EMP, devices within the generating equipment that control power generation can be vulnerable. The long lines used in civilian power systems can pick up significant amounts of EMP energy, which can cause damage to equipment connected to this grid.

Sun stuff
Sunspot and solar flare activity is typically on 11 year cycles during which violent storms or bursts on the surface of the sun increase solar output or brightness and through coronal mass ejections, send enormous waves of highly charged solar particles (plasma) through space which can affect electrical distribution systems, satellites and radio/TV signals on earth. Power distribution interruptions were created in Quebec in 1989 and 2000 and Sweden in 2003. Pager and credit card transaction interruptions, relying on satellite communications, were attributed to a solar flare in April 1998.

A huge solar flare on August 4, 1972, knocked out long-distance telephone communication across Illinois. That event, caused AT&T to redesign its power system for transatlantic cables. A similar flare on March 13, 1989, provoked geomagnetic storms that disrupted electric power transmission from the Hydro Québec generating station in Canada, blacking out most of the province and plunging 6 million people into darkness for 9 hours; aurora-induced power surges even melted power transformers in New Jersey. Some of the most powerful storms recorded battered the Earth from October 31 to November 7 in what was known as the “Halloween Storms of 2003”, causing aircraft navigation re-routes, and communications and power outages. In December 2006, X-rays from another solar storm disrupted satellite-to-ground communications and Global Positioning System (GPS) navigation signals for about 10 minutes.

The largest flare recorded is known as the Carrington Event in September 1859. Normally, the coronal mass ejection from solar flares takes three to four days to reach earth. Less than eighteen hours following the observation the massive solar flare, telegraph wires in both the United States and Europe spontaneously shorted out, causing numerous fires, while the Northern Lights were documented as far south as Rome, Havana and Hawaii, with similar effects at the South Pole. Not only was this coronal mass ejection an extremely fast mover, the magnetic fields contained within it were extremely intense AND in direct opposition with Earth's magnetic fields. That meant the coronal mass ejection overwhelmed Earth's own magnetic field, allowing charged particles to penetrate into Earth's upper atmosphere. (http://science.nasa.gov/headlines/y2003/23oct_superstorm.htm) While there was no monitoring equipment to measure the intensity of the storm at the time, scientists are able to examine the amounts of nitrites and beryllium-10 found in ice cores to determine the intensity of the storms. The Carrington Event is believed to be the strongest in the last 500 years.

A space storm's impact is measured in nano-Teslas (nT). The lower the figure, using negative numbers, the more powerful the storm. A moderate storm can be around -100 nT; extreme and damaging storms have been logged at around -300 nT. The 1989 coronal mass ejection that knocked out power to all of Quebec, Canada measured -589 nT. The 1859 perfect storm was estimated to have been -1,760 nT. (http://www.space.com/scienceastronomy/mystery_monday_031027.html)

A US map of vulnerable transformers with areas of probable system collapse encircled is at: http://science.nasa.gov/headlines/y2009/images/severespaceweather/transformermap.jpg

After reading "Nuclear Weapons Effects Technology", I lowered the likelihood of an EMP attack in my personal risk assessment due to the requirement of a High Altitude EMP strike (HEMP) to affect a large area.

A HEMP attack must use a relatively large warhead to be effective (perhaps on the order of one megaton), and new proliferators are unlikely to be able to construct such a device, much less make it small enough to be lofted to high altitude by a ballistic missile or space launcher. Russia and China are likely the only nations which have the capabilities to deliver a single weapon large enough to affect the entire U.S. That's not to say that they wouldn't encourage and enable others. At this time, the likelihood of Russia or China launching an EMP attack is not great, though not impossible, but they are fully aware that our technology is our Maginot line.

#201302 - 05/03/10 03:37 AM Re: Protecting against EMP [Re: Tirec]
Art_in_FL Offline

Registered: 09/01/07
Posts: 2432
On the practical side I don't see this as an issue. Not for personal, or even community preparations. I'm just not that dependent on such things and consider the threat minimal.

The wider issue of EMP is, has been, and will be used to push for missile defense and to demonize selected political targets. The committee cited is, in effect a, taxpayer funded, missile defense, and radical GOP international relations advocacy group.


Fear mongering for fun and profit. It is a perennial favorite of a scary story for reposing. And everyone loves a good scary story.

Edited to change offensive phrase that IMHO wasn't very offensive. Evidently you can't use the term "R*ght-w*ng". I find much of what they do offensive but to ban the phrase seems petty. Oh well, not my site; not my rules.

Edited by Art_in_FL (05/03/10 03:48 AM)

#201309 - 05/03/10 10:59 AM Re: Protecting against EMP [Re: Tirec]
Am_Fear_Liath_Mor Offline
Carpal Tunnel

Registered: 08/03/07
Posts: 3078
At this time, the likelihood of Russia or China launching an EMP attack is not great, though not impossible, but they are fully aware that our technology is our Maginot line.

Ahh, long gone are the days of those Spetznas GRU with their sharpened shovels digging up the telephone cables outside Semi Autonomous Ground Environment control centres, where Lee Harvey Oswald (Mr Black of the NSA, ahem...Oops one of my own conspiracy theories laugh ) used to work during his day job. wink

Edited by Am_Fear_Liath_Mor (05/03/10 11:13 AM)

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