Electromagnetic Pulse (20 page)

1834: Faraday’s Laws of Electrolysis

Faraday was one of the major players in the founding of the science of electrochemistry—what happens at the interface of an electrode with an ionic substance. Electrochemistry is the science that has produced the Lithium-ion battery and the metal hydride battery, both capable of powering modern mobile technology. Faraday’s laws are vital to our understanding of electrode reactions.

1836: Invention of the Faraday Cage

Faraday discovered that when an electrical conductor becomes charged, all of the extra charge sits on the outside of the conductor. This means that the additional charge does not appear on the inside of a room or cage made of metal. In addition to offering protection for people, sensitive electrical or electrochemical experiments can be placed inside a Faraday Cage to prevent interference from the external electrical activity. Faraday cages can also create dead zones for mobile communications.

1845: Discovery of the Faraday Effect – a magneto-optical effect

This was another vital experiment in the history of science. Faraday was the first to link electromagnetism and light – a link finally described fully by James Clerk Maxwell’s equations in 1864, which established that light is an electromagnetic wave. Faraday discovered that a magnetic field causes the plane of light polarization to rotate.

Michael Faraday died in London, aged 75, on August 25, 1867. He was survived by his wife, Sarah. They had no children. He had been a devout Christian all of his life.

He will be remembered by the following quote:

Nature is our kindest friend and best critic in experimental science if we only allow her intimations to fall unbiased on our minds
.

Pieter Zeeman, 1902 Nobel Prize in Physics, wrote about Faraday when recalling the two titles of Faraday’s fundamental work:
Magnetization of light
and
Illumination of lines of force
.

"They appear to us to be almost prophesies, because we have now seen that light can in fact be magnetized, and in nature itself, in the northern lights, an example of illumination of the magnetic lines of force of the Earth by the electrons escaping from the sun."

Prophetic indeed.

Chapter Nineteen
Introduction to the Faraday Cage

A Faraday cage or Faraday shield is an enclosure formed by conductive material or by a mesh of such material, used to block electric fields. Faraday cages sometimes go by other names. They can be called Faraday boxes, RF (radio frequency) shields, or EMF (electromotive force) cages. No matter what you call them, Faraday cages are most often used in scientific labs, either in experiments or product development.

A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference. Faraday cages are also used to enclose devices that produce radio frequencies, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents, such as lightning strikes and electrostatic discharges, since the cage conducts the electric current around the outside of the enclosed space and none passes through to the interior.

Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation. For example, certain computer forensic test procedures of electronic systems that require an environment free of electromagnetic interference can be carried out within a screened room. These are separate spaces that are completely enclosed by one or more layers of a fine metal mesh or perforated sheet metal. The metal layers are grounded to dissipate any electric currents generated from external or internal electromagnetic fields. Thus, they block a large amount of the electromagnetic interference.

A Faraday cage is designed to protect against an electromagnetic pulse that may be the result of a high-altitude nuclear detonation resulting in an EMP. A Faraday cage protects electronics by three different principles:

·
        
the conductive layer reflects incoming fields

·
        
the conductor absorbs incoming energy

·
        
the cage acts to create opposing fields.

In concert, these principles safeguard the contents from excessive energy levels.

For most geomagnetic storms, a Faraday cage is not necessary to protect against the size and scope of the most common coronal mass ejections because solar disturbances are at much lower, E3-level frequencies. A solar event doesn’t transfer energy in sufficient amounts into small electronics, except through wires coming into the system, which act as an antenna. A simple precaution against solar events is to unplug electronics or use high-quality surge suppressors.

Faraday cages may have holes as long as they are small. This is why fine conductive/shielding fabric can be used when constructing a Faraday cage. In practice, the cage’s lid or door usually causes the most leakage. Taping the seam with aluminum tape prevents gaps. The gaps and seams must remain tiny for the item to be effective.

A lot has been written about the grounding of a Faraday cage. The grounding of the cage, by attaching it to a steel rod driven into the earth, has little effect on the field levels seen inside the Faraday cage itself. Grounding primarily helps to keep the cage from becoming charged and perhaps re-radiating. In practice, an ungrounded Faraday cage protects the contents from harmful electromagnetic pulses as well as a grounded one.

Some experts argue that grounding your Faraday cage is a bad idea. Although EMPs and lightning strikes are very different regarding intensity, you might consider how lightning strikes affect a flying plane. The metal shell of the aircraft acts as a giant Faraday cage, dispersing the electromagnetic energy around the plane. The airplane isn’t grounded. Therefore the effects of lightning strikes are minimal.

A recent invention, the anti-static bag, is readily available to protect electronic components against EMPs. They can be purchased in many different sizes, including some large enough to hold radio equipment. Dr. Arthur T. Bradley, author and recognized preparedness expert, opined that while they do offer shielding from EMP, not all products are created equal. He found testing confirmed that products certified to MIL-PRF-8170 and/or MIL-PRF-131 provide the greatest protection from an EMP. Further, when selecting an anti-static bag, consider not only the shielding effectiveness, but also the physical ruggedness of the bag. A tear or large hole can compromise the bag by allowing EMP energy to enter.

Storing a larger set of electronics might require a closet or more considerable space. A DIY shield room can be made by lining a small closet with conductive/shielding mesh, covering the entire room, and then sealing the gaps left by the entry with aluminum tape.

There are three principal methods of protecting vulnerable electronic devices from a damaging EMP attack and natural EMP events;

·
        
Put equipment in a shielded room based on Faraday Cage principles

·
        
Hide it deep into mountain plants or underground bunkers

·
        
Place it in the center of a substantial building behind thick reinforced concrete walls and roof – primarily underground.

The first alternative typically gives necessary protection, assuming that correct and solid construction is met.

The protection effectiveness in a mountain plant or bunker depends on several factors like type of rock and soil, the degree of coverage, cable length, protection devices like gates and other barriers in front of the tunnel, etc.

The last alternative gives only a limited level of protection and is normally not sufficient unless it’s combined with additional solutions; like a Faraday Cage.

Chapter Twenty
Construct a Simple Faraday Cage

The primary method to protect electronic equipment from lightning strikes, electrostatic discharges and EMP is the Faraday Cage. For the majority of household electronics, such as audio-visual, communication, or appliances that can be unplugged from their power source, a Faraday Cage is the easiest way of protecting the smallest electrical equipment. Generally speaking, a Faraday Cage could be a metal box, a trash can, or a manufactured mesh structure designed to divert the electromagnetic pulse. It is important that the objects placed inside the Faraday Cage be insulated from the inside surface of the box, ensuring the object will not be affected by the electronic pulse traveling around the outside metal surface of the box.

A simple and inexpensive design can be achieved through DIY containers suitable for most Faraday Cage purposes. Some examples include cookie tins, ammunition cans, microwave ovens, metal filing cabinets, and galvanized steel trash cans. Faraday Cages do NOT have to be airtight, due to the long wavelength of an electromagnetic pulse. However, the design of the Faraday Cage using a conductive mesh needs to be impeccable. A Faraday Cage can be made of wire screen or other porous metal and provide the necessary protection for your devices.

To construct a simple Faraday Cage using a galvanized trash can, you can follow the step-by-step instructions found on our website:
FreedomPreppers.com
. Here are the basics.

The primary requirements for protection when designing a Faraday Cage are:

·
        
The electrical equipment inside the box cannot touch the metal container. Insulating with foam, cardboard, rubber, plastic or even wads of paper are acceptable methods.

·
        
The metal shielding must be continuous. There can be no large holes or gaps in the shielding material.

Now that you understand the basic principles let’s apply them to a simple Faraday Cage for home use.

There are a few decisions you have to make before starting your homemade Faraday Cage:

·
        
The shape. The cage can have any shape you like: spherical, triangular, oddly shaped, and so on. If you decide to go with the classic rectangular shape, that’s acceptable, as long as you know that the shape doesn’t affect the cage’s effectiveness. As always, keep it simple.

·
        
The conductor material. You must choose the material you want to put on the outside of the cage. This should be a simple decision, as the material doesn’t influence the cage’s activity (as long as it is capable to conduct electricity as discussed above). A heavy-duty, galvanized trash can be the most cost-effective material for an efficient DIY Faraday Cage.

·
        
Holes or no holes. A Faraday Cage can have holes in its walls as long as they are not too big to let the electromagnetic wave in. That’s why you can use an aluminum mesh as the outer layer of the cage. However, don’t risk a design flaw. After an EMP attack, you don’t get a do-over. Use a galvanized trash can and seal the lid with aluminum tape. Make sure the lid is secured firmly to the garbage can.

·
        
Cushioning material. Use a variety of cushioning material to protect the electronics from the inside walls of the Faraday Cage. We suggest upholstery foam that can be purchased in rolls and cut to fit.

·
        
Grounding the Faraday Cage. The debate will rage on regarding this requirement. It’s not necessary, in our opinion.

·
        
Protection against moisture. This is an often overlooked necessity. Moisture will ruin electronics. Your Faraday Cage must be moisture absorbent to create a safe and dry environment for the devices inside. They won’t do you any good if they survive an EMP but they cease to function from moisture damage because of the excessive humidity. Add 50-gram desiccant packs to the inside before sealing.