EMP Myths and Faraday Cages--by Guest Contributor Scott Bishop
We talk about EMPs and Faraday cages periodically on here as well as our Facebook page and it seems that every time we do, we discover a LOT of misconceptions about the two. There’s no shortage of completely bogus and illogical YouTube videos published on the topic—even by those claiming to be engineers or PhD holders. Unfortunately, far too many are buying into such nonsense at the risk of losing a critical asset amidst a crisis. So, I begged and bribed my brainiac sweetheart to write an article for our readers and specifically address the most common misconceptions that people have about EMPs and Faraday cages. As you can see, he gave in to my bribing. *grin*
Here it is. (Thanks, Honey!)
The basics of an EMP
An Electro-Magnetic Pulse (EMP for short) is a short and powerful burst of electro-magnetic energy. This phenomenon occurs whenever an electro-magnetic wave occurs forcefully and suddenly. This can happen in a number of ways. For instance, an EMP attends each and every lightning strike, albeit on an extremely small scale. This type of EMP, though common, is of little concern, however, because the amount of energy is relatively small and is spread out over a large amount of time (relatively speaking). This is important to understand when discussing the myths surrounding EMPs that may cause widespread damage.
EMPs occur throughout the nation, on a daily basis. Why aren’t we concerned about them? Because, generally speaking, they are limited in their effect, not being forceful enough, or not occurring in a short enough burst for any real damage to occur.
The EMP that is of concern though is one which is powerful enough to affect a wide area and which occurs in a short enough burst that it excites electrons in the stratosphere to the point that they will be thrust downward rapidly, generating a large amount of current. This generally occurs only in two situations, one being caused by nature, and the other being man-made, but both having similar effects.
Our sun, as wonderful as it is, is an EMP generator. We are constantly and consistently bombarded with EMPs from the sun, yet most are not powerful enough to have any real effect, let alone a lasting one. Sun-made EMPs (more popularly known as solar flares or coronal mass ejections) are brought about as explosions occur on the surface of the sun, which propels electro-magnetic energy outward. Once in a while, these explosions occur at just the right moment and in just the right place on the surface of the sun that when they travel directly outward from the sun, they directly impact the earth. When these explosions, and the resulting waves of electro-magnetic energy they cause are strong enough, they can damage electronics, knocking out communications, causing computer crashes, etc. This type of effect occurred during a solar storm in 1859, known as the Carrington Event, which damaged telegraph systems across the nation, and caused telegraph wires to catch on fire.
Above the stratosphere, the effects of a sun-made EMP are of fairly limited effect, both in scope and duration. This is because the EMP at that stage is nothing more than electro-magnetic force, in the form of high-powered high-frequencies. This has the effect of raising the noise floor of any electronic circuit within range of the EMP, causing modulator, demodulator, and other electronic circuits (built from transistors, diodes, etc.) to not be able to distinguish between the two levels of voltage they were designed for. This is called circuit overloading, and is usually temporary, existing only for the duration of the EMP and a short time after, as computer circuits reboot. (A similar effect can be seen on your car radio when one radio station begins to “walk” all over another radio station of the same or similar frequency.)
The larger problem occurs as those high-powered high-frequencies smash into the stratosphere, causing electrons to be propelled downward toward earth, which creates a large amount of current. It is these electrons, and the attending current, which cause damage to electronic circuits by shattering diode junctions (transistors are essentially two diode junctions, and electronic circuits include transistors and diodes). Of course, this only occurs when enough force is applied by the solar flare to begin with.
Man-made EMPs can be categorized both as local and regional, as well as high-altitude and low-altitude.
Local man-made EMPs are of the variety being tested and used by both military and police forces, in the form of mobile EMP-generators. These emit electro-magnetic waves, and are directed at a specific target, such as a speeding car. Because this variety produces only an electro-magnetic wave, its effect is only that of circuit-overloading, and the electronic circuits will survive to live another day, though they’ll be off-line for a period of time.
Regional man-made EMPs are the truly scary variety that most people are concerned about. The only real executable application of this type is the HEMP (High-altitude EMP), which occurs when a nuclear device is detonated at, or slightly above, the stratosphere. The photons generated by this nuclear explosion travel down through the stratosphere, having the same effect as a high-powered solar flare, but with much higher power (being generated closer to earth). The current generated by an HEMP is high enough to damage any unprotected diode junction within line of sight of the HEMP. Because it relies to a great extent upon line-of-sight, it would take 2-3 HEMPs to cover the continental United States.
Let’s dispel some Myths about EMPs and Faraday Cages
- “Foil and other like resources can protect electronics from EMPs/solar flare damage. I know! I saw it on Youtube!”
Not likely! There is a big difference between relatively low-power radio frequencies and high-power high-frequency EMPs. Foil may be enough to stop radio frequencies from getting through, but it is not substantial enough to handle the current generated by an EMP. Using foil to guard against an EMP would be similar to using 24 gauge wire for a car battery; it is likely to burn through. The Carrington Event of 1859 proved this point when it caused telegraph wires much thicker than foil to catch fire.
- “Batteries will be destroyed due to an EMP”
Not likely! Most batteries do not contain a diode junction. The diode junction is the electronic part most likely to be damaged by an EMP. Batteries are made of relatively thick plates of metal, very dissimilar to the very small, narrow junctions used to create diode junctions. If anything, the short, yet powerful, pulse of an EMP may actually cause an extra charge to your battery, not that it will be that noticeable, since all of the electronics you run off of that battery will likely be fried.
- “A person’s vicinity to an EMP doesn’t make any difference.”
Untrue! Just as light operates within the bounds of the physics, Law of Squares, so does electro-magnetic current. The further you are from the electro-magnetic field generator, the less of an affect it will have on you (or more specifically on your circuits). Close, line-of-sight objects will be the most susceptible to an EMP, while objects hidden behind mountains, or underground, will be much less affected.
- “A car is already protected against an EMP, and it won’t stop driving in its tracks because of one.”
Untrue! Unless you are one of the few lucky enough to own a car not controlled by a computer of some sort (think pre-1967), your car is likely to be affected by an EMP which covers your area. Cars, like so many other things in today’s society, are controlled by computer, which is made of millions of tiny diode junctions (see discussion above). Even if you’re lucky enough to have your car underground when the lights go out, don’t plan on having much gas to put in your car as the computer-controlled pumps are likely to be out of commission.
- “Planes will fall out of the sky when an EMP hits.”
Not likely! Though the electronic circuits, which make planes so much easier to control, will likely be damaged beyond repair, planes operate on the basic principles of lift and thrust. Though they will likely be turned into permanent one-time-use gliders, planes will not be forced down just because their engine controls have become useless pieces of waste; though I wouldn’t want to be one of the many pilots trying to find a field big enough to call a landing space for a 777, and particularly not without any ground lights for guidance or reference if an EMP event should happen at night.
What other EMP myths or mysteries have you heard that you’d like our take on? We’ll address them in future articles.
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