Survivor's Notebook #1
The EMP Threat and How to Deal With It
The EMP or Electro-Magnetic Pulse was discovered after early nuclear tests knocked out power and
communications systems many miles away from the test site. The government has conducted extensive
research on EMP but since the cold war ended research has been cut back and much of the information is
still classified. Hence good hard facts are scarce concerning the specific effects of an EMP attack. It is
generally accepted that a major EMP attack would cause severe damage to our national infrastructure and
to your own personal electronics as well.
An EMP attack would most likely occur as a powerful high altitude nuclear blast over the central United
States. Rouge nations with limited capabilities such as North Korea or Iran may soon be able to launch an
effective EMP attack. Other devices called e-bombs some of which can reportedly be constructed with
conventional explosives and easily obtained electrical components present a more localized threat. The
prevention is the same for e-bombs.
EMP is similar to a radio wave in that it will penetrate some materials easily and be blocked or attenuated by
others. EMP is a pulse of electromagnetic energy rather than a radio wave, EMP will arrive through the air
in a line of sight pattern, but also a second, slightly delayed pulse will arrive over the power, phone lines
and cable lines. Power and telephone lines will absorb a great deal of EMP energy because they will act like
very long antennas. This energy will then be dumped it into your power outlets and phone jacks destroying
most of the electronics connected to them. External antennas will also absorb EMP energy and the larger
the antenna the more it will absorb. Any large metal structure will collect or absorb EMP energy; if it is
grounded such as a water tower might be, then the energy will dissipate into the earth.
The amount of damage will depend on several things; the power of the EMP device(s), the amount of
shielding between the electronics and the EMP source, and the delicacy of the electronics.
Semiconductors and microcircuit chips are the most susceptible. EMP will damage your electronics even if
it is turned off because the EMP induces an electrical current into any conductor it hits and in a matter of
only a few microseconds it can burn out sensitive circuits. Personally, you will probably not feel a thing,
although I have found no reliable information about how a pacemaker or other medical electronic device
might be affected.
The effects of an EMP attack could be hap-hazard and hit and miss, taking out some things and missing
others. Partial shielding in steel framed or sided buildings or metal bodied cars could mean less damage to
the electronics than in a wood framed house or a fiber bodied car. Your car might survive due to its metal
body but that shielding has gaps, so maybe it won't, it's kind of dicey to predict. Also where the car is
located when the EMP attack occurs will figure in. The electronics may be temporarily disabled and recover
at least partially after excess electrical charges dissipate. Older cars without electronic ignition will
probably be fine. If your cell phone survives it may be useless because satellites and ground stations may
be out. The exact effects are hard to predict.
The good news is that it is fairly easy and inexpensive to protect your survival electronics from EMP
damage by using what is known as a Faraday cage or shielding. The tin box that cookies sometimes come in
is a good example of what a Faraday cage is. Whatever is inside the cookie tin has some protection from
EMP. Although some claim this is not a necessary step, put some foam rubber or other non-conducting
material inside the tin, sit the electronics in the foam rubber, close the tin and you have some protection
from EMP. Put that tin inside your metal gun cabinet or file cabinet and not touching the metal of the cabinet
and now you have even more protection. It's all about shielding.
The Faraday cage or shielding is best if it made from a continuous fairly thick metal enclosure that is a very
good conductor of electricity such as copper or aluminum. It ideally should have no holes or gaps in its
surface and all sides should make electrical contact. That would be the ideal shield, but a lesser shield may
be more quickly produced and offer sufficient EMP protection to withstand a less severe attack.
A washer or dryer could be used in a pinch if it has metal on all sides, top and bottom. An old microwave
oven would offer only partial protection because of the screen shield used in the front window which is
tuned to filter out the microwave from the oven, not EMP. As a last resort if nothing else is available and
attack seems eminent, wrapping a cardboard box with aluminum foil in several layers is better than no
shielding at all.
Faraday cages can be as small or as large as needed. An entire house could be shielded or just your cell
phone. A small Faraday cage for EMP protection does not need to be grounded although some instructions
call for grounding. Keep in mind that the grounds in the electrical system of a house or even cold water
pipes could possibly become charged if the attack is very strong. For larger structures such as a garage, a
good proper earth ground would be needed.
Military equipment is to some extent already protected from EMP, but probably most civilian equipment is
not, so look for wide spread outages of essential services; the power grid may be out for a long time, police
and emergency services could be severely hampered. Hospitals may lose essential medical devices, radio
stations may be off the air, phone communications and traffic controls could be knocked out.
In the event of such an EMP attack the HAM radio operators who are knowledgeable about protection from
EMP will be an invaluable resource. It is imperative that your emergency radio receivers have short wave
bands so that you can tune in and listen for vital information the HAM operators may be passing over the air
waves. Also with these radios you can listen to news reports from around the world. They should be battery
or hand crank powered, remember the power grid may be out.
Devices such as lightning arrestors or surge protectors that are rated by their manufacturer to protect
against EMP are a probably a good investment, but because we have never have had an actual EMP attack
these devices are unproven in real world scenarios. Remember shielding is a big part of the equation and
those devices may not protect you from the airborne pulse striking your electronics directly. When looking
at specifications for EMI or RFI shielding remember this shielding is not adequate for EMP although it may
mitigate damage in some cases. EMI and RFI are electro-magnetic and radio frequency interference.
The bottom line is; if it is essential survival electronics, keep it adequately shielded and disconnected from
external cables and antennas. That way it stands a better chance to be available when you need it most.
A caveat: the methods described as providing protection from
EMP attack are unproven and not guaranteed. They will help
protect your equipment and could make the difference of
surviving an attack or not.
The author has over 35 years of experience in electronics and computers systems both military and civilian.
© Copyright 2007 - 2013 Tim Thomas, all rights reserved
|This 50 Cal ammo can from an army
surplus store and some scrap foam for
padding and insulation make an
inexpensive, easy to carry means of
protecting essential electronics gear.
Total cost $16.
|In a pinch this hastily constructed shoe box
with multiple layers of aluminum foil will be
better than nothing at all. I have also put this
small multi-band radio inside a cookie tin
wrapped in its cloth cover which provides
another layer of protection.
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