The Electromagnetic Pulse (EMP) effect was first discovered during the Starfish Prime high altitude hydrogen bomb test in 1962 where electrical systems were damaged in Hawaii, 800 miles from the blast. EMP has become the big voodoo sci-fi scare among survivalists right up there with radiation zombies on our list of expensive priorities. EMP can be combated without massive expense by using common sense and some easily made preparations. EMP is a wide spectrum short duration radio pulse generated most famously by a nuclear detonation in the atmosphere. Any conductive object is an antenna, radio waves resonating in a conductor create an electrical field and voltage and amperage are generated, just like your crystal radio set made enough electricity to actuate the earphone from the radio/electrical resonance of your long wire antenna. What is at risk? Anything with a run of metal can couple a voltage spike when exposed to EMP, simple electrical motors and radio tubes are unaffected by EMP just like static electricity would not do them any damage. The most vulnerable devices are those connected to a wire, both the power cable and the antenna both couple EMP, in fact the power cable is connected to the grid which acts as a giant antenna. What can we do? There are two options for most people: shield or divert the EMP. Shielding can be complex like wallpapering the walls, ceiling, floor, windows, and door with metal screen and grounding it making a Faraday cage. Almost no RF energy could enter or exit this room, but external antenna feeds would be required for any radio equipment. A simpler way is to remove or fold all antennas and wrap your device in aluminum foil. Shielding is fine for stored electronics but if antenna or power supply extends your protection is eliminated, if a radio device is able to receive your shielding is not effective.
Diverting or discharging EMP is how “in use” electronics are protected. EMP can be in the thousands to million volts range but its amperage is typically very low and not a health hazard. These voltages will quickly run to the closest ground when the correct equipment is used. Gas discharge dissipation eliminates high voltages by using a gas filled tube (typically neon) which once ionized conducts electricity, it is shorter to dump across the ionized gap and to ground than burning through your expensive solid state radio. A proper ground is required to be most effective a copper rod driven 6 feet into damp earth is excellent. Also very good is a cold water pipe to well or municipal water. A dissipator can be made by splitting a piece of copper tube and running your antenna line through the tube. Solder one or more neon lamps between antenna and the tubing then solder up the seam connect the tube to the cables ground jacket run an extra grounding cable. these can be placed throughout your antenna system or you can purchase higher quality factory models especially for the connection to your radio. The longer the wire or antenna the higher the risk of developing damaging voltages. Dissipation for grid power is quite easy, cheap, and readily available now. A quality surge protector is designed to protect from our common EMP problem–lightning. If you or your home has survived a near lightning strike than you have experienced something like an EMP attack!
EMP is not voodoo and like many Cold War topics it was blow out or proportion by Hollywood. While having a spare distributor with points instead of a GM High Energy Ignition (HEI) system can’t hurt (any spare is good), it may be better to have a long life burned-in HEI rig which will last much longer and keep your vehicle running over all circumstances other than a nearby nuclear strike which would likely melt your car shortly after destroying your ignition. HEI ignition is already uses high voltages and sparks, short wire runs won’t develop the energy required to burn out older heavy duty HEI systems. I make no claims on later model computer driven systems. The phone system was very EMP hardened in the old Bell system days, deregulation has likely reduced these preparations as has the Cold War threat reduction. Power grid is questionable with many miles of “antenna” ready to fry regulating components. Have no doubt that your DSL and cable modems will die a quick death, likely shoving a serious spike through your wired network, the tiny WiFi antennas with 1-2 db gain will likely survive even if the WiFi card fails so this may actually protect your laptop if it is properly surge protected again you can make dischargers for your network cable if you want to take the time. DSLAM‘s on the Telco side have no requirement to be EMP resistant, so it is likely all broadband will die after a EMP incident.
BTW, up to the old Intel 386 there was EMP hardening designed into processors I am not sure which 386 model was the last to include this feature.
References:
http://www.fas.org/nuke/intro/nuke/emp.htm
http://www.geocities.com/HotSprings/Falls/1984/emp.htm