This essay discusses electronic interference from multiple perspectives including its use as an attack on systems as well as natural causes. It defines the phenomenon and outlines basic communication theory. It reviews various types of interference and it impacts on the general public. It also looks at the EMP weapon, its ability to create interference, and cause significant damage to systems.
Electronic Interference has existed since the advent of the telephone. The strategy of conducting warfare using this tactic truly developed throughout the Cold War. The chess game played between the superpowers, as well as regional conflicts afforded an opportunity for the development of these technologies. At the same time, technological advancements in other forms of communication have created additional sources and methods of such interference. As a strategy, electronic warfare has suffered since the end of the Cold War.  However, like many military applications, electronic interference has gone "mainstream" and is now more readily available to civilians, friend and foe.
For the purpose of this essay, electronic interference can be defined in several ways. First, it can be defined as jamming signals introduced to cause failures in electronic communications.  Or more broadly, an electrical or electromagnetic disturbance that causes an undesirable response in electronic equipment.  Interference can also result naturally. Electronic Interference refers specifically to interference caused by the operation of electrical apparatus that is not designed to radiate electromagnetic energy.  In order to truly understand interference, it is critical to have a basic understanding of communications.
Electromagnetic energy carries all communications. Signals are waves that traverse some medium and are characterized in terms of frequencies.  Additionally, signals are broken into various bands and are measured in units called hertz. These frequencies make up the electromagnetic spectrum; they can range from high to low. Radios, cellular phones, and television all use different frequency bands to communicate. While all of these mediums exist to improve and enhance everyday life, they are vulnerable to interference. As this essay will show, interference can be caused naturally, it can be purposeful, or it can be used as a defense.
Electronic Interference can occur naturally. Frequency bands can accidentally cross; many experience this when they can hear other individuals' conversations from their telephone. The earth is a constant source for such interference. Geography creates interference with differences in topology. Mountains and valleys can often disrupt the various mediums over which some communications travel. The weather is yet another source of interference.  Wind, rain, and clouds are the usual suspects. Manmade obstructions are a frequent source of electronic interference. Interference is common in large populated urban areas. Finally, the sun can produce disruptions in electronic equipment through solar flares. In 1989, the largest solar flare on record disrupted power grids in Canada.  Flares produce a great deal of electromagnetic energy, which in turn can impact electronic apparatus on earth. Interference can also occur unintentionally. Malfunctioning equipment or user error can produce these unintended effects.  The impact of electronic interference is obvious, so is its potential as a weapon.
An electronic attack is the transmission of electronic jamming signals, which disrupt communications and other signal emitter systems.  Additionally, jamming signals can transmit false communications, which deceive the target through their own information collection systems.  One of the most common types of interference is barrage jamming, which is simultaneous electronic jamming over a broad band of frequencies.  This is done to eliminate a target's ability to communicate through any technologically advanced medium. In war for example, barrage jamming can force a commander to lose tactical control of air and surface assets. Global Positioning Systems have become critical to conducting modern warfare; these systems are often targets of such jamming efforts. Consequently, there is a method known as support jamming. With this method, sources of electromagnetic energy are searched for, located, and identified through a process called Electronic Warfare Support (ES).  Finally, there is the electromagnetic pulse. This type of attack can result from a nuclear weapon blast or a short intense burst of electromagnetic energy similar to lighting.  This type of weapon has existed since the dawn of nuclear weapons, and has the ability to effectively interfere with both civilian and military assets. It is believed that such a weapon was used during the latest Gulf War to disrupt Iraqi communications and command structures.
As stated earlier, electronic warfare can be used as a defensive tactic. Electronic Protection (EP) seeks to protect the "friendly" use of the electromagnetic spectrum.  This method is employed to protect command, control, and communication (C3I) from enemy attack and disruption efforts.  In the United States, protection is generally accomplished through legislation that prohibits creating the purposeful interference. It is clear that understanding the various mediums and frequencies is critical to developing attack and defense strategies.
Existing high-powered radio jamming systems are generally very cumbersome in their design and operations. They are also inefficient in their operation and desired performance.  Hence, the present day threat of major intentional interference efforts may be minimal. Activities on smaller scale could include disruption of cellular and wireless technology including wireless LAN's. However, with the continued advancement of technology it must be acknowledged that major disruption efforts of communication mediums through interference are viable.
The threat appears to be greatest for first responders. In a first responder scenario, barrage jamming could be used to amplify a physical attack. The tragic losses from 9/11 show the significance of communications to these individuals. Critical infrastructure, particularly SCADA embedded systems would be vulnerable to such attacks. The electronic systems, which control energy, fuel, and other resources could be disrupted or damaged from an attack using electronic interference. Again, the impact could be immeasurable.
One of the greatest threats from electronic interference is the result of unintended actions. Poor design of building structures, communications apparatus, crowded mediums, and a lack of standardization are representative of the problem.  The lack of standard communication protocols like those in Europe is particularly challenging for first responders. Multiple mediums of communication can create unintended and dangerous electronic interference.
Finally, there is the ever-growing threat of the Electromagnetic Pulse. While the pulse is usually short-lived the effects can be devastating. It is theorized that a nuclear burst 200 miles above the state of Kansas could create an EMP that would envelop the entire country.  The EMP could then effectively wipe out much of the communication apparatus, financial markets, as well as other critical infrastructure. More concerning would be the use of a nuclear device or EMP weapon by terrorists. The relative low cost and limited physics required to create what some have dubbed an E-Bomb, make this threat a real possibility.  To detonate such a device in a major urban area like New York or Chicago could effectively destroy all communications within a given radius. Additionally, an E-bomb could wipe out the SCADA controls for a facility like the Hoover Dam, which could result in a catastrophic loss of life and property. 
In reviewing electronic interference, it is clear that as dependence on technology has grown so to has its potential impact. Interference can be used as a weapon in times of war or in terrorist acts. Interference can be unintentional, yet equally as impacting. It appears that over the coming years it will become easier to create interference and much more difficult to protect against. While the Cold War may be over, it appears that the need remains for diligent research and development in the area of electronic interference causes, weapons, and countermeasures.
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[This article focuses of Military applications of EI]
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[The article focuses of Military applications of EI]
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Achilles Heel" Navy Documents. Fall 2001. http://www.chips.navy.mil/archives/01_fall/electromagnetic_interference
[Conley is a career communicator with 25 years of Telecom experience. He currently heads the EMI Program at Dahlgren, VA]
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[Information on the design of EI devices]
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[Gabrielson highlights the topic of EMP and lightning as a source of EI]
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[Research on EMP weapons and their impact]
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[General article on SOlar Flares and their interference of systems on Earth]
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[Article discusses E-bombs and potential impacts]