Disrupting Signal

Disrupting Signal


Disrupting signal

Cyber warfare and electronic warfare share one situation in common. Both are expanding at a rapid rate unseen in any other type of conflict.

Electronic warfare is sub-divided into two branches -electronic support measures and electronic counter-measures. Jammers fall into the second category and they are proliferating as fast as electronic systems expand.

Wherever one hears talk of electronic counter measures (ECM) and Electronic Counter Counter Measures (ECCM) one would be entering an archane world of listening devices and jammers. Some of the jammers can accomplish their task of disruption of communications between two or more points just by churning up a din in the electronic spectrum (noise).

Yet many others would operate in a specified bandwidth in the audio department and others that create virtual images that in effect block out the real object and prevent it from being targeted.

It all began with an inadvertent interception of an enemy radio transmission that indicated preparations for an attack on a specified target. The Russians, trying to defend themselves against the Japanese, began transmitting loud sound on the same wavelength as the Japanese transmitter and prevented it from being heard cogently. The plan to attack had to be shelved.

Since then jamming has become an audio/visual mirage of sound and effect and the creation of virtual images that replicate reality at distances that confuses the attacking munitions guided by a thermal image and hence decoy the attacker to positions away from the main target. 

Decoying and spoofing to create “activity” at places where nothing is happening may not be jamming in the strictest sense of the term but it makes the enemy complete its act-in a totally different direction.

Countering interception

In a nutshell, jamming is the disruption of the transmission of information. Information in warfare usually is the transmission of instructions from the higher command to units at the forward edge of battle.

To be able to intercept, interpret and counter by spoofing and injection of deception is part of the larger architecture of what is generally described as jamming. Thus the activity moves away from just noise generation on specific frequencies to more subtle methods that prevent a signal being received through a modulation of the transmission frequency. 

In the ‘in your face’ jamming where a nation does not want its citizens to be influenced by foreign radio stations the unsubtle use of noise,  be it songs or chatter or machine noise, distorted speech or just the hissing sound of wind on waves. The effect is that the underlying intent of the transmitter is blocked out or covered up by the more powerful transmission of the noise.

During World War II radar came to play a very important role in detection and destruction of enemy aircraft, ships and submarines. After the initial successes in jamming radar among the first methods employed was the dispersion of chaff (thin metal strips) to show what appeared to be an aircraft on radar screens.

Shots fired at such a bloom in the sky naturally pierced thin air. Radar jamming (and acoustic homing torpedoes at sea) was deflected by echos so that radar and sonar do not get a clear fix on the position of the target aircraft/ship. Transponders are used to increase the virtual image of small decoys to look like the real-life aircraft/ships and thereby attract enemy missiles and torpedoes.

The most modern methods of deception/deflection is coating the aircraft/ship with paint that absorbs radiated electromagnetic  waves or shaping the structure in a way that it deflects not just sound but also infra-red reflection that betray presence of heat from an engine source. Stealth technology is an outgrowth of the jamming techniques that have evolved over time.  

The early growth of jamming as a national activity was the product of what came to be called the “Cold War”. It was the creation of two contending politico-military blocs-one controlled by the former Soviet Union in Eastern Europe and the Western bloc led by the US and its allies. The Cold War was characterized by the need to undermine the political system of the Soviet bloc. Communism was antithetical to all that was Capitalism.

There was, thus, an ideological underpinning to the use of the airwaves as a subversive tool. Radio transmission became a means of reaching out to the masses enclosed in what came to be called the Iron Curtain. The message was that those behind the curtain were being held in thrall against their will and that the West would do everything to help the oppressed peoples to break out of bondage.

Jamming of foreign radio broadcasts during the Cold War era was intended to prevent people from listening to the propaganda dispersed by enemy countries. It began to manifest itself in a continually escalating process of increasing radio noise accompanied by frequent change in frequencies. In many ways it was war by other means. It was seen that a transmitter, tuned to the same frequency as the opponents’ receiving equipment and with the same type of modulation, can, with enough power, override any signal at the receiver. Hence, it was the absence of “reception” and a clear example of being “jammed”.            

Radio Free Europe, Radio Liberty, Voice of America and the BBC World Service were the main targets of Soviet jammers because they led the phalanx of nations of the western bloc in carrying on propaganda and political instigation against the Soviet bloc countries.

East Germany was a particular target because West Berlin which was under the Western bloc because it was liberated by the US, France and Britain during World War II was surrounded by East Germany. The Berlin Wall built to separate the two halves of Berlin was cause for a sustained propaganda offensive against the Soviet block, particularly when persons from East Berlin defected to West Berlin by either going over or under the wall. With the collapse of the Soviet Union and the disintegration of the military Warsaw Pact nations in the late 90s the raison d’etre for jamming of radio broadcast has largely disappeared in Europe.

New threats

But other kinds of threats have emerged. Jihadi terrorism and the international network that has been created by Osama bin Laden’s Al Qaeda and Pakistan’s Taliban and United Jihad Council have given rise to a national requirement for target nations to remain aware of likely strikes by these organizations. The requirement is not as much for jamming but to listen in or eavesdrop on conversations and communications between jihadi commanders and their sleeper cells across the world.

After years of roadside bombings and being victims of improvised explosive devices fashioned by foreign inspired terrorists and homegrown insurgents Indian security forces have learned to defuse or render inert at least one type of IED-the remotely triggered explosive device.

This they do by jamming the radio frequency at which the terrorist transmits the command through a wireless trigger. Such a transmission is broadband and “sweeps” the area through which the vehicle is travelling in a manner that the transmitted message from the remote-control device does not reach the trigger embedded in the improvised explosive device.

Therefore, it does not explode and the vehicle makes a safe passage. This is a good defence against car bombs and static deployment of explosives where a suicide bomber is not employed. However, there is no defence against an IED triggered by a wired plunger device controlled from a distance from the chosen blast site.

The situation has given rise to a plethora of jamming devices intended to disarm IEDs. Be it the suitcase or manpack suppressor or devices that can jam V-Sat and GPS navigation systems by blocking the downlink transmission to the receiver on the ground. These are dual-use civil-military technologies. For purely military applications the blocking of high-frequency and very high frequency transmissions between artillery units and their forward observers, who radio correction data to the gun crew, can have a very significant effect on the battlefield situation.

The US is working on fitting an airborne Electronic Counter Measure aircraft with active electronically scanned array (AESA) antennas to be able to ensure a more focused beam of electro-magnetic waves.

Also, it is trying to produce a cheap method of jamming hostile emissions without collateral damage to radios of friendly forces in the vicinity. This will be a boon in urban guerrilla warfare where radio transmissions take place in closely confined space and blanket jamming occurs where transmissions of all combatants both enemy and friendly forces are adversely affected.

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