Slitherine

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he US military has for weeks been training Ukrainian forces in US tactics, but the commander of US Army Europe says Ukrainian forces, who are fighting Russian-backed separatists, have much to teach their US trainers.

Ukrainian forces have grappled with formidable Russian electronic warfare capabilities that analysts say would prove withering even to the US ground forces. The US Army has also jammed insurgent communications from the air and ground on a limited basis, and it is developing a powerful arsenal of jamming systems, but these are not expected until 2023.

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ORIGINAL: Sakai007

...can't jam a bear...

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"We replicate what it would be like if an adversary fought back and tried to take away the force enhancement capabilities from the warfighters," said Crimm. "This may include communication, GPS or any space systems that we could use to leverage against the enemy. Our aggressors will try to take those away from the blue forces in an exercise environment."

During those exercises, the 527 SAS conducts adversarial tactics including jamming satellite communications and GPS receivers in an attempt to teach the warfighters the effects of the adversaries' weapon systems. The blue forces then attempt to mitigate the problems associated with these tactics.

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"We ask them before we begin 'How much pain do you want?' " the lieutenant colonel said. "We're not out to wreak havoc on them just for the sake of wreaking havoc. We want to show them what they're likely to realistically encounter. As a squadron, we will only play within the certified boundaries of what we know the opposition's tactics and capabilities are. We can replicate any adversary with space capabilities. And if we do it correctly, blue forces will build countermeasures for air and space superiority as the commander has intended. It makes for a more efficient and effective force."

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WASHINGTON (Reuters) - The U.S. Air Force quietly has put into service a new weapon designed to jam enemy satellite communications, a significant step toward U.S. control of space.

The so-called Counter Communications System was declared operational late last month at Peterson Air Force Base in Colorado Springs, the Air Force Space Command said Friday in e-mailed replies to questions from Reuters.

The ground-based jammer uses electromagnetic radio frequency energy to knock out transmissions on a temporary and reversible basis, without frying components, the command said. "A reversible effect ensures that during the time of need, the adversary's space-based capability to threaten our forces is diminished," said Capt. Angie Blair, a spokeswoman. "Following the time of need, the space-based capabilities used by the adversary can return to its original state."

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Jammers have shown their efficiency in the Iraq war in 2003 [9] by jamming Global Positioning System (GPS) receivers. In general, a jammer has large operating range, e.g., a GPS jammer made by the Russian firm Aviaconversia [10] is claimed to have a 150 – 200 km operating range. The basis of a jammer is that the jamming emitter transmits signals falling in the target receiver’s working bandwidth, whose power is much larger than the target receiver’s desired signal, and therefore, the target receiver’s desired signal is flooded by the jamming signal. Actually, all the receivers are possible to be jammed, and the receivers with high sensitivity are more vulnerable to jamming, e.g., GPS receivers, radar receivers, and communication systems.


Anti-jam techniques include spread spectrum [11], smart antenna technique [12], and localizing and destroy. In the spread spectrum technique, the desired signal is spread over a wide frequency band via direct sequence spread spectrum (DSSS) or frequency-hopping spread spectrum (FHSS) method. If the jamming signal is narrow band, in the de-spreading process, the jamming signal would be pressed and the jamming effect is alleviated. In the system that applies antenna technique to compete with the jammer, a smart beam pattern is generated to achieve a maximized signal to jamming ratio by directing the lowest antenna gain to the jammer. The de-spreading gain and the antenna’s directionality are limited. For example, (1) GPS C/A code includes 1024 bits and the processing gain is about 30dB, if the jamming signal is larger than the GPS signal 30dB or more, the GPS receiver would be totally jammed. (2) The signal to jamming ratio that a smart antenna can mitigate depends on the smart antenna’s beam pattern, which is determined by the number of the elements in the smart antenna (which is limited by the array size), and the number of jammers and their distribution. When the jamming transmitter’s power is enhanced, the efficiency of the spread spectrum and antenna technique would fade. On the other hand, a jammer with higher power would be easier to be localized. When the jammer is localized w ith high accuracy, we can either avoid it or destroy it.