United States is conducting a massive GPS jammer exercise

A major source of the GPS jamming will be Red Flag 18-1, the first phase of the air war games staged every year from Nellis Air Force Base in Nevada, with events ranging as far north as the Seattle air traffic control area. Electronic warfare aircraft, including the Navy's EA-18 Growler and the Air Force's EC-130 Compass Call, will play a role in shutting down the satellite navigation system for everything within as large as a 450 nautical mile radius.

That's where the GPS jamming comes in. The US and allied military forces lean heavily on GPS navigation, especially in the air—even some weapons systems depend on GPS for guidance. But because of the relative low power of GPS signals from satellites—as we've pointed out on a number of occasions—GPS is particularly prone to jamming or spoofing. Is that why GPS jamming weapons need to be developed

South Korea uses jamming devices with U.S. support

South Korean government officials report that the jamming operation, which began in late March, has been targeting aircraft navigation equipment. North Korea has reportedly broadcast a jamming signal on 100 occasions. A total of 962 planes have been affected by the jamming, as well as nearly 700 fishing vessels. The jamming has also affected cell phone base stations.

North Korea developed its GPS jamming capability in response to GPS-guided weapons that could be used by South Korean and U.S. forces in the event of war. The country maintains a regiment-sized GPS jamming unit near the capital of Pyongyang and battalion-sized units near the demilitarized zone. Jamming in 2012 was traced to the town of Kaesong, just over the border.

GPS’s relatively weak signals are often unreliable and susceptible to interference, also known as “military jammer” This has prompted the Defense Advance Research Projects Agency (DARPA) to begin developing navigational aids that function when satellite access is unavailable.

Russia experimented with jamming equipment in the Baltic sea

Phone services in Latvia, Norway and Sweden’s Oeland islands were reported to have been shut down for a few hours during the Sept. 14-20 Zapad exercises that Russia held with Belarus. The jamming is suspected to have been launched by a Russian communications ship from the Baltic Sea.

In the future, while USA will hopefully never fight Russia or China, USA almost certainly will fight someone who has bought advanced jamming and electronic warfare systems from them or even some of our own allies. The Pentagon doesn't discuss its GPS jamming capabilities, especially in time of war, but information readily available on the Web provides an insight into the power of the GPS jammers in its inventory.

The China Lake signal jammer cover a wide area, according to a Notice to Airmen (NOTAM) published by the Coast Guard Navigation Center in Alexandria, Va. The notice warned of "unreliable'' GPS signals within 300 nautical miles of the test range from Oct. 22 through Nov. 2. The U.S. Department of Transportation, which includes the U.S. Coast Guard, jointly manages civilian GPS signals with the Defense Department. Langley said that such a NOTAM indicates that China Lake is conducting jamming tests and shows that the U.S. military possesses the capability to jam GPS signals anywhere it wants.