FAA notifies...
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The FAA issued an advisory warning pilots on Saturday that global positioning systems (GPS) could be unreliable during six different days this month, primarily in the Southwestern United States. On June 7, 9, 21, 23, 28, and 30th the GPS interference testing will be taking place between 9:30am and 3:30pm Pacific time. But if you’re on the ground, you probably won’t notice interference.
The testing will be centered on China Lake, California—home to the Navy’s 1.1 million acre Naval Air Weapons Center in the Mojave Desert. The potentially lost signals will stretch hundreds of miles in each direction and will affect various types of GPS, reaching the furthest at higher altitudes. But the jamming will only affect aircraft above 5,000 feet. As you can see from the FAA map below, the jamming will almost reach the California-Oregon border at 4o,000 feet above sea level and 505 nautical miles at its greatest range.
There were a fair number of tests on Yuma Proving Ground, while I was working there,that basically jammed GPS signals.
Our upper air instruments depended on GPS, so it was a significant problem on some days.
This was available at least 10 years ago.